🧮 Math code blocks for GitHub Flavored Markdown (#524)

See executablebooks/MyST-Parser#798

Author: rowanc1

.changeset/strong-ducks-appear.md

@@ -0,0 +1,7 @@
+---
+'myst-transforms': patch
+'myst-cli': patch
+'mystmd': patch
+---
+
+Transform code blocks with `math` language to be math blocks. This is GitHub markdown.

packages/myst-transforms/src/basic.ts

@@ -8,14 +8,15 @@ import { admonitionBlockquoteTransform, admonitionHeadersTransform } from './adm
 import { blockMetadataTransform, blockNestingTransform } from './blocks.js';
 import { htmlIdsTransform } from './htmlIds.js';
 import { imageAltTextTransform } from './images.js';
-import { mathLabelTransform, mathNestingTransform } from './math.js';
+import { mathCodeBlockTransform, mathLabelTransform, mathNestingTransform } from './math.js';
 import { blockquoteTransform } from './blockquote.js';
 
 export function basicTransformations(tree: Root, file: VFile) {
   // lifting roles and directives must happen before the mystTarget transformation
   liftMystDirectivesAndRolesTransform(tree);
   // Some specifics about the ordering are noted below
   captionParagraphTransform(tree);
+  mathCodeBlockTransform(tree, file);
   mathNestingTransform(tree, file);
   // Math labelling should happen before the target-transformation
   mathLabelTransform(tree, file);

packages/myst-transforms/src/math.spec.ts

@@ -1,7 +1,7 @@
 import { describe, expect, test } from 'vitest';
 import { unified } from 'unified';
 import { VFile } from 'vfile';
-import { mathTransform, mathPlugin, mathNestingTransform } from './math';
+import { mathTransform, mathPlugin, mathNestingTransform, mathCodeBlockTransform } from './math';
 
 const ARRAY_ALIGN = `\\begin{align*}
   L=
@@ -124,3 +124,14 @@ describe('Test math nesting transformation', () => {
     expect(mdast.children[0].children[2].class).toBe('importantClass');
   });
 });
+
+describe('Test math code block transformation', () => {
+  test('Block paragraph', () => {
+    const file = new VFile();
+    const mdast = { children: [{ type: 'code', lang: 'math', value: 'Ax = b' }] } as any;
+    mathCodeBlockTransform(mdast, file);
+    expect(mdast.children[0].type).toBe('math');
+    expect(mdast.children[0].lang).toBeUndefined();
+    expect(mdast.children[0].value).toBe('Ax = b');
+  });
+});

packages/myst-transforms/src/math.ts

@@ -2,7 +2,7 @@ import type { Plugin } from 'unified';
 import type { VFile } from 'vfile';
 import katex from 'katex';
 import type { Root } from 'mdast';
-import type { Math, InlineMath, Node } from 'myst-spec';
+import type { Math, InlineMath, Node, Code } from 'myst-spec';
 import { selectAll } from 'unist-util-select';
 import type { GenericParent } from 'myst-common';
 import { copyNode, fileError, fileWarn, normalizeLabel } from 'myst-common';
@@ -239,13 +239,26 @@ export function mathLabelTransform(tree: Root, file: VFile) {
   });
 }
 
+// eslint-disable-next-line @typescript-eslint/no-unused-vars
+export function mathCodeBlockTransform(tree: Root, file: VFile) {
+  const nodes = selectAll('code[lang="math"]', tree) as Code[];
+  nodes.forEach((node) => {
+    (node as unknown as Math).type = 'math';
+    delete node.lang;
+  });
+}
+
 export function mathTransform(tree: Root, file: VFile, opts?: Options) {
   const nodes = selectAll('math,inlineMath', tree) as (Math | InlineMath)[];
   nodes.forEach((node) => {
     renderEquation(file, node, opts);
   });
 }
 
+export const mathCodeBlockPlugin: Plugin<[], Root, Root> = () => (tree, file) => {
+  mathCodeBlockTransform(tree, file);
+};
+
 export const mathNestingPlugin: Plugin<[], Root, Root> = () => (tree, file) => {
   mathNestingTransform(tree, file);
 };