feat: add support for import assertions

CHANGELOG.md

@@ -19,7 +19,8 @@
 - `[jest-mock]` fix mockReset and resetAllMocks undefined return ([#13692](https://github.com/facebook/jest/pull/13692))
 - `[jest-resolve]` Add global paths to `require.resolve.paths` ([#13633](https://github.com/facebook/jest/pull/13633))
 - `[jest-runtime]` Support Wasm files that import JS resources ([#13608](https://github.com/facebook/jest/pull/13608))
-- `[jest-runtime]` Using the scriptTransformer cache in jest-runner ([#13735](https://github.com/facebook/jest/pull/13735))
+- `[jest-runtime]` Using the scriptTransformer cache in `jest-runner` ([#13735](https://github.com/facebook/jest/pull/13735))
+- `[jest-runtime]` Enforce import assertions when importing JSON in ESM ([#12755](https://github.com/facebook/jest/pull/12755))
 - `[jest-snapshot]` Make sure to import `babel` outside of the sandbox ([#13694](https://github.com/facebook/jest/pull/13694))
 - `[jest-transform]` Ensure the correct configuration is passed to preprocessors specified multiple times in the `transform` option ([#13770](https://github.com/facebook/jest/pull/13770))
 

e2e/__tests__/__snapshots__/nativeEsm.test.ts.snap

@@ -1,5 +1,13 @@
 // Jest Snapshot v1, https://goo.gl/fbAQLP
 
+exports[`on node <16.12.0 does not enforce import assertions 1`] = `
+"Test Suites: 1 passed, 1 total
+Tests:       1 passed, 1 total
+Snapshots:   0 total
+Time:        <<REPLACED>>
+Ran all test suites matching /native-esm-import-assertions.test/i."
+`;
+
 exports[`on node >=16.9.0 support re-exports from CJS of dual packages 1`] = `
 "Test Suites: 1 passed, 1 total
 Tests:       1 passed, 1 total

e2e/__tests__/nativeEsm.test.ts

@@ -79,3 +79,37 @@ test('runs WebAssembly (Wasm) test with native ESM', () => {
   expect(stdout).toBe('');
   expect(exitCode).toBe(0);
 });
+
+// version where `vm` API gets `import assertions`
+onNodeVersions('>=16.12.0', () => {
+  test('enforces import assertions', () => {
+    const {exitCode, stderr, stdout} = runJest(
+      DIR,
+      ['native-esm-import-assertions.test'],
+      {nodeOptions: '--experimental-vm-modules --no-warnings'},
+    );
+
+    const {rest} = extractSummary(stderr);
+
+    expect(rest).toContain(
+      'package.json" needs an import assertion of type "json"',
+    );
+    expect(stdout).toBe('');
+    expect(exitCode).toBe(1);
+  });
+});
+onNodeVersions('<16.12.0', () => {
+  test('does not enforce import assertions', () => {
+    const {exitCode, stderr, stdout} = runJest(
+      DIR,
+      ['native-esm-import-assertions.test'],
+      {nodeOptions: '--experimental-vm-modules --no-warnings'},
+    );
+
+    const {summary} = extractSummary(stderr);
+
+    expect(summary).toMatchSnapshot();
+    expect(stdout).toBe('');
+    expect(exitCode).toBe(0);
+  });
+});

e2e/native-esm/__tests__/native-esm-import-assertions.test.js

@@ -0,0 +1,12 @@
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates. All Rights Reserved.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+import json from '../package.json';
+
+test('supports top level await', () => {
+  expect(json).toHaveProperty('jest.testEnvironment', 'node');
+});

packages/jest-runtime/package.json

@@ -37,13 +37,15 @@
     "jest-resolve": "workspace:^",
     "jest-snapshot": "workspace:^",
     "jest-util": "workspace:^",
+    "semver": "^7.3.5",
     "slash": "^3.0.0",
     "strip-bom": "^4.0.0"
   },
   "devDependencies": {
     "@jest/test-utils": "workspace:^",
     "@types/glob": "^7.1.1",
     "@types/graceful-fs": "^4.1.3",
+    "@types/semver": "^7.1.0",
     "jest-environment-node": "workspace:^"
   },
   "engines": {

packages/jest-runtime/src/index.ts

@@ -21,6 +21,7 @@ import {
 import {parse as parseCjs} from 'cjs-module-lexer';
 import {CoverageInstrumenter, V8Coverage} from 'collect-v8-coverage';
 import * as fs from 'graceful-fs';
+import {satisfies as semverSatisfies} from 'semver';
 import slash = require('slash');
 import stripBOM = require('strip-bom');
 import type {
@@ -62,6 +63,11 @@ import {
 
 const esmIsAvailable = typeof SourceTextModule === 'function';
 
+const runtimeSupportsImportAssertions = semverSatisfies(
+  process.versions.node,
+  '^16.12.0 || >=17.0.0',
+);
+
 const dataURIRegex =
   /^data:(?<mime>text\/javascript|application\/json|application\/wasm)(?:;(?<encoding>charset=utf-8|base64))?,(?<code>.*)$/;
 
@@ -409,11 +415,26 @@ export default class Runtime {
     );
   }
 
-  // not async _now_, but transform will be
   private async loadEsmModule(
     modulePath: string,
     query = '',
+    importAssertions: ImportAssertions = {},
   ): Promise<VMModule> {
+    if (
+      runtimeSupportsImportAssertions &&
+      modulePath.endsWith('.json') &&
+      importAssertions.type !== 'json'
+    ) {
+      const error: NodeJS.ErrnoException = new Error(
+        `Module "${
+          modulePath + (query ? `?${query}` : '')
+        }" needs an import assertion of type "json"`,
+      );
+      error.code = 'ERR_IMPORT_ASSERTION_TYPE_MISSING';
+
+      throw error;
+    }
+
     const cacheKey = modulePath + query;
 
     if (this._fileTransformsMutex.has(cacheKey)) {
@@ -451,6 +472,7 @@ export default class Runtime {
           this.readFileBuffer(modulePath),
           modulePath,
           context,
+          importAssertions,
         );
 
         this._esmoduleRegistry.set(cacheKey, wasm);
@@ -477,39 +499,54 @@ export default class Runtime {
       });
 
       try {
-        const module = new SourceTextModule(transformedCode, {
-          context,
-          identifier: modulePath,
-          importModuleDynamically: async (
-            specifier: string,
-            referencingModule: VMModule,
-          ) => {
-            invariant(
-              runtimeSupportsVmModules,
-              'You need to run with a version of node that supports ES Modules in the VM API. See https://jestjs.io/docs/ecmascript-modules',
-            );
-            const module = await this.resolveModule(
-              specifier,
-              referencingModule.identifier,
-              referencingModule.context,
-            );
+        let module;
+        if (modulePath.endsWith('.json')) {
+          module = new SyntheticModule(
+            ['default'],
+            function () {
+              const obj = JSON.parse(transformedCode);
+              // @ts-expect-error: TS doesn't know what `this` is
+              this.setExport('default', obj);
+            },
+            {context, identifier: modulePath},
+          );
+        } else {
+          module = new SourceTextModule(transformedCode, {
+            context,
+            identifier: modulePath,
+            importModuleDynamically: async (
+              specifier: string,
+              referencingModule: VMModule,
+              importAssertions?: ImportAssertions,
+            ) => {
+              invariant(
+                runtimeSupportsVmModules,
+                'You need to run with a version of node that supports ES Modules in the VM API. See https://jestjs.io/docs/ecmascript-modules',
+              );
+              const module = await this.resolveModule(
+                specifier,
+                referencingModule.identifier,
+                referencingModule.context,
+                importAssertions,
+              );
 
-            return this.linkAndEvaluateModule(module);
-          },
-          initializeImportMeta: (meta: JestImportMeta) => {
-            meta.url = pathToFileURL(modulePath).href;
+              return this.linkAndEvaluateModule(module);
+            },
+            initializeImportMeta: (meta: JestImportMeta) => {
+              meta.url = pathToFileURL(modulePath).href;
 
-            let jest = this.jestObjectCaches.get(modulePath);
+              let jest = this.jestObjectCaches.get(modulePath);
 
-            if (!jest) {
-              jest = this._createJestObjectFor(modulePath);
+              if (!jest) {
+                jest = this._createJestObjectFor(modulePath);
 
-              this.jestObjectCaches.set(modulePath, jest);
-            }
+                this.jestObjectCaches.set(modulePath, jest);
+              }
 
-            meta.jest = jest;
-          },
-        });
+              meta.jest = jest;
+            },
+          });
+        }
 
         invariant(
           !this._esmoduleRegistry.has(cacheKey),
@@ -539,6 +576,7 @@ export default class Runtime {
     specifier: string,
     referencingIdentifier: string,
     context: VMContext,
+    importAssertions: ImportAssertions = {},
   ): Promise<T> {
     if (this.isTornDown) {
       this._logFormattedReferenceError(
@@ -599,6 +637,7 @@ export default class Runtime {
           Buffer.from(match.groups.code, 'base64'),
           specifier,
           context,
+          importAssertions,
         );
       } else {
         let code = match.groups.code;
@@ -627,6 +666,7 @@ export default class Runtime {
             importModuleDynamically: async (
               specifier: string,
               referencingModule: VMModule,
+              importAssertions?: ImportAssertions,
             ) => {
               invariant(
                 runtimeSupportsVmModules,
@@ -636,6 +676,7 @@ export default class Runtime {
                 specifier,
                 referencingModule.identifier,
                 referencingModule.context,
+                importAssertions,
               );
 
               return this.linkAndEvaluateModule(module);
@@ -672,9 +713,11 @@ export default class Runtime {
 
     if (
       this._resolver.isCoreModule(resolved) ||
-      this.unstable_shouldLoadAsEsm(resolved)
+      this.unstable_shouldLoadAsEsm(resolved) ||
+      // json files are modules when imported in modules
+      resolved.endsWith('.json')
     ) {
-      return this.loadEsmModule(resolved, query);
+      return this.loadEsmModule(resolved, query, importAssertions);
     }
 
     return this.loadCjsAsEsm(referencingIdentifier, resolved, context);
@@ -696,12 +739,18 @@ export default class Runtime {
       // this method can await it
       this._esmModuleLinkingMap.set(
         module,
-        module.link((specifier: string, referencingModule: VMModule) =>
-          this.resolveModule(
-            specifier,
-            referencingModule.identifier,
-            referencingModule.context,
-          ),
+        module.link(
+          (
+            specifier: string,
+            referencingModule: VMModule,
+            importCallOptions?: ImportCallOptions,
+          ) =>
+            this.resolveModule(
+              specifier,
+              referencingModule.identifier,
+              referencingModule.context,
+              importCallOptions?.assert,
+            ),
         ),
       );
     }
@@ -1628,7 +1677,11 @@ export default class Runtime {
         displayErrors: true,
         filename: scriptFilename,
         // @ts-expect-error: Experimental ESM API
-        importModuleDynamically: async (specifier: string) => {
+        importModuleDynamically: async (
+          specifier: string,
+          _script: Script,
+          importAssertions?: ImportAssertions,
+        ) => {
           invariant(
             runtimeSupportsVmModules,
             'You need to run with a version of node that supports ES Modules in the VM API. See https://jestjs.io/docs/ecmascript-modules',
@@ -1642,6 +1695,7 @@ export default class Runtime {
             specifier,
             scriptFilename,
             context,
+            importAssertions,
           );
 
           return this.linkAndEvaluateModule(module);
@@ -1693,6 +1747,7 @@ export default class Runtime {
     source: Buffer,
     identifier: string,
     context: VMContext,
+    importAssertions: ImportAssertions | undefined,
   ) {
     const wasmModule = await WebAssembly.compile(source);
 
@@ -1706,6 +1761,7 @@ export default class Runtime {
           module,
           identifier,
           context,
+          importAssertions,
         );
 
         moduleLookup[module] = await this.linkAndEvaluateModule(resolvedModule);

yarn.lock

@@ -13014,6 +13014,7 @@ __metadata:
     "@types/glob": ^7.1.1
     "@types/graceful-fs": ^4.1.3
     "@types/node": "*"
+    "@types/semver": ^7.1.0
     chalk: ^4.0.0
     cjs-module-lexer: ^1.0.0
     collect-v8-coverage: ^1.0.0
@@ -13027,6 +13028,7 @@ __metadata:
     jest-resolve: "workspace:^"
     jest-snapshot: "workspace:^"
     jest-util: "workspace:^"
+    semver: ^7.3.5
     slash: ^3.0.0
     strip-bom: ^4.0.0
   languageName: unknown