disallow console.error

Summary:
This method can be used in a test to ensure that there is no unexpected console errors are logged.

We should use `warning` / `invariant` in the Relay to inform developers about runtime exceptions/errors.

Directly using `console.error` makes the output in the tests very hard to read.

Reviewed By: josephsavona

Differential Revision: D34276063

fbshipit-source-id: 9265b2c701706adde9bcfefddd8614ed9f4b6b26

packages/relay-test-utils-internal/consoleError.js

@@ -0,0 +1,42 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @emails oncall+relay
+ * @flow strict-local
+ * @format
+ */
+
+'use strict';
+
+/* global jest, afterEach */
+
+let installed = false;
+
+/**
+ * Similar to disallowWarnings.
+ * This method mocks the console.error and throws in the error is printed in the console.
+ */
+function disallowConsoleErrors(): void {
+  if (installed) {
+    throw new Error('`disallowConsoleErrors` should be called at most once');
+  }
+  installed = true;
+  let errors = [];
+  jest.spyOn(console, 'error').mockImplementation(message => {
+    errors.push(`Unexpected \`console.error\`:\n${message}.`);
+  });
+  afterEach(() => {
+    if (errors.length > 0) {
+      const message = errors.join('\n');
+      errors = [];
+      throw new Error(message);
+    }
+  });
+}
+
+module.exports = {
+  disallowConsoleErrors,
+};

packages/relay-test-utils-internal/index.js

@@ -12,6 +12,7 @@
 
 'use strict';
 
+const {disallowConsoleErrors} = require('./consoleError');
 const describeWithFeatureFlags = require('./describeWithFeatureFlags');
 const {
   FIXTURE_TAG,
@@ -50,10 +51,11 @@ module.exports = {
   cannotReadPropertyOfUndefined__DEPRECATED,
   createMockEnvironment,
   describeWithFeatureFlags,
+  disallowConsoleErrors,
+  disallowWarnings,
   expectToWarn,
   expectToWarnMany,
   expectWarningWillFire,
-  disallowWarnings,
   FIXTURE_TAG,
   generateTestsFromFixtures,
   matchers: Matchers,