Change runScript return type to unknown

Author: Mikael Lirbank

packages/jest-environment/src/index.ts

@@ -22,18 +22,23 @@ export type EnvironmentContext = {
 // TODO: type this better: https://nodejs.org/api/modules.html#modules_the_module_wrapper
 type ModuleWrapper = (...args: Array<unknown>) => unknown;
 
+export function hasModuleWrapper(
+  obj: unknown,
+): obj is {[ScriptTransformer.EVAL_RESULT_VARIABLE]: ModuleWrapper} {
+  return (
+    typeof obj === 'object' &&
+    !!obj &&
+    obj.hasOwnProperty(ScriptTransformer.EVAL_RESULT_VARIABLE)
+  );
+}
+
 export declare class JestEnvironment {
   constructor(config: Config.ProjectConfig);
   constructor(config: Config.ProjectConfig, context: EnvironmentContext);
   global: Global.Global;
   fakeTimers: FakeTimers<unknown> | null;
   moduleMocker: ModuleMocker | null;
-  // runScript(
-  //   script: Script,
-  // ): {[ScriptTransformer.EVAL_RESULT_VARIABLE]: ModuleWrapper} | null | unknown;
-  runScript(
-    script: Script,
-  ): {[ScriptTransformer.EVAL_RESULT_VARIABLE]: ModuleWrapper} | null;
+  runScript(script: Script): unknown;
   setup(): Promise<void>;
   teardown(): Promise<void>;
 }

packages/jest-runtime/src/index.ts

@@ -12,6 +12,7 @@ import {
   JestEnvironment,
   LocalModuleRequire,
   Module,
+  hasModuleWrapper
 } from '@jest/environment';
 import jestMock, {MockFunctionMetadata} from 'jest-mock';
 import HasteMap, {ModuleMap} from 'jest-haste-map';
@@ -679,7 +680,7 @@ class Runtime {
 
     const runScript = this._environment.runScript(transformedFile.script);
 
-    if (runScript === null) {
+    if (!hasModuleWrapper(runScript)) {
       this._logFormattedReferenceError(
         'You are trying to `import` a file after the Jest environment has been torn down.',
       );