fix(frontend): preserve code during Markdown table normalization

frontend/src/utils/markdownTableNormalize.test.ts

@@ -0,0 +1,49 @@
+import assert from 'node:assert/strict';
+import test from 'node:test';
+
+import { normalizeSpuriousTablePrefixes } from './markdownTableNormalize.ts';
+
+const brokenTable = '| | |\n| --- | --- |\n| Name | Value |\n| alpha | beta |';
+const normalizedTable = '| Name | Value |\n| --- | --- |\n| alpha | beta |';
+
+test('repairs spurious table prefixes outside code', () => {
+  assert.equal(normalizeSpuriousTablePrefixes(brokenTable), normalizedTable);
+  assert.equal(normalizeSpuriousTablePrefixes(normalizedTable), normalizedTable);
+});
+
+for (const fence of ['```', '~~~', '````', '~~~~']) {
+  test(`preserves literal table examples inside ${fence} fences`, () => {
+    const source = `${fence}markdown\n${brokenTable}\n${fence}`;
+    assert.equal(normalizeSpuriousTablePrefixes(source), source);
+  });
+}
+
+test('preserves indented code containing pipe-delimited rows', () => {
+  for (const indent of ['    ', '\t']) {
+    const source = brokenTable.split('\n').map(line => indent + line).join('\n');
+    assert.equal(normalizeSpuriousTablePrefixes(source), source);
+  }
+});
+
+test('resumes table repair after a code fence closes', () => {
+  const code = `  ~~~markdown\n${brokenTable}\n  ~~~~  `;
+  assert.equal(
+    normalizeSpuriousTablePrefixes(`${code}\n\n${brokenTable}`),
+    `${code}\n\n${normalizedTable}`,
+  );
+});
+
+test('shorter, opposite-character and nonblank-suffix fences do not close code', () => {
+  const source = `\`\`\`\`markdown\n${brokenTable}\n\`\`\`\n~~~\n\`\`\`\`suffix\n${brokenTable}\n\`\`\`\``;
+  assert.equal(normalizeSpuriousTablePrefixes(source), source);
+});
+
+test('an unclosed fence protects the rest of the document', () => {
+  const source = `~~~markdown\n${brokenTable}\n\n${brokenTable}`;
+  assert.equal(normalizeSpuriousTablePrefixes(source), source);
+});
+
+test('a backtick in the info string does not start a backtick fence', () => {
+  const source = `\`\`\`invalid\`info\n${brokenTable}`;
+  assert.equal(normalizeSpuriousTablePrefixes(source), `\`\`\`invalid\`info\n${normalizedTable}`);
+});

frontend/src/utils/markdownTableNormalize.ts

@@ -17,6 +17,10 @@ function splitRowCells(line: string): string[] {
 }
 
 function isTableRow(line: string): boolean {
+  // Four-space and tab-indented rows are literal code, not Markdown tables.
+  if (!/^ {0,3}\|/.test(line)) {
+    return false;
+  }
   const stripped = line.trim();
   return stripped.startsWith('|') && stripped.includes('|', 1);
 }
@@ -50,12 +54,28 @@ function normalizeTableBlock(block: string[]): string[] {
   return rows;
 }
 
-/** Fix MarkItDown-style tables: empty row + separator before real rows. */
+/** Fix MarkItDown-style tables outside literal fenced and indented code. */
 export function normalizeSpuriousTablePrefixes(content: string): string {
   const lines = content.split('\n');
   const out: string[] = [];
   let i = 0;
+  let fence: string | undefined;
   while (i < lines.length) {
+    const marker = /^ {0,3}(`{3,}|~{3,})(.*)$/.exec(lines[i]);
+    if (fence) {
+      if (marker && marker[1][0] === fence[0] && marker[1].length >= fence.length && /^[ \t\r]*$/.test(marker[2])) {
+        fence = undefined;
+      }
+      out.push(lines[i]);
+      i += 1;
+      continue;
+    }
+    if (marker && (marker[1][0] === '~' || !marker[2].includes('`'))) {
+      fence = marker[1];
+      out.push(lines[i]);
+      i += 1;
+      continue;
+    }
     if (!isTableRow(lines[i])) {
       out.push(lines[i]);
       i += 1;