module: unflag import assertions

doc/api/errors.md

@@ -1108,6 +1108,14 @@ The JS execution context is not associated with a Node.js environment.
 This may occur when Node.js is used as an embedded library and some hooks
 for the JS engine are not set up properly.
 
+<a id="ERR_FAILED_IMPORT_ASSERTION"></a>
+### `ERR_FAILED_IMPORT_ASSERTION`
+<!-- YAML
+added: REPLACEME
+-->
+
+An import assertion has failed, preventing the specified module to be imported.
+
 <a id="ERR_FALSY_VALUE_REJECTION"></a>
 ### `ERR_FALSY_VALUE_REJECTION`
 

doc/api/vm.md

@@ -54,6 +54,10 @@ executed in specific contexts.
 <!-- YAML
 added: v0.3.1
 changes:
+  - version: REPLACEME
+    pr-url: https://github.com/nodejs/node/pull/39921
+    description: Added suppoort of import assertions to the
+                 `importModuleDynamically` parameter.
   - version: v10.6.0
     pr-url: https://github.com/nodejs/node/pull/20300
     description: The `produceCachedData` is deprecated in favour of
@@ -91,6 +95,8 @@ changes:
     using it in a production environment.
     * `specifier` {string} specifier passed to `import()`
     * `script` {vm.Script}
+    * `import_assertions` {Object} The `"assert"` value passed to the
+      `optionExpression` optional parameter.
     * Returns: {Module Namespace Object|vm.Module} Returning a `vm.Module` is
       recommended in order to take advantage of error tracking, and to avoid
       issues with namespaces that contain `then` function exports.
@@ -642,6 +648,13 @@ The `vm.SourceTextModule` class provides the [Source Text Module Record][] as
 defined in the ECMAScript specification.
 
 ### `new vm.SourceTextModule(code[, options])`
+<!-- YAML
+changes:
+  - version: REPLACEME
+    pr-url: https://github.com/nodejs/node/pull/39921
+    description: Added suppoort of import assertions to the
+                 `importModuleDynamically` parameter.
+-->
 
 * `code` {string} JavaScript Module code to parse
 * `options`
@@ -667,6 +680,8 @@ defined in the ECMAScript specification.
     `import()` will reject with [`ERR_VM_DYNAMIC_IMPORT_CALLBACK_MISSING`][].
     * `specifier` {string} specifier passed to `import()`
     * `module` {vm.Module}
+    * `import_assertions` {Object} The `"assert"` value passed to the
+      `optionExpression` optional parameter.
     * Returns: {Module Namespace Object|vm.Module} Returning a `vm.Module` is
       recommended in order to take advantage of error tracking, and to avoid
       issues with namespaces that contain `then` function exports.
@@ -852,6 +867,10 @@ const vm = require('vm');
 <!-- YAML
 added: v10.10.0
 changes:
+  - version: REPLACEME
+    pr-url: https://github.com/nodejs/node/pull/39921
+    description: Added suppoort of import assertions to the
+                 `importModuleDynamically` parameter.
   - version: v15.9.0
     pr-url: https://github.com/nodejs/node/pull/35431
     description: Added `importModuleDynamically` option again.
@@ -893,6 +912,8 @@ changes:
     considered stable.
     * `specifier` {string} specifier passed to `import()`
     * `function` {Function}
+    * `import_assertions` {Object} The `"assert"` value passed to the
+      `optionExpression` optional parameter.
     * Returns: {Module Namespace Object|vm.Module} Returning a `vm.Module` is
       recommended in order to take advantage of error tracking, and to avoid
       issues with namespaces that contain `then` function exports.
@@ -1068,6 +1089,10 @@ vm.measureMemory({ mode: 'detailed', execution: 'eager' })
 <!-- YAML
 added: v0.3.1
 changes:
+  - version: REPLACEME
+    pr-url: https://github.com/nodejs/node/pull/39921
+    description: Added suppoort of import assertions to the
+                 `importModuleDynamically` parameter.
   - version: v6.3.0
     pr-url: https://github.com/nodejs/node/pull/6635
     description: The `breakOnSigint` option is supported now.
@@ -1113,6 +1138,8 @@ changes:
     using it in a production environment.
     * `specifier` {string} specifier passed to `import()`
     * `script` {vm.Script}
+    * `import_assertions` {Object} The `"assert"` value passed to the
+      `optionExpression` optional parameter.
     * Returns: {Module Namespace Object|vm.Module} Returning a `vm.Module` is
       recommended in order to take advantage of error tracking, and to avoid
       issues with namespaces that contain `then` function exports.
@@ -1145,6 +1172,10 @@ console.log(contextObject);
 <!-- YAML
 added: v0.3.1
 changes:
+  - version: REPLACEME
+    pr-url: https://github.com/nodejs/node/pull/39921
+    description: Added suppoort of import assertions to the
+                 `importModuleDynamically` parameter.
   - version: v14.6.0
     pr-url: https://github.com/nodejs/node/pull/34023
     description: The `microtaskMode` option is supported now.
@@ -1211,6 +1242,8 @@ changes:
     using it in a production environment.
     * `specifier` {string} specifier passed to `import()`
     * `script` {vm.Script}
+    * `import_assertions` {Object} The `"assert"` value passed to the
+      `optionExpression` optional parameter.
     * Returns: {Module Namespace Object|vm.Module} Returning a `vm.Module` is
       recommended in order to take advantage of error tracking, and to avoid
       issues with namespaces that contain `then` function exports.
@@ -1247,6 +1280,10 @@ console.log(contextObject);
 <!-- YAML
 added: v0.3.1
 changes:
+  - version: REPLACEME
+    pr-url: https://github.com/nodejs/node/pull/39921
+    description: Added suppoort of import assertions to the
+                 `importModuleDynamically` parameter.
   - version: v6.3.0
     pr-url: https://github.com/nodejs/node/pull/6635
     description: The `breakOnSigint` option is supported now.
@@ -1290,6 +1327,8 @@ changes:
     using it in a production environment.
     * `specifier` {string} specifier passed to `import()`
     * `script` {vm.Script}
+    * `import_assertions` {Object} The `"assert"` value passed to the
+      `optionExpression` optional parameter.
     * Returns: {Module Namespace Object|vm.Module} Returning a `vm.Module` is
       recommended in order to take advantage of error tracking, and to avoid
       issues with namespaces that contain `then` function exports.

lib/internal/errors.js

@@ -953,6 +953,9 @@ E('ERR_ENCODING_NOT_SUPPORTED', 'The "%s" encoding is not supported',
   RangeError);
 E('ERR_EVAL_ESM_CANNOT_PRINT', '--print cannot be used with ESM input', Error);
 E('ERR_EVENT_RECURSION', 'The event "%s" is already being dispatched', Error);
+E('ERR_FAILED_IMPORT_ASSERTION', (request, key, expectedValue, actualValue) => {
+  return `Failed to load module "${request}", expected ${key} to be ${JSONStringify(expectedValue)}, got ${JSONStringify(actualValue)} instead`;
+}, TypeError);
 E('ERR_FALSY_VALUE_REJECTION', function(reason) {
   this.reason = reason;
   return 'Promise was rejected with falsy value';

lib/internal/modules/cjs/loader.js

@@ -1021,9 +1021,10 @@ function wrapSafe(filename, content, cjsModuleInstance) {
       filename,
       lineOffset: 0,
       displayErrors: true,
-      importModuleDynamically: async (specifier) => {
+      importModuleDynamically: async (specifier, _, import_assertions) => {
         const loader = asyncESM.esmLoader;
-        return loader.import(specifier, normalizeReferrerURL(filename));
+        return loader.import(specifier, normalizeReferrerURL(filename),
+                             import_assertions);
       },
     });
   }
@@ -1036,9 +1037,10 @@ function wrapSafe(filename, content, cjsModuleInstance) {
       '__dirname',
     ], {
       filename,
-      importModuleDynamically(specifier) {
+      importModuleDynamically(specifier, _, import_assertions) {
         const loader = asyncESM.esmLoader;
-        return loader.import(specifier, normalizeReferrerURL(filename));
+        return loader.import(specifier, normalizeReferrerURL(filename),
+                             import_assertions);
       },
     });
   } catch (err) {

lib/internal/modules/esm/loader.js

@@ -20,6 +20,7 @@ const {
 } = primordials;
 
 const {
+  ERR_FAILED_IMPORT_ASSERTION,
   ERR_INVALID_ARG_TYPE,
   ERR_INVALID_ARG_VALUE,
   ERR_INVALID_MODULE_SPECIFIER,
@@ -202,33 +203,48 @@ class ESMLoader {
       const { ModuleWrap, callbackMap } = internalBinding('module_wrap');
       const module = new ModuleWrap(url, undefined, source, 0, 0);
       callbackMap.set(module, {
-        importModuleDynamically: (specifier, { url }) => {
-          return this.import(specifier, url);
+        importModuleDynamically: (specifier, { url }, import_assertions) => {
+          return this.import(specifier, url, import_assertions);
         }
       });
 
       return module;
     };
     const job = new ModuleJob(this, url, evalInstance, false, false);
-    this.moduleMap.set(url, job);
+    this.moduleMap.set(url, job, undefined);
     const { module } = await job.run();
 
     return {
       namespace: module.getNamespace(),
     };
   }
 
-  async getModuleJob(specifier, parentURL) {
+  async getModuleJob(specifier, parentURL, import_assertions) {
     const { format, url } = await this.resolve(specifier, parentURL);
-    let job = this.moduleMap.get(url);
-    // CommonJS will set functions for lazy job evaluation.
-    if (typeof job === 'function') this.moduleMap.set(url, job = job());
 
-    if (job !== undefined) return job;
+    let job
+    const jobMap = this.moduleMap.get(url);
+
+    if (jobMap != null) {
+      // To avoid race conditions, always wait for non assertion job to fulfill
+      if(import_assertions.type != null) await jobMap[undefined];
+
+      let job = jobMap[import_assertions.type];
+
+      // CommonJS will set functions for lazy job evaluation.
+      if (typeof job === 'function') this.moduleMap.set(url, job = job(), import_assertions.type);
+
+      if (job !== undefined) return job;
+    }
 
     const moduleProvider = async (url, isMain) => {
       const { format: finalFormat, source } = await this.load(url, { format });
 
+      if (import_assertions.type === 'json' && finalFormat !== 'json') {
+        throw new ERR_FAILED_IMPORT_ASSERTION(
+          url, 'type', import_assertions.type, finalFormat);
+      }
+
       const translator = translators.get(finalFormat);
 
       if (!translator) throw new ERR_UNKNOWN_MODULE_FORMAT(finalFormat);
@@ -249,7 +265,7 @@ class ESMLoader {
       inspectBrk
     );
 
-    this.moduleMap.set(url, job);
+    this.moduleMap.set(url, job, import_assertions.type);
 
     return job;
   }
@@ -262,18 +278,19 @@ class ESMLoader {
    * loader module.
    *
    * @param {string | string[]} specifiers Path(s) to the module
-   * @param {string} [parentURL] Path of the parent importing the module
-   * @returns {object | object[]} A list of module export(s)
+   * @param {string} parentURL Path of the parent importing the module
+   * @param {Record<string, Record<string, string>>} import_assertions
+   * @returns {Promise<object | object[]>} A list of module export(s)
    */
-  async import(specifiers, parentURL) {
+  async import(specifiers, parentURL, import_assertions) {
     const wasArr = ArrayIsArray(specifiers);
     if (!wasArr) specifiers = [specifiers];
 
     const count = specifiers.length;
     const jobs = new Array(count);
 
     for (let i = 0; i < count; i++) {
-      jobs[i] = this.getModuleJob(specifiers[i], parentURL)
+      jobs[i] = this.getModuleJob(specifiers[i], parentURL, import_assertions)
         .then((job) => job.run())
         .then(({ module }) => module.getNamespace());
     }

lib/internal/modules/esm/module_job.js

@@ -72,8 +72,8 @@ class ModuleJob {
       // so that circular dependencies can't cause a deadlock by two of
       // these `link` callbacks depending on each other.
       const dependencyJobs = [];
-      const promises = this.module.link(async (specifier) => {
-        const jobPromise = this.loader.getModuleJob(specifier, url);
+      const promises = this.module.link(async (specifier, assertions) => {
+        const jobPromise = this.loader.getModuleJob(specifier, url, assertions);
         ArrayPrototypePush(dependencyJobs, jobPromise);
         const job = await jobPromise;
         return job.modulePromise;

lib/internal/modules/esm/module_map.js

@@ -2,6 +2,7 @@
 
 const ModuleJob = require('internal/modules/esm/module_job');
 const {
+  ObjectCreate,
   SafeMap,
 } = primordials;
 let debug = require('internal/util/debuglog').debuglog('esm', (fn) => {
@@ -17,14 +18,16 @@ class ModuleMap extends SafeMap {
     validateString(url, 'url');
     return super.get(url);
   }
-  set(url, job) {
+  set(url, job, import_assertion_type) {
     validateString(url, 'url');
     if (job instanceof ModuleJob !== true &&
         typeof job !== 'function') {
       throw new ERR_INVALID_ARG_TYPE('job', 'ModuleJob', job);
     }
     debug(`Storing ${url} in ModuleMap`);
-    return super.set(url, job);
+    const jobMap = super.get(url) ?? ObjectCreate(null);
+    jobMap[import_assertion_type] = job
+    return super.set(url, jobMap);
   }
   has(url) {
     validateString(url, 'url');

lib/internal/modules/esm/translators.js

@@ -107,8 +107,8 @@ function errPath(url) {
   return url;
 }
 
-async function importModuleDynamically(specifier, { url }) {
-  return asyncESM.esmLoader.import(specifier, url);
+async function importModuleDynamically(specifier, { url }, assertions) {
+  return asyncESM.esmLoader.import(specifier, url, assertions);
 }
 
 function createImportMetaResolve(defaultParentUrl) {

lib/internal/modules/run_main.js

@@ -1,6 +1,7 @@
 'use strict';
 
 const {
+  ObjectCreate,
   StringPrototypeEndsWith,
 } = primordials;
 const CJSLoader = require('internal/modules/cjs/loader');
@@ -46,9 +47,8 @@ function runMainESM(mainPath) {
 
   handleMainPromise(loadESM((esmLoader) => {
     const main = path.isAbsolute(mainPath) ?
-      pathToFileURL(mainPath).href :
-      mainPath;
-    return esmLoader.import(main);
+      pathToFileURL(mainPath).href : mainPath;
+    return esmLoader.import(main, undefined, ObjectCreate(null));
   }));
 }
 

lib/internal/process/esm_loader.js

@@ -1,5 +1,9 @@
 'use strict';
 
+const {
+  ObjectCreate,
+} = primordials;
+
 const {
   ERR_VM_DYNAMIC_IMPORT_CALLBACK_MISSING,
 } = require('internal/errors').codes;
@@ -22,13 +26,14 @@ exports.initializeImportMetaObject = function(wrap, meta) {
   }
 };
 
-exports.importModuleDynamicallyCallback = async function(wrap, specifier) {
+exports.importModuleDynamicallyCallback =
+async function importModuleDynamicallyCallback(wrap, specifier, assertions) {
   const { callbackMap } = internalBinding('module_wrap');
   if (callbackMap.has(wrap)) {
     const { importModuleDynamically } = callbackMap.get(wrap);
     if (importModuleDynamically !== undefined) {
       return importModuleDynamically(
-        specifier, getModuleFromWrap(wrap) || wrap);
+        specifier, getModuleFromWrap(wrap) || wrap, assertions);
     }
   }
   throw new ERR_VM_DYNAMIC_IMPORT_CALLBACK_MISSING();
@@ -69,6 +74,7 @@ async function initializeLoader() {
   const exports = await internalEsmLoader.import(
     customLoaders,
     pathToFileURL(cwd).href,
+    ObjectCreate(null),
   );
 
   // Hooks must then be added to external/public loader

lib/internal/process/execution.js

@@ -82,9 +82,9 @@ function evalScript(name, body, breakFirstLine, print) {
       filename: name,
       displayErrors: true,
       [kVmBreakFirstLineSymbol]: !!breakFirstLine,
-      async importModuleDynamically(specifier) {
-        const loader = await asyncESM.esmLoader;
-        return loader.import(specifier, baseUrl);
+      importModuleDynamically(specifier, _, import_assertions) {
+        const loader = asyncESM.esmLoader;
+        return loader.import(specifier, baseUrl, import_assertions);
       }
     }));
   if (print) {