feat: warn when there are multiple configs

e2e/Utils.ts

@@ -176,20 +176,23 @@ interface JestPackageJson extends PackageJson {
 }
 
 const DEFAULT_PACKAGE_JSON: JestPackageJson = {
-  description: 'THIS IS AN AUTOGENERATED FILE AND SHOULD NOT BE ADDED TO GIT',
   jest: {
     testEnvironment: 'node',
   },
 };
 
 export const createEmptyPackage = (
   directory: Config.Path,
-  packageJson = DEFAULT_PACKAGE_JSON,
+  packageJson: PackageJson = DEFAULT_PACKAGE_JSON,
 ) => {
+  const packageJsonWithDefaults = {
+    ...packageJson,
+    description: 'THIS IS AN AUTOGENERATED FILE AND SHOULD NOT BE ADDED TO GIT',
+  };
   fs.mkdirSync(directory, {recursive: true});
   fs.writeFileSync(
     path.resolve(directory, 'package.json'),
-    JSON.stringify(packageJson, null, 2),
+    JSON.stringify(packageJsonWithDefaults, null, 2),
   );
 };
 

e2e/__tests__/__snapshots__/multipleConfigs.ts.snap

@@ -0,0 +1,34 @@
+// Jest Snapshot v1, https://goo.gl/fbAQLP
+
+exports[`multiple configs will throw matching error 1`] = `
+"● Multiple configurations found:
+    * <rootDir>/e2e/multiple-configs/jest.config.js
+    * <rootDir>/e2e/multiple-configs/jest.config.json
+    * <rootDir>/e2e/multiple-configs/package.json
+
+  Implicit config resolution does not allow multiple configuration files.
+  Either remove unused config files or select one explicitly with \`--config\`.
+
+  Configuration Documentation:
+  https://jestjs.io/docs/configuration.html
+● Multiple configurations found:
+    * <rootDir>/e2e/multiple-configs/jest.config.js
+    * <rootDir>/e2e/multiple-configs/jest.config.json
+    * <rootDir>/e2e/multiple-configs/package.json
+
+  Implicit config resolution does not allow multiple configuration files.
+  Either remove unused config files or select one explicitly with \`--config\`.
+
+  Configuration Documentation:
+  https://jestjs.io/docs/configuration.html
+PASS Config from js file __tests__/test.js
+  ✓ dummy test"
+`;
+
+exports[`multiple configs will throw matching error 2`] = `
+"Test Suites: 1 passed, 1 total
+Tests:       1 passed, 1 total
+Snapshots:   0 total
+Time:        <<REPLACED>>
+Ran all test suites."
+`;

e2e/__tests__/configOverride.test.ts

@@ -0,0 +1,24 @@
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates. All Rights Reserved.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+import {getConfig} from '../runJest';
+
+test('reads config from cjs file', () => {
+  const {configs} = getConfig(
+    'config-override',
+    ['--config', 'different-config.json'],
+    {
+      skipPkgJsonCheck: true,
+    },
+  );
+
+  expect(configs).toHaveLength(1);
+  expect(configs[0].displayName).toEqual({
+    color: 'white',
+    name: 'Config from different-config.json file',
+  });
+});

e2e/__tests__/dependencyClash.test.ts

@@ -18,7 +18,7 @@ const hasteImplModulePath = path
 
 beforeEach(() => {
   cleanup(tempDir);
-  createEmptyPackage(tempDir);
+  createEmptyPackage(tempDir, {});
 });
 
 // This test case is checking that when having both

e2e/__tests__/multipleConfigs.ts

@@ -0,0 +1,41 @@
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates. All Rights Reserved.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+import * as path from 'path';
+import {extractSummary} from '../Utils';
+import runJest from '../runJest';
+
+const MULTIPLE_CONFIGS_WARNING_TEXT = 'Multiple configurations found';
+
+test('multiple configs will throw matching error', () => {
+  const rootDir = path.resolve(__dirname, '..', '..');
+  const {exitCode, stderr} = runJest('multiple-configs', [], {
+    skipPkgJsonCheck: true,
+  });
+
+  expect(exitCode).toBe(0);
+  expect(stderr).toContain(MULTIPLE_CONFIGS_WARNING_TEXT);
+
+  const cleanStdErr = stderr.replace(new RegExp(rootDir, 'g'), '<rootDir>');
+  const {rest, summary} = extractSummary(cleanStdErr);
+
+  expect(rest).toMatchSnapshot();
+  expect(summary).toMatchSnapshot();
+});
+
+test('multiple configs error can be remove by --config', () => {
+  const {exitCode, stderr} = runJest(
+    'multiple-configs',
+    ['--config', 'jest.config.json'],
+    {
+      skipPkgJsonCheck: true,
+    },
+  );
+
+  expect(exitCode).toBe(0);
+  expect(stderr).not.toContain(MULTIPLE_CONFIGS_WARNING_TEXT);
+});

e2e/config-override/__tests__/test.js

@@ -0,0 +1,10 @@
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates. All Rights Reserved.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+test('dummy test', () => {
+  expect(1).toBe(1);
+});

e2e/config-override/different-config.json

@@ -0,0 +1,3 @@
+{
+  "displayName": "Config from different-config.json file"
+}

e2e/config-override/jest.config.json

@@ -0,0 +1,3 @@
+{
+  "displayName": "Config from json file"
+}

e2e/config-override/package.json

@@ -0,0 +1,3 @@
+{
+  "name": "config-override"
+}

e2e/esm-config/cjs/package.json

@@ -1,3 +1,3 @@
 {
-  "jest": {}
+  "name": "cjs-config"
 }

e2e/esm-config/mjs/package.json

@@ -1,3 +1,3 @@
 {
-  "jest": {}
+  "name": "mjs-config"
 }

e2e/multiple-configs/__tests__/test.js

@@ -0,0 +1,10 @@
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates. All Rights Reserved.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+test('dummy test', () => {
+  expect(1).toBe(1);
+});

e2e/multiple-configs/jest.config.js

@@ -0,0 +1,3 @@
+module.exports = {
+  displayName: 'Config from js file',
+};

e2e/multiple-configs/jest.config.json

@@ -0,0 +1,3 @@
+{
+  "displayName": "Config from json file"
+}

e2e/multiple-configs/package.json

@@ -0,0 +1,5 @@
+{
+  "jest": {
+    "displayName": "Config from package.json file"
+  }
+}

packages/jest-config/src/__tests__/resolveConfigPath.test.ts

@@ -14,6 +14,17 @@ import resolveConfigPath from '../resolveConfigPath';
 const DIR = path.resolve(tmpdir(), 'resolve_config_path_test');
 const ERROR_PATTERN = /Could not find a config file based on provided values/;
 const NO_ROOT_DIR_ERROR_PATTERN = /Can't find a root directory/;
+const MULTIPLE_CONFIGS_ERROR_PATTERN = /Multiple configurations found/;
+
+const mockConsoleWarn = () => {
+  jest.spyOn(console, 'warn');
+  const mockedConsoleWarn = console.warn as jest.Mock<void, Array<any>>;
+
+  // We will mock console.warn because it would produce a lot of noise in the tests
+  mockedConsoleWarn.mockImplementation(() => {});
+
+  return mockedConsoleWarn;
+};
 
 beforeEach(() => cleanup(DIR));
 afterEach(() => cleanup(DIR));
@@ -45,6 +56,8 @@ describe.each(JEST_CONFIG_EXT_ORDER.slice(0))(
     });
 
     test(`directory path with "${extension}"`, () => {
+      const mockedConsoleWarn = mockConsoleWarn();
+
       const relativePackageJsonPath = 'a/b/c/package.json';
       const absolutePackageJsonPath = path.resolve(
         DIR,
@@ -53,9 +66,9 @@ describe.each(JEST_CONFIG_EXT_ORDER.slice(0))(
       const relativeJestConfigPath = `a/b/c/jest.config${extension}`;
       const absoluteJestConfigPath = path.resolve(DIR, relativeJestConfigPath);
 
+      // no configs yet. should throw
       writeFiles(DIR, {[`a/b/c/some_random_file${extension}`]: ''});
 
-      // no configs yet. should throw
       expect(() =>
         // absolute
         resolveConfigPath(path.dirname(absoluteJestConfigPath), DIR),
@@ -68,6 +81,7 @@ describe.each(JEST_CONFIG_EXT_ORDER.slice(0))(
 
       writeFiles(DIR, {[relativePackageJsonPath]: ''});
 
+      mockedConsoleWarn.mockClear();
       // absolute
       expect(
         resolveConfigPath(path.dirname(absolutePackageJsonPath), DIR),
@@ -77,20 +91,45 @@ describe.each(JEST_CONFIG_EXT_ORDER.slice(0))(
       expect(
         resolveConfigPath(path.dirname(relativePackageJsonPath), DIR),
       ).toBe(absolutePackageJsonPath);
+      expect(mockedConsoleWarn).not.toBeCalled();
 
+      // jest.config.js takes precedence
       writeFiles(DIR, {[relativeJestConfigPath]: ''});
 
-      // jest.config.js takes precedence
+      mockedConsoleWarn.mockClear();
+      // absolute
+      expect(
+        resolveConfigPath(path.dirname(absolutePackageJsonPath), DIR),
+      ).toBe(absoluteJestConfigPath);
+
+      // relative
+      expect(
+        resolveConfigPath(path.dirname(relativePackageJsonPath), DIR),
+      ).toBe(absoluteJestConfigPath);
+      expect(mockedConsoleWarn).not.toBeCalled();
+
+      // jest.config.js and package.json with 'jest' cannot be used together
+      writeFiles(DIR, {[relativePackageJsonPath]: JSON.stringify({jest: {}})});
 
       // absolute
+      mockedConsoleWarn.mockClear();
       expect(
         resolveConfigPath(path.dirname(absolutePackageJsonPath), DIR),
       ).toBe(absoluteJestConfigPath);
+      expect(mockedConsoleWarn).toBeCalledTimes(1);
+      expect(mockedConsoleWarn.mock.calls[0].join()).toMatch(
+        MULTIPLE_CONFIGS_ERROR_PATTERN,
+      );
 
       // relative
+      mockedConsoleWarn.mockClear();
       expect(
         resolveConfigPath(path.dirname(relativePackageJsonPath), DIR),
       ).toBe(absoluteJestConfigPath);
+      expect(mockedConsoleWarn).toBeCalledTimes(1);
+      expect(mockedConsoleWarn.mock.calls[0].join()).toMatch(
+        MULTIPLE_CONFIGS_ERROR_PATTERN,
+      );
 
       expect(() => {
         resolveConfigPath(
@@ -101,3 +140,47 @@ describe.each(JEST_CONFIG_EXT_ORDER.slice(0))(
     });
   },
 );
+
+const pickPairsWithSameOrder = <T>(array: ReadonlyArray<T>) =>
+  array
+    .map((value1, idx, arr) =>
+      arr.slice(idx + 1).map(value2 => [value1, value2]),
+    )
+    .flat();
+
+test('pickPairsWithSameOrder', () => {
+  expect(pickPairsWithSameOrder([1, 2, 3])).toStrictEqual([
+    [1, 2],
+    [1, 3],
+    [2, 3],
+  ]);
+});
+
+describe.each(pickPairsWithSameOrder(JEST_CONFIG_EXT_ORDER))(
+  'Using multiple configs shows warning',
+  (extension1, extension2) => {
+    test(`Using jest.config${extension1} and jest.config${extension2} shows warning`, () => {
+      const mockedConsoleWarn = mockConsoleWarn();
+
+      const relativeJestConfigPaths = [
+        `a/b/c/jest.config${extension1}`,
+        `a/b/c/jest.config${extension2}`,
+      ];
+
+      writeFiles(DIR, {
+        [relativeJestConfigPaths[0]]: '',
+        [relativeJestConfigPaths[1]]: '',
+      });
+
+      // multiple configs here, should print warning
+      mockedConsoleWarn.mockClear();
+      expect(
+        resolveConfigPath(path.dirname(relativeJestConfigPaths[0]), DIR),
+      ).toBe(path.resolve(DIR, relativeJestConfigPaths[0]));
+      expect(mockedConsoleWarn).toBeCalledTimes(1);
+      expect(mockedConsoleWarn.mock.calls[0].join()).toMatch(
+        MULTIPLE_CONFIGS_ERROR_PATTERN,
+      );
+    });
+  },
+);