fix(editor): require non-space delimiters for inline math

The upstream tokenizer matched `$([^$]+)$` with no delimiter rule, so a
second dollar sign anywhere in the paragraph turned prose into a math
span: `Costs are US$ 5,000 and R$ 40,000` lost the space after `US$`.

Require a non-space next to each delimiter and forbid a newline inside,
matching the common dialect. Real math still parses.

src/renderer/src/components/editor/rich-markdown-extensions.ts

@@ -9,7 +9,7 @@ import { createRichMarkdownTable } from './rich-markdown-table'
 import { TableCell } from '@tiptap/extension-table-cell'
 import { TableHeader } from '@tiptap/extension-table-header'
 import { TableRow } from '@tiptap/extension-table-row'
-import { BlockMath, InlineMath } from '@tiptap/extension-mathematics'
+import { BlockMath } from '@tiptap/extension-mathematics'
 import { createRichMarkdownExtension } from './rich-markdown-extension'
 import { createLowlight, common } from 'lowlight'
 import {
@@ -38,6 +38,7 @@ import { createRichMarkdownHtmlSuperscriptLink } from './rich-markdown-html-supe
 import type { RichMarkdownHtmlSuperscriptLinkContext } from './rich-markdown-html-superscript-link-context'
 import { RichMarkdownOrderedList } from './rich-markdown-ordered-list'
 import { RichMarkdownParagraph } from './rich-markdown-paragraph'
+import { RichMarkdownInlineMath } from './rich-markdown-inline-math'
 import { RichMarkdownCodeBlockLowlight } from './rich-markdown-lowlight'
 import { RichMarkdownTaskList } from './rich-markdown-task-list'
 import { createCachedLowlight } from './rich-markdown-lowlight-cache'
@@ -224,7 +225,7 @@ export function createRichMarkdownExtensions({
     TableRow,
     TableHeader,
     TableCell,
-    InlineMath.configure({
+    RichMarkdownInlineMath.configure({
       katexOptions: {
         throwOnError: false
       }

src/renderer/src/components/editor/rich-markdown-inline-math.test.ts

@@ -0,0 +1,64 @@
+import { Editor } from '@tiptap/core'
+import { describe, expect, it } from 'vitest'
+import { encodeRawMarkdownHtmlForRichEditor } from './raw-markdown-html'
+import { createRichMarkdownExtensions } from './rich-markdown-extensions'
+import { createRichMarkdownEditorCodec } from './rich-markdown-source-transport'
+
+function withEditor<T>(source: string, read: (editor: Editor) => T): T {
+  const codec = createRichMarkdownEditorCodec()
+  const editor = new Editor({
+    element: null,
+    extensions: createRichMarkdownExtensions({ codec }),
+    content: encodeRawMarkdownHtmlForRichEditor(source, codec),
+    contentType: 'markdown'
+  })
+  try {
+    return read(editor)
+  } finally {
+    editor.destroy()
+  }
+}
+
+function roundTrip(source: string): string {
+  return withEditor(source, (editor) => editor.getMarkdown().trimEnd())
+}
+
+function countInlineMath(source: string): number {
+  return withEditor(source, (editor) => {
+    let total = 0
+    editor.state.doc.descendants((node) => {
+      if (node.type.name === 'inlineMath') {
+        total += 1
+      }
+    })
+    return total
+  })
+}
+
+describe('inline math delimiters', () => {
+  it.each([
+    ['Costs are US$ 5,000 and R$ 40,000 total.'],
+    ['R$ 40,000 and R$ 50,000'],
+    ['The fee is $ 100 and the tax is $ 20.'],
+    ['one $ two $ three'],
+    ['$ not math $'],
+    ['R$ 40,000 and US$5,000 in one paragraph.'],
+    ['A line with US$ 5,000 here\nand another with R$ 40,000 there.']
+  ])('leaves %j untouched', (source) => {
+    expect(roundTrip(source)).toBe(source)
+    expect(countInlineMath(source)).toBe(0)
+  })
+
+  it.each([
+    ['$x$', 1],
+    ['Real math: $E = mc^2$ here.', 1],
+    ['$a+b$ and $c+d$ two real', 2]
+  ])('still parses math in %j', (source, expected) => {
+    expect(roundTrip(source)).toBe(source)
+    expect(countInlineMath(source)).toBe(expected)
+  })
+
+  it('does not span a soft line break', () => {
+    expect(countInlineMath('A line with US$ 5,000 here\nand another with R$ 40,000 there.')).toBe(0)
+  })
+})

src/renderer/src/components/editor/rich-markdown-inline-math.ts

@@ -0,0 +1,27 @@
+import { InlineMath } from '@tiptap/extension-mathematics'
+
+// Why: the common dialect requires a non-space next to each delimiter and forbids a
+// newline inside, which is what keeps `US$ 5,000 and R$ 40,000` out of a math span.
+const INLINE_MATH = /^\$(?![\s$])((?:[^$\n]*[^\s$])?)\$(?!\$)/
+
+const baseTokenizer = InlineMath.config.markdownTokenizer
+if (!baseTokenizer) {
+  throw new Error('InlineMath must provide a Markdown tokenizer')
+}
+
+export const RichMarkdownInlineMath = InlineMath.extend({
+  markdownTokenizer: {
+    ...baseTokenizer,
+    tokenize(src) {
+      const match = src.match(INLINE_MATH)
+      if (!match) {
+        return undefined
+      }
+      return {
+        type: 'inlineMath',
+        raw: match[0],
+        latex: match[1]
+      }
+    }
+  }
+})