fix: silently ignore non-zero post-processor exit codes

Post-processors like ESLint and Oxfmt exit non-zero for non-fatal
reasons (all files ignored, no matching files). Warnings from
console.warn break CI pipelines that treat stderr as errors. Only
actual spawn failures (ENOENT) are reported.

Author: pullfrog[bot]

packages/shared/src/config/output/__tests__/postprocess.test.ts

@@ -122,48 +122,28 @@ describe('postprocessOutput', () => {
     ).toThrow('Post-processor "My Formatter" failed to run: spawnSync my-formatter ENOENT');
   });
 
-  it('should warn when the process exits with a non-zero status code', () => {
-    mockSync.mockReturnValue({ error: undefined, status: 1, stderr: Buffer.from('') } as any);
-    const warnSpy = vi.spyOn(console, 'warn').mockImplementation(() => {});
-
-    postprocessOutput(
-      { ...baseConfig, postProcess: [{ args: ['{{path}}'], command: 'prettier' }] },
-      noopPostProcessors,
-      '',
-    );
-
-    expect(warnSpy).toHaveBeenCalledWith(
-      expect.stringContaining('Post-processor "prettier" exited with code 1'),
-    );
-    warnSpy.mockRestore();
-  });
-
-  it('should include stderr in warning when process exits with non-zero status', () => {
+  it('should silently ignore non-zero exit codes', () => {
     mockSync.mockReturnValue({
       error: undefined,
-      status: 2,
-      stderr: Buffer.from('error: file not found'),
+      status: 1,
+      stderr: Buffer.from('some error'),
     } as any);
     const warnSpy = vi.spyOn(console, 'warn').mockImplementation(() => {});
 
     postprocessOutput(
-      { ...baseConfig, postProcess: [{ args: ['{{path}}'], command: 'biome' }] },
+      { ...baseConfig, postProcess: [{ args: ['{{path}}'], command: 'prettier' }] },
       noopPostProcessors,
       '',
     );
 
-    expect(warnSpy).toHaveBeenCalledTimes(1);
-    const warnArg = warnSpy.mock.calls[0]![0] as string;
-    expect(warnArg).toContain('Post-processor "biome" exited with code 2:');
-    expect(warnArg).toContain('error: file not found');
+    expect(warnSpy).not.toHaveBeenCalled();
     warnSpy.mockRestore();
   });
 
   it('should continue processing after a non-zero exit code', () => {
     mockSync
       .mockReturnValueOnce({ error: undefined, status: 1, stderr: Buffer.from('') } as any)
       .mockReturnValueOnce({ error: undefined, status: 0 } as any);
-    vi.spyOn(console, 'warn').mockImplementation(() => {});
 
     postprocessOutput(
       {

packages/shared/src/config/output/postprocess.ts

@@ -79,13 +79,9 @@ export function postprocessOutput(
       throw new ConfigError(`Post-processor "${name}" failed to run: ${result.error.message}`);
     }
 
-    if (result.status !== null && result.status !== 0) {
-      let message = `Post-processor "${name}" exited with code ${result.status}`;
-      const stderr = result.stderr?.toString().trim();
-      if (stderr) {
-        message += `:\n${stderr}`;
-      }
-      console.warn(`${jobPrefix}${colors.yellow(`⚠️ ${message}`)}`);
-    }
+    // non-zero exit codes are silently ignored — post-processors like
+    // ESLint and Oxfmt exit non-zero for non-fatal reasons (e.g. all
+    // files ignored, no matching files) and warnings break CI pipelines
+    // that treat any stderr output as an error
   }
 }