feat(jest-config): merge preset globals with project globals

CHANGELOG.md

@@ -8,6 +8,7 @@
 - `[expect]` Add `BigInt` support to `toBeGreaterThan`, `toBeGreaterThanOrEqual`, `toBeLessThan` and `toBeLessThanOrEqual` ([#8382](https://github.com/facebook/jest/pull/8382))
 - `[jest-config]` Throw the full error message and stack when a Jest preset is missing a dependency ([#8924](https://github.com/facebook/jest/pull/8924))
 - `[jest-config]` [**BREAKING**] Set default display name color based on runner ([#8689](https://github.com/facebook/jest/pull/8689))
+- `[jest-config]` Merge preset globals with project globals ([#9027](https://github.com/facebook/jest/pull/9027))
 - `[jest-diff]` Add options for colors and symbols ([#8841](https://github.com/facebook/jest/pull/8841))
 - `[jest-diff]` [**BREAKING**] Export as ECMAScript module ([#8873](https://github.com/facebook/jest/pull/8873))
 - `[jest-diff]` Add `includeChangeCounts` and rename `Indicator` options ([#8881](https://github.com/facebook/jest/pull/8881))

packages/jest-config/src/__tests__/normalize.test.js

@@ -1219,6 +1219,62 @@ describe('preset', () => {
   });
 });
 
+describe('preset with globals', () => {
+  beforeEach(() => {
+    const Resolver = require('jest-resolve');
+    Resolver.findNodeModule = jest.fn(name => {
+      if (name === 'global-foo/jest-preset') {
+        return '/node_modules/global-foo/jest-preset.json';
+      }
+
+      return '/node_modules/' + name;
+    });
+    jest.doMock(
+      '/node_modules/global-foo/jest-preset.json',
+      () => ({
+        globals: {
+          config: {
+            hereToStay: 'This should stay here',
+          },
+        },
+      }),
+      {virtual: true},
+    );
+  });
+
+  afterEach(() => {
+    jest.dontMock('/node_modules/global-foo/jest-preset.json');
+  });
+
+  test('should merge the globals preset correctly', () => {
+    const {options} = normalize(
+      {
+        preset: 'global-foo',
+        rootDir: '/root/path/foo',
+        globals: {
+          textValue: 'This is just text',
+          config: {
+            sideBySide: 'This should also live another day',
+          },
+        },
+      },
+      {},
+    );
+
+    expect(options).toEqual(
+      expect.objectContaining({
+        globals: {
+          textValue: 'This is just text',
+          config: {
+            hereToStay: 'This should stay here',
+            sideBySide: 'This should also live another day',
+          },
+        },
+      }),
+    );
+  });
+});
+
 describe('preset without setupFiles', () => {
   let Resolver;
   beforeEach(() => {

packages/jest-config/src/normalize.ts

@@ -73,6 +73,20 @@ const mergeTransformWithPreset = (
   }
 };
 
+const mergeGlobalsWithPreset = (
+  options: Config.InitialOptions,
+  preset: Config.InitialOptions,
+) => {
+  if (options['globals'] && preset['globals']) {
+    for (const p in preset['globals']) {
+      options['globals'][p] = {
+        ...preset['globals'][p],
+        ...options['globals'][p],
+      };
+    }
+  }
+};
+
 const setupPreset = (
   options: Config.InitialOptions,
   optionsPreset: string,
@@ -149,6 +163,7 @@ const setupPreset = (
   }
   mergeModuleNameMapperWithPreset(options, preset);
   mergeTransformWithPreset(options, preset);
+  mergeGlobalsWithPreset(options, preset);
 
   return {...preset, ...options};
 };