Feat/load referenced config from packagejson

CHANGELOG.md

@@ -2,6 +2,8 @@
 
 ### Features
 
+- `[jest-config]` Loads `.json` config file from provided path in package.json ([#14044](https://github.com/facebook/jest/pull/14044))
+
 ### Fixes
 
 ### Chore & Maintenance

docs/Configuration.md

@@ -81,6 +81,15 @@ Alternatively Jest's configuration can be defined through the `"jest"` key in th
 }
 ```
 
+Also Jest's configuration json file can be referenced through the `"jest"` key in the `package.json` of your project:
+
+```json title="package.json"
+{
+  "name": "my-project",
+  "jest": "<path_to_config_file.json>"
+}
+```
+
 ## Options
 
 :::info
@@ -1177,6 +1186,7 @@ export default config;
 ```
 
 We hope to support Prettier v3 seamlessly out of the box in a future version of Jest. See [this](https://github.com/jestjs/jest/issues/14305) tracking issue.
+
 </details>
 
 ### `projects` \[array&lt;string | ProjectConfig&gt;]

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

@@ -45,6 +45,57 @@ describe.each(JEST_CONFIG_EXT_ORDER.slice(0))(
       );
     });
 
+    test('file path from "jest" key', () => {
+      // Arrange
+      const anyFileName = `anyJestConfigfile${extension}`;
+      const relativePackageJsonPath = 'a/b/c/package.json';
+      const relativeAnyFilePath = `a/b/c/conf/${anyFileName}`;
+      const absolutePackageJsonPath = path.resolve(
+        DIR,
+        relativePackageJsonPath,
+      );
+      const absoluteAnyFilePath = path.resolve(DIR, relativeAnyFilePath);
+
+      writeFiles(DIR, {
+        'a/b/c/package.json': `{ "jest": "conf/${anyFileName}" }`,
+      });
+      writeFiles(DIR, {[relativeAnyFilePath]: ''});
+
+      // Act
+      const result = resolveConfigPath(
+        path.dirname(absolutePackageJsonPath),
+        DIR,
+      );
+
+      // Assert
+      expect(result).toBe(absoluteAnyFilePath);
+    });
+
+    test('not a file path from "jest" key', () => {
+      // Arrange
+      const anyFileName = `anyJestConfigfile${extension}`;
+      const relativePackageJsonPath = 'a/b/c/package.json';
+      const relativeAnyFilePath = `a/b/c/conf/${anyFileName}`;
+      const absolutePackageJsonPath = path.resolve(
+        DIR,
+        relativePackageJsonPath,
+      );
+
+      writeFiles(DIR, {
+        'a/b/c/package.json': '{ "jest": {"verbose": true} }',
+      });
+      writeFiles(DIR, {[relativeAnyFilePath]: ''});
+
+      // Act
+      const result = resolveConfigPath(
+        path.dirname(absolutePackageJsonPath),
+        DIR,
+      );
+
+      // Assert
+      expect(result).toBe(absolutePackageJsonPath);
+    });
+
     test(`directory path with "${extension}"`, () => {
       const relativePackageJsonPath = 'a/b/c/package.json';
       const absolutePackageJsonPath = path.resolve(

packages/jest-config/src/resolveConfigPath.ts

@@ -75,8 +75,15 @@ const resolveConfigPathByTraversing = (
   ).filter(isFile);
 
   const packageJson = findPackageJson(pathToResolve);
-  if (packageJson && hasPackageJsonJestKey(packageJson)) {
-    configFiles.push(packageJson);
+
+  if (packageJson) {
+    const packageContent = fs.readFileSync(packageJson, 'utf8');
+    const packagePath = path.dirname(packageJson);
+    const resolvedKey = resolveJestKey(packageContent, packagePath);
+
+    if (hasPackageJsonJestKey(packageContent)) {
+      configFiles.push(resolvedKey || packageJson);
+    }
   }
 
   if (!skipMultipleConfigError && configFiles.length > 1) {
@@ -111,10 +118,23 @@ const findPackageJson = (pathToResolve: string) => {
   return undefined;
 };
 
-const hasPackageJsonJestKey = (packagePath: string) => {
-  const content = fs.readFileSync(packagePath, 'utf8');
+const resolveJestKey = (packageContent: any, packagePath: string) => {
+  if (hasPackageJsonJestKey(packageContent)) {
+    const {jest} = JSON.parse(packageContent);
+
+    if (jest && typeof jest === 'string') {
+      const resolvedConfigFile = path.resolve(packagePath, jest);
+
+      return isFile(resolvedConfigFile) ? resolvedConfigFile : undefined;
+    }
+  }
+
+  return undefined;
+};
+
+const hasPackageJsonJestKey = (packageContent: any) => {
   try {
-    return 'jest' in JSON.parse(content);
+    return 'jest' in JSON.parse(packageContent);
   } catch {
     // If package is not a valid JSON
     return false;

website/versioned_docs/version-29.6/Configuration.md

@@ -1177,6 +1177,7 @@ export default config;
 ```
 
 We hope to support Prettier v3 seamlessly out of the box in a future version of Jest. See [this](https://github.com/jestjs/jest/issues/14305) tracking issue.
+
 </details>
 
 ### `projects` \[array&lt;string | ProjectConfig&gt;]