feat: support inserted text element in message markdown rendering

src/components/ChannelPreview/utils.tsx

@@ -6,12 +6,13 @@ import type { Channel, PollVote, TranslationLanguages, UserResponse } from 'stre
 import type { TranslationContextValue } from '../../context/TranslationContext';
 import type { ChatContextValue } from '../../context';
 import type { PluggableList } from 'unified';
-import { htmlToTextPlugin } from '../Message';
+import { htmlToTextPlugin, plusPlusToEmphasis } from '../Message';
 import remarkGfm from 'remark-gfm';
 
 const remarkPlugins: PluggableList = [
   htmlToTextPlugin,
   [remarkGfm, { singleTilde: false }],
+  plusPlusToEmphasis,
 ];
 
 export const renderPreviewText = (text: string) => (

src/components/Message/renderText/__tests__/renderText.test.js

@@ -1,8 +1,12 @@
 import React from 'react';
 import { findAndReplace } from 'hast-util-find-and-replace';
 import { u } from 'unist-builder';
-import { render } from '@testing-library/react';
-import { htmlToTextPlugin, keepLineBreaksPlugin } from '../remarkPlugins';
+import { render, screen } from '@testing-library/react';
+import {
+  htmlToTextPlugin,
+  keepLineBreaksPlugin,
+  plusPlusToEmphasis,
+} from '../remarkPlugins';
 import { defaultAllowedTagNames, renderText } from '../renderText';
 import '@testing-library/jest-dom';
 
@@ -433,3 +437,30 @@ describe('htmlToTextPlugin', () => {
     expect(container).toMatchSnapshot();
   });
 });
+
+describe('plusPlusToEmphasis', () => {
+  const renderTextPlusPlus = (text, withPlugin = true) => {
+    const Markdown = renderText(
+      text,
+      {},
+      { getRemarkPlugins: () => (withPlugin ? [plusPlusToEmphasis] : []) },
+    );
+    return render(Markdown).container;
+  };
+
+  it('++…++ renders as <ins> and ignores code/links', () => {
+    renderTextPlusPlus('This is ++inserted++ and `++not++` and [x](y) ++also++');
+    expect(screen.getByText('inserted', { selector: 'ins' })).toBeInTheDocument();
+    expect(screen.getByText('++not++', { selector: 'code' })).toBeInTheDocument();
+    // link text exists; its inner text shouldn't be transformed
+    // expect(screen.getByRole('link', { name: 'x' })).toBeInTheDocument();
+  });
+
+  it('does not render ++…++  as <ins> if not present', () => {
+    renderTextPlusPlus('This is ++inserted++ and `++not++` and [x](y) ++also++', false);
+    expect(screen.queryByText('inserted', { selector: 'ins' })).not.toBeInTheDocument();
+    expect(screen.getByText('++not++', { selector: 'code' })).toBeInTheDocument();
+    // link text exists; its inner text shouldn't be transformed
+    // expect(screen.getByRole('link', { name: 'x' })).toBeInTheDocument();
+  });
+});

src/components/Message/renderText/remarkPlugins/index.ts

@@ -1,2 +1,3 @@
 export * from './htmlToTextPlugin';
 export * from './keepLineBreaksPlugin';
+export * from './plusPlusToEmphasis';

src/components/Message/renderText/remarkPlugins/plusPlusToEmphasis.ts

@@ -0,0 +1,77 @@
+// remark-plusplus-ins.ts
+import type { Plugin } from 'unified';
+import { SKIP, visit } from 'unist-util-visit';
+import type { Visitor } from 'unist-util-visit';
+import type { Parent, PhrasingContent, Text } from 'mdast';
+
+/**
+ * \S → first char must be non-whitespace
+ * (?:...)?→ optional middle+closing when length > 1
+ * [\s\S]*?→ anything (including newlines), lazy
+ * final \S→ last char non-whitespace (only required when there’s more than 1)
+ *
+ * Matches:
+ * ++a++
+ * Does not match:
+ * ++++
+ * ++ ++
+ */
+const INS_REGEX = /\+\+(\S(?:[\s\S]*?\S)?)\+\+/g;
+const IGNORE_NODE_TYPES = new Set([
+  'code',
+  'inlineCode',
+  'link',
+  'linkReference',
+  'definition',
+  'math',
+  'inlineMath',
+]);
+
+/**
+ * Converts MD "++Some text++" to inserted text element rendered in HTML as <ins>Some text</ins>
+ * https://developer.mozilla.org/en-US/docs/Web/HTML/Reference/Elements/ins
+ */
+export const plusPlusToEmphasis: Plugin<[]> = () => {
+  const visitor: Visitor = (node, index, parent) => {
+    // 1) Don’t traverse inside ignored nodes
+    if (IGNORE_NODE_TYPES.has(node.type)) return SKIP;
+
+    // 2) Only transform text nodes with a valid parent + index
+    if (node.type !== 'text' || parent == null || typeof index !== 'number') return;
+
+    const value = (node as Text).value;
+
+    // Reset lastIndex to 0 per node so each node is scanned from the beginning
+    INS_REGEX.lastIndex = 0;
+
+    let match: RegExpExecArray | null;
+    let last = 0;
+    const out: PhrasingContent[] = [];
+
+    while ((match = INS_REGEX.exec(value))) {
+      const [full, inner] = match;
+      const start = match.index;
+
+      if (start > last) out.push({ type: 'text', value: value.slice(last, start) });
+
+      // Render as <ins>…</ins> (remark-rehype respects data.hName)
+      out.push({
+        children: [{ type: 'text', value: inner }],
+        data: { hName: 'ins' },
+        type: 'emphasis',
+      });
+
+      last = start + full.length;
+    }
+
+    if (out.length === 0) return; // nothing to change
+    if (last < value.length) out.push({ type: 'text', value: value.slice(last) });
+
+    (parent as Parent).children.splice(index, 1, ...out);
+
+    // Skip re-visiting the replaced range; continue after inserted nodes
+    return [SKIP, index + out.length];
+  };
+
+  return (tree) => visit(tree, visitor);
+};

src/components/Message/renderText/renderText.tsx

@@ -10,7 +10,11 @@ import type { PluggableList } from 'unified'; // A sub-dependency of react-markd
 import { Anchor, Emoji, Mention } from './componentRenderers';
 import { detectHttp, matchMarkdownLinks, messageCodeBlocks } from './regex';
 import { emojiMarkdownPlugin, mentionsMarkdownPlugin } from './rehypePlugins';
-import { htmlToTextPlugin, keepLineBreaksPlugin } from './remarkPlugins';
+import {
+  htmlToTextPlugin,
+  keepLineBreaksPlugin,
+  plusPlusToEmphasis,
+} from './remarkPlugins';
 import { ErrorBoundary } from '../../UtilityComponents';
 import type { MentionProps } from './componentRenderers';
 
@@ -51,6 +55,7 @@ export const defaultAllowedTagNames: Array<
   'h4',
   'h5',
   'h6',
+  'ins',
 ];
 
 function formatUrlForDisplay(url: string) {
@@ -169,6 +174,7 @@ export const renderText = (
     htmlToTextPlugin,
     keepLineBreaksPlugin,
     [remarkGfm, { singleTilde: false }],
+    plusPlusToEmphasis,
   ];
   const rehypePlugins: PluggableList = [emojiMarkdownPlugin];