feat(utils): helper function to convert unknown errors to string

packages/utils/src/index.ts

@@ -1,5 +1,6 @@
 export { exists } from '@code-pushup/models';
 export { Diff, comparePairs, matchArrayItemsByKey } from './lib/diff';
+export { stringifyError } from './lib/errors';
 export {
   ProcessConfig,
   ProcessError,

packages/utils/src/lib/errors.ts

@@ -0,0 +1,13 @@
+export function stringifyError(error: unknown): string {
+  // TODO: special handling for ZodError instances
+  if (error instanceof Error) {
+    if (error.name === 'Error' || error.message.startsWith(error.name)) {
+      return error.message;
+    }
+    return `${error.name}: ${error.message}`;
+  }
+  if (typeof error === 'string') {
+    return error;
+  }
+  return JSON.stringify(error);
+}

packages/utils/src/lib/errors.unit.test.ts

@@ -0,0 +1,25 @@
+import { stringifyError } from './errors';
+
+describe('stringifyError', () => {
+  it('should use only message from plain Error instance', () => {
+    expect(stringifyError(new Error('something went wrong'))).toBe(
+      'something went wrong',
+    );
+  });
+
+  it('should use class name and message from Error extensions', () => {
+    expect(stringifyError(new TypeError('invalid value'))).toBe(
+      'TypeError: invalid value',
+    );
+  });
+
+  it('should keep strings "as is"', () => {
+    expect(stringifyError('something went wrong')).toBe('something went wrong');
+  });
+
+  it('should format objects as JSON', () => {
+    expect(stringifyError({ status: 400, statusText: 'Bad Request' })).toBe(
+      '{"status":400,"statusText":"Bad Request"}',
+    );
+  });
+});