ExceptionsManager: Minor Code Cleanup

Summary:
Cleans up `reactConsoleErrorHandler` in `ExceptionsManager` using modern language features, and fixes a minor edge case with how warning-like errors are handled.

Changelog:
[General][Fixed] - Avoid downgrading `console.error` when passed warning-like objects.

Reviewed By: GijsWeterings

Differential Revision: D28418488

fbshipit-source-id: 394e8608c2c81c794c9a0fc155142dcfcfe1c661

Libraries/Core/ExceptionsManager.js

@@ -175,9 +175,9 @@ function handleException(e: mixed, isFatal: boolean) {
  }
 }
 
-function reactConsoleErrorHandler() {
+function reactConsoleErrorHandler(...args) {
  // bubble up to any original handlers
- console._errorOriginal.apply(console, arguments);
+ console._errorOriginal(...args);
  if (!console.reportErrorsAsExceptions) {
  return;
  }
@@ -213,31 +213,33 @@ function reactConsoleErrorHandler() {
  return;
  }
 
- if (arguments[0] && arguments[0].stack) {
+ let error;
+
+ const firstArg = args[0];
+ if (firstArg?.stack) {
  // reportException will console.error this with high enough fidelity.
- reportException(
- arguments[0],
- /* isFatal */ false,
- /*reportToConsole*/ false,
- );
+ error = firstArg;
  } else {
  const stringifySafe = require('../Utilities/stringifySafe').default;
- const str = Array.prototype.map
- .call(arguments, value =>
- typeof value === 'string' ? value : stringifySafe(value),
- )
- .join(' ');
-
- if (str.slice(0, 9) === 'Warning: ') {
+ if (typeof firstArg === 'string' && firstArg.startsWith('Warning: ')) {
  // React warnings use console.error so that a stack trace is shown, but
  // we don't (currently) want these to show a redbox
  // (Note: Logic duplicated in polyfills/console.js.)
  return;
  }
- const error: ExtendedError = new SyntheticError(str);
+ const message = args
+ .map(arg => (typeof arg === 'string' ? arg : stringifySafe(arg)))
+ .join(' ');
+
+ error = new SyntheticError(message);
  error.name = 'console.error';
- reportException(error, /* isFatal */ false, /*reportToConsole*/ false);
  }
+
+ reportException(
+ error,
+ false, // isFatal
+ false, // reportToConsole
+ );
 }
 
 /**

Libraries/Core/__tests__/ExceptionsManager-test.js

@@ -358,6 +358,18 @@ describe('ExceptionsManager', () => {
  expect(mockError.mock.calls[0]).toEqual(args);
  });
 
+ test('logging a warning-looking object', () => {
+ // Forces `strignifySafe` to invoke `toString()`.
+ const object = {toString: () => 'Warning: Some error may have happened'};
+ object.cycle = object;
+
+ const args = [object];
+
+ console.error(...args);
+
+ expect(nativeReportException).toHaveBeenCalled();
+ });
+
  test('reportErrorsAsExceptions = false', () => {
  console.reportErrorsAsExceptions = false;
  const message = 'Some error happened';