fix(testing): handle different jest config files in configurations wh…

…en migrating to inferred (#26591)

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## Current Behavior
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## Expected Behavior
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Fixes #

packages/jest/src/generators/convert-to-inferred/convert-to-inferred.spec.ts

@@ -100,20 +100,19 @@ const defaultTestProjectOptions: TestProjectOptions = {
 function writeJestConfig(
   tree: Tree,
   projectRoot: string,
-  jestConfig: any | undefined
+  jestConfig: any | undefined,
+  configFileName = 'jest.config.js'
 ) {
   jestConfig ??= {
     coverageDirectory: `../../coverage/${projectRoot}`,
   };
   const jestConfigContents = `module.exports = ${JSON.stringify(jestConfig)};`;
 
-  tree.write(`${projectRoot}/jest.config.js`, jestConfigContents);
-  fs.createFileSync(`${projectRoot}/jest.config.js`, jestConfigContents);
-  jest.doMock(
-    join(fs.tempDir, projectRoot, 'jest.config.js'),
-    () => jestConfig,
-    { virtual: true }
-  );
+  tree.write(`${projectRoot}/${configFileName}`, jestConfigContents);
+  fs.createFileSync(`${projectRoot}/${configFileName}`, jestConfigContents);
+  jest.doMock(join(fs.tempDir, projectRoot, configFileName), () => jestConfig, {
+    virtual: true,
+  });
 }
 
 function createTestProject(
@@ -1013,6 +1012,43 @@ describe('Jest - Convert Executors To Plugin', () => {
       const updatedProject2 = readProjectConfiguration(tree, project2.name);
       expect(updatedProject2.targets.test).toStrictEqual(project2TestTarget);
     });
+
+    it('should keep the "jestConfig" and set it to "config" when present in configurations', async () => {
+      const project = createTestProject(tree);
+      project.targets.test.configurations = {
+        production: {
+          jestConfig: `${defaultTestProjectOptions.appRoot}/jest.config.prod.js`,
+        },
+      };
+      updateProjectConfiguration(tree, project.name, project);
+      writeJestConfig(
+        tree,
+        defaultTestProjectOptions.appRoot,
+        undefined,
+        'jest.config.prod.js'
+      );
+      const project2 = createTestProject(tree, {
+        appRoot: 'apps/project2',
+        appName: 'project2',
+      });
+      const project2TestTarget = project2.targets.test;
+
+      await convertToInferred(tree, {
+        project: project.name,
+        skipFormat: true,
+      });
+
+      // assert updated project configuration
+      const updatedProject = readProjectConfiguration(tree, project.name);
+      expect(
+        updatedProject.targets.test.configurations.production
+      ).toStrictEqual({
+        config: `./jest.config.prod.js`,
+      });
+      // assert other projects were not modified
+      const updatedProject2 = readProjectConfiguration(tree, project2.name);
+      expect(updatedProject2.targets.test).toStrictEqual(project2TestTarget);
+    });
   });
 
   describe('all projects', () => {

packages/jest/src/generators/convert-to-inferred/convert-to-inferred.ts

@@ -71,7 +71,7 @@ async function postTargetTransformer(
     );
 
   if (target.options) {
-    await updateOptions(
+    await updateOptionsObject(
       target.options,
       projectDetails.root,
       tree.root,
@@ -81,7 +81,7 @@ async function postTargetTransformer(
 
   if (target.configurations) {
     for (const [configName, config] of Object.entries(target.configurations)) {
-      await updateOptions(
+      await updateConfigurationObject(
         config,
         projectDetails.root,
         tree.root,
@@ -118,7 +118,7 @@ async function postTargetTransformer(
 
 export default convertToInferred;
 
-async function updateOptions(
+async function updateOptionsObject(
   targetOptions: any,
   projectRoot: string,
   workspaceRoot: string,
@@ -130,6 +130,49 @@ async function updateOptions(
   delete targetOptions.jestConfig;
   delete targetOptions.config;
 
+  await updateOptions(
+    targetOptions,
+    projectRoot,
+    workspaceRoot,
+    jestConfigPath
+  );
+}
+
+async function updateConfigurationObject(
+  targetOptions: any,
+  projectRoot: string,
+  workspaceRoot: string,
+  defaultJestConfigPath: string | undefined
+) {
+  const jestConfigPath = targetOptions.jestConfig ?? defaultJestConfigPath;
+
+  if (targetOptions.jestConfig) {
+    targetOptions.config = toProjectRelativePath(
+      targetOptions.jestConfig,
+      projectRoot
+    );
+    delete targetOptions.jestConfig;
+  } else if (targetOptions.config) {
+    targetOptions.config = toProjectRelativePath(
+      targetOptions.config,
+      projectRoot
+    );
+  }
+
+  await updateOptions(
+    targetOptions,
+    projectRoot,
+    workspaceRoot,
+    jestConfigPath
+  );
+}
+
+async function updateOptions(
+  targetOptions: any,
+  projectRoot: string,
+  workspaceRoot: string,
+  jestConfigPath: string | undefined
+) {
   // deprecated and unused
   delete targetOptions.tsConfig;