Reduce duplication (#149)

.github/workflows/dotnet.yaml

@@ -1,3 +1,4 @@
+# yaml-language-server: $schema=https://raw.githubusercontent.com/SchemaStore/schemastore/master/src/schemas/json/github-workflow.json
 name: .NET
 
 on:
@@ -86,6 +87,27 @@ jobs:
       - name: Run Fantomas
         run: nix run .#fantomas -- --check .
 
+  check-accurate-generations:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+        with:
+          fetch-depth: 0 # so that NerdBank.GitVersioning has access to history
+      - name: Install Nix
+        uses: cachix/install-nix-action@V27
+        with:
+          extra_nix_config: |
+            access-tokens = github.com=${{ secrets.GITHUB_TOKEN }}
+      - name: Whitespace change
+        run: "echo ' ' >> ConsumePlugin/List.fs"
+      - name: Generate code
+        run: nix develop --command dotnet build
+      - name: Run Fantomas
+        run: nix run .#fantomas -- .
+      - name: Verify there is no diff
+        run: git diff --name-only --no-color --exit-code
+
   check-nix-format:
     runs-on: ubuntu-latest
     steps:
@@ -174,8 +196,27 @@ jobs:
         # Verify that there is exactly one nupkg in the artifact that would be NuGet published
         run: if [[ $(find packed-attribute -maxdepth 1 -name 'WoofWare.Myriad.Plugins.Attributes.*.nupkg' -printf c | wc -c) -ne "1" ]]; then exit 1; fi
 
+  github-release-plugin-dry-run:
+    needs: [nuget-pack]
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - name: Download NuGet artifact (plugin)
+        uses: actions/download-artifact@v4
+        with:
+          name: nuget-package-plugin
+      - name: Download NuGet artifact (attribute)
+        uses: actions/download-artifact@v4
+        with:
+          name: nuget-package-attribute
+      - name: Tag and release plugin
+        env:
+          DRY_RUN: 1
+          GITHUB_TOKEN: mock-token
+        run: sh .github/workflows/tag.sh
+
   all-required-checks-complete:
-    needs: [check-dotnet-format, check-nix-format, build, build-nix, linkcheck, flake-check, analyzers, nuget-pack, expected-pack]
+    needs: [check-dotnet-format, check-nix-format, check-accurate-generations, build, build-nix, linkcheck, flake-check, analyzers, nuget-pack, expected-pack, github-release-plugin-dry-run]
     runs-on: ubuntu-latest
     steps:
       - run: echo "All required checks complete."

.github/workflows/tag.sh

@@ -1,6 +1,13 @@
-#!/bin/sh
+#!/bin/bash
 
-find . -maxdepth 1 -type f -name '*.nupkg' -exec sh -c 'tag=$(basename "$1" .nupkg); git tag "$tag"; git push origin "$tag"' shell {} \;
+echo "Dry-run? $DRY_RUN!"
+
+find . -maxdepth 1 -type f ! -name "$(printf "*\n*")" -name '*.nupkg' | while IFS= read -r file
+do
+    tag=$(basename "$file" .nupkg)
+    git tag "$tag"
+    ${DRY_RUN:+echo} git push origin "$tag"
+done
 
 export TAG
 TAG=$(find . -maxdepth 1 -type f -name 'WoofWare.Myriad.Plugins.*.nupkg' -exec sh -c 'basename "$1" .nupkg' shell {} \; | grep -v Attributes)
@@ -14,4 +21,100 @@ case "$TAG" in
 esac
 
 # target_commitish empty indicates the repo default branch
-curl -L -X POST -H "Accept: application/vnd.github+json" -H "Authorization: Bearer $GITHUB_TOKEN" -H "X-GitHub-Api-Version: 2022-11-28" https://api.github.com/repos/Smaug123/WoofWare.Myriad/releases -d '{"tag_name":"'"$TAG"'","target_commitish":"","name":"'"$TAG"'","draft":false,"prerelease":false,"generate_release_notes":false}'
+curl_body='{"tag_name":"'"$TAG"'","target_commitish":"","name":"'"$TAG"'","draft":false,"prerelease":false,"generate_release_notes":false}'
+
+echo "cURL body: $curl_body"
+
+failed_output=$(cat <<'EOF'
+{
+  "message": "Validation Failed",
+  "errors": [
+    {
+      "resource": "Release",
+      "code": "already_exists",
+      "field": "tag_name"
+    }
+  ],
+  "documentation_url": "https://docs.github.com/rest/releases/releases#create-a-release"
+}
+EOF
+)
+
+success_output=$(cat <<'EOF'
+{
+  "url": "https://api.github.com/repos/Smaug123/WoofWare.Myriad/releases/158152116",
+  "assets_url": "https://api.github.com/repos/Smaug123/WoofWare.Myriad/releases/158152116/assets",
+  "upload_url": "https://uploads.github.com/repos/Smaug123/WoofWare.Myriad/releases/158152116/assets{?name,label}",
+  "html_url": "https://github.com/Smaug123/WoofWare.Myriad/releases/tag/WoofWare.Myriad.Plugins.2.1.30",
+  "id": 158152116,
+  "author": {
+    "login": "github-actions[bot]",
+    "id": 41898282,
+    "node_id": "MDM6Qm90NDE4OTgyODI=",
+    "avatar_url": "https://avatars.githubusercontent.com/in/15368?v=4",
+    "gravatar_id": "",
+    "url": "https://api.github.com/users/github-actions%5Bbot%5D",
+    "html_url": "https://github.com/apps/github-actions",
+    "followers_url": "https://api.github.com/users/github-actions%5Bbot%5D/followers",
+    "following_url": "https://api.github.com/users/github-actions%5Bbot%5D/following{/other_user}",
+    "gists_url": "https://api.github.com/users/github-actions%5Bbot%5D/gists{/gist_id}",
+    "starred_url": "https://api.github.com/users/github-actions%5Bbot%5D/starred{/owner}{/repo}",
+    "subscriptions_url": "https://api.github.com/users/github-actions%5Bbot%5D/subscriptions",
+    "organizations_url": "https://api.github.com/users/github-actions%5Bbot%5D/orgs",
+    "repos_url": "https://api.github.com/users/github-actions%5Bbot%5D/repos",
+    "events_url": "https://api.github.com/users/github-actions%5Bbot%5D/events{/privacy}",
+    "received_events_url": "https://api.github.com/users/github-actions%5Bbot%5D/received_events",
+    "type": "Bot",
+    "site_admin": false
+  },
+  "node_id": "RE_kwDOJfksgc4JbTW0",
+  "tag_name": "WoofWare.Myriad.Plugins.2.1.30",
+  "target_commitish": "main",
+  "name": "WoofWare.Myriad.Plugins.2.1.30",
+  "draft": false,
+  "prerelease": false,
+  "created_at": "2024-05-30T11:00:55Z",
+  "published_at": "2024-05-30T11:03:02Z",
+  "assets": [
+
+  ],
+  "tarball_url": "https://api.github.com/repos/Smaug123/WoofWare.Myriad/tarball/WoofWare.Myriad.Plugins.2.1.30",
+  "zipball_url": "https://api.github.com/repos/Smaug123/WoofWare.Myriad/zipball/WoofWare.Myriad.Plugins.2.1.30",
+  "body": null
+}
+EOF
+)
+
+HANDLE_OUTPUT=''
+handle_error() {
+    ERROR_OUTPUT="$1"
+    exit_message=$(echo "$ERROR_OUTPUT" | jq -r --exit-status 'if .errors | length == 1 then .errors[0].code else null end')
+    if [ "$exit_message" = "already_exists" ] ; then
+        HANDLE_OUTPUT="Did not create GitHub release because it already exists at this version."
+    else
+        echo "Unexpected error output from curl: $(cat curl_output.json)"
+        echo "JQ output: $(exit_message)"
+        exit 2
+    fi
+}
+
+run_tests() {
+    handle_error "$failed_output"
+    if [ "$HANDLE_OUTPUT" != "Did not create GitHub release because it already exists at this version." ]; then
+        echo "Bad output from handler: $HANDLE_OUTPUT"
+        exit 3
+    fi
+    HANDLE_OUTPUT=''
+    echo "Tests passed."
+}
+
+run_tests
+
+if [ "$DRY_RUN" != 1 ] ; then
+    if curl --fail-with-body -L -X POST -H "Accept: application/vnd.github+json" -H "Authorization: Bearer $GITHUB_TOKEN" -H "X-GitHub-Api-Version: 2022-11-28" https://api.github.com/repos/Smaug123/WoofWare.Myriad/releases -d "$curl_body" > curl_output.json; then
+        echo "Curl succeeded."
+    else
+        handle_error "$(cat curl_output.json)"
+        echo "$HANDLE_OUTPUT"
+    fi
+fi

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/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

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/version.json

@@ -3,5 +3,13 @@
   "publicReleaseRefSpec": [
     "^refs/heads/main$"
   ],
-  "pathFilters": null
-}
+  "pathFilters": [
+    ":/README.md",
+    ":/LICENSE",
+    ":/WoofWare.Myriad.Plugins/logo.png",
+    ":/Directory.Build.props",
+    ":/global.json",
+    "./",
+    "^./Test"
+  ]
+}

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/JsonParseGenerator.fs

@@ -357,7 +357,7 @@ module internal JsonParseGenerator =
         | [ _ ; "JsonNumberHandling" ; "Serialization" ; "Json" ; "Text" ; "System" ] -> true
         | _ -> false
 
-    let createMaker (spec : JsonParseOutputSpec) (typeName : LongIdent) (fields : SynField list) =
+    let createMaker (spec : JsonParseOutputSpec) (typeName : LongIdent) (fields : SynFieldData<Ident> list) =
         let xmlDoc = PreXmlDoc.Create " Parse from a JSON node."
 
         let returnInfo =
@@ -391,22 +391,15 @@ module internal JsonParseGenerator =
 
         let assignments =
             fields
-            |> List.map (fun (SynField (attrs, _, id, fieldType, _, _, _, _, _)) ->
-                let id =
-                    match id with
-                    | None -> failwith "didn't get an ID on field"
-                    | Some id -> id
-
-                let attrs = attrs |> List.collect (fun l -> l.Attributes)
-
+            |> List.map (fun fieldData ->
                 let propertyNameAttr =
-                    attrs
+                    fieldData.Attrs
                     |> List.tryFind (fun attr ->
                         attr.TypeName.AsString.EndsWith ("JsonPropertyName", StringComparison.Ordinal)
                     )
 
                 let options =
-                    (JsonParseOption.None, attrs)
+                    (JsonParseOption.None, fieldData.Attrs)
                     ||> List.fold (fun options attr ->
                         if attr.TypeName.AsString.EndsWith ("JsonNumberHandling", StringComparison.Ordinal) then
                             let qualifiedEnumValue =
@@ -438,18 +431,18 @@ module internal JsonParseGenerator =
                 let propertyName =
                     match propertyNameAttr with
                     | None ->
-                        let sb = StringBuilder id.idText.Length
-                        sb.Append (Char.ToLowerInvariant id.idText.[0]) |> ignore
+                        let sb = StringBuilder fieldData.Ident.idText.Length
+                        sb.Append (Char.ToLowerInvariant fieldData.Ident.idText.[0]) |> ignore
 
-                        if id.idText.Length > 1 then
-                            sb.Append id.idText.[1..] |> ignore
+                        if fieldData.Ident.idText.Length > 1 then
+                            sb.Append fieldData.Ident.idText.[1..] |> ignore
 
                         sb.ToString () |> SynConst.CreateString |> SynExpr.CreateConst
                     | Some name -> name.ArgExpr
 
                 let pattern =
                     SynPat.LongIdent (
-                        SynLongIdent.CreateFromLongIdent [ id ],
+                        SynLongIdent.CreateFromLongIdent [ fieldData.Ident ],
                         None,
                         None,
                         SynArgPats.Empty,
@@ -460,7 +453,7 @@ module internal JsonParseGenerator =
                 SynBinding.Let (
                     isInline = false,
                     isMutable = false,
-                    expr = createParseRhs options propertyName fieldType,
+                    expr = createParseRhs options propertyName fieldData.Type,
                     valData = inputVal,
                     pattern = pattern
                 )
@@ -468,14 +461,9 @@ module internal JsonParseGenerator =
 
         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
-
-                (SynLongIdent.CreateFromLongIdent [ id ], true),
-                Some (SynExpr.CreateLongIdent (SynLongIdent.CreateFromLongIdent [ id ]))
+            |> List.map (fun fieldData ->
+                (SynLongIdent.CreateFromLongIdent [ fieldData.Ident ], true),
+                Some (SynExpr.CreateLongIdent (SynLongIdent.CreateFromLongIdent [ fieldData.Ident ]))
             )
             |> AstHelper.instantiateRecord
 
@@ -566,61 +554,65 @@ 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, fields, _range), _) ->
+                let fields = fields |> List.map SynField.extractWithIdent
+                [ createMaker spec ident fields ]
+            | SynTypeDefnRepr.Simple (SynTypeDefnSimpleRepr.Union (_accessibility, cases, _range), _) ->
+                // [ createMaker spec ident cases ]
+                failwith "Unions are not yet supported"
+            | _ -> failwithf "Not a record or union 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 +626,20 @@ 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 +667,9 @@ 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

@@ -117,15 +117,13 @@ module internal JsonSerializeGenerator =
                         SynExpr.CreateIdentString "arr"
                     ],
                 range0,
-                {
-                    InKeyword = None
-                }
+                SynExprLetOrUseTrivia.empty
             )
             |> SynExpr.createLambda "field"
-        | IDictionaryType (keyType, valueType)
-        | DictionaryType (keyType, valueType)
-        | IReadOnlyDictionaryType (keyType, valueType)
-        | MapType (keyType, valueType) ->
+        | IDictionaryType (_keyType, valueType)
+        | DictionaryType (_keyType, valueType)
+        | IReadOnlyDictionaryType (_keyType, valueType)
+        | MapType (_keyType, valueType) ->
             // fun field ->
             //    let ret = JsonObject ()
             //    for (KeyValue(key, value)) in field do
@@ -188,9 +186,7 @@ module internal JsonSerializeGenerator =
                         SynExpr.CreateIdentString "ret"
                     ],
                 range0,
-                {
-                    InKeyword = None
-                }
+                SynExprLetOrUseTrivia.empty
             )
             |> SynExpr.createLambda "field"
         | _ ->
@@ -204,22 +200,50 @@ 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 =
-            SynExpr.CreateParenedTuple
-                [
-                    propertyName
-                    SynExpr.CreateApp (
-                        serializeNode fieldType,
-                        SynExpr.CreateLongIdent (SynLongIdent.CreateFromLongIdent [ Ident.Create "input" ; fieldId ])
-                    )
-                ]
+            [
+                propertyName
+                SynExpr.CreateApp (
+                    serializeNode fieldType,
+                    SynExpr.CreateLongIdent (SynLongIdent.CreateFromLongIdent [ Ident.Create "input" ; fieldId ])
+                )
+            ]
+            |> SynExpr.CreateParenedTuple
 
         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
+
+    /// `populateNode` will be inserted before we return the `node` variable.
+    ///
+    /// That is, we give you access to a `JsonObject` called `node`,
+    /// and you have access to a variable `inputArgName` which is of type `typeName`.
+    /// Your job is to provide a `populateNode` expression which has the side effect
+    /// of mutating `node` to faithfully reflect the value of `inputArgName`.
+    let scaffolding
+        (spec : JsonSerializeOutputSpec)
+        (typeName : LongIdent)
+        (inputArgName : Ident)
+        (populateNode : SynExpr)
+        : SynModuleDecl
+        =
         let xmlDoc = PreXmlDoc.Create " Serialize to a JSON node"
 
         let returnInfo =
@@ -227,7 +251,6 @@ module internal JsonSerializeGenerator =
                 SynType.LongIdent (SynLongIdent.Create [ "System" ; "Text" ; "Json" ; "Nodes" ; "JsonNode" ])
             )
 
-        let inputArg = Ident.Create "input"
         let functionName = Ident.Create "toJsonNode"
 
         let inputVal =
@@ -245,7 +268,7 @@ module internal JsonSerializeGenerator =
                 else
                     None
 
-            let thisIdOpt = if spec.ExtensionMethods then None else Some inputArg
+            let thisIdOpt = if spec.ExtensionMethods then None else Some inputArgName
 
             SynValData.SynValData (
                 memberFlags,
@@ -253,62 +276,6 @@ module internal JsonSerializeGenerator =
                 thisIdOpt
             )
 
-        let assignments =
-            fields
-            |> List.map (fun (SynField (attrs, _, id, fieldType, _, _, _, _, _)) ->
-                let id =
-                    match id with
-                    | None -> failwith "didn't get an ID on field"
-                    | Some id -> id
-
-                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 ],
-                        None,
-                        None,
-                        SynArgPats.Empty,
-                        None,
-                        range0
-                    )
-
-                createSerializeRhs 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
-
-                (SynLongIdent.CreateFromLongIdent [ id ], true),
-                Some (SynExpr.CreateLongIdent (SynLongIdent.CreateFromLongIdent [ id ]))
-            )
-            |> AstHelper.instantiateRecord
-
-        let assignments = assignments |> SynExpr.CreateSequential
-
         let assignments =
             SynExpr.LetOrUse (
                 false,
@@ -327,13 +294,11 @@ module internal JsonSerializeGenerator =
                 ],
                 SynExpr.CreateSequential
                     [
-                        SynExpr.Do (assignments, range0)
+                        populateNode
                         SynExpr.Upcast (SynExpr.CreateIdentString "node", SynType.Anon range0, range0)
                     ],
                 range0,
-                {
-                    InKeyword = None
-                }
+                SynExprLetOrUseTrivia.empty
             )
 
         let pattern =
@@ -344,7 +309,7 @@ module internal JsonSerializeGenerator =
                 SynArgPats.Pats
                     [
                         SynPat.CreateTyped (
-                            SynPat.CreateNamed inputArg,
+                            SynPat.CreateNamed inputArgName,
                             SynType.LongIdent (SynLongIdent.CreateFromLongIdent typeName)
                         )
                         |> SynPat.CreateParen
@@ -406,7 +371,116 @@ module internal JsonSerializeGenerator =
 
             SynModuleDecl.CreateLet [ binding ]
 
-    let createRecordModule
+    let recordModule (spec : JsonSerializeOutputSpec) (typeName : LongIdent) (fields : SynField list) =
+        let inputArg = Ident.Create "input"
+        let fields = fields |> List.map SynField.extractWithIdent
+
+        fields
+        |> List.map (fun fieldData ->
+            let propertyName = getPropertyName fieldData.Ident fieldData.Attrs
+            createSerializeRhsRecord propertyName fieldData.Ident fieldData.Type
+        )
+        |> SynExpr.CreateSequential
+        |> fun expr -> SynExpr.Do (expr, range0)
+        |> scaffolding spec typeName inputArg
+
+    let unionModule (spec : JsonSerializeOutputSpec) (typeName : LongIdent) (cases : SynUnionCase list) =
+        let inputArg = Ident.Create "input"
+        let fields = cases |> List.map SynUnionCase.extract
+
+        fields
+        |> List.map (fun unionCase ->
+            let propertyName = getPropertyName unionCase.Ident unionCase.Attrs
+
+            let caseNames = unionCase.Fields |> List.mapi (fun i _ -> Ident.Create $"arg%i{i}")
+
+            let argPats = SynArgPats.create caseNames
+
+            let pattern =
+                SynPat.LongIdent (
+                    SynLongIdent.CreateFromLongIdent (typeName @ [ unionCase.Ident ]),
+                    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 =
+                (unionCase.Fields, caseNames)
+                ||> List.zip
+                |> List.map (fun (fieldData, caseName) ->
+                    let propertyName = getPropertyName (Option.get fieldData.Ident) fieldData.Attrs
+                    let func = SynExpr.CreateLongIdent (SynLongIdent.Create [ "dataNode" ; "Add" ])
+
+                    let node =
+                        SynExpr.CreateApp (serializeNode fieldData.Type, 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)
+        )
+        |> fun clauses -> SynExpr.CreateMatch (SynExpr.CreateIdent inputArg, clauses)
+        |> scaffolding spec typeName inputArg
+
+    let createModule
         (namespaceId : LongIdent)
         (opens : SynOpenDeclTarget list)
         (spec : JsonSerializeOutputSpec)
@@ -415,60 +489,62 @@ 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 +558,20 @@ 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 +601,10 @@ 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/RemoveOptionsGenerator.fs

@@ -63,7 +63,7 @@ module internal RemoveOptionsGenerator =
 
         SynModuleDecl.Types ([ typeDecl ], range0)
 
-    let createMaker (withOptionsType : LongIdent) (withoutOptionsType : LongIdent) (fields : SynField list) =
+    let createMaker (withOptionsType : LongIdent) (withoutOptionsType : LongIdent) (fields : SynFieldData<Ident> list) =
         let xmlDoc = PreXmlDoc.Create " Remove the optional members of the input."
 
         let returnInfo =
@@ -81,17 +81,17 @@ module internal RemoveOptionsGenerator =
 
         let body =
             fields
-            |> List.map (fun (SynField (_, _, id, fieldType, _, _, _, _, _)) ->
-                let id =
-                    match id with
-                    | None -> failwith "Expected record field to have an identifying name"
-                    | Some id -> id
-
+            |> List.map (fun fieldData ->
                 let accessor =
-                    SynExpr.LongIdent (false, SynLongIdent ([ inputArg ; id ], [ range0 ], []), None, range0)
+                    SynExpr.LongIdent (
+                        false,
+                        SynLongIdent ([ inputArg ; fieldData.Ident ], [ range0 ], []),
+                        None,
+                        range0
+                    )
 
                 let body =
-                    match fieldType with
+                    match fieldData.Type with
                     | OptionType _ ->
                         SynExpr.CreateApp (
                             SynExpr.CreateAppInfix (
@@ -111,14 +111,15 @@ module internal RemoveOptionsGenerator =
                                 SynExpr.CreateLongIdent (SynLongIdent.CreateString "Option.defaultWith"),
                                 SynExpr.CreateLongIdent (
                                     SynLongIdent.CreateFromLongIdent (
-                                        withoutOptionsType @ [ Ident.Create (sprintf "Default%s" id.idText) ]
+                                        withoutOptionsType
+                                        @ [ Ident.Create (sprintf "Default%s" fieldData.Ident.idText) ]
                                     )
                                 )
                             )
                         )
                     | _ -> accessor
 
-                (SynLongIdent.CreateFromLongIdent [ id ], true), Some body
+                (SynLongIdent.CreateFromLongIdent [ fieldData.Ident ], true), Some body
             )
             |> AstHelper.instantiateRecord
 
@@ -160,12 +161,13 @@ module internal RemoveOptionsGenerator =
             synComponentInfo
 
         match synTypeDefnRepr with
-        | SynTypeDefnRepr.Simple (SynTypeDefnSimpleRepr.Record (accessibility, recordFields, _recordRange), _) ->
+        | SynTypeDefnRepr.Simple (SynTypeDefnSimpleRepr.Record (accessibility, fields, _range), _) ->
+            let fieldData = fields |> List.map SynField.extractWithIdent
 
             let decls =
                 [
-                    createType (Some doc) accessibility typeParams recordFields
-                    createMaker [ Ident.Create "Short" ] recordId recordFields
+                    createType (Some doc) accessibility typeParams fields
+                    createMaker [ Ident.Create "Short" ] recordId fieldData
                 ]
 
             let attributes =

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/SynExpr/SynField.fs

@@ -0,0 +1,39 @@
+namespace WoofWare.Myriad.Plugins
+
+open Fantomas.FCS.Syntax
+
+type internal SynFieldData<'Ident> =
+    {
+        Attrs : SynAttribute list
+        Ident : 'Ident
+        Type : SynType
+    }
+
+[<RequireQualifiedAccess>]
+module internal SynField =
+    /// Get the useful information out of a SynField.
+    let extract (SynField (attrs, _, id, fieldType, _, _, _, _, _)) : SynFieldData<Ident option> =
+        {
+            Attrs = attrs |> List.collect (fun l -> l.Attributes)
+            Ident = id
+            Type = fieldType
+        }
+
+    let mapIdent<'a, 'b> (f : 'a -> 'b) (x : SynFieldData<'a>) : SynFieldData<'b> =
+        let ident = f x.Ident
+
+        {
+            Attrs = x.Attrs
+            Ident = ident
+            Type = x.Type
+        }
+
+    /// Throws if the field has no identifier.
+    let extractWithIdent (f : SynField) : SynFieldData<Ident> =
+        f
+        |> extract
+        |> mapIdent (fun ident ->
+            match ident with
+            | None -> failwith "expected field identifier to have a value, but it did not"
+            | Some i -> i
+        )

WoofWare.Myriad.Plugins/SynExpr/SynUnionCase.fs

@@ -0,0 +1,32 @@
+namespace WoofWare.Myriad.Plugins
+
+open Fantomas.FCS.Syntax
+
+type internal UnionCase<'Ident> =
+    {
+        Fields : SynFieldData<'Ident> list
+        Attrs : SynAttribute list
+        Ident : Ident
+    }
+
+[<RequireQualifiedAccess>]
+module internal SynUnionCase =
+    let extract (SynUnionCase (attrs, id, caseType, _, _, _, _)) : UnionCase<Ident option> =
+        match caseType with
+        | SynUnionCaseKind.FullType _ -> failwith "WoofWare.Myriad does not support FullType union cases."
+        | SynUnionCaseKind.Fields fields ->
+
+        let fields = fields |> List.map SynField.extract
+
+        let id =
+            match id with
+            | SynIdent.SynIdent (ident, _) -> ident
+
+        // 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)
+
+        {
+            Fields = fields
+            Attrs = attrs
+            Ident = id
+        }

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

@@ -27,9 +27,13 @@
     <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="SynExpr\SynField.fs" />
+    <Compile Include="SynExpr\SynUnionCase.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/"
+  ]
+}