Allow $ to literally denote quantities of USD in chat (#95)

Co-authored-by: david qiu <44106031+dlqqq@users.noreply.github.com>

Author: brichet

packages/jupyter-chat/src/components/rendermime-markdown.tsx

@@ -24,14 +24,74 @@ type RendermimeMarkdownProps = {
 };
 
 /**
- * Takes \( and returns \\(. Escapes LaTeX delimeters by adding extra backslashes where needed for proper rendering by @jupyterlab/rendermime.
+ * Escapes backslashes in LaTeX delimiters such that they appear in the DOM
+ * after the initial MarkDown render. For example, this function takes '\(` and
+ * returns `\\(`.
+ *
+ * Required for proper rendering of MarkDown + LaTeX markup in the chat by
+ * `ILatexTypesetter`.
  */
 function escapeLatexDelimiters(text: string) {
   return text
-    .replace('\\(', '\\\\(')
-    .replace('\\)', '\\\\)')
-    .replace('\\[', '\\\\[')
-    .replace('\\]', '\\\\]');
+    .replace('\\(/g', '\\\\(')
+    .replace('\\)/g', '\\\\)')
+    .replace('\\[/g', '\\\\[')
+    .replace('\\]/g', '\\\\]');
+}
+
+/**
+ * Type predicate function that determines whether a given DOM Node is a Text
+ * node.
+ */
+function isTextNode(node: Node | null): node is Text {
+  return node?.nodeType === Node.TEXT_NODE;
+}
+
+/**
+ * Escapes all `$` symbols present in an HTML element except those within the
+ * following elements: `pre`, `code`, `samp`, `kbd`.
+ *
+ * This prevents `$` symbols from being used as inline math delimiters, allowing
+ * `$` symbols to be used literally to denote quantities of USD. This does not
+ * escape literal `$` within elements that display their contents literally,
+ * like code elements. This overrides JupyterLab's default rendering of MarkDown
+ * w/ LaTeX.
+ *
+ * The Jupyter AI system prompt should explicitly request that the LLM not use
+ * `$` as an inline math delimiter. This is the default behavior.
+ */
+function escapeDollarSymbols(el: HTMLElement) {
+  // Get all text nodes that are not within pre, code, samp, or kbd elements
+  const walker = document.createTreeWalker(el, NodeFilter.SHOW_TEXT, {
+    acceptNode: node => {
+      const isInSkippedElements = node.parentElement?.closest(
+        'pre, code, samp, kbd'
+      );
+      return isInSkippedElements
+        ? NodeFilter.FILTER_SKIP
+        : NodeFilter.FILTER_ACCEPT;
+    }
+  });
+
+  // Collect all valid text nodes in an array.
+  const textNodes: Text[] = [];
+  let currentNode: Node | null;
+  while ((currentNode = walker.nextNode())) {
+    if (isTextNode(currentNode)) {
+      textNodes.push(currentNode);
+    }
+  }
+
+  // Replace each `$` symbol with `\$` for each text node, unless there is
+  // another `$` symbol adjacent or it is already escaped. Examples:
+  // - `$10 - $5` => `\$10 - \$5` (escaped)
+  // - `$$ \infty $$` => `$$ \infty $$` (unchanged)
+  // - `\$10` => `\$10` (unchanged, already escaped)
+  textNodes.forEach(node => {
+    if (node.textContent) {
+      node.textContent = node.textContent.replace(/(?<![$\\])\$(?!\$)/g, '\\$');
+    }
+  });
 }
 
 function RendermimeMarkdownBase(props: RendermimeMarkdownProps): JSX.Element {
@@ -47,12 +107,15 @@ function RendermimeMarkdownBase(props: RendermimeMarkdownProps): JSX.Element {
 
   useEffect(() => {
     const renderContent = async () => {
+      // initialize mime model
       const mdStr = escapeLatexDelimiters(props.markdownStr);
       const model = props.rmRegistry.createModel({
         data: { [MD_MIME_TYPE]: mdStr }
       });
 
       const renderer = props.rmRegistry.createRenderer(MD_MIME_TYPE);
+
+      // step 1: render markdown
       await renderer.renderModel(model);
       props.rmRegistry.latexTypesetter?.typeset(renderer.node);
       if (!renderer.node) {
@@ -61,6 +124,10 @@ function RendermimeMarkdownBase(props: RendermimeMarkdownProps): JSX.Element {
         );
       }
 
+      // step 2: render LaTeX via MathJax, while escaping single dollar symbols.
+      escapeDollarSymbols(renderer.node);
+      props.rmRegistry.latexTypesetter?.typeset(renderer.node);
+
       const newCodeToolbarDefns: [HTMLDivElement, CodeToolbarProps][] = [];
 
       // Attach CodeToolbar root element to each <pre> block