Fix missing columns in Markdown tables without outer pipes

src/utils/markdown-table.test.ts

@@ -0,0 +1,35 @@
+import { describe, expect, test } from 'bun:test';
+import { formatResponse, parseMarkdownTable, renderBoxTable } from './markdown-table.js';
+
+describe('markdown table outer pipes', () => {
+  const headers = ['Name', 'Revenue', 'Profit'];
+  const rows = [['Acme', '100', '20']];
+  const borders = [
+    { name: 'no outer pipes', left: '', right: '' },
+    { name: 'a leading pipe only', left: '| ', right: '' },
+    { name: 'a trailing pipe only', left: '', right: ' |' },
+    { name: 'both outer pipes', left: '| ', right: ' |' },
+  ];
+
+  for (const { name, left, right } of borders) {
+    test(`keeps all columns with ${name}`, () => {
+      const table = [headers, ['---', '---', '---'], ...rows]
+        .map(cells => `${left}${cells.join(' | ')}${right}`)
+        .join('\n');
+
+      expect(parseMarkdownTable(table)).toEqual({ headers, rows });
+      expect(formatResponse(table)).toBe(renderBoxTable(headers, rows));
+    });
+  }
+
+  for (const emptyIndex of [0, 1, 2]) {
+    test(`preserves an empty header in column ${emptyIndex + 1}`, () => {
+      const emptyHeaders = headers.map((header, index) => index === emptyIndex ? '' : header);
+      const table = [emptyHeaders, ['---', '---', '---'], ...rows]
+        .map(cells => `| ${cells.join(' | ')} |`)
+        .join('\n');
+
+      expect(parseMarkdownTable(table)).toEqual({ headers: emptyHeaders, rows });
+    });
+  }
+});

src/utils/markdown-table.ts

@@ -45,16 +45,11 @@ export function parseMarkdownTable(tableText: string): { headers: string[]; rows
 
   const headers = headerLine
     .split('|')
-    .map(cell => cell.trim())
-    .filter((_, i, arr) => i > 0 && i < arr.length - 1 || arr.length === 1);
-
-  // Handle edge case where there's no leading/trailing pipe
-  if (headers.length === 0) {
-    const rawHeaders = headerLine.split('|').map(cell => cell.trim());
-    if (rawHeaders.length > 0) {
-      headers.push(...rawHeaders);
-    }
-  }
+    .map(cell => cell.trim());
+
+  // Remove only the empty cells introduced by outer pipes.
+  if (headerLine.startsWith('|')) headers.shift();
+  if (headerLine.endsWith('|')) headers.pop();
 
   if (headers.length === 0) return null;