If present, print error.cause.message in top-level error handler (#928)

Author: edwardfoyle

.changeset/honest-pumas-fold.md

@@ -0,0 +1,5 @@
+---
+'@aws-amplify/backend-cli': patch
+---
+
+If present, print error.cause.message in top-level error handler. This gives customers more debugging information when the error cause rather than the error contains the root cause of the issue.

packages/cli/src/error_handler.test.ts

@@ -71,6 +71,21 @@ void describe('generateCommandFailureHandler', () => {
     assert.match(mockPrint.mock.calls[0].arguments[0], new RegExp(errMsg));
     assert.equal(mockPrint.mock.calls[0].arguments[1], COLOR.RED);
   });
+
+  void it('prints error cause message, if any', () => {
+    const errorMessage = 'this is the upstream cause';
+    generateCommandFailureHandler(parser)(
+      '',
+      new Error('some error msg', { cause: new Error(errorMessage) })
+    );
+    assert.equal(mockExit.mock.callCount(), 1);
+    assert.equal(mockPrint.mock.callCount(), 2);
+    assert.match(
+      mockPrint.mock.calls[1].arguments[0],
+      new RegExp(errorMessage)
+    );
+    assert.equal(mockPrint.mock.calls[1].arguments[1], COLOR.RED);
+  });
 });
 
 void describe('attachUnhandledExceptionListeners', { concurrency: 1 }, () => {

packages/cli/src/error_handler.ts

@@ -50,15 +50,15 @@ export const generateCommandFailureHandler = (
    * @param message error message set by the yargs:check validations
    * @param error error thrown by yargs handler
    */
-  const handleCommandFailure = (message: string, error: Error) => {
+  const handleCommandFailure = (message: string, error?: Error) => {
     const printHelp = () => {
       Printer.printNewLine();
       parser.showHelp();
       Printer.printNewLine();
     };
 
     handleError(error, printHelp, message);
-    parser.exit(1, error);
+    parser.exit(1, error || new Error(message));
   };
   return handleCommandFailure;
 };
@@ -71,7 +71,7 @@ export const generateCommandFailureHandler = (
  * (Note that we don't do all of those things yet, but this is where they should go)
  */
 const handleError = (
-  error: Error,
+  error?: Error,
   printMessagePreamble?: () => void,
   message?: string
 ) => {
@@ -87,9 +87,23 @@ const handleError = (
 
   printMessagePreamble?.();
   Printer.print(message || String(error), COLOR.RED);
+  if (errorHasCauseMessage(error)) {
+    Printer.print(error.cause.message, COLOR.RED);
+  }
   Printer.printNewLine();
 };
 
-const isUserForceClosePromptError = (err: Error): boolean => {
-  return err?.message.includes('User force closed the prompt');
+const isUserForceClosePromptError = (err?: Error): boolean => {
+  return !!err && err?.message.includes('User force closed the prompt');
+};
+
+const errorHasCauseMessage = (
+  error?: Error
+): error is Error & { cause: { message: string } } => {
+  return (
+    typeof error?.cause === 'object' &&
+    !!error.cause &&
+    'message' in error.cause &&
+    typeof error.cause.message === 'string'
+  );
 };