fix: lint --format markdown renders report instead of [object Object]

packages/cli/src/utils.test.ts

@@ -0,0 +1,91 @@
+// Copyright 2026 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+import { describe, it, expect } from 'bun:test';
+import { formatOutput } from './utils.js';
+
+describe('formatOutput', () => {
+  describe('--format markdown', () => {
+    it('renders a lint report instead of [object Object]', () => {
+      const lintOutput = {
+        findings: [
+          { severity: 'warning', path: 'colors.surface', message: "'surface' is defined but never referenced." },
+          { severity: 'info', message: 'Design system defines 10 colors.' },
+        ],
+        summary: { errors: 0, warnings: 1, infos: 1 },
+      };
+
+      const result = formatOutput(lintOutput, { format: 'markdown' });
+      expect(result).not.toContain('[object Object]');
+      expect(result).toContain('# Lint Report');
+      expect(result).toContain('**0 errors**');
+      expect(result).toContain('**1 warnings**');
+      expect(result).toContain('**1 infos**');
+      expect(result).toContain("'surface' is defined but never referenced.");
+      expect(result).toContain('`colors.surface`');
+    });
+
+    it('renders findings without a path', () => {
+      const lintOutput = {
+        findings: [
+          { severity: 'info', message: 'Token count summary.' },
+        ],
+        summary: { errors: 0, warnings: 0, infos: 1 },
+      };
+
+      const result = formatOutput(lintOutput, { format: 'markdown' });
+      expect(result).toContain('- **info**: Token count summary.');
+    });
+
+    it('renders an empty findings section when there are none', () => {
+      const lintOutput = {
+        findings: [],
+        summary: { errors: 0, warnings: 0, infos: 0 },
+      };
+
+      const result = formatOutput(lintOutput, { format: 'markdown' });
+      expect(result).toContain('# Lint Report');
+      expect(result).not.toContain('## Findings');
+    });
+
+    it('handles the --format md alias', () => {
+      const lintOutput = {
+        findings: [],
+        summary: { errors: 0, warnings: 0, infos: 0 },
+      };
+
+      const result = formatOutput(lintOutput, { format: 'md' });
+      expect(result).toContain('# Lint Report');
+    });
+
+    it('preserves legacy fixer shape with string summary', () => {
+      const fixerOutput = {
+        summary: 'Fixed 3 issues',
+        details: 'Some details here',
+      };
+
+      const result = formatOutput(fixerOutput, { format: 'markdown' });
+      expect(result).toContain('# Fixed 3 issues');
+      expect(result).toContain('## Details');
+    });
+  });
+
+  describe('default format (JSON)', () => {
+    it('returns valid JSON', () => {
+      const data = { findings: [], summary: { errors: 0, warnings: 0, infos: 0 } };
+      const result = formatOutput(data, {});
+      expect(JSON.parse(result)).toEqual(data);
+    });
+  });
+});

packages/cli/src/utils.ts

@@ -52,25 +52,72 @@ export function formatOutput(data: unknown, args: { format?: string }): string {
 }
 
 function formatAsMarkdown(data: unknown): string {
-  if (typeof data === 'object' && data !== null) {
-    const obj = data as Record<string, unknown>;
-    let result = '';
-    if (obj.summary) {
-      result += `# ${obj.summary}\n\n`;
-    }
-    if (obj.details) {
-      result += `## Details\n\n`;
-      result += formatAsText(obj.details);
-      result += '\n';
-    }
-    if (obj.patches && Array.isArray(obj.patches) && obj.patches.length > 0) {
-      result += `## Patches\n\n`;
-      result += formatAsText(obj.patches);
-      result += '\n';
+  if (typeof data !== 'object' || data === null) {
+    return String(data);
+  }
+
+  const obj = data as Record<string, unknown>;
+
+  // Lint output: { findings: [...], summary: { errors, warnings, infos } }
+  if (isLintOutput(obj)) {
+    return formatLintAsMarkdown(obj);
+  }
+
+  // Legacy fixer/diff shape: { summary: string, details?, patches? }
+  let result = '';
+  if (typeof obj.summary === 'string') {
+    result += `# ${obj.summary}\n\n`;
+  }
+  if (obj.details) {
+    result += `## Details\n\n`;
+    result += formatAsText(obj.details);
+    result += '\n';
+  }
+  if (obj.patches && Array.isArray(obj.patches) && obj.patches.length > 0) {
+    result += `## Patches\n\n`;
+    result += formatAsText(obj.patches);
+    result += '\n';
+  }
+  return result || formatAsText(data);
+}
+
+interface LintSummary {
+  errors: number;
+  warnings: number;
+  infos: number;
+}
+
+interface LintFinding {
+  severity: string;
+  message: string;
+  path?: string;
+}
+
+function isLintOutput(obj: Record<string, unknown>): boolean {
+  if (!Array.isArray(obj.findings)) return false;
+  if (typeof obj.summary !== 'object' || obj.summary === null) return false;
+  const s = obj.summary as Record<string, unknown>;
+  return typeof s.errors === 'number'
+    && typeof s.warnings === 'number'
+    && typeof s.infos === 'number';
+}
+
+function formatLintAsMarkdown(obj: Record<string, unknown>): string {
+  const summary = obj.summary as LintSummary;
+  const findings = obj.findings as LintFinding[];
+
+  let result = '# Lint Report\n\n';
+  result += `**${summary.errors} errors**, **${summary.warnings} warnings**, **${summary.infos} infos**\n`;
+
+  if (findings.length > 0) {
+    result += '\n## Findings\n\n';
+    for (const f of findings) {
+      const location = f.path ? ` \`${f.path}\`:` : ':';
+      result += `- **${f.severity}**${location} ${f.message}\n`;
     }
-    return result || formatAsText(data);
   }
-  return String(data);
+
+  return result;
 }
 
 function formatAsText(data: unknown, indent = 0): string {