feat: Add markdown table rendering support (#1955)

Co-authored-by: heartyguy <heartyguy@users.noreply.github.com>
Co-authored-by: Allen Hutchison <adh@google.com>

packages/cli/src/ui/utils/MarkdownDisplay.test.tsx

@@ -0,0 +1,280 @@
+/**
+ * @license
+ * Copyright 2025 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import { render } from 'ink-testing-library';
+import { MarkdownDisplay } from './MarkdownDisplay.js';
+
+describe('MarkdownDisplay', () => {
+  describe('Table Rendering', () => {
+    it('should render a simple table', () => {
+      const tableMarkdown = `
+| Name | Age | City |
+|------|-----|------|
+| John | 25  | NYC  |
+| Jane | 30  | LA   |
+`;
+
+      const { lastFrame } = render(
+        <MarkdownDisplay
+          text={tableMarkdown}
+          isPending={false}
+          terminalWidth={80}
+        />,
+      );
+
+      expect(lastFrame()).toContain('Name');
+      expect(lastFrame()).toContain('Age');
+      expect(lastFrame()).toContain('City');
+      expect(lastFrame()).toContain('John');
+      expect(lastFrame()).toContain('25');
+      expect(lastFrame()).toContain('NYC');
+      expect(lastFrame()).toContain('Jane');
+      expect(lastFrame()).toContain('30');
+      expect(lastFrame()).toContain('LA');
+    });
+
+    it('should handle tables with varying column widths', () => {
+      const tableMarkdown = `
+| Short | Medium Column | Very Long Column Name |
+|-------|---------------|----------------------|
+| A     | Some text     | This is a longer text content |
+| B     | More content  | Another piece of content here |
+`;
+
+      const { lastFrame } = render(
+        <MarkdownDisplay
+          text={tableMarkdown}
+          isPending={false}
+          terminalWidth={80}
+        />,
+      );
+
+      expect(lastFrame()).toContain('Short');
+      expect(lastFrame()).toContain('Medium Column');
+      expect(lastFrame()).toContain('Very Long Column Name');
+    });
+
+    it('should handle empty cells in tables', () => {
+      const tableMarkdown = `
+| Col1 | Col2 | Col3 |
+|------|------|------|
+| A    |      | C    |
+|      | B    |      |
+`;
+
+      const { lastFrame } = render(
+        <MarkdownDisplay
+          text={tableMarkdown}
+          isPending={false}
+          terminalWidth={80}
+        />,
+      );
+
+      expect(lastFrame()).toContain('Col1');
+      expect(lastFrame()).toContain('Col2');
+      expect(lastFrame()).toContain('Col3');
+      expect(lastFrame()).toContain('A');
+      expect(lastFrame()).toContain('B');
+      expect(lastFrame()).toContain('C');
+    });
+
+    it('should handle mixed content with tables', () => {
+      const mixedMarkdown = `
+# Header
+
+Some paragraph text before the table.
+
+| Feature | Status | Notes |
+|---------|--------|-------|
+| Auth    | Done   | OAuth |
+| API     | WIP    | REST  |
+
+Some text after the table.
+`;
+
+      const { lastFrame } = render(
+        <MarkdownDisplay
+          text={mixedMarkdown}
+          isPending={false}
+          terminalWidth={80}
+        />,
+      );
+
+      expect(lastFrame()).toContain('Header');
+      expect(lastFrame()).toContain('Some paragraph text before the table.');
+      expect(lastFrame()).toContain('Feature');
+      expect(lastFrame()).toContain('Status');
+      expect(lastFrame()).toContain('Auth');
+      expect(lastFrame()).toContain('Done');
+      expect(lastFrame()).toContain('Some text after the table.');
+    });
+
+    it('should handle tables with empty cells at edges', () => {
+      const tableMarkdown = `
+| | Middle | |
+|-|--------|-|
+| | Value  | |
+`;
+
+      const { lastFrame } = render(
+        <MarkdownDisplay
+          text={tableMarkdown}
+          isPending={false}
+          terminalWidth={80}
+        />,
+      );
+
+      expect(lastFrame()).toContain('Middle');
+      expect(lastFrame()).toContain('Value');
+      // Should maintain column structure even with empty edge cells
+    });
+
+    it('should handle PR reviewer test case 1', () => {
+      const tableMarkdown = `
+| Package | Lines of Code |
+|---------|---------------|
+| CLI     | 18407         |
+| Core    | 14445         |
+`;
+
+      const { lastFrame } = render(
+        <MarkdownDisplay
+          text={tableMarkdown}
+          isPending={false}
+          terminalWidth={80}
+        />,
+      );
+
+      const output = lastFrame();
+      expect(output).toContain('Package');
+      expect(output).toContain('Lines of Code');
+      expect(output).toContain('CLI');
+      expect(output).toContain('18407');
+      expect(output).toContain('Core');
+      expect(output).toContain('14445');
+    });
+
+    it('should handle PR reviewer test case 2 - long table', () => {
+      const tableMarkdown = `
+| Letter | Count |
+|--------|-------|
+| a      | 15    |
+| b      | 2     |
+| c      | 26    |
+| Total  | 283   |
+`;
+
+      const { lastFrame } = render(
+        <MarkdownDisplay
+          text={tableMarkdown}
+          isPending={false}
+          terminalWidth={80}
+        />,
+      );
+
+      const output = lastFrame();
+      expect(output).toContain('Letter');
+      expect(output).toContain('Count');
+      expect(output).toContain('a');
+      expect(output).toContain('15');
+      expect(output).toContain('Total');
+      expect(output).toContain('283');
+    });
+
+    it('should not render malformed tables', () => {
+      const malformedMarkdown = `
+| This looks like a table |
+But there's no separator line
+| So it shouldn't render as table |
+`;
+
+      const { lastFrame } = render(
+        <MarkdownDisplay
+          text={malformedMarkdown}
+          isPending={false}
+          terminalWidth={80}
+        />,
+      );
+
+      // Should render as regular text, not a table
+      expect(lastFrame()).toContain('| This looks like a table |');
+      expect(lastFrame()).toContain("But there's no separator line");
+      expect(lastFrame()).toContain("| So it shouldn't render as table |");
+    });
+
+    it('should not crash when rendering a very wide table in a narrow terminal', () => {
+      const wideTable = `
+| Col 1 | Col 2 | Col 3 | Col 4 | Col 5 | Col 6 | Col 7 | Col 8 | Col 9 | Col 10 |
+|-------|-------|-------|-------|-------|-------|-------|-------|-------|--------|
+| ${'a'.repeat(20)} | ${'b'.repeat(20)} | ${'c'.repeat(20)} | ${'d'.repeat(
+        20,
+      )} | ${'e'.repeat(20)} | ${'f'.repeat(20)} | ${'g'.repeat(20)} | ${'h'.repeat(
+        20,
+      )} | ${'i'.repeat(20)} | ${'j'.repeat(20)} |
+    `;
+
+      const renderNarrow = () =>
+        render(
+          <MarkdownDisplay
+            text={wideTable}
+            isPending={false}
+            terminalWidth={40}
+          />,
+        );
+
+      // The important part is that this does not throw an error.
+      expect(renderNarrow).not.toThrow();
+
+      // We can also check that it rendered *something*.
+      const { lastFrame } = renderNarrow();
+      expect(lastFrame()).not.toBe('');
+    });
+  });
+
+  describe('Existing Functionality', () => {
+    it('should render headers correctly', () => {
+      const headerMarkdown = `
+# H1 Header
+## H2 Header
+### H3 Header
+#### H4 Header
+`;
+
+      const { lastFrame } = render(
+        <MarkdownDisplay
+          text={headerMarkdown}
+          isPending={false}
+          terminalWidth={80}
+        />,
+      );
+
+      expect(lastFrame()).toContain('H1 Header');
+      expect(lastFrame()).toContain('H2 Header');
+      expect(lastFrame()).toContain('H3 Header');
+      expect(lastFrame()).toContain('H4 Header');
+    });
+
+    it('should render code blocks correctly', () => {
+      const codeMarkdown = `
+\`\`\`javascript
+const x = 42;
+console.log(x);
+\`\`\`
+`;
+
+      const { lastFrame } = render(
+        <MarkdownDisplay
+          text={codeMarkdown}
+          isPending={false}
+          terminalWidth={80}
+        />,
+      );
+
+      expect(lastFrame()).toContain('const x = 42;');
+      expect(lastFrame()).toContain('console.log(x);');
+    });
+  });
+});