🫓 Flatten inlineCode (that may have children) (#920)

When tex is being parsed, it is possible for inline code `\texttt{}` to have children. If all of those children are text, then the children are transformed into be a single node with `.value`.

.changeset/fuzzy-mayflies-punch.md

@@ -0,0 +1,5 @@
+---
+"myst-common": patch
+---
+
+Add inline code rule for errors

.changeset/great-goats-search.md

@@ -0,0 +1,5 @@
+---
+"myst-transforms": patch
+---
+
+Flatten inline code by default

packages/myst-common/src/ruleids.ts

@@ -85,6 +85,7 @@ export enum RuleId {
   codeMetatagsValid = 'code-metatags-valid',
   codeLangDefined = 'code-lang-defined',
   codeMetadataLoads = 'code-metadata-loads',
+  inlineCodeMalformed = 'inline-code-malformed',
   inlineExpressionRenders = 'inline-expression-renders',
   // Static file rules
   staticFileCopied = 'static-file-copied',

packages/myst-transforms/src/basic.ts

@@ -10,7 +10,7 @@ import { htmlIdsTransform } from './htmlIds.js';
 import { imageAltTextTransform } from './images.js';
 import { mathLabelTransform, mathNestingTransform, subequationTransform } from './math.js';
 import { blockquoteTransform } from './blockquote.js';
-import { codeBlockToDirectiveTransform } from './code.js';
+import { codeBlockToDirectiveTransform, inlineCodeFlattenTransform } from './code.js';
 import { removeUnicodeTransform } from './removeUnicode.js';
 import { containerChildrenTransform } from './containers.js';
 import { headingDepthTransform } from './headings.js';
@@ -41,6 +41,7 @@ export function basicTransformations(tree: GenericParent, file: VFile, opts: Rec
   blockquoteTransform(tree);
   removeUnicodeTransform(tree);
   headingDepthTransform(tree, file, opts);
+  inlineCodeFlattenTransform(tree, file);
 }
 
 export const basicTransformationsPlugin: Plugin<

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

@@ -1,6 +1,6 @@
 import { describe, expect, test } from 'vitest';
 import { VFile } from 'vfile';
-import { codeTransform } from './code';
+import { codeTransform, inlineCodeFlattenTransform } from './code';
 
 describe('Test codeTransform', () => {
   test('simple code block returns self', async () => {
@@ -67,4 +67,47 @@ describe('Test codeTransform', () => {
     });
     expect(file.messages.length).toBe(1);
   });
+
+  test('inline code with text children will flatten', async () => {
+    const mdast = {
+      type: 'root',
+      children: [
+        {
+          type: 'inlineCode',
+          children: [
+            { type: 'text', value: 'one ' },
+            { type: 'text', value: 'two' },
+          ],
+        },
+      ],
+    };
+    const file = new VFile();
+    inlineCodeFlattenTransform(mdast, file);
+    expect(mdast).toEqual({
+      type: 'root',
+      children: [{ type: 'inlineCode', value: 'one two' }],
+    });
+  });
+
+  test('inline code with children and value warns', async () => {
+    const mdast = {
+      type: 'root',
+      children: [
+        {
+          type: 'inlineCode',
+          value: 'blah',
+          children: [{ type: 'text', value: 'x' }],
+        },
+      ],
+    };
+    const file = new VFile();
+    inlineCodeFlattenTransform(mdast, file);
+    expect(mdast).toEqual({
+      type: 'root',
+      // No changes
+      children: [{ type: 'inlineCode', value: 'blah', children: [{ type: 'text', value: 'x' }] }],
+    });
+    // A warning was created
+    expect(file.messages.length).toBe(1);
+  });
 });

packages/myst-transforms/src/code.ts

@@ -3,13 +3,35 @@ import { selectAll } from 'unist-util-select';
 import type { GenericNode, GenericParent } from 'myst-common';
 import { RuleId, fileWarn } from 'myst-common';
 import type { VFile } from 'vfile';
-import type { Code } from 'myst-spec';
+import type { Code, InlineCode } from 'myst-spec';
 
 type Options = {
   lang?: string;
   transformPython?: boolean;
 };
 
+/**
+ * Flatten any inline code that only has text in it to a single value.
+ */
+export function inlineCodeFlattenTransform(mdast: GenericParent, file: VFile) {
+  const code = selectAll('inlineCode', mdast) as (InlineCode & { children?: GenericNode[] })[];
+  code.forEach((node) => {
+    if (!node?.children) return;
+    if (node.value) {
+      fileWarn(file, 'Both children and value defined for inline code.', {
+        node,
+        ruleId: RuleId.inlineCodeMalformed,
+      });
+      // This is a warning, but can be ignored.
+      return;
+    }
+    if (!node.children.reduce((b, c) => b && c.type === 'text', true)) return;
+    // All the children are now text nodes
+    node.value = node.children.reduce((t, c) => t + c.value, '');
+    delete node.children;
+  });
+}
+
 export function codeTransform(mdast: GenericParent, file: VFile, opts?: Options) {
   const code = selectAll('code', mdast) as Code[];
   code.forEach((node) => {
@@ -65,3 +87,8 @@ export const codeBlockToDirectivePlugin: Plugin<
 > = (opts) => (tree, file) => {
   codeBlockToDirectiveTransform(tree, file, opts);
 };
+
+export const inlineCodeFlattenPlugin: Plugin<[], GenericParent, GenericParent> =
+  () => (tree, file) => {
+    inlineCodeFlattenTransform(tree, file);
+  };

packages/myst-transforms/src/index.ts

@@ -33,7 +33,12 @@ export {
   blockMetadataPlugin,
   blockMetadataTransform,
 } from './blocks.js';
-export { codePlugin, codeTransform } from './code.js';
+export {
+  codePlugin,
+  codeTransform,
+  inlineCodeFlattenPlugin,
+  inlineCodeFlattenTransform,
+} from './code.js';
 export { blockquotePlugin, blockquoteTransform } from './blockquote.js';
 export { imageAltTextPlugin, imageAltTextTransform } from './images.js';
 export {