esm: consolidate ESM loader hooks

doc: update ESM hook examples

esm: fix unsafe primordial

doc: fix ESM example linting

esm: allow source of type ArrayBuffer

doc: update ESM hook changelog to include resolve format

esm: allow all ArrayBuffers and TypedArrays for load hook source

doc: tidy code & API docs

doc: convert ESM source table header from Title Case to Sentence case

doc: add detailed explanation for getPackageType

esm: add caveat that ESMLoader::import() must NOT be renamed

esm: tidy code declaration of getFormat protocolHandlers

doc: correct ESM doc link (bad conflict resolution)

doc: update ESM hook limitation for CJS

esm: tweak preload description

doc: update ESM getPackageType() example explanation

PR-URL: #37468
Reviewed-By: Antoine du Hamel <duhamelantoine1995@gmail.com>
Reviewed-By: Guy Bedford <guybedford@gmail.com>
Reviewed-By: Bradley Farias <bradley.meck@gmail.com>
Reviewed-By: Geoffrey Booth <webmaster@geoffreybooth.com>

lib/internal/modules/cjs/loader.js

@@ -981,14 +981,14 @@ Module.prototype.load = function(filename) {
   Module._extensions[extension](this, filename);
   this.loaded = true;
 
-  const ESMLoader = asyncESM.ESMLoader;
+  const esmLoader = asyncESM.esmLoader;
   // Create module entry at load time to snapshot exports correctly
   const exports = this.exports;
   // Preemptively cache
   if ((module?.module === undefined ||
        module.module.getStatus() < kEvaluated) &&
-      !ESMLoader.cjsCache.has(this))
-    ESMLoader.cjsCache.set(this, exports);
+      !esmLoader.cjsCache.has(this))
+    esmLoader.cjsCache.set(this, exports);
 };
 
 
@@ -1022,7 +1022,7 @@ function wrapSafe(filename, content, cjsModuleInstance) {
       lineOffset: 0,
       displayErrors: true,
       importModuleDynamically: async (specifier) => {
-        const loader = asyncESM.ESMLoader;
+        const loader = asyncESM.esmLoader;
         return loader.import(specifier, normalizeReferrerURL(filename));
       },
     });
@@ -1037,7 +1037,7 @@ function wrapSafe(filename, content, cjsModuleInstance) {
     ], {
       filename,
       importModuleDynamically(specifier) {
-        const loader = asyncESM.ESMLoader;
+        const loader = asyncESM.esmLoader;
         return loader.import(specifier, normalizeReferrerURL(filename));
       },
     });

lib/internal/modules/esm/get_format.js

@@ -1,7 +1,9 @@
 'use strict';
 const {
+  ObjectAssign,
+  ObjectCreate,
+  ObjectPrototypeHasOwnProperty,
   RegExpPrototypeExec,
-  StringPrototypeStartsWith,
 } = primordials;
 const { extname } = require('path');
 const { getOptionValue } = require('internal/options');
@@ -36,26 +38,25 @@ if (experimentalWasmModules)
 if (experimentalJsonModules)
   extensionFormatMap['.json'] = legacyExtensionFormatMap['.json'] = 'json';
 
-function defaultGetFormat(url, context, defaultGetFormatUnused) {
-  if (StringPrototypeStartsWith(url, 'node:')) {
-    return { format: 'builtin' };
-  }
-  const parsed = new URL(url);
-  if (parsed.protocol === 'data:') {
+const protocolHandlers = ObjectAssign(ObjectCreate(null), {
+  'data:'(parsed) {
     const { 1: mime } = RegExpPrototypeExec(
       /^([^/]+\/[^;,]+)(?:[^,]*?)(;base64)?,/,
       parsed.pathname,
-    ) || [ , null ];
+    ) || [, null];
     const format = ({
       '__proto__': null,
       'text/javascript': 'module',
       'application/json': experimentalJsonModules ? 'json' : null,
       'application/wasm': experimentalWasmModules ? 'wasm' : null
     })[mime] || null;
-    return { format };
-  } else if (parsed.protocol === 'file:') {
+
+    return format;
+  },
+  'file:'(parsed, url) {
     const ext = extname(parsed.pathname);
     let format;
+
     if (ext === '.js') {
       format = getPackageType(parsed.href) === 'module' ? 'module' : 'commonjs';
     } else {
@@ -71,9 +72,18 @@ function defaultGetFormat(url, context, defaultGetFormatUnused) {
         throw new ERR_UNKNOWN_FILE_EXTENSION(ext, fileURLToPath(url));
       }
     }
-    return { format: format || null };
-  }
-  return { format: null };
+
+    return format || null;
+  },
+  'node:'() { return 'builtin'; },
+});
+
+function defaultGetFormat(url, context) {
+  const parsed = new URL(url);
+
+  return ObjectPrototypeHasOwnProperty(protocolHandlers, parsed.protocol) ?
+    protocolHandlers[parsed.protocol](parsed, url) :
+    null;
 }
 
 module.exports = {

lib/internal/modules/esm/get_source.js

@@ -40,6 +40,6 @@ async function defaultGetSource(url, { format } = {}, defaultGetSource) {
   if (policy?.manifest) {
     policy.manifest.assertIntegrity(parsed, source);
   }
-  return { source };
+  return source;
 }
 exports.defaultGetSource = defaultGetSource;

lib/internal/modules/esm/load.js

@@ -0,0 +1,32 @@
+'use strict';
+
+const { defaultGetFormat } = require('internal/modules/esm/get_format');
+const { defaultGetSource } = require('internal/modules/esm/get_source');
+const { translators } = require('internal/modules/esm/translators');
+
+async function defaultLoad(url, context) {
+  let {
+    format,
+    source,
+  } = context;
+
+  if (!translators.has(format)) format = defaultGetFormat(url);
+
+  if (
+    format === 'builtin' ||
+    format === 'commonjs'
+  ) {
+    source = null;
+  } else if (source == null) {
+    source = await defaultGetSource(url, { format });
+  }
+
+  return {
+    format,
+    source,
+  };
+}
+
+module.exports = {
+  defaultLoad,
+};