chore: replace as many Object.assign with object spread as possible

CHANGELOG.md

@@ -153,6 +153,7 @@
 - `[*]` Standardize file names ([#7316](https://github.com/facebook/jest/pull/7316), [#7266](https://github.com/facebook/jest/pull/7266), [#7238](https://github.com/facebook/jest/pull/7238), [#7314](https://github.com/facebook/jest/pull/7314), [#7467](https://github.com/facebook/jest/pull/7467), [#7464](https://github.com/facebook/jest/pull/7464)), [#7471](https://github.com/facebook/jest/pull/7471))
 - `[docs]` Add `testPathIgnorePatterns` in CLI documentation ([#7440](https://github.com/facebook/jest/pull/7440))
 - `[docs]` Removed misleading text about `describe()` grouping together tests into a test suite ([#7434](https://github.com/facebook/jest/pull/7434))
+- `[*]` Replace as many `Object.assign` with object spread as possible
 
 ### Performance
 

TestUtils.js

@@ -134,7 +134,7 @@ export const makeGlobalConfig = (overrides: Object = {}): GlobalConfig => {
     `);
   }
 
-  return Object.assign({}, DEFAULT_GLOBAL_CONFIG, overrides);
+  return {...DEFAULT_GLOBAL_CONFIG, ...overrides};
 };
 
 export const makeProjectConfig = (overrides: Object = {}): ProjectConfig => {
@@ -148,5 +148,5 @@ export const makeProjectConfig = (overrides: Object = {}): ProjectConfig => {
     `);
   }
 
-  return Object.assign({}, DEFAULT_PROJECT_CONFIG, overrides);
+  return {...DEFAULT_GLOBAL_CONFIG, ...overrides};
 };

e2e/runJest.js

@@ -49,7 +49,7 @@ export default function runJest(
     );
   }
 
-  const env = Object.assign({}, process.env, {FORCE_COLOR: 0});
+  const env = {...process.env, FORCE_COLOR: 0};
   if (options.nodePath) env['NODE_PATH'] = options.nodePath;
   const result = spawnSync(JEST_PATH, args || [], {
     cwd: dir,
@@ -119,7 +119,7 @@ export const until = async function(
     );
   }
 
-  const env = Object.assign({}, process.env, {FORCE_COLOR: 0});
+  const env = {...process.env, FORCE_COLOR: 0};
   if (options.nodePath) env['NODE_PATH'] = options.nodePath;
 
   const jestPromise = execa(JEST_PATH, args || [], {

examples/module-mock/__tests__/partial_mock.js

@@ -12,10 +12,12 @@ jest.mock('../fruit', () => {
   const mockedModule = jest.genMockFromModule('../fruit');
 
   //Mock the default export and named export 'apple'.
-  return Object.assign({}, mockedModule, originalModule, {
+  return {
+    ...mockedModule,
+    ...originalModule,
     apple: 'mocked apple',
     default: jest.fn(() => 'mocked fruit'),
-  });
+  };
 });
 
 it('does a partial mock', () => {

packages/expect/src/index.js

@@ -234,27 +234,22 @@ const makeThrowingMatcher = (
 ): ThrowingMatcherFn =>
   function throwingMatcher(...args): any {
     let throws = true;
-    const utils = Object.assign({}, matcherUtils, {
-      iterableEquality,
-      subsetEquality,
-    });
+    const utils = {...matcherUtils, iterableEquality, subsetEquality};
 
-    const matcherContext: MatcherState = Object.assign(
+    const matcherContext: MatcherState = {
       // When throws is disabled, the matcher will not throw errors during test
       // execution but instead add them to the global matcher state. If a
       // matcher throws, test execution is normally stopped immediately. The
       // snapshot matcher uses it because we want to log all snapshot
       // failures in a test.
-      {dontThrow: () => (throws = false)},
-      getState(),
-      {
-        equals,
-        error: err,
-        isNot,
-        promise,
-        utils,
-      },
-    );
+      dontThrow: () => (throws = false),
+      ...getState(),
+      equals,
+      error: err,
+      isNot,
+      promise,
+      utils,
+    };
 
     const processResult = (result: SyncExpectationResult) => {
       _validateResult(result);

packages/jest-changed-files/src/hg.js

@@ -13,9 +13,7 @@ import type {Options, SCMAdapter} from 'types/ChangedFiles';
 import path from 'path';
 import execa from 'execa';
 
-const env = Object.assign({}, process.env, {
-  HGPLAIN: 1,
-});
+const env = {...process.env, HGPLAIN: 1};
 
 const ANCESTORS = [
   // Parent commit to this one.

packages/jest-changed-files/src/index.js

@@ -27,7 +27,7 @@ export const getChangedFilesForRoots = async (
 ): ChangedFilesPromise => {
   const repos = await findRepos(roots);
 
-  const changedFilesOptions = Object.assign({}, {includePaths: roots}, options);
+  const changedFilesOptions = {includePaths: roots, ...options};
 
   const gitPromises = Array.from(repos.git).map(repo =>
     git.findChangedFiles(repo, changedFilesOptions),

packages/jest-cli/src/FailedTestsCache.js

@@ -41,8 +41,7 @@ export default class FailedTestsCache {
     if (!this._enabledTestsMap) {
       return globalConfig;
     }
-    // $FlowFixMe Object.assign
-    const newConfig: GlobalConfig = Object.assign({}, globalConfig);
+    const newConfig: GlobalConfig = {...globalConfig};
     newConfig.enabledTestsMap = this._enabledTestsMap;
     return Object.freeze(newConfig);
   }

packages/jest-cli/src/SearchSource.js

@@ -275,10 +275,10 @@ export default class SearchSource {
         filterResult.filtered.map(result => result.test),
       );
 
-      // $FlowFixMe: Object.assign with empty object causes troubles to Flow.
-      return Object.assign({}, searchResult, {
+      return {
+        ...searchResult,
         tests: tests.filter(test => filteredSet.has(test.path)),
-      });
+      };
     }
 
     return searchResult;

packages/jest-cli/src/__tests__/notify_reporter.test.js

@@ -69,11 +69,7 @@ const notifyEvents = [
 ];
 
 test('.addReporter() .removeReporter()', () => {
-  const scheduler = new TestScheduler(
-    {},
-    {},
-    Object.assign({}, initialContext),
-  );
+  const scheduler = new TestScheduler({}, {}, {...initialContext});
   const reporter = new NotifyReporter();
   scheduler.addReporter(reporter);
   expect(scheduler._dispatcher._reporters).toContain(reporter);

packages/jest-cli/src/__tests__/runJestWithCoverage.test.js

@@ -70,13 +70,12 @@ describe('collectCoverageFrom patterns', () => {
   it('should apply collectCoverageFrom patterns coming from SearchSource', async () => {
     expect.assertions(1);
 
-    await runJest(
-      Object.assign({}, defaults, {
-        globalConfig: {
-          rootDir: '',
-        },
-      }),
-    );
+    await runJest({
+      ...defaults,
+      globalConfig: {
+        rootDir: '',
+      },
+    });
     expect(globalConfig.collectCoverageFrom).toEqual([
       'foo.js',
       'dont/cover.js',
@@ -86,29 +85,27 @@ describe('collectCoverageFrom patterns', () => {
   it('excludes coverage from files outside the global collectCoverageFrom config', async () => {
     expect.assertions(1);
 
-    await runJest(
-      Object.assign({}, defaults, {
-        globalConfig: {
-          collectCoverageFrom: ['**/dont/*.js'],
-          rootDir: '',
-        },
-      }),
-    );
+    await runJest({
+      ...defaults,
+      globalConfig: {
+        collectCoverageFrom: ['**/dont/*.js'],
+        rootDir: '',
+      },
+    });
     expect(globalConfig.collectCoverageFrom).toEqual(['dont/cover.js']);
   });
 
   it('respects coveragePathIgnorePatterns', async () => {
     expect.assertions(1);
 
-    await runJest(
-      Object.assign({}, defaults, {
-        globalConfig: {
-          collectCoverageFrom: ['**/*.js'],
-          coveragePathIgnorePatterns: ['dont'],
-          rootDir: '',
-        },
-      }),
-    );
+    await runJest({
+      ...defaults,
+      globalConfig: {
+        collectCoverageFrom: ['**/*.js'],
+        coveragePathIgnorePatterns: ['dont'],
+        rootDir: '',
+      },
+    });
     expect(globalConfig.collectCoverageFrom).toEqual(['foo.js']);
   });
 });