Add JSON serialisation of DUs (#144)

* Bump Microsoft.NET.Test.Sdk from 17.9.0 to 17.10.0

Bumps [Microsoft.NET.Test.Sdk](https://github.com/microsoft/vstest) from 17.9.0 to 17.10.0.
- [Release notes](https://github.com/microsoft/vstest/releases)
- [Changelog](https://github.com/microsoft/vstest/blob/main/docs/releases.md)
- [Commits](https://github.com/microsoft/vstest/compare/v17.9.0...v17.10.0)

---
updated-dependencies:
- dependency-name: Microsoft.NET.Test.Sdk
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

* Bump ApiSurface from 4.0.39 to 4.0.40

Bumps [ApiSurface](https://github.com/G-Research/ApiSurface) from 4.0.39 to 4.0.40.
- [Release notes](https://github.com/G-Research/ApiSurface/releases)
- [Commits](https://github.com/G-Research/ApiSurface/compare/ApiSurface.4.0.39...ApiSurface.4.0.40)

---
updated-dependencies:
- dependency-name: ApiSurface
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <support@github.com>

* Update deps

---------

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
Co-authored-by: Smaug123 <3138005+Smaug123@users.noreply.github.com>

CHANGELOG.md

@@ -1,6 +1,18 @@
 Notable changes are recorded here.
 
-# WoofWare.Myriad.Plugins 1.4 -> 2.0
+# WoofWare.Myriad.Plugins 2.1.20, WoofWare.Myriad.Plugins.Attributes 3.0.1
+
+We now bundle copies of the RestEase attributes in `WoofWare.Myriad.Plugins.Attributes`, in case you don't want to take a dependency on RestEase.
+
+# WoofWare.Myriad.Plugins 2.1.15
+
+The `GenerateMock` generator now permits a limited amount of inheritance in the record we're mocking out (specifically, `IDisposable`).
+
+# WoofWare.Myriad.Plugins 2.1.8
+
+No change to the packages, but this is when we started creating and tagging GitHub releases, which are a better source of truth than this file.
+
+# WoofWare.Myriad.Plugins 2.0
 
 This transition split the attributes (e.g. `[<JsonParseAttribute>]`) into their own assembly, WoofWare.Myriad.Plugins.Attributes.
 The new assembly has minimal dependencies, so you may safely use it from your own code.

ConsumePlugin/GeneratedCatamorphism.fs

@@ -60,7 +60,7 @@ module TreeCata =
             instructions.RemoveAt (instructions.Count - 1)
 
             match currentInstruction with
-            | Instruction.Process__TreeBuilder x ->
+            | Instruction.Process__TreeBuilder (x) ->
                 match x with
                 | TreeBuilder.Child (arg0_0) ->
                     instructions.Add Instruction.TreeBuilder_Child
@@ -68,7 +68,7 @@ module TreeCata =
                 | TreeBuilder.Parent (arg0_0) ->
                     instructions.Add Instruction.TreeBuilder_Parent
                     instructions.Add (Instruction.Process__Tree arg0_0)
-            | Instruction.Process__Tree x ->
+            | Instruction.Process__Tree (x) ->
                 match x with
                 | Tree.Const (arg0_0, arg1_0) -> cata.Tree.Const arg0_0 arg1_0 |> treeStack.Add
                 | Tree.Pair (arg0_0, arg1_0, arg2_0) ->

ConsumePlugin/GeneratedFileSystem.fs

@@ -41,7 +41,7 @@ module FileSystemItemCata =
             instructions.RemoveAt (instructions.Count - 1)
 
             match currentInstruction with
-            | Instruction.Process__FileSystemItem x ->
+            | Instruction.Process__FileSystemItem (x) ->
                 match x with
                 | FileSystemItem.Directory ({
                                                 Name = name
@@ -116,7 +116,7 @@ module GiftCata =
             instructions.RemoveAt (instructions.Count - 1)
 
             match currentInstruction with
-            | Instruction.Process__Gift x ->
+            | Instruction.Process__Gift (x) ->
                 match x with
                 | Gift.Book (arg0_0) -> cata.Gift.Book arg0_0 |> giftStack.Add
                 | Gift.Chocolate (arg0_0) -> cata.Gift.Chocolate arg0_0 |> giftStack.Add

ConsumePlugin/GeneratedSerde.fs

@@ -149,6 +149,37 @@ module JsonRecordTypeWithBothJsonSerializeExtension =
                 )
 
             node :> _
+namespace ConsumePlugin
+
+open System
+open System.Collections.Generic
+open System.Text.Json.Serialization
+
+/// Module containing JSON serializing extension members for the FirstDu type
+[<AutoOpen>]
+module FirstDuJsonSerializeExtension =
+    /// Extension methods for JSON parsing
+    type FirstDu with
+
+        /// Serialize to a JSON node
+        static member toJsonNode (input : FirstDu) : System.Text.Json.Nodes.JsonNode =
+            let node = System.Text.Json.Nodes.JsonObject ()
+
+            match input with
+            | FirstDu.EmptyCase -> node.Add ("type", System.Text.Json.Nodes.JsonValue.Create "emptyCase")
+            | FirstDu.Case1 (arg0) ->
+                node.Add ("type", System.Text.Json.Nodes.JsonValue.Create "case1")
+                let dataNode = System.Text.Json.Nodes.JsonObject ()
+                dataNode.Add ("data", System.Text.Json.Nodes.JsonValue.Create<string> arg0)
+                node.Add ("data", dataNode)
+            | FirstDu.Case2 (arg0, arg1) ->
+                node.Add ("type", System.Text.Json.Nodes.JsonValue.Create "case2")
+                let dataNode = System.Text.Json.Nodes.JsonObject ()
+                dataNode.Add ("record", JsonRecordTypeWithBoth.toJsonNode arg0)
+                dataNode.Add ("i", System.Text.Json.Nodes.JsonValue.Create<int> arg1)
+                node.Add ("data", dataNode)
+
+            node :> _
 
 namespace ConsumePlugin
 

ConsumePlugin/GeneratedVault.fs

@@ -543,3 +543,201 @@ module VaultClient =
                 }
                 |> (fun a -> Async.StartAsTask (a, ?cancellationToken = ct))
         }
+namespace ConsumePlugin
+
+open System
+open System.Collections.Generic
+open System.Text.Json.Serialization
+open System.Threading
+open System.Threading.Tasks
+open RestEase
+
+/// Module for constructing a REST client.
+[<CompilationRepresentation(CompilationRepresentationFlags.ModuleSuffix)>]
+[<RequireQualifiedAccess>]
+module VaultClientNonExtensionMethod =
+    /// Create a REST client.
+    let make (client : System.Net.Http.HttpClient) : IVaultClientNonExtensionMethod =
+        { new IVaultClientNonExtensionMethod with
+            member _.GetSecret
+                (jwt : JwtVaultResponse, path : string, mountPoint : string, ct : CancellationToken option)
+                =
+                async {
+                    let! ct = Async.CancellationToken
+
+                    let uri =
+                        System.Uri (
+                            (match client.BaseAddress with
+                             | null ->
+                                 raise (
+                                     System.ArgumentNullException (
+                                         nameof (client.BaseAddress),
+                                         "No base address was supplied on the type, and no BaseAddress was on the HttpClient."
+                                     )
+                                 )
+                             | v -> v),
+                            System.Uri (
+                                "v1/{mountPoint}/{path}"
+                                    .Replace("{path}", path.ToString () |> System.Web.HttpUtility.UrlEncode)
+                                    .Replace (
+                                        "{mountPoint}",
+                                        mountPoint.ToString () |> System.Web.HttpUtility.UrlEncode
+                                    ),
+                                System.UriKind.Relative
+                            )
+                        )
+
+                    let httpMessage =
+                        new System.Net.Http.HttpRequestMessage (
+                            Method = System.Net.Http.HttpMethod.Get,
+                            RequestUri = uri
+                        )
+
+                    let! response = client.SendAsync (httpMessage, ct) |> Async.AwaitTask
+                    let response = response.EnsureSuccessStatusCode ()
+                    let! responseStream = response.Content.ReadAsStreamAsync ct |> Async.AwaitTask
+
+                    let! jsonNode =
+                        System.Text.Json.Nodes.JsonNode.ParseAsync (responseStream, cancellationToken = ct)
+                        |> Async.AwaitTask
+
+                    return JwtSecretResponse.jsonParse jsonNode
+                }
+                |> (fun a -> Async.StartAsTask (a, ?cancellationToken = ct))
+
+            member _.GetJwt (role : string, jwt : string, ct : CancellationToken option) =
+                async {
+                    let! ct = Async.CancellationToken
+
+                    let uri =
+                        System.Uri (
+                            (match client.BaseAddress with
+                             | null ->
+                                 raise (
+                                     System.ArgumentNullException (
+                                         nameof (client.BaseAddress),
+                                         "No base address was supplied on the type, and no BaseAddress was on the HttpClient."
+                                     )
+                                 )
+                             | v -> v),
+                            System.Uri ("v1/auth/jwt/login", System.UriKind.Relative)
+                        )
+
+                    let httpMessage =
+                        new System.Net.Http.HttpRequestMessage (
+                            Method = System.Net.Http.HttpMethod.Get,
+                            RequestUri = uri
+                        )
+
+                    let! response = client.SendAsync (httpMessage, ct) |> Async.AwaitTask
+                    let response = response.EnsureSuccessStatusCode ()
+                    let! responseStream = response.Content.ReadAsStreamAsync ct |> Async.AwaitTask
+
+                    let! jsonNode =
+                        System.Text.Json.Nodes.JsonNode.ParseAsync (responseStream, cancellationToken = ct)
+                        |> Async.AwaitTask
+
+                    return JwtVaultResponse.jsonParse jsonNode
+                }
+                |> (fun a -> Async.StartAsTask (a, ?cancellationToken = ct))
+        }
+namespace ConsumePlugin
+
+open System
+open System.Collections.Generic
+open System.Text.Json.Serialization
+open System.Threading
+open System.Threading.Tasks
+open RestEase
+
+/// Extension methods for constructing a REST client.
+[<AutoOpen>]
+module VaultClientExtensionMethodHttpClientExtension =
+    /// Extension methods for HTTP clients
+    type VaultClientExtensionMethod with
+
+        /// Create a REST client.
+        static member make (client : System.Net.Http.HttpClient) : IVaultClientExtensionMethod =
+            { new IVaultClientExtensionMethod with
+                member _.GetSecret
+                    (jwt : JwtVaultResponse, path : string, mountPoint : string, ct : CancellationToken option)
+                    =
+                    async {
+                        let! ct = Async.CancellationToken
+
+                        let uri =
+                            System.Uri (
+                                (match client.BaseAddress with
+                                 | null ->
+                                     raise (
+                                         System.ArgumentNullException (
+                                             nameof (client.BaseAddress),
+                                             "No base address was supplied on the type, and no BaseAddress was on the HttpClient."
+                                         )
+                                     )
+                                 | v -> v),
+                                System.Uri (
+                                    "v1/{mountPoint}/{path}"
+                                        .Replace("{path}", path.ToString () |> System.Web.HttpUtility.UrlEncode)
+                                        .Replace (
+                                            "{mountPoint}",
+                                            mountPoint.ToString () |> System.Web.HttpUtility.UrlEncode
+                                        ),
+                                    System.UriKind.Relative
+                                )
+                            )
+
+                        let httpMessage =
+                            new System.Net.Http.HttpRequestMessage (
+                                Method = System.Net.Http.HttpMethod.Get,
+                                RequestUri = uri
+                            )
+
+                        let! response = client.SendAsync (httpMessage, ct) |> Async.AwaitTask
+                        let response = response.EnsureSuccessStatusCode ()
+                        let! responseStream = response.Content.ReadAsStreamAsync ct |> Async.AwaitTask
+
+                        let! jsonNode =
+                            System.Text.Json.Nodes.JsonNode.ParseAsync (responseStream, cancellationToken = ct)
+                            |> Async.AwaitTask
+
+                        return JwtSecretResponse.jsonParse jsonNode
+                    }
+                    |> (fun a -> Async.StartAsTask (a, ?cancellationToken = ct))
+
+                member _.GetJwt (role : string, jwt : string, ct : CancellationToken option) =
+                    async {
+                        let! ct = Async.CancellationToken
+
+                        let uri =
+                            System.Uri (
+                                (match client.BaseAddress with
+                                 | null ->
+                                     raise (
+                                         System.ArgumentNullException (
+                                             nameof (client.BaseAddress),
+                                             "No base address was supplied on the type, and no BaseAddress was on the HttpClient."
+                                         )
+                                     )
+                                 | v -> v),
+                                System.Uri ("v1/auth/jwt/login", System.UriKind.Relative)
+                            )
+
+                        let httpMessage =
+                            new System.Net.Http.HttpRequestMessage (
+                                Method = System.Net.Http.HttpMethod.Get,
+                                RequestUri = uri
+                            )
+
+                        let! response = client.SendAsync (httpMessage, ct) |> Async.AwaitTask
+                        let response = response.EnsureSuccessStatusCode ()
+                        let! responseStream = response.Content.ReadAsStreamAsync ct |> Async.AwaitTask
+
+                        let! jsonNode =
+                            System.Text.Json.Nodes.JsonNode.ParseAsync (responseStream, cancellationToken = ct)
+                            |> Async.AwaitTask
+
+                        return JwtVaultResponse.jsonParse jsonNode
+                    }
+                    |> (fun a -> Async.StartAsTask (a, ?cancellationToken = ct))
+            }

ConsumePlugin/ListCata.fs

@@ -41,7 +41,7 @@ module MyListCata =
             instructions.RemoveAt (instructions.Count - 1)
 
             match currentInstruction with
-            | Instruction.Process__MyList x ->
+            | Instruction.Process__MyList (x) ->
                 match x with
                 | MyList.Nil -> cata.MyList.Nil |> myListStack.Add
                 | MyList.Cons ({
@@ -97,7 +97,7 @@ module MyList2Cata =
             instructions.RemoveAt (instructions.Count - 1)
 
             match currentInstruction with
-            | Instruction.Process__MyList2 x ->
+            | Instruction.Process__MyList2 (x) ->
                 match x with
                 | MyList2.Nil -> cata.MyList2.Nil |> myList2Stack.Add
                 | MyList2.Cons (arg0_0, arg1_0) ->

ConsumePlugin/SerializationAndDeserialization.fs

@@ -27,3 +27,9 @@ type JsonRecordTypeWithBoth =
         E : string array
         F : int[]
     }
+
+[<WoofWare.Myriad.Plugins.JsonSerialize true>]
+type FirstDu =
+    | EmptyCase
+    | Case1 of data : string
+    | Case2 of record : JsonRecordTypeWithBoth * i : int

ConsumePlugin/Vault.fs

@@ -76,3 +76,33 @@ type IVaultClient =
 
     [<Get "v1/auth/jwt/login">]
     abstract GetJwt : role : string * jwt : string * ?ct : CancellationToken -> Task<JwtVaultResponse>
+
+[<WoofWare.Myriad.Plugins.HttpClient false>]
+type IVaultClientNonExtensionMethod =
+    [<Get "v1/{mountPoint}/{path}">]
+    abstract GetSecret :
+        jwt : JwtVaultResponse *
+        [<Path "path">] path : string *
+        [<Path "mountPoint">] mountPoint : string *
+        ?ct : CancellationToken ->
+            Task<JwtSecretResponse>
+
+    [<Get "v1/auth/jwt/login">]
+    abstract GetJwt : role : string * jwt : string * ?ct : CancellationToken -> Task<JwtVaultResponse>
+
+[<WoofWare.Myriad.Plugins.HttpClient(true)>]
+type IVaultClientExtensionMethod =
+    [<Get "v1/{mountPoint}/{path}">]
+    abstract GetSecret :
+        jwt : JwtVaultResponse *
+        [<Path "path">] path : string *
+        [<Path "mountPoint">] mountPoint : string *
+        ?ct : CancellationToken ->
+            Task<JwtSecretResponse>
+
+    [<Get "v1/auth/jwt/login">]
+    abstract GetJwt : role : string * jwt : string * ?ct : CancellationToken -> Task<JwtVaultResponse>
+
+[<RequireQualifiedAccess>]
+type VaultClientExtensionMethod =
+    static member thisClashes = 99

README.md

@@ -143,6 +143,9 @@ module InnerTypeWithBoth =
         node
 ```
 
+Also includes an *opinionated* serializer for discriminated unions.
+(Any such serializer must be opinionated, because JSON does not natively model DUs.)
+
 As in `JsonParse`, you can optionally supply the boolean `true` to the attribute,
 which will cause Myriad to stamp out an extension method rather than a module with the same name as the type.
 

WoofWare.Myriad.Plugins.Attributes/Attributes.fs

@@ -60,8 +60,17 @@ type JsonParseAttribute (isExtensionMethod : bool) =
 /// generator should apply during build.
 /// This generator is intended to replicate much of the functionality of RestEase,
 /// i.e. to stamp out HTTP REST clients from interfaces defining the API.
-type HttpClientAttribute () =
+///
+/// If you supply isExtensionMethod = true, you will get extension methods.
+/// These can only be consumed from F#, but the benefit is that they don't use up the module name
+/// (since by default we create a module called "{TypeName}").
+type HttpClientAttribute (isExtensionMethod : bool) =
     inherit Attribute ()
+    /// The default value of `isExtensionMethod`, the optional argument to the HttpClientAttribute constructor.
+    static member DefaultIsExtensionMethod = false
+
+    /// Shorthand for the "isExtensionMethod = false" constructor; see documentation there for details.
+    new () = HttpClientAttribute HttpClientAttribute.DefaultIsExtensionMethod
 
 /// Attribute indicating a DU type to which the "create catamorphism" Myriad
 /// generator should apply during build.

WoofWare.Myriad.Plugins.Attributes/SurfaceBaseline.txt

@@ -6,7 +6,10 @@ WoofWare.Myriad.Plugins.GenerateMockAttribute..ctor [constructor]: unit
 WoofWare.Myriad.Plugins.GenerateMockAttribute.DefaultIsInternal [static property]: [read-only] bool
 WoofWare.Myriad.Plugins.GenerateMockAttribute.get_DefaultIsInternal [static method]: unit -> bool
 WoofWare.Myriad.Plugins.HttpClientAttribute inherit System.Attribute
+WoofWare.Myriad.Plugins.HttpClientAttribute..ctor [constructor]: bool
 WoofWare.Myriad.Plugins.HttpClientAttribute..ctor [constructor]: unit
+WoofWare.Myriad.Plugins.HttpClientAttribute.DefaultIsExtensionMethod [static property]: [read-only] bool
+WoofWare.Myriad.Plugins.HttpClientAttribute.get_DefaultIsExtensionMethod [static method]: unit -> bool
 WoofWare.Myriad.Plugins.JsonParseAttribute inherit System.Attribute
 WoofWare.Myriad.Plugins.JsonParseAttribute..ctor [constructor]: bool
 WoofWare.Myriad.Plugins.JsonParseAttribute..ctor [constructor]: unit

WoofWare.Myriad.Plugins.Attributes/Test/WoofWare.Myriad.Plugins.Attributes.Test.fsproj

@@ -12,8 +12,8 @@
     </ItemGroup>
 
     <ItemGroup>
-        <PackageReference Include="ApiSurface" Version="4.0.39" />
-        <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.9.0"/>
+        <PackageReference Include="ApiSurface" Version="4.0.40" />
+        <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.10.0"/>
         <PackageReference Include="NUnit" Version="4.1.0"/>
         <PackageReference Include="NUnit3TestAdapter" Version="4.5.0"/>
     </ItemGroup>

WoofWare.Myriad.Plugins.Attributes/version.json

@@ -1,7 +1,15 @@
 {
-  "version": "3.0",
+  "version": "3.1",
   "publicReleaseRefSpec": [
     "^refs/heads/main$"
   ],
-  "pathFilters": null
-}
+  "pathFilters": [
+    ":/README.md",
+    ":/LICENSE",
+    ":/WoofWare.Myriad.Plugins/logo.png",
+    ":/Directory.Build.props",
+    ":/global.json",
+    "./",
+    "^./Test"
+  ]
+}

WoofWare.Myriad.Plugins.Test/TestHttpClient/TestVaultClient.fs

@@ -87,8 +87,10 @@ module TestVaultClient =
     }
 }"""
 
-    [<Test>]
-    let ``URI example`` () =
+    [<TestCase 1>]
+    [<TestCase 2>]
+    [<TestCase 3>]
+    let ``URI example`` (vaultClientId : int) =
         let proc (message : HttpRequestMessage) : HttpResponseMessage Async =
             async {
                 message.Method |> shouldEqual HttpMethod.Get
@@ -112,10 +114,25 @@ module TestVaultClient =
             }
 
         use client = HttpClientMock.make (Uri "https://my-vault.com") proc
-        let api = VaultClient.make client
 
-        let vaultResponse = api.GetJwt("role", "jwt").Result
-        let value = api.GetSecret(vaultResponse, "path", "mount").Result
+        let value =
+            match vaultClientId with
+            | 1 ->
+                let api = VaultClient.make client
+                let vaultResponse = api.GetJwt("role", "jwt").Result
+                let value = api.GetSecret(vaultResponse, "path", "mount").Result
+                value
+            | 2 ->
+                let api = VaultClientNonExtensionMethod.make client
+                let vaultResponse = api.GetJwt("role", "jwt").Result
+                let value = api.GetSecret(vaultResponse, "path", "mount").Result
+                value
+            | 3 ->
+                let api = VaultClientExtensionMethod.make client
+                let vaultResponse = api.GetJwt("role", "jwt").Result
+                let value = api.GetSecret(vaultResponse, "path", "mount").Result
+                value
+            | _ -> failwith $"Unrecognised ID: %i{vaultClientId}"
 
         value.Data
         |> Seq.toList
@@ -168,3 +185,5 @@ module TestVaultClient =
                 "key8_1", "https://example.com/data8/1"
                 "key8_2", "https://example.com/data8/2"
             ]
+
+    let _canSeePastExtensionMethod = VaultClientExtensionMethod.thisClashes

WoofWare.Myriad.Plugins.Test/TestJsonParse/TestJsonParse.fs

@@ -7,6 +7,8 @@ open FsUnitTyped
 
 [<TestFixture>]
 module TestJsonParse =
+    let _canSeePastExtensionMethod = ToGetExtensionMethod.thisModuleWouldClash
+
     [<Test>]
     let ``Single example`` () =
         let s =

WoofWare.Myriad.Plugins.Test/WoofWare.Myriad.Plugins.Test.fsproj

@@ -33,10 +33,10 @@
   </ItemGroup>
 
   <ItemGroup>
-    <PackageReference Include="ApiSurface" Version="4.0.39"/>
+    <PackageReference Include="ApiSurface" Version="4.0.40"/>
     <PackageReference Include="FsCheck" Version="2.16.6"/>
     <PackageReference Include="FsUnit" Version="6.0.0"/>
-    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.9.0"/>
+    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.10.0"/>
     <PackageReference Include="NUnit" Version="4.1.0"/>
     <PackageReference Include="NUnit3TestAdapter" Version="4.5.0"/>
   </ItemGroup>

WoofWare.Myriad.Plugins/CataGenerator.fs

@@ -1113,7 +1113,7 @@ module internal CataGenerator =
                 analysis.AssociatedProcessInstruction,
                 None,
                 None,
-                SynArgPats.Pats [ SynPat.CreateNamed (Ident.Create "x") ],
+                SynArgPats.create [ Ident.Create "x" ],
                 None,
                 range0
             ),
@@ -1162,22 +1162,16 @@ module internal CataGenerator =
                     |> Seq.mapi (fun i x -> (i, x))
                     |> Seq.choose (fun (i, case) ->
                         match case.Description with
-                        | FieldDescription.NonRecursive _ -> SynPat.CreateNamed case.ArgName |> Some
-                        | FieldDescription.ListSelf _ -> SynPat.CreateNamed case.ArgName |> Some
+                        | FieldDescription.NonRecursive _ -> case.ArgName |> Some
+                        | FieldDescription.ListSelf _ -> case.ArgName |> Some
                         | FieldDescription.Self _ -> None
                     )
                     |> Seq.toList
 
-                let lhs =
-                    match lhsNames with
-                    | [] -> []
-                    | lhsNames ->
-                        SynPat.Tuple (false, lhsNames, List.replicate (lhsNames.Length - 1) range0, range0)
-                        |> SynPat.CreateParen
-                        |> List.singleton
+                let lhs = SynArgPats.create lhsNames
 
                 let pat =
-                    SynPat.LongIdent (unionCase.AssociatedInstruction, None, None, SynArgPats.Pats lhs, None, range0)
+                    SynPat.LongIdent (unionCase.AssociatedInstruction, None, None, lhs, None, range0)
 
                 let populateArgs =
                     unionCase.FlattenedFields

WoofWare.Myriad.Plugins/HttpClientGenerator.fs

@@ -6,6 +6,11 @@ open Fantomas.FCS.SyntaxTrivia
 open Fantomas.FCS.Xml
 open Myriad.Core
 
+type internal HttpClientGeneratorOutputSpec =
+    {
+        ExtensionMethods : bool
+    }
+
 [<RequireQualifiedAccess>]
 module internal HttpClientGenerator =
     open Fantomas.FCS.Text.Range
@@ -811,7 +816,7 @@ module internal HttpClientGenerator =
     let createModule
         (opens : SynOpenDeclTarget list)
         (ns : LongIdent)
-        (interfaceType : SynTypeDefn)
+        (interfaceType : SynTypeDefn, spec : HttpClientGeneratorOutputSpec)
         : SynModuleOrNamespace
         =
         let interfaceType = AstHelper.parseInterface interfaceType
@@ -959,7 +964,13 @@ module internal HttpClientGenerator =
 
         let members = propertyMembers @ nonPropertyMembers
 
-        let docString = PreXmlDoc.Create " Module for constructing a REST client."
+        let docString =
+            (if spec.ExtensionMethods then
+                 "Extension methods"
+             else
+                 "Module")
+            |> sprintf " %s for constructing a REST client."
+            |> PreXmlDoc.Create
 
         let interfaceImpl =
             SynExpr.ObjExpr (
@@ -995,38 +1006,38 @@ module internal HttpClientGenerator =
                 " Create a REST client."
             else
                 " Create a REST client. The input functions will be re-evaluated on every HTTP request to obtain the required values for the corresponding header properties."
+            |> PreXmlDoc.Create
 
-        let createFunc =
-            SynBinding.SynBinding (
-                None,
-                SynBindingKind.Normal,
-                false,
-                false,
-                [],
-                PreXmlDoc.Create xmlDoc,
-                SynValData.SynValData (
-                    None,
-                    SynValInfo.SynValInfo (
-                        [ [ SynArgInfo.SynArgInfo ([], false, Some (Ident.Create "client")) ] ],
-                        SynArgInfo.Empty
-                    ),
+        let functionName = Ident.Create "client"
+
+        let valData =
+            let memberFlags =
+                if spec.ExtensionMethods then
+                    {
+                        SynMemberFlags.IsInstance = false
+                        SynMemberFlags.IsDispatchSlot = false
+                        SynMemberFlags.IsOverrideOrExplicitImpl = false
+                        SynMemberFlags.IsFinal = false
+                        SynMemberFlags.GetterOrSetterIsCompilerGenerated = false
+                        SynMemberFlags.MemberKind = SynMemberKind.Member
+                    }
+                    |> Some
+                else
                     None
-                ),
-                SynPat.CreateLongIdent (SynLongIdent.CreateString "make", headerArgs @ [ clientCreationArg ]),
-                Some (
-                    SynBindingReturnInfo.Create (
-                        SynType.LongIdent (SynLongIdent.CreateFromLongIdent interfaceType.Name)
-                    )
-                ),
-                interfaceImpl,
-                range0,
-                DebugPointAtBinding.NoneAtLet,
-                SynExpr.synBindingTriviaZero false
-            )
-            |> List.singleton
-            |> SynModuleDecl.CreateLet
 
-        let moduleName : LongIdent =
+            SynValData.SynValData (
+                memberFlags,
+                SynValInfo.SynValInfo ([ [ SynArgInfo.SynArgInfo ([], false, Some functionName) ] ], SynArgInfo.Empty),
+                None
+            )
+
+        let pattern =
+            SynPat.CreateLongIdent (SynLongIdent.CreateString "make", headerArgs @ [ clientCreationArg ])
+
+        let returnInfo =
+            SynBindingReturnInfo.Create (SynType.LongIdent (SynLongIdent.CreateFromLongIdent interfaceType.Name))
+
+        let nameWithoutLeadingI =
             List.last interfaceType.Name
             |> _.idText
             |> fun s ->
@@ -1034,14 +1045,84 @@ module internal HttpClientGenerator =
                     s.[1..]
                 else
                     failwith $"Expected interface type to start with 'I', but was: %s{s}"
-            |> Ident.Create
-            |> List.singleton
+
+        let createFunc =
+            if spec.ExtensionMethods then
+                let binding =
+                    SynBinding.SynBinding (
+                        None,
+                        SynBindingKind.Normal,
+                        false,
+                        false,
+                        [],
+                        xmlDoc,
+                        valData,
+                        pattern,
+                        Some returnInfo,
+                        interfaceImpl,
+                        range0,
+                        DebugPointAtBinding.NoneAtInvisible,
+                        {
+                            LeadingKeyword = SynLeadingKeyword.StaticMember (range0, range0)
+                            InlineKeyword = None
+                            EqualsRange = Some range0
+                        }
+                    )
+
+                let mem = SynMemberDefn.Member (binding, range0)
+
+                let containingType =
+                    SynTypeDefn.SynTypeDefn (
+                        SynComponentInfo.Create (
+                            [ Ident.Create nameWithoutLeadingI ],
+                            xmldoc = PreXmlDoc.Create " Extension methods for HTTP clients"
+                        ),
+                        SynTypeDefnRepr.ObjectModel (SynTypeDefnKind.Augmentation range0, [], range0),
+                        [ mem ],
+                        None,
+                        range0,
+                        {
+                            LeadingKeyword = SynTypeDefnLeadingKeyword.Type range0
+                            EqualsRange = None
+                            WithKeyword = None
+                        }
+                    )
+
+                SynModuleDecl.Types ([ containingType ], range0)
+
+            else
+                SynBinding.SynBinding (
+                    None,
+                    SynBindingKind.Normal,
+                    false,
+                    false,
+                    [],
+                    xmlDoc,
+                    valData,
+                    pattern,
+                    Some returnInfo,
+                    interfaceImpl,
+                    range0,
+                    DebugPointAtBinding.NoneAtLet,
+                    SynExpr.synBindingTriviaZero false
+                )
+                |> List.singleton
+                |> SynModuleDecl.CreateLet
+
+        let moduleName : LongIdent =
+            if spec.ExtensionMethods then
+                [ Ident.Create (nameWithoutLeadingI + "HttpClientExtension") ]
+            else
+                [ Ident.Create nameWithoutLeadingI ]
 
         let attribs =
-            [
-                SynAttributeList.Create SynAttribute.compilationRepresentation
-                SynAttributeList.Create (SynAttribute.RequireQualifiedAccess ())
-            ]
+            if spec.ExtensionMethods then
+                [ SynAttributeList.Create SynAttribute.autoOpen ]
+            else
+                [
+                    SynAttributeList.Create SynAttribute.compilationRepresentation
+                    SynAttributeList.Create (SynAttribute.RequireQualifiedAccess ())
+                ]
 
         let modInfo =
             SynComponentInfo.Create (
@@ -1079,9 +1160,29 @@ type HttpClientGenerator () =
             let namespaceAndTypes =
                 types
                 |> List.choose (fun (ns, types) ->
-                    match types |> List.filter Ast.hasAttribute<HttpClientAttribute> with
-                    | [] -> None
-                    | types -> Some (ns, types)
+                    types
+                    |> List.choose (fun typeDef ->
+                        match Ast.getAttribute<HttpClientAttribute> typeDef with
+                        | None -> None
+                        | Some attr ->
+                            let arg =
+                                match SynExpr.stripOptionalParen attr.ArgExpr with
+                                | SynExpr.Const (SynConst.Bool value, _) -> value
+                                | SynExpr.Const (SynConst.Unit, _) -> JsonParseAttribute.DefaultIsExtensionMethod
+                                | arg ->
+                                    failwith
+                                        $"Unrecognised argument %+A{arg} to [<%s{nameof HttpClientAttribute}>]. Literals are not supported. Use `true` or `false` (or unit) only."
+
+                            let spec =
+                                {
+                                    ExtensionMethods = arg
+                                }
+
+                            Some (typeDef, spec)
+                    )
+                    |> function
+                        | [] -> None
+                        | ty -> Some (ns, ty)
                 )
 
             let modules =

WoofWare.Myriad.Plugins/JsonParseGenerator.fs

@@ -566,61 +566,61 @@ module internal JsonParseGenerator =
 
             SynModuleDecl.CreateLet [ binding ]
 
-    let createRecordModule (namespaceId : LongIdent) (spec : JsonParseOutputSpec) (typeDefn : SynTypeDefn) =
+    let createModule (namespaceId : LongIdent) (spec : JsonParseOutputSpec) (typeDefn : SynTypeDefn) =
         let (SynTypeDefn (synComponentInfo, synTypeDefnRepr, _members, _implicitCtor, _, _)) =
             typeDefn
 
-        let (SynComponentInfo (_attributes, _typeParams, _constraints, recordId, _, _preferPostfix, _access, _)) =
+        let (SynComponentInfo (_attributes, _typeParams, _constraints, ident, _, _preferPostfix, _access, _)) =
             synComponentInfo
 
-        match synTypeDefnRepr with
-        | SynTypeDefnRepr.Simple (SynTypeDefnSimpleRepr.Record (_accessibility, recordFields, _recordRange), _) ->
+        let attributes =
+            if spec.ExtensionMethods then
+                [ SynAttributeList.Create SynAttribute.autoOpen ]
+            else
+                [
+                    SynAttributeList.Create (SynAttribute.RequireQualifiedAccess ())
+                    SynAttributeList.Create SynAttribute.compilationRepresentation
+                ]
 
-            let decls = [ createMaker spec recordId recordFields ]
+        let xmlDoc =
+            let fullyQualified = ident |> Seq.map (fun i -> i.idText) |> String.concat "."
 
-            let attributes =
+            let description =
                 if spec.ExtensionMethods then
-                    [ SynAttributeList.Create SynAttribute.autoOpen ]
+                    "extension members"
                 else
-                    [
-                        SynAttributeList.Create (SynAttribute.RequireQualifiedAccess ())
-                        SynAttributeList.Create SynAttribute.compilationRepresentation
-                    ]
+                    "methods"
 
-            let xmlDoc =
-                let fullyQualified = recordId |> Seq.map (fun i -> i.idText) |> String.concat "."
+            $" Module containing JSON parsing %s{description} for the %s{fullyQualified} type"
+            |> PreXmlDoc.Create
 
-                let description =
-                    if spec.ExtensionMethods then
-                        "extension members"
-                    else
-                        "methods"
+        let moduleName =
+            if spec.ExtensionMethods then
+                match ident with
+                | [] -> failwith "unexpectedly got an empty identifier for record name"
+                | ident ->
+                    let expanded =
+                        List.last ident
+                        |> fun i -> i.idText
+                        |> fun s -> s + "JsonParseExtension"
+                        |> Ident.Create
 
-                $" Module containing JSON parsing %s{description} for the %s{fullyQualified} type"
-                |> PreXmlDoc.Create
+                    List.take (List.length ident - 1) ident @ [ expanded ]
+            else
+                ident
 
-            let moduleName =
-                if spec.ExtensionMethods then
-                    match recordId with
-                    | [] -> failwith "unexpectedly got an empty identifier for record name"
-                    | recordId ->
-                        let expanded =
-                            List.last recordId
-                            |> fun i -> i.idText
-                            |> fun s -> s + "JsonParseExtension"
-                            |> Ident.Create
+        let info =
+            SynComponentInfo.Create (moduleName, attributes = attributes, xmldoc = xmlDoc)
 
-                        List.take (List.length recordId - 1) recordId @ [ expanded ]
-                else
-                    recordId
+        let decls =
+            match synTypeDefnRepr with
+            | SynTypeDefnRepr.Simple (SynTypeDefnSimpleRepr.Record (_accessibility, recordFields, _recordRange), _) ->
+                [ createMaker spec ident recordFields ]
+            | _ -> failwithf "Not a record type"
 
-            let info =
-                SynComponentInfo.Create (moduleName, attributes = attributes, xmldoc = xmlDoc)
+        let mdl = SynModuleDecl.CreateNestedModule (info, decls)
 
-            let mdl = SynModuleDecl.CreateNestedModule (info, decls)
-
-            SynModuleOrNamespace.CreateNamespace (namespaceId, decls = [ mdl ])
-        | _ -> failwithf "Not a record type"
+        SynModuleOrNamespace.CreateNamespace (namespaceId, decls = [ mdl ])
 
 /// Myriad generator that provides a method (possibly an extension method) for a record type,
 /// containing a JSON parse function.
@@ -634,10 +634,20 @@ type JsonParseGenerator () =
             let ast, _ =
                 Ast.fromFilename context.InputFilename |> Async.RunSynchronously |> Array.head
 
-            let records = Ast.extractRecords ast
+            let recordsAndUnions =
+                Ast.extractTypeDefn ast
+                |> List.map (fun (name, defns) ->
+                    defns
+                    |> List.choose (fun defn ->
+                        if Ast.isRecord defn then Some defn
+                        elif Ast.isDu defn then Some defn
+                        else None
+                    )
+                    |> fun defns -> name, defns
+                )
 
-            let namespaceAndRecords =
-                records
+            let namespaceAndTypes =
+                recordsAndUnions
                 |> List.choose (fun (ns, types) ->
                     types
                     |> List.choose (fun typeDef ->
@@ -665,13 +675,9 @@ type JsonParseGenerator () =
                 )
 
             let modules =
-                namespaceAndRecords
-                |> List.collect (fun (ns, records) ->
-                    records
-                    |> List.map (fun (record, spec) ->
-                        let recordModule = JsonParseGenerator.createRecordModule ns spec record
-                        recordModule
-                    )
+                namespaceAndTypes
+                |> List.collect (fun (ns, types) ->
+                    types |> List.map (fun (ty, spec) -> JsonParseGenerator.createModule ns spec ty)
                 )
 
             Output.Ast modules

WoofWare.Myriad.Plugins/JsonSerializeGenerator.fs

@@ -117,9 +117,7 @@ module internal JsonSerializeGenerator =
                         SynExpr.CreateIdentString "arr"
                     ],
                 range0,
-                {
-                    InKeyword = None
-                }
+                SynExprLetOrUseTrivia.empty
             )
             |> SynExpr.createLambda "field"
         | IDictionaryType (keyType, valueType)
@@ -188,9 +186,7 @@ module internal JsonSerializeGenerator =
                         SynExpr.CreateIdentString "ret"
                     ],
                 range0,
-                {
-                    InKeyword = None
-                }
+                SynExprLetOrUseTrivia.empty
             )
             |> SynExpr.createLambda "field"
         | _ ->
@@ -204,7 +200,7 @@ module internal JsonSerializeGenerator =
 
     /// propertyName is probably a string literal, but it could be a [<Literal>] variable
     /// `node.Add ({propertyName}, {toJsonNode})`
-    let createSerializeRhs (propertyName : SynExpr) (fieldId : Ident) (fieldType : SynType) : SynExpr =
+    let createSerializeRhsRecord (propertyName : SynExpr) (fieldId : Ident) (fieldType : SynType) : SynExpr =
         let func = SynExpr.CreateLongIdent (SynLongIdent.Create [ "node" ; "Add" ])
 
         let args =
@@ -219,7 +215,24 @@ module internal JsonSerializeGenerator =
 
         SynExpr.CreateApp (func, args)
 
-    let createMaker (spec : JsonSerializeOutputSpec) (typeName : LongIdent) (fields : SynField list) =
+    let getPropertyName (fieldId : Ident) (attrs : SynAttribute list) : SynExpr =
+        let propertyNameAttr =
+            attrs
+            |> List.tryFind (fun attr -> attr.TypeName.AsString.EndsWith ("JsonPropertyName", StringComparison.Ordinal))
+
+        match propertyNameAttr with
+        | None ->
+            let sb = StringBuilder fieldId.idText.Length
+            sb.Append (Char.ToLowerInvariant fieldId.idText.[0]) |> ignore
+
+            if fieldId.idText.Length > 1 then
+                sb.Append fieldId.idText.[1..] |> ignore
+
+            sb.ToString () |> SynConst.CreateString |> SynExpr.CreateConst
+        | Some name -> name.ArgExpr
+
+
+    let recordModule (spec : JsonSerializeOutputSpec) (typeName : LongIdent) (fields : SynField list) =
         let xmlDoc = PreXmlDoc.Create " Serialize to a JSON node"
 
         let returnInfo =
@@ -253,7 +266,7 @@ module internal JsonSerializeGenerator =
                 thisIdOpt
             )
 
-        let assignments =
+        let fields =
             fields
             |> List.map (fun (SynField (attrs, _, id, fieldType, _, _, _, _, _)) ->
                 let id =
@@ -261,26 +274,14 @@ module internal JsonSerializeGenerator =
                     | None -> failwith "didn't get an ID on field"
                     | Some id -> id
 
+                attrs, id, fieldType
+            )
+
+        let assignments =
+            fields
+            |> List.map (fun (attrs, id, fieldType) ->
                 let attrs = attrs |> List.collect (fun l -> l.Attributes)
 
-                let propertyNameAttr =
-                    attrs
-                    |> List.tryFind (fun attr ->
-                        attr.TypeName.AsString.EndsWith ("JsonPropertyName", StringComparison.Ordinal)
-                    )
-
-                let propertyName =
-                    match propertyNameAttr with
-                    | None ->
-                        let sb = StringBuilder id.idText.Length
-                        sb.Append (Char.ToLowerInvariant id.idText.[0]) |> ignore
-
-                        if id.idText.Length > 1 then
-                            sb.Append id.idText.[1..] |> ignore
-
-                        sb.ToString () |> SynConst.CreateString |> SynExpr.CreateConst
-                    | Some name -> name.ArgExpr
-
                 let pattern =
                     SynPat.LongIdent (
                         SynLongIdent.CreateFromLongIdent [ id ],
@@ -291,17 +292,14 @@ module internal JsonSerializeGenerator =
                         range0
                     )
 
-                createSerializeRhs propertyName id fieldType
+                let propertyName = getPropertyName id attrs
+
+                createSerializeRhsRecord propertyName id fieldType
             )
 
         let finalConstruction =
             fields
-            |> List.map (fun (SynField (_, _, id, _, _, _, _, _, _)) ->
-                let id =
-                    match id with
-                    | None -> failwith "Expected record field to have an identifying name"
-                    | Some id -> id
-
+            |> List.map (fun (_, id, _) ->
                 (SynLongIdent.CreateFromLongIdent [ id ], true),
                 Some (SynExpr.CreateLongIdent (SynLongIdent.CreateFromLongIdent [ id ]))
             )
@@ -331,9 +329,7 @@ module internal JsonSerializeGenerator =
                         SynExpr.Upcast (SynExpr.CreateIdentString "node", SynType.Anon range0, range0)
                     ],
                 range0,
-                {
-                    InKeyword = None
-                }
+                SynExprLetOrUseTrivia.empty
             )
 
         let pattern =
@@ -406,7 +402,247 @@ module internal JsonSerializeGenerator =
 
             SynModuleDecl.CreateLet [ binding ]
 
-    let createRecordModule
+    let unionModule (spec : JsonSerializeOutputSpec) (typeName : LongIdent) (cases : SynUnionCase list) =
+        let xmlDoc = PreXmlDoc.Create " Serialize to a JSON node"
+
+        let returnInfo =
+            SynBindingReturnInfo.Create (
+                SynType.LongIdent (SynLongIdent.Create [ "System" ; "Text" ; "Json" ; "Nodes" ; "JsonNode" ])
+            )
+
+        let inputArg = Ident.Create "input"
+        let functionName = Ident.Create "toJsonNode"
+
+        let inputVal =
+            let memberFlags =
+                if spec.ExtensionMethods then
+                    {
+                        SynMemberFlags.IsInstance = false
+                        SynMemberFlags.IsDispatchSlot = false
+                        SynMemberFlags.IsOverrideOrExplicitImpl = false
+                        SynMemberFlags.IsFinal = false
+                        SynMemberFlags.GetterOrSetterIsCompilerGenerated = false
+                        SynMemberFlags.MemberKind = SynMemberKind.Member
+                    }
+                    |> Some
+                else
+                    None
+
+            let thisIdOpt = if spec.ExtensionMethods then None else Some inputArg
+
+            SynValData.SynValData (
+                memberFlags,
+                SynValInfo.SynValInfo ([ [ SynArgInfo.CreateId functionName ] ], SynArgInfo.Empty),
+                thisIdOpt
+            )
+
+        let cases =
+            cases
+            |> List.map (fun (SynUnionCase (attrs, SynIdent.SynIdent (id, _), caseType, _, _, _, _)) ->
+                match caseType with
+                | SynUnionCaseKind.FullType _ -> failwith "WoofWare.Myriad does not support FullType union cases."
+                | SynUnionCaseKind.Fields fields ->
+
+                let fields =
+                    fields
+                    |> List.map (fun (SynField (attrs, _, id, fieldType, _, _, _, _, _)) ->
+                        match id with
+                        | None -> failwith "WoofWare.Myriad requires all union fields to have names"
+                        | Some id ->
+
+                        let attrs = attrs |> List.collect (fun l -> l.Attributes)
+                        attrs, id, fieldType
+                    )
+                // As far as I can tell, there's no way to get any attributes here? :shrug:
+                let attrs = attrs |> List.collect (fun l -> l.Attributes)
+                attrs, id, fields
+            )
+
+        let matchClauses : SynMatchClause list =
+            cases
+            |> List.map (fun (attrs, id, caseType) ->
+                let propertyName = getPropertyName id attrs
+
+                let caseNames = caseType |> List.mapi (fun i _ -> Ident.Create $"arg%i{i}")
+
+                let argPats = SynArgPats.create caseNames
+
+                let pattern =
+                    SynPat.LongIdent (
+                        SynLongIdent.CreateFromLongIdent (typeName @ [ id ]),
+                        None,
+                        None,
+                        argPats,
+                        None,
+                        range0
+                    )
+
+                let typeLine =
+                    let func = SynExpr.CreateLongIdent (SynLongIdent.Create [ "node" ; "Add" ])
+
+                    let args =
+                        SynExpr.CreateParenedTuple
+                            [
+                                SynExpr.CreateConstString "type"
+                                SynExpr.CreateApp (
+                                    SynExpr.CreateLongIdent (
+                                        SynLongIdent.CreateString "System.Text.Json.Nodes.JsonValue.Create"
+                                    ),
+                                    propertyName
+                                )
+                            ]
+
+                    SynExpr.CreateApp (func, args)
+
+                let dataNode =
+                    SynBinding.Let (
+                        pattern = SynPat.CreateNamed (Ident.Create "dataNode"),
+                        expr =
+                            SynExpr.CreateApp (
+                                SynExpr.CreateLongIdent (
+                                    SynLongIdent.Create [ "System" ; "Text" ; "Json" ; "Nodes" ; "JsonObject" ]
+                                ),
+                                SynExpr.CreateConst SynConst.Unit
+                            )
+                    )
+
+                let dataBindings =
+                    (caseType, caseNames)
+                    ||> List.zip
+                    |> List.map (fun ((attrs, ident, synType), caseName) ->
+                        let propertyName = getPropertyName ident attrs
+                        let func = SynExpr.CreateLongIdent (SynLongIdent.Create [ "dataNode" ; "Add" ])
+                        let node = SynExpr.CreateApp (serializeNode synType, SynExpr.CreateIdent caseName)
+
+                        SynExpr.CreateApp (func, SynExpr.CreateParenedTuple [ propertyName ; node ])
+                    )
+
+                let assignToNode =
+                    let func = SynExpr.CreateLongIdent (SynLongIdent.Create [ "node" ; "Add" ])
+
+                    let args =
+                        SynExpr.CreateParenedTuple
+                            [ SynExpr.CreateConstString "data" ; SynExpr.CreateIdentString "dataNode" ]
+
+                    SynExpr.CreateApp (func, args)
+
+                let dataNode =
+                    SynExpr.LetOrUse (
+                        false,
+                        false,
+                        [ dataNode ],
+                        SynExpr.CreateSequential (dataBindings @ [ assignToNode ]),
+                        range0,
+                        SynExprLetOrUseTrivia.empty
+                    )
+
+                let action =
+                    [
+                        yield typeLine
+                        if not dataBindings.IsEmpty then
+                            yield dataNode
+                    ]
+                    |> SynExpr.CreateSequential
+
+                SynMatchClause.Create (pattern, None, action)
+            )
+
+        let assignments =
+            SynExpr.LetOrUse (
+                false,
+                false,
+                [
+                    SynBinding.Let (
+                        pattern = SynPat.CreateNamed (Ident.Create "node"),
+                        expr =
+                            SynExpr.CreateApp (
+                                SynExpr.CreateLongIdent (
+                                    SynLongIdent.Create [ "System" ; "Text" ; "Json" ; "Nodes" ; "JsonObject" ]
+                                ),
+                                SynExpr.CreateConst SynConst.Unit
+                            )
+                    )
+                ],
+                SynExpr.CreateSequential
+                    [
+                        SynExpr.CreateMatch (SynExpr.CreateIdent inputArg, matchClauses)
+                        SynExpr.Upcast (SynExpr.CreateIdentString "node", SynType.Anon range0, range0)
+                    ],
+                range0,
+                SynExprLetOrUseTrivia.empty
+            )
+
+        let pattern =
+            SynPat.LongIdent (
+                SynLongIdent.CreateFromLongIdent [ functionName ],
+                None,
+                None,
+                SynArgPats.Pats
+                    [
+                        SynPat.CreateTyped (
+                            SynPat.CreateNamed inputArg,
+                            SynType.LongIdent (SynLongIdent.CreateFromLongIdent typeName)
+                        )
+                        |> SynPat.CreateParen
+                    ],
+                None,
+                range0
+            )
+
+        if spec.ExtensionMethods then
+            let binding =
+                SynBinding.SynBinding (
+                    None,
+                    SynBindingKind.Normal,
+                    false,
+                    false,
+                    [],
+                    xmlDoc,
+                    inputVal,
+                    pattern,
+                    Some returnInfo,
+                    assignments,
+                    range0,
+                    DebugPointAtBinding.NoneAtInvisible,
+                    {
+                        LeadingKeyword = SynLeadingKeyword.StaticMember (range0, range0)
+                        InlineKeyword = None
+                        EqualsRange = Some range0
+                    }
+                )
+
+            let mem = SynMemberDefn.Member (binding, range0)
+
+            let containingType =
+                SynTypeDefn.SynTypeDefn (
+                    SynComponentInfo.Create (typeName, xmldoc = PreXmlDoc.Create " Extension methods for JSON parsing"),
+                    SynTypeDefnRepr.ObjectModel (SynTypeDefnKind.Augmentation range0, [], range0),
+                    [ mem ],
+                    None,
+                    range0,
+                    {
+                        LeadingKeyword = SynTypeDefnLeadingKeyword.Type range0
+                        EqualsRange = None
+                        WithKeyword = None
+                    }
+                )
+
+            SynModuleDecl.Types ([ containingType ], range0)
+        else
+            let binding =
+                SynBinding.Let (
+                    isInline = false,
+                    isMutable = false,
+                    xmldoc = xmlDoc,
+                    returnInfo = returnInfo,
+                    expr = assignments,
+                    valData = inputVal,
+                    pattern = pattern
+                )
+
+            SynModuleDecl.CreateLet [ binding ]
+
+    let createModule
         (namespaceId : LongIdent)
         (opens : SynOpenDeclTarget list)
         (spec : JsonSerializeOutputSpec)
@@ -415,60 +651,62 @@ module internal JsonSerializeGenerator =
         let (SynTypeDefn (synComponentInfo, synTypeDefnRepr, _members, _implicitCtor, _, _)) =
             typeDefn
 
-        let (SynComponentInfo (_attributes, _typeParams, _constraints, recordId, _, _preferPostfix, _access, _)) =
+        let (SynComponentInfo (_attributes, _typeParams, _constraints, ident, _, _preferPostfix, _access, _)) =
             synComponentInfo
 
-        match synTypeDefnRepr with
-        | SynTypeDefnRepr.Simple (SynTypeDefnSimpleRepr.Record (_accessibility, recordFields, _recordRange), _) ->
+        let attributes =
+            if spec.ExtensionMethods then
+                [ SynAttributeList.Create SynAttribute.autoOpen ]
+            else
+                [
+                    SynAttributeList.Create (SynAttribute.RequireQualifiedAccess ())
+                    SynAttributeList.Create SynAttribute.compilationRepresentation
+                ]
 
-            let decls = [ createMaker spec recordId recordFields ]
+        let xmlDoc =
+            let fullyQualified = ident |> Seq.map (fun i -> i.idText) |> String.concat "."
 
-            let attributes =
+            let description =
                 if spec.ExtensionMethods then
-                    [ SynAttributeList.Create SynAttribute.autoOpen ]
+                    "extension members"
                 else
-                    [
-                        SynAttributeList.Create (SynAttribute.RequireQualifiedAccess ())
-                        SynAttributeList.Create SynAttribute.compilationRepresentation
-                    ]
+                    "methods"
 
-            let xmlDoc =
-                let fullyQualified = recordId |> Seq.map (fun i -> i.idText) |> String.concat "."
+            $" Module containing JSON serializing %s{description} for the %s{fullyQualified} type"
+            |> PreXmlDoc.Create
 
-                let description =
-                    if spec.ExtensionMethods then
-                        "extension members"
-                    else
-                        "methods"
+        let moduleName =
+            if spec.ExtensionMethods then
+                match ident with
+                | [] -> failwith "unexpectedly got an empty identifier for type name"
+                | ident ->
+                    let expanded =
+                        List.last ident
+                        |> fun i -> i.idText
+                        |> fun s -> s + "JsonSerializeExtension"
+                        |> Ident.Create
 
-                $" Module containing JSON serializing %s{description} for the %s{fullyQualified} type"
-                |> PreXmlDoc.Create
+                    List.take (List.length ident - 1) ident @ [ expanded ]
+            else
+                ident
 
-            let moduleName =
-                if spec.ExtensionMethods then
-                    match recordId with
-                    | [] -> failwith "unexpectedly got an empty identifier for record name"
-                    | recordId ->
-                        let expanded =
-                            List.last recordId
-                            |> fun i -> i.idText
-                            |> fun s -> s + "JsonSerializeExtension"
-                            |> Ident.Create
+        let info =
+            SynComponentInfo.Create (moduleName, attributes = attributes, xmldoc = xmlDoc)
 
-                        List.take (List.length recordId - 1) recordId @ [ expanded ]
-                else
-                    recordId
+        let decls =
+            match synTypeDefnRepr with
+            | SynTypeDefnRepr.Simple (SynTypeDefnSimpleRepr.Record (_accessibility, recordFields, _range), _) ->
+                [ recordModule spec ident recordFields ]
+            | SynTypeDefnRepr.Simple (SynTypeDefnSimpleRepr.Union (_accessibility, unionFields, _range), _) ->
+                [ unionModule spec ident unionFields ]
+            | _ -> failwithf "Only record types currently supported."
 
-            let info =
-                SynComponentInfo.Create (moduleName, attributes = attributes, xmldoc = xmlDoc)
+        let mdl = SynModuleDecl.CreateNestedModule (info, decls)
 
-            let mdl = SynModuleDecl.CreateNestedModule (info, decls)
-
-            SynModuleOrNamespace.CreateNamespace (
-                namespaceId,
-                decls = (opens |> List.map SynModuleDecl.CreateOpen) @ [ mdl ]
-            )
-        | _ -> failwithf "Not a record type"
+        SynModuleOrNamespace.CreateNamespace (
+            namespaceId,
+            decls = (opens |> List.map SynModuleDecl.CreateOpen) @ [ mdl ]
+        )
 
 /// Myriad generator that provides a method (possibly an extension method) for a record type,
 /// containing a JSON serialization function.
@@ -482,10 +720,20 @@ type JsonSerializeGenerator () =
             let ast, _ =
                 Ast.fromFilename context.InputFilename |> Async.RunSynchronously |> Array.head
 
-            let records = Ast.extractRecords ast
+            let recordsAndUnions =
+                Ast.extractTypeDefn ast
+                |> List.map (fun (name, defns) ->
+                    defns
+                    |> List.choose (fun defn ->
+                        if Ast.isRecord defn then Some defn
+                        elif Ast.isDu defn then Some defn
+                        else None
+                    )
+                    |> fun defns -> name, defns
+                )
 
-            let namespaceAndRecords =
-                records
+            let namespaceAndTypes =
+                recordsAndUnions
                 |> List.choose (fun (ns, types) ->
                     types
                     |> List.choose (fun typeDef ->
@@ -515,13 +763,10 @@ type JsonSerializeGenerator () =
             let opens = AstHelper.extractOpens ast
 
             let modules =
-                namespaceAndRecords
-                |> List.collect (fun (ns, records) ->
-                    records
-                    |> List.map (fun (record, spec) ->
-                        let recordModule = JsonSerializeGenerator.createRecordModule ns opens spec record
-                        recordModule
-                    )
+                namespaceAndTypes
+                |> List.collect (fun (ns, types) ->
+                    types
+                    |> List.map (fun (ty, spec) -> JsonSerializeGenerator.createModule ns opens spec ty)
                 )
 
             Output.Ast modules

WoofWare.Myriad.Plugins/SynExpr/SynArgPats.fs

@@ -0,0 +1,18 @@
+namespace WoofWare.Myriad.Plugins
+
+open Fantomas.FCS.Syntax
+open Fantomas.FCS.Text.Range
+
+[<RequireQualifiedAccess>]
+module internal SynArgPats =
+    let create (caseNames : Ident list) : SynArgPats =
+        if caseNames.IsEmpty then
+            SynArgPats.Pats []
+        else
+
+        caseNames
+        |> List.map (fun ident -> SynPat.Named (SynIdent.SynIdent (ident, None), false, None, range0))
+        |> fun ps -> SynPat.Tuple (false, ps, List.replicate (ps.Length - 1) range0, range0)
+        |> fun p -> SynPat.Paren (p, range0)
+        |> List.singleton
+        |> SynArgPats.Pats

WoofWare.Myriad.Plugins/SynExpr/SynExprLetOrUseTrivia.fs

@@ -0,0 +1,10 @@
+namespace WoofWare.Myriad.Plugins
+
+open Fantomas.FCS.SyntaxTrivia
+
+[<RequireQualifiedAccess>]
+module internal SynExprLetOrUseTrivia =
+    let empty : SynExprLetOrUseTrivia =
+        {
+            InKeyword = None
+        }

WoofWare.Myriad.Plugins/WoofWare.Myriad.Plugins.fsproj

@@ -27,9 +27,11 @@
     <Compile Include="List.fs"/>
     <Compile Include="Ident.fs" />
     <Compile Include="AstHelper.fs"/>
-    <Compile Include="SynExpr.fs" />
-    <Compile Include="SynType.fs"/>
-    <Compile Include="SynAttribute.fs"/>
+    <Compile Include="SynExpr\SynExpr.fs" />
+    <Compile Include="SynExpr\SynType.fs" />
+    <Compile Include="SynExpr\SynAttribute.fs" />
+    <Compile Include="SynExpr\SynArgPats.fs" />
+    <Compile Include="SynExpr\SynExprLetOrUseTrivia.fs" />
     <Compile Include="RemoveOptionsGenerator.fs"/>
     <Compile Include="InterfaceMockGenerator.fs"/>
     <Compile Include="JsonSerializeGenerator.fs"/>

WoofWare.Myriad.Plugins/version.json

@@ -3,5 +3,10 @@
   "publicReleaseRefSpec": [
     "^refs/heads/main$"
   ],
-  "pathFilters": null
-}
+  "pathFilters": [
+    ":/",
+    ":^WoofWare.Myriad.Plugins.Test/",
+    ":^WoofWare.Myriad.Plugins.Attributes/Test/",
+    ":^/.github/"
+  ]
+}

nix/deps.nix

@@ -13,8 +13,8 @@
   })
   (fetchNuGet {
     pname = "ApiSurface";
-    version = "4.0.39";
-    sha256 = "sha256-I4K5nJbltsfL/1r+KPTIo2wUd30zsCC2pkrnIRnsRHM=";
+    version = "4.0.40";
+    sha256 = "1c9z0b6minlripwrjmv4yd5w8zj4lcpak4x41izh7ygx8kgmbvx0";
   })
   (fetchNuGet {
     pname = "Fantomas.Core";
@@ -118,13 +118,13 @@
   })
   (fetchNuGet {
     pname = "Microsoft.CodeCoverage";
-    version = "17.9.0";
-    sha256 = "1gljgi69k0fz8vy8bn6xlyxabj6q4vls2zza9wz7ng6ix3irm89r";
+    version = "17.10.0";
+    sha256 = "0s0v7jmrq85n356xv7zixvwa4z94fszjcr5vll8x4im1a2lp00f9";
   })
   (fetchNuGet {
     pname = "Microsoft.NET.Test.Sdk";
-    version = "17.9.0";
-    sha256 = "1lls1fly2gr1n9n1xyl9k33l2v4pwfmylyzkq8v4v5ldnwkl1zdb";
+    version = "17.10.0";
+    sha256 = "13g8fwl09li8fc71nk13dgkb7gahd4qhamyg2xby7am63nlchhdf";
   })
   (fetchNuGet {
     pname = "Microsoft.NETCore.App.Host.linux-arm64";
@@ -268,13 +268,13 @@
   })
   (fetchNuGet {
     pname = "Microsoft.TestPlatform.ObjectModel";
-    version = "17.9.0";
-    sha256 = "1kgsl9w9fganbm9wvlkqgk0ag9hfi58z88rkfybc6kvg78bx89ca";
+    version = "17.10.0";
+    sha256 = "07j69cw8r39533w4p39mnj00kahazz38760in3jfc45kmlcdb26x";
   })
   (fetchNuGet {
     pname = "Microsoft.TestPlatform.TestHost";
-    version = "17.9.0";
-    sha256 = "19ffh31a1jxzn8j69m1vnk5hyfz3dbxmflq77b8x82zybiilh5nl";
+    version = "17.10.0";
+    sha256 = "1bl471s7fx9jycr0cc8rylwf34mrvlg9qn1an6l86nisavfcyb7v";
   })
   (fetchNuGet {
     pname = "Myriad.Core";
@@ -308,33 +308,33 @@
   })
   (fetchNuGet {
     pname = "NuGet.Common";
-    version = "6.9.1";
-    sha256 = "0ic3d46r9v05pkczpmskw86yzixm6iwshbw0ya8i2957nhhlymw8";
+    version = "6.10.0";
+    sha256 = "0nizrnilmlcqbm945293h8q3wfqfchb4xi8g50x4kjn0rbpd1kbh";
   })
   (fetchNuGet {
     pname = "NuGet.Configuration";
-    version = "6.9.1";
-    sha256 = "07z4qgbibpg59j2r05ifnqdyqf2xinm33rx7gjyr1f73kzg01m33";
+    version = "6.10.0";
+    sha256 = "1aqaknaawnqx4mnvx9qw73wvj48jjzv0d78dzwl7m9zjlrl9myhz";
   })
   (fetchNuGet {
     pname = "NuGet.Frameworks";
-    version = "6.9.1";
-    sha256 = "0s3az3ac53icjnmb14hfjcmkvzscvrkm62jgqf48yvsbysyhqm5s";
+    version = "6.10.0";
+    sha256 = "0hrd8y31zx9a0wps49czw0qgbrakb49zn3abfgylc9xrq990zkqk";
   })
   (fetchNuGet {
     pname = "NuGet.Packaging";
-    version = "6.9.1";
-    sha256 = "0w0arkmzg3qh1brq4vm10zrsjm7nw706ld4y5kqcmvjpd16f4b4y";
+    version = "6.10.0";
+    sha256 = "18s53cvrf51lihmaqqdf48p2qi6ky1l48jv0hvbp76cxwdg7rba4";
   })
   (fetchNuGet {
     pname = "NuGet.Protocol";
-    version = "6.7.0";
-    sha256 = "1v5ibnq2mp801vw68zyj169hkj3xm7h55824i33n1jxxj2vs3vbk";
+    version = "6.10.0";
+    sha256 = "0hmv4q0ks9i34mfgpb13l01la9v3jjllfh1qd3aqv105xrqrdxac";
   })
   (fetchNuGet {
     pname = "NuGet.Versioning";
-    version = "6.9.1";
-    sha256 = "0xrs82dydy9cgxf0qypr01wawwnq1nf6fc7rwisb4y5v4r259fdm";
+    version = "6.10.0";
+    sha256 = "1x19njx4x0sw9fz8y5fibi15xfsrw5avir0cx0599yd7p3ykik5g";
   })
   (fetchNuGet {
     pname = "NUnit";
@@ -433,12 +433,12 @@
   })
   (fetchNuGet {
     pname = "System.Text.Encodings.Web";
-    version = "6.0.0";
-    sha256 = "06n9ql3fmhpjl32g3492sj181zjml5dlcc5l76xq2h38c4f87sai";
+    version = "7.0.0";
+    sha256 = "1151hbyrcf8kyg1jz8k9awpbic98lwz9x129rg7zk1wrs6vjlpxl";
   })
   (fetchNuGet {
     pname = "System.Text.Json";
-    version = "6.0.0";
-    sha256 = "1si2my1g0q0qv1hiqnji4xh9wd05qavxnzj9dwgs23iqvgjky0gl";
+    version = "7.0.3";
+    sha256 = "0zjrnc9lshagm6kdb9bdh45dmlnkpwcpyssa896sda93ngbmj8k9";
   })
 ]