fix: false positive in fallback mode (#57)

src/environment-hooks.ts

@@ -2,7 +2,7 @@ import { inspect } from 'util';
 import type { EnvironmentContext, JestEnvironment, JestEnvironmentConfig } from '@jest/environment';
 import type { Circus } from '@jest/types';
 import { JestMetadataError } from './errors';
-import { realm, injectRealmIntoSandbox } from './realms';
+import { injectRealmIntoSandbox, realm, detectDuplicateRealms } from './realms';
 import { jestUtils, SemiAsyncEmitter } from './utils';
 
 const emitterMap: WeakMap<object, SemiAsyncEmitter<ForwardedCircusEvent>> = new WeakMap();
@@ -12,6 +12,7 @@ export function onTestEnvironmentCreate(
   jestEnvironmentConfig: JestEnvironmentConfig,
   environmentContext: EnvironmentContext,
 ): void {
+  detectDuplicateRealms(true);
   injectRealmIntoSandbox(jestEnvironment.global, realm);
   const testFilePath = environmentContext.testPath;
   realm.environmentHandler.handleEnvironmentCreated(testFilePath);
@@ -103,6 +104,8 @@ export async function onTestEnvironmentSetup(_env: JestEnvironment): Promise<voi
 }
 
 export async function onTestEnvironmentTeardown(_env: JestEnvironment): Promise<void> {
+  detectDuplicateRealms(false);
+
   if (realm.type === 'child_process') {
     await realm.ipc.stop();
   }

src/realms/detect.ts

@@ -28,10 +28,27 @@ export function injectRealmIntoSandbox(sandbox: any, realm: ProcessRealm): Proce
   return realm;
 }
 
+/**
+ * Workaround for the fallback mode, when Jest uses jest-environment-node.
+ * Jest blindly copies `globalThis` into the sandbox, so it is not enough to
+ * simply check that __JEST_METADATA_SANDBOX__ is not truthy.
+ *
+ * This is especially bad in Jest's single worker mode, because
+ * reporter's globalThis === testEnvironment's globalThis == sandbox.
+ *
+ * This hook is enabled after the copying happens, and disabled at later stages
+ * when all potentially conflicting packages are loaded. It is not easy to
+ * grasp, but it works.
+ */
+export function detectDuplicateRealms(enabled: boolean): void {
+  const globalAny = globalThis as any;
+  globalAny.__JEST_METADATA_SANDBOX__ = enabled ? false : undefined;
+}
+
 export function getSandboxedRealm(): ProcessRealm | undefined {
   const globalAny = globalThis as any;
   const realm = globalAny.__JEST_METADATA__;
-  if (realm && !globalAny.__JEST_METADATA_SANDBOX__) {
+  if (realm && globalAny.__JEST_METADATA_SANDBOX__ === false) {
     console.warn(
       '[jest-metadata] Detected duplicate jest-metadata package in the same process. This may lead to unexpected behavior.',
     );

src/realms/index.ts

@@ -1,4 +1,4 @@
-export { injectRealmIntoSandbox } from './detect';
+export { injectRealmIntoSandbox, detectDuplicateRealms } from './detect';
 export { default as realm } from './realm';
 export type { ParentProcessRealm } from './ParentProcessRealm';
 export type { ChildProcessRealm } from './ChildProcessRealm';

src/reporter.ts

@@ -10,11 +10,13 @@ import type {
   TestResult,
 } from '@jest/reporters';
 import { JestMetadataError } from './errors';
-import { realm as unknownRealm } from './realms';
+import { detectDuplicateRealms, realm as unknownRealm } from './realms';
 import type { ParentProcessRealm } from './realms';
 
 const realm = unknownRealm as ParentProcessRealm;
 
+detectDuplicateRealms(true);
+
 export const query = realm.query;
 
 /**
@@ -32,6 +34,7 @@ export class JestMetadataReporter implements Reporter {
   }
 
   onRunStart(_results: AggregatedResult, _options: ReporterOnStartOptions): Promise<void> {
+    detectDuplicateRealms(false);
     return realm.reporterServer.onRunStart();
   }