feat(test runner): error out when one test file imports another (#21357)

This situation is not supported, and we can now detect it by looking at
collected file dependencies.

Fixes #21270.

packages/playwright-test/src/common/compilationCache.ts

@@ -173,6 +173,10 @@ export function collectAffectedTestFiles(dependency: string, testFileCollector:
   }
 }
 
+export function dependenciesForTestFile(filename: string): Set<string> {
+  return fileDependencies.get(filename) || new Set();
+}
+
 // These two are only used in the dev mode, they are specifically excluding
 // files from packages/playwright*. In production mode, node_modules covers
 // that.

packages/playwright-test/src/runner/loadUtils.ts

@@ -26,6 +26,7 @@ import { buildProjectsClosure, collectFilesForProject, filterProjects } from './
 import { requireOrImport } from '../common/transform';
 import { buildFileSuiteForProject, filterByFocusedLine, filterByTestIds, filterOnly, filterTestsRemoveEmptySuites } from '../common/suiteUtils';
 import { filterForShard } from './testGroups';
+import { dependenciesForTestFile } from '../common/compilationCache';
 
 export async function loadAllTests(mode: 'out-of-process' | 'in-process', config: FullConfigInternal, projectsToIgnore: Set<FullProjectInternal>, fileMatcher: Matcher, errors: TestError[], shouldFilterOnly: boolean): Promise<Suite> {
   const projects = filterProjects(config.projects, config._internal.cliProjectFilter);
@@ -78,7 +79,7 @@ export async function loadAllTests(mode: 'out-of-process' | 'in-process', config
   }
 
   // Load all test files and create a preprocessed root. Child suites are files there.
-  const fileSuits: Suite[] = [];
+  const fileSuites: Suite[] = [];
   {
     const loaderHost = mode === 'out-of-process' ? new OutOfProcessLoaderHost(config) : new InProcessLoaderHost(config);
     const allTestFiles = new Set<string>();
@@ -86,13 +87,28 @@ export async function loadAllTests(mode: 'out-of-process' | 'in-process', config
       files.forEach(file => allTestFiles.add(file));
     for (const file of allTestFiles) {
       const fileSuite = await loaderHost.loadTestFile(file, errors);
-      fileSuits.push(fileSuite);
+      fileSuites.push(fileSuite);
     }
     await loaderHost.stop();
+
+    // Check that no test file imports another test file.
+    // Loader must be stopped first, since it popuplates the dependency tree.
+    for (const file of allTestFiles) {
+      for (const dependency of dependenciesForTestFile(file)) {
+        if (allTestFiles.has(dependency)) {
+          const importer = path.relative(config.rootDir, file);
+          const importee = path.relative(config.rootDir, dependency);
+          errors.push({
+            message: `Error: test file "${importer}" should not import test file "${importee}"`,
+            location: { file, line: 1, column: 1 },
+          });
+        }
+      }
+    }
   }
 
   // Complain about duplicate titles.
-  errors.push(...createDuplicateTitlesErrors(config, fileSuits));
+  errors.push(...createDuplicateTitlesErrors(config, fileSuites));
 
   // Create root suites with clones for the projects.
   const rootSuite = new Suite('', 'root');
@@ -105,7 +121,7 @@ export async function loadAllTests(mode: 'out-of-process' | 'in-process', config
 
   // First iterate leaf projects to focus only, then add all other projects.
   for (const project of topLevelProjects) {
-    const projectSuite = await createProjectSuite(fileSuits, project, { cliFileFilters, cliTitleMatcher, testIdMatcher: config._internal.testIdMatcher }, filesToRunByProject.get(project)!);
+    const projectSuite = await createProjectSuite(fileSuites, project, { cliFileFilters, cliTitleMatcher, testIdMatcher: config._internal.testIdMatcher }, filesToRunByProject.get(project)!);
     if (projectSuite)
       rootSuite._addSuite(projectSuite);
   }
@@ -123,7 +139,7 @@ export async function loadAllTests(mode: 'out-of-process' | 'in-process', config
 
   // Prepend the projects that are dependencies.
   for (const project of dependencyProjects) {
-    const projectSuite = await createProjectSuite(fileSuits, project, { cliFileFilters: [], cliTitleMatcher: undefined }, filesToRunByProject.get(project)!);
+    const projectSuite = await createProjectSuite(fileSuites, project, { cliFileFilters: [], cliTitleMatcher: undefined }, filesToRunByProject.get(project)!);
     if (projectSuite)
       rootSuite._prependSuite(projectSuite);
   }

tests/playwright-test/loader.spec.ts

@@ -641,3 +641,25 @@ test('should support node imports', async ({ runInlineTest, nodeVersion }) => {
   expect(result.passed).toBe(1);
   expect(result.exitCode).toBe(0);
 });
+
+test('should complain when one test file imports another', async ({ runInlineTest }) => {
+  const result = await runInlineTest({
+    'a.test.ts': `
+      import { test, expect } from '@playwright/test';
+      import { foo } from './b.test';
+
+      test('pass1', async () => {
+        expect(foo).toBe('foo');
+      });
+    `,
+    'b.test.ts': `
+      import { test, expect } from '@playwright/test';
+      export const foo = 'foo';
+
+      test('pass2', async () => {
+      });
+    `,
+  });
+  expect(result.exitCode).toBe(1);
+  expect(result.output).toContain(`test file "a.test.ts" should not import test file "b.test.ts"`);
+});