🐛 Top level AMS Math environments are not wrapped. (#1526)

Fixes #1519

.changeset/chilly-eyes-smash.md

@@ -0,0 +1,6 @@
+---
+"myst-to-tex": patch
+"mystmd": patch
+---
+
+Top level AMS environments are not wrapped

packages/myst-to-tex/src/math.ts

@@ -3,31 +3,22 @@ import { addIndexEntries } from './utils.js';
 
 // Top level environments in amsmath version 2.1 (and eqnarray), see:
 // http://anorien.csc.warwick.ac.uk/mirrors/CTAN/macros/latex/required/amsmath/amsldoc.pdf
-const ENVIRONMENTS = [
+const TOP_LEVEL_ENVIRONMENTS = [
   'equation',
   'multline',
   'gather',
   'align',
   'alignat',
   'flalign',
-  'matrix',
-  'pmatrix',
-  'bmatrix',
-  'Bmatrix',
-  'vmatrix',
-  'Vmatrix',
   'eqnarray',
 ];
+// The other environments can be inside of an equation
+// const MATRIX_ENVIRONMENTS = ['matrix', 'pmatrix', 'bmatrix', 'Bmatrix', 'vmatrix', 'Vmatrix'];
 
-const RE_OPEN = new RegExp(`^\\\\begin{(${ENVIRONMENTS.join('|')})([*]?)}`);
+const RE_OPEN = new RegExp(`^\\\\begin{(${TOP_LEVEL_ENVIRONMENTS.join('|')})([*]?)}`);
 
-function isAmsmathEnvironment(value: string): boolean {
+function isTopLevelAmsmathEnvironment(value: string): boolean {
   // First test if there are multiple environments in this equation
-  const matches = value.trim().matchAll(new RegExp(`\\\\begin{(${ENVIRONMENTS.join('|')})}`, 'g'));
-  if ([...matches].length > 1) {
-    // If there are multiple amsmath environments, ensure we always return something with the equation wrappers
-    return false;
-  }
   const matchOpen = value.trim().match(RE_OPEN);
   if (!matchOpen) return false;
   const [, environment, star] = matchOpen;
@@ -90,7 +81,7 @@ const math: Handler = (node, state) => {
     state.write(' \\)');
   } else {
     // Check if the node is an AMSMath environment, if so, render it directly
-    const isAmsMath = isAmsmathEnvironment(node.value);
+    const isAmsMath = isTopLevelAmsmathEnvironment(node.value);
     if (isAmsMath) {
       // TODO: labels may be stripped previously in the transform, we may need to back that out
       state.ensureNewLine();

packages/myst-to-tex/tests/amsmath.yml

@@ -47,3 +47,39 @@ cases:
       = \frac{1}{r} \begin{pmatrix}- \sin\theta^1 & \cos\theta^1 \\ - \sin\theta^2 & \cos\theta^2 \\ - \sin\theta^3 & \cos\theta^3 \end{pmatrix}
       \begin{pmatrix}v_x \\ v_y \end{pmatrix}
       \end{equation}
+  - title: bmatrix environment
+    mdast:
+      type: root
+      children:
+        - type: math
+          value: |-
+            \begin{bmatrix}
+            3 & \textbf{3} & \textbf{3} & \textbf{5} & 5 & 5 & 5 & 2 & 2 & 2 \\
+            3 & 0 & \textbf{2} & 2 & 0 & 0 & -3 & -3 & 0 & -2
+            \end{bmatrix}
+    latex: |-
+      \begin{equation}
+      \begin{bmatrix}
+      3 & \textbf{3} & \textbf{3} & \textbf{5} & 5 & 5 & 5 & 2 & 2 & 2 \\
+      3 & 0 & \textbf{2} & 2 & 0 & 0 & -3 & -3 & 0 & -2
+      \end{bmatrix}
+      \end{equation}
+  - title: align environment
+    mdast:
+      type: root
+      children:
+        - type: math
+          value: |-
+            \begin{align}
+            \begin{bmatrix}
+            3 & \textbf{3} & \textbf{3} & \textbf{5} & 5 & 5 & 5 & 2 & 2 & 2 \\
+            3 & 0 & \textbf{2} & 2 & 0 & 0 & -3 & -3 & 0 & -2
+            \end{bmatrix}
+            \end{align}
+    latex: |-
+      \begin{align}
+      \begin{bmatrix}
+      3 & \textbf{3} & \textbf{3} & \textbf{5} & 5 & 5 & 5 & 2 & 2 & 2 \\
+      3 & 0 & \textbf{2} & 2 & 0 & 0 & -3 & -3 & 0 & -2
+      \end{bmatrix}
+      \end{align}