esm: refactor DefaultModuleLoader

Fixes nodejs#48515
Fixes nodejs#48439

Author: izaakschroeder

doc/api/errors.md

@@ -1233,23 +1233,6 @@ provided.
 Encoding provided to `TextDecoder()` API was not one of the
 [WHATWG Supported Encodings][].
 
-<a id="ERR_ESM_LOADER_REGISTRATION_UNAVAILABLE"></a>
-
-### `ERR_ESM_LOADER_REGISTRATION_UNAVAILABLE`
-
-<!-- YAML
-added: REPLACEME
--->
-
-Programmatically registering custom ESM loaders
-currently requires at least one custom loader to have been
-registered via the `--experimental-loader` flag. A no-op
-loader registered via CLI is sufficient
-(for example: `--experimental-loader data:text/javascript,`;
-do not omit the necessary trailing comma).
-A future version of Node.js will support the programmatic
-registration of loaders without needing to also use the flag.
-
 <a id="ERR_EVAL_ESM_CANNOT_PRINT"></a>
 
 ### `ERR_EVAL_ESM_CANNOT_PRINT`

lib/internal/errors.js

@@ -1036,11 +1036,6 @@ E('ERR_ENCODING_INVALID_ENCODED_DATA', function(encoding, ret) {
 }, TypeError);
 E('ERR_ENCODING_NOT_SUPPORTED', 'The "%s" encoding is not supported',
   RangeError);
-E('ERR_ESM_LOADER_REGISTRATION_UNAVAILABLE', 'Programmatically registering custom ESM loaders ' +
-  'currently requires at least one custom loader to have been registered via the --experimental-loader ' +
-  'flag. A no-op loader registered via CLI is sufficient (for example: `--experimental-loader ' +
-  '"data:text/javascript,"` with the necessary trailing comma). A future version of Node.js ' +
-  'will remove this requirement.', Error);
 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_FALSY_VALUE_REJECTION', function(reason) {

lib/internal/modules/esm/hooks.js

@@ -80,7 +80,6 @@ let debug = require('internal/util/debuglog').debuglog('esm', (fn) => {
 
 // [2] `validate...()`s throw the wrong error
 
-
 class Hooks {
   #chains = {
     /**
@@ -126,16 +125,18 @@ class Hooks {
    */
   async register(urlOrSpecifier, parentURL) {
     const moduleLoader = require('internal/process/esm_loader').esmLoader;
-
     const keyedExports = await moduleLoader.import(
       urlOrSpecifier,
       parentURL,
       kEmptyObject,
     );
-
     this.addCustomLoader(urlOrSpecifier, keyedExports);
   }
 
+  allowImportMetaResolve() {
+    return false;
+  }
+
   /**
    * Collect custom/user-defined module loader hook(s).
    * After all hooks have been collected, the global preload hook(s) must be initialized.
@@ -150,13 +151,16 @@ class Hooks {
     } = pluckHooks(exports);
 
     if (globalPreload) {
-      ArrayPrototypePush(this.#chains.globalPreload, { fn: globalPreload, url });
+      const next = this.#chains.globalPreload[this.#chains.globalPreload.length - 1];
+      ArrayPrototypePush(this.#chains.globalPreload, { fn: globalPreload, url, next });
     }
     if (resolve) {
-      ArrayPrototypePush(this.#chains.resolve, { fn: resolve, url });
+      const next = this.#chains.resolve[this.#chains.resolve.length - 1];
+      ArrayPrototypePush(this.#chains.resolve, { fn: resolve, url, next });
     }
     if (load) {
-      ArrayPrototypePush(this.#chains.load, { fn: load, url });
+      const next = this.#chains.load[this.#chains.load.length - 1];
+      ArrayPrototypePush(this.#chains.load, { fn: load, url, next });
     }
   }
 
@@ -233,7 +237,6 @@ class Hooks {
       chainFinished: null,
       context,
       hookErrIdentifier: '',
-      hookIndex: chain.length - 1,
       hookName: 'resolve',
       shortCircuited: false,
     };
@@ -256,7 +259,7 @@ class Hooks {
       }
     };
 
-    const nextResolve = nextHookFactory(chain, meta, { validateArgs, validateOutput });
+    const nextResolve = nextHookFactory(chain[chain.length - 1], meta, { validateArgs, validateOutput });
 
     const resolution = await nextResolve(originalSpecifier, context);
     const { hookErrIdentifier } = meta; // Retrieve the value after all settled
@@ -349,7 +352,6 @@ class Hooks {
       chainFinished: null,
       context,
       hookErrIdentifier: '',
-      hookIndex: chain.length - 1,
       hookName: 'load',
       shortCircuited: false,
     };
@@ -391,7 +393,7 @@ class Hooks {
       }
     };
 
-    const nextLoad = nextHookFactory(chain, meta, { validateArgs, validateOutput });
+    const nextLoad = nextHookFactory(chain[chain.length - 1], meta, { validateArgs, validateOutput });
 
     const loaded = await nextLoad(url, context);
     const { hookErrIdentifier } = meta; // Retrieve the value after all settled
@@ -528,7 +530,17 @@ class HooksProxy {
         debug('wait for signal from worker');
         AtomicsWait(this.#lock, WORKER_TO_MAIN_THREAD_NOTIFICATION, 0);
         const response = this.#worker.receiveMessageSync();
-        if (response.message.status === 'exit') { return; }
+        if (response.message.status === 'exit') {
+          // TODO: I do not understand why this is necessary.
+          // node \
+          //   --no-warnings --experimental-loader 'data:text/javascript,process.exit(42)'
+          //   ./test/fixtures/empty.js
+          // Does not trigger `this.#worker.on('exit', process.exit);`.
+          // I think it is because `makeSyncRequest` keeps waiting to see another
+          // message and blocks the thread from ANY other activity including the exit.
+          process.exit(response.message.body);
+          return;
+        }
         const { preloadScripts } = this.#unwrapMessage(response);
         this.#executePreloadScripts(preloadScripts);
       }
@@ -684,46 +696,34 @@ function pluckHooks({
  * A utility function to iterate through a hook chain, track advancement in the
  * chain, and generate and supply the `next<HookName>` argument to the custom
  * hook.
- * @param {KeyedHook[]} chain The whole hook chain.
+ * @param {Hook} hook The first hook in the chain.
  * @param {object} meta Properties that change as the current hook advances
  * along the chain.
  * @param {boolean} meta.chainFinished Whether the end of the chain has been
  * reached AND invoked.
  * @param {string} meta.hookErrIdentifier A user-facing identifier to help
  *  pinpoint where an error occurred. Ex "file:///foo.mjs 'resolve'".
- * @param {number} meta.hookIndex A non-negative integer tracking the current
- * position in the hook chain.
  * @param {string} meta.hookName The kind of hook the chain is (ex 'resolve')
  * @param {boolean} meta.shortCircuited Whether a hook signaled a short-circuit.
  * @param {(hookErrIdentifier, hookArgs) => void} validate A wrapper function
  *  containing all validation of a custom loader hook's intermediary output. Any
  *  validation within MUST throw.
  * @returns {function next<HookName>(...hookArgs)} The next hook in the chain.
  */
-function nextHookFactory(chain, meta, { validateArgs, validateOutput }) {
+function nextHookFactory(hook, meta, { validateArgs, validateOutput }) {
   // First, prepare the current
   const { hookName } = meta;
-  const {
-    fn: hook,
-    url: hookFilePath,
-  } = chain[meta.hookIndex];
+  const { fn, url, next } = hook;
 
   // ex 'nextResolve'
   const nextHookName = `next${
     StringPrototypeToUpperCase(hookName[0]) +
     StringPrototypeSlice(hookName, 1)
   }`;
 
-  // When hookIndex is 0, it's reached the default, which does not call next()
-  // so feed it a noop that blows up if called, so the problem is obvious.
-  const generatedHookIndex = meta.hookIndex;
   let nextNextHook;
-  if (meta.hookIndex > 0) {
-    // Now, prepare the next: decrement the pointer so the next call to the
-    // factory generates the next link in the chain.
-    meta.hookIndex--;
-
-    nextNextHook = nextHookFactory(chain, meta, { validateArgs, validateOutput });
+  if (next) {
+    nextNextHook = nextHookFactory(next, meta, { validateArgs, validateOutput });
   } else {
     // eslint-disable-next-line func-name-matching
     nextNextHook = function chainAdvancedTooFar() {
@@ -736,21 +736,20 @@ function nextHookFactory(chain, meta, { validateArgs, validateOutput }) {
   return ObjectDefineProperty(
     async (arg0 = undefined, context) => {
       // Update only when hook is invoked to avoid fingering the wrong filePath
-      meta.hookErrIdentifier = `${hookFilePath} '${hookName}'`;
+      meta.hookErrIdentifier = `${url} '${hookName}'`;
 
       validateArgs(`${meta.hookErrIdentifier} hook's ${nextHookName}()`, arg0, context);
 
-      const outputErrIdentifier = `${chain[generatedHookIndex].url} '${hookName}' hook's ${nextHookName}()`;
+      const outputErrIdentifier = `${url} '${hookName}' hook's ${nextHookName}()`;
 
       // Set when next<HookName> is actually called, not just generated.
-      if (generatedHookIndex === 0) { meta.chainFinished = true; }
+      if (!next) { meta.chainFinished = true; }
 
       if (context) { // `context` has already been validated, so no fancy check needed.
         ObjectAssign(meta.context, context);
       }
 
-      const output = await hook(arg0, meta.context, nextNextHook);
-
+      const output = await fn(arg0, meta.context, nextNextHook);
       validateOutput(outputErrIdentifier, output);
 
       if (output?.shortCircuit === true) { meta.shortCircuited = true; }

lib/internal/modules/esm/initialize_import_meta.js

@@ -1,7 +1,14 @@
 'use strict';
 
+const { Symbol } = primordials;
+
 const { getOptionValue } = require('internal/options');
 const experimentalImportMetaResolve = getOptionValue('--experimental-import-meta-resolve');
+const kResolveSync = Symbol('sync');
+
+const importAssertions = {
+  [kResolveSync]: true,
+};
 
 /**
  * Generate a function to be used as import.meta.resolve for a particular module.
@@ -14,7 +21,7 @@ function createImportMetaResolve(defaultParentUrl, loader) {
     let url;
 
     try {
-      ({ url } = loader.resolve(specifier, parentUrl));
+      ({ url } = loader.resolve(specifier, parentUrl, importAssertions));
     } catch (error) {
       if (error?.code === 'ERR_UNSUPPORTED_DIR_IMPORT') {
         ({ url } = error);
@@ -38,7 +45,7 @@ function initializeImportMeta(meta, context, loader) {
   const { url } = context;
 
   // Alphabetical
-  if (experimentalImportMetaResolve && loader.loaderType !== 'internal') {
+  if (experimentalImportMetaResolve && loader.allowImportMetaResolve()) {
     meta.resolve = createImportMetaResolve(url, loader);
   }
 
@@ -49,4 +56,5 @@ function initializeImportMeta(meta, context, loader) {
 
 module.exports = {
   initializeImportMeta,
+  kResolveSync,
 };