feat: support {align}, {align*}, {alignat}, and {alignat*} (#2341)

* Support {align}, {align*}, {alignat}, and {alignat*}

* Specify display mode for screenshots

* Add bogus screenshots

* Some screenshotter progress

* Update screenshots

docs/support_table.md

@@ -73,9 +73,11 @@ table td {
 |\alef|$\alef$||
 |\alefsym|$\alefsym$||
 |\aleph|$\aleph$||
-|{align}|<span style="color:firebrick;">Not supported</span>|see `{aligned}`|
+|{align}|$$\begin{align}a&=b+c\\d+e&=f\end{align}$$|`\begin{align}`<br>&nbsp;&nbsp;&nbsp;`a&=b+c \\`<br>&nbsp;&nbsp;&nbsp;`d+e&=f`<br>`\end{align}`|
+|{align\*}|$$\begin{align*}a&=b+c\\d+e&=f\end{align*}$$|`\begin{align*}`<br>&nbsp;&nbsp;&nbsp;`a&=b+c \\`<br>&nbsp;&nbsp;&nbsp;`d+e&=f`<br>`\end{align*}`|
 |{aligned}|$\begin{aligned}a&=b+c\\d+e&=f\end{aligned}$|`\begin{aligned}`<br>&nbsp;&nbsp;&nbsp;`a&=b+c \\`<br>&nbsp;&nbsp;&nbsp;`d+e&=f`<br>`\end{aligned}`|
-|{alignat}|<span style="color:firebrick;">Not supported</span>|see `{alignedat}`|
+|{alignat}|$$\begin{alignat}{2}10&x+&3&y=2\\3&x+&13&y=4\end{alignat}$$|`\begin{alignat}{2}`<br>&nbsp;&nbsp;&nbsp;`10&x+ &3&y = 2 \\`<br>&nbsp;&nbsp;&nbsp;` 3&x+&13&y = 4`<br>`\end{alignat}`|
+|{alignat\*}|$$\begin{alignat*}{2}10&x+&3&y=2\\3&x+&13&y=4\end{alignat*}$$|`\begin{alignat*}{2}`<br>&nbsp;&nbsp;&nbsp;`10&x+ &3&y = 2 \\`<br>&nbsp;&nbsp;&nbsp;` 3&x+&13&y = 4`<br>`\end{alignat*}`|
 |{alignedat}|$\begin{alignedat}{2}10&x+&3&y=2\\3&x+&13&y=4\end{alignedat}$|`\begin{alignedat}{2}`<br>&nbsp;&nbsp;&nbsp;`10&x+ &3&y = 2 \\`<br>&nbsp;&nbsp;&nbsp;` 3&x+&13&y = 4`<br>`\end{alignedat}`|
 |\allowbreak|||
 |\Alpha|$\Alpha$||

docs/supported.md

@@ -83,7 +83,9 @@ $( \big( \Big( \bigg( \Bigg($ `( \big( \Big( \bigg( \Bigg(`
 |$\begin{pmatrix} a & b \\ c & d \end{pmatrix}$ |`\begin{pmatrix}`<br>&nbsp;&nbsp;&nbsp;`a & b \\`<br>&nbsp;&nbsp;&nbsp;`c & d`<br>`\end{pmatrix}` |$\begin{bmatrix} a & b \\ c & d \end{bmatrix}$ | `\begin{bmatrix}`<br>&nbsp;&nbsp;&nbsp;`a & b \\`<br>&nbsp;&nbsp;&nbsp;`c & d`<br>`\end{bmatrix}`
 |$\begin{vmatrix} a & b \\ c & d \end{vmatrix}$ |`\begin{vmatrix}`<br>&nbsp;&nbsp;&nbsp;`a & b \\`<br>&nbsp;&nbsp;&nbsp;`c & d`<br>`\end{vmatrix}` |$\begin{Vmatrix} a & b \\ c & d \end{Vmatrix}$ |`\begin{Vmatrix}`<br>&nbsp;&nbsp;&nbsp;`a & b \\`<br>&nbsp;&nbsp;&nbsp;`c & d`<br>`\end{Vmatrix}`
 |$\begin{Bmatrix} a & b \\ c & d \end{Bmatrix}$ |`\begin{Bmatrix}`<br>&nbsp;&nbsp;&nbsp;`a & b \\`<br>&nbsp;&nbsp;&nbsp;`c & d`<br>`\end{Bmatrix}`|$\def\arraystretch{1.5}\begin{array}{c:c:c} a & b & c \\ \hline d & e & f \\ \hdashline g & h & i \end{array}$|`\def\arraystretch{1.5}`<br>&nbsp;&nbsp;&nbsp;`\begin{array}{c:c:c}`<br>&nbsp;&nbsp;&nbsp;`a & b & c \\ \hline`<br>&nbsp;&nbsp;&nbsp;`d & e & f \\`<br>&nbsp;&nbsp;&nbsp;`\hdashline`<br>&nbsp;&nbsp;&nbsp;`g & h & i`<br>`\end{array}`
-|$\begin{aligned} a&=b+c \\ d+e&=f \end{aligned}$ |`\begin{aligned}`<br>&nbsp;&nbsp;&nbsp;`a&=b+c \\`<br>&nbsp;&nbsp;&nbsp;`d+e&=f`<br>`\end{aligned}`|$\begin{alignedat}{2}10&x+&3&y=2\\3&x+&13&y=4\end{alignedat}$ |`\begin{alignedat}{2}`<br>&nbsp;&nbsp;&nbsp;`10&x+ &3&y = 2 \\`<br>&nbsp;&nbsp;&nbsp;` 3&x+&13&y = 4`<br>`\end{alignedat}`
+|$$\begin{align} a&=b+c \\ d+e&=f \end{align}$$ |`\begin{align}`<br>&nbsp;&nbsp;&nbsp;`a&=b+c \\`<br>&nbsp;&nbsp;&nbsp;`d+e&=f`<br>`\end{align}`|$$\begin{alignat}{2}10&x+&3&y=2\\3&x+&13&y=4\end{alignat}$$ |
+|$$\begin{align*} a&=b+c \\ d+e&=f \end{align*}$$ |`\begin{align*}`<br>&nbsp;&nbsp;&nbsp;`a&=b+c \\`<br>&nbsp;&nbsp;&nbsp;`d+e&=f`<br>`\end{align*}`|$\begin{aligned} a&=b+c \\ d+e&=f \end{aligned}$ |`\begin{aligned}`<br>&nbsp;&nbsp;&nbsp;`a&=b+c \\`<br>&nbsp;&nbsp;&nbsp;`d+e&=f`<br>`\end{aligned}`|
+`\begin{alignedat}{2}`<br>&nbsp;&nbsp;&nbsp;`10&x+ &3&y = 2 \\`<br>&nbsp;&nbsp;&nbsp;` 3&x+&13&y = 4`<br>`\end{alignedat}`|$\begin{alignedat}{2}10&x+&3&y=2\\3&x+&13&y=4\end{alignedat}$ |`\begin{alignedat}{2}`<br>&nbsp;&nbsp;&nbsp;`10&x+ &3&y = 2 \\`<br>&nbsp;&nbsp;&nbsp;` 3&x+&13&y = 4`<br>`\end{alignedat}`
 |$$\begin{gather} a=b \\ e=b+c \end{gather}$$ |`\begin{gather}`<br>&nbsp;&nbsp;&nbsp;`a=b \\ `<br>&nbsp;&nbsp;&nbsp;`e=b+c`<br>`\end{gather}`|$\begin{gathered} a=b \\ e=b+c \end{gathered}$ |`\begin{gathered}`<br>&nbsp;&nbsp;&nbsp;`a=b \\ `<br>&nbsp;&nbsp;&nbsp;`e=b+c`<br>`\end{gathered}`|
 |$x = \begin{cases} a &\text{if } b \\ c &\text{if } d \end{cases}$ |`x = \begin{cases}`<br>&nbsp;&nbsp;&nbsp;`a &\text{if } b  \\`<br>&nbsp;&nbsp;&nbsp;`c &\text{if } d`<br>`\end{cases}`|$\begin{rcases} a &\text{if } b \\ c &\text{if } d \end{rcases}⇒…$ |`\begin{rcases}`<br>&nbsp;&nbsp;&nbsp;`a &\text{if } b  \\`<br>&nbsp;&nbsp;&nbsp;`c &\text{if } d`<br>`\end{rcases}⇒…`|
 |$\begin{smallmatrix} a & b \\ c & d \end{smallmatrix}$ | `\begin{smallmatrix}`<br>&nbsp;&nbsp;&nbsp;`a & b \\`<br>&nbsp;&nbsp;&nbsp;`c & d`<br>`\end{smallmatrix}` |||

src/environments/array.js

@@ -577,10 +577,30 @@ const mathmlBuilder: MathMLBuilder<"array"> = function(group, options) {
     return table;
 };
 
-// Convenience function for aligned and alignedat environments.
+// Convenience function for align, align*, aligned, alignat, alignat*, alignedat.
 const alignedHandler = function(context, args) {
+    if (context.envName.indexOf("ed") === -1) {
+        // Check if this environment call is allowed.
+        const settings = context.parser.settings;
+        if (!settings.displayMode) {
+            throw new ParseError(`{${context.envName}} cannot be used inline.`);
+        } else if (settings.strict && !settings.topEnv) {
+            settings.reportNonstrict("textEnv",
+                `{${context.envName}} called from math mode.`);
+        }
+    }
     const cols = [];
-    const res = parseArray(context.parser, {cols, addJot: true}, "display");
+    const separationType = context.envName.indexOf("at") > -1 ? "alignat" : "align";
+    const res = parseArray(context.parser,
+        {
+            cols,
+            addJot: true,
+            addEqnNum: context.envName === "align" || context.envName === "alignat",
+            colSeparationType: separationType,
+            leqno: context.parser.settings.leqno,
+        },
+        "display"
+    );
 
     // Determining number of columns.
     // 1. If the first argument is given, we use it as a number of columns,
@@ -848,13 +868,15 @@ defineEnvironment({
     mathmlBuilder,
 });
 
-// An aligned environment is like the align* environment
+// In the align environment, one uses ampersands, &, to specify number of
-// except it operates within math mode.
+// columns in each row, and to locate spacing between each column.
+// align gets automatic numbering. align* and aligned do not.
+// The alignedat environment can be used in math mode.
 // Note that we assume \nomallineskiplimit to be zero,
 // so that \strut@ is the same as \strut.
 defineEnvironment({
     type: "array",
-    names: ["aligned"],
+    names: ["align", "align*", "aligned"],
     props: {
         numArgs: 0,
     },
@@ -903,10 +925,7 @@ defineEnvironment({
 // each columns.
 defineEnvironment({
     type: "array",
-    names: ["alignedat"],
+    names: ["alignat", "alignat*", "alignedat"],
-    // One for numbered and for unnumbered;
-    // but, KaTeX doesn't supports math numbering yet,
-    // they make no difference for now.
     props: {
         numArgs: 1,
     },

test/katex-spec.js

@@ -2726,25 +2726,26 @@ describe("An aligned environment", function() {
     });
 });
 
-describe("A gather environment", function() {
+describe("AMS environments", function() {
     const nonStrictDisplay = new Settings({displayMode: true, strict: false});
 
     it("should fail outside display mode", () => {
         expect`\begin{gather}a+b\\c+d\end{gather}`.not.toParse(nonstrictSettings);
-    });
-
-    it("should fail outside display mode", () => {
         expect`\begin{gather*}a+b\\c+d\end{gather*}`.not.toParse(nonstrictSettings);
+        expect`\begin{align}a&=b+c\\d+e&=f\end{align}`.not.toParse(nonstrictSettings);
+        expect`\begin{align*}a&=b+c\\d+e&=f\end{align*}`.not.toParse(nonstrictSettings);
+        expect`\begin{alignat}{2}10&x+ &3&y = 2\\3&x+&13&y = 4\end{alignat}`.not.toParse(nonstrictSettings);
+        expect`\begin{alignat*}{2}10&x+ &3&y = 2\\3&x+&13&y = 4\end{alignat*}`.not.toParse(nonstrictSettings);
     });
 
-    it("should build if in display mode", () => {
+    it("should build if in non-strict display mode", () => {
         expect`\begin{gather}a+b\\c+d\end{gather}`.toBuild(nonStrictDisplay);
-    });
-
-    it("should build if in display mode", () => {
         expect`\begin{gather*}a+b\\c+d\end{gather*}`.toBuild(nonStrictDisplay);
+        expect`\begin{align}a&=b+c\\d+e&=f\end{align}`.toBuild(nonStrictDisplay);
+        expect`\begin{align*}a&=b+c\\d+e&=f\end{align*}`.toBuild(nonStrictDisplay);
+        expect`\begin{alignat}{2}10&x+ &3&y = 2\\3&x+&13&y = 4\end{alignat}`.toBuild(nonStrictDisplay);
+        expect`\begin{alignat*}{2}10&x+ &3&y = 2\\3&x+&13&y = 4\end{alignat*}`.toBuild(nonStrictDisplay);
     });
-
 });
 
 describe("operatorname support", function() {

test/screenshotter/ss_data.yaml

@@ -22,6 +22,9 @@ AccentsText: |
     \text{\'A} & \text{\.A} & \text{\`A} & \text{\"A} & \text{\H{A}} & \text{\r{A}} \\
     \text{\.I İ} & \text{\H e e̋} & \text{\i ı}
     \end{array}
+Align:
+    tex: \begin{align}a &= 1 & b &= 2 \\ 3a &= 3 & 17b &= 34\end{align}
+    display: 1
 Aligned: |
     \begin{aligned}
         a &= 1 & b &= 2 \\