esm: support loading data URLs

Co-Authored-By: Jan Olaf Krems <jan.krems@gmail.com>

PR-URL: https://github.com/nodejs/node/pull/28614
Reviewed-By: Jan Krems <jan.krems@gmail.com>

3 files changed, 87 insertions, 28 deletions

diff --git a/lib/internal/modules/esm/default_resolve.js b/lib/internal/modules/esm/default_resolve.js
index 46e7b2415a..580419deac 100644
--- a/lib/internal/modules/esm/default_resolve.js
+++ b/lib/internal/modules/esm/default_resolve.js
@@ -12,7 +12,7 @@ const typeFlag = getOptionValue('--input-type');
 const experimentalWasmModules = getOptionValue('--experimental-wasm-modules');
 const { resolve: moduleWrapResolve,
         getPackageType } = internalBinding('module_wrap');
-const { pathToFileURL, fileURLToPath } = require('internal/url');
+const { URL, pathToFileURL, fileURLToPath } = require('internal/url');
 const { ERR_INPUT_TYPE_NOT_ALLOWED,
         ERR_UNKNOWN_FILE_EXTENSION } = require('internal/errors').codes;
 
@@ -45,12 +45,32 @@ if (experimentalWasmModules)
   extensionFormatMap['.wasm'] = legacyExtensionFormatMap['.wasm'] = 'wasm';
 
 function resolve(specifier, parentURL) {
+  try {
+    const parsed = new URL(specifier);
+    if (parsed.protocol === 'data:') {
+      const [ , mime ] = /^([^/]+\/[^;,]+)(;base64)?,/.exec(parsed.pathname) || [ null, null, null ];
+      const format = ({
+        '__proto__': null,
+        'text/javascript': 'module',
+        'application/json': 'json',
+        'application/wasm': experimentalWasmModules ? 'wasm' : null
+      })[mime] || null;
+      return {
+        url: specifier,
+        format
+      };
+    }
+  } catch {}
   if (NativeModule.canBeRequiredByUsers(specifier)) {
     return {
       url: specifier,
       format: 'builtin'
     };
   }
+  if (parentURL && parentURL.startsWith('data:')) {
+    // This is gonna blow up, we want the error
+    new URL(specifier, parentURL);
+  }
 
   const isMain = parentURL === undefined;
   if (isMain)
diff --git a/lib/internal/modules/esm/loader.js b/lib/internal/modules/esm/loader.js
index bffefa884e..09109d3c71 100644
--- a/lib/internal/modules/esm/loader.js
+++ b/lib/internal/modules/esm/loader.js
@@ -102,9 +102,12 @@ class Loader {
       }
     }
 
-    if (format !== 'dynamic' && !url.startsWith('file:'))
+    if (format !== 'dynamic' &&
+      !url.startsWith('file:') &&
+      !url.startsWith('data:')
+    )
       throw new ERR_INVALID_RETURN_PROPERTY(
-        'file: url', 'loader resolve', 'url', url
+        'file: or data: url', 'loader resolve', 'url', url
       );
 
     return { url, format };
diff --git a/lib/internal/modules/esm/translators.js b/lib/internal/modules/esm/translators.js
index d693b79448..9cb0781ab9 100644
--- a/lib/internal/modules/esm/translators.js
+++ b/lib/internal/modules/esm/translators.js
@@ -9,6 +9,8 @@ const {
   StringPrototype
 } = primordials;
 
+const { Buffer } = require('buffer');
+
 const {
   stripShebang,
   stripBOM,
@@ -24,6 +26,8 @@ const { debuglog } = require('internal/util/debuglog');
 const { promisify } = require('internal/util');
 const esmLoader = require('internal/process/esm_loader');
 const {
+  ERR_INVALID_URL,
+  ERR_INVALID_URL_SCHEME,
   ERR_UNKNOWN_BUILTIN_MODULE
 } = require('internal/errors').codes;
 const readFileAsync = promisify(fs.readFile);
@@ -34,6 +38,31 @@ const debug = debuglog('esm');
 const translators = new SafeMap();
 exports.translators = translators;
 
+const DATA_URL_PATTERN = /^[^/]+\/[^,;]+(;base64)?,([\s\S]*)$/;
+function getSource(url) {
+  const parsed = new URL(url);
+  if (parsed.protocol === 'file:') {
+    return readFileAsync(parsed);
+  } else if (parsed.protocol === 'data:') {
+    const match = DATA_URL_PATTERN.exec(parsed.pathname);
+    if (!match) {
+      throw new ERR_INVALID_URL(url);
+    }
+    const [ , base64, body ] = match;
+    return Buffer.from(body, base64 ? 'base64' : 'utf8');
+  } else {
+    throw new ERR_INVALID_URL_SCHEME(['file', 'data']);
+  }
+}
+
+function errPath(url) {
+  const parsed = new URL(url);
+  if (parsed.protocol === 'file:') {
+    return fileURLToPath(parsed);
+  }
+  return url;
+}
+
 function initializeImportMeta(meta, { url }) {
   meta.url = url;
 }
@@ -45,7 +74,7 @@ async function importModuleDynamically(specifier, { url }) {
 
 // Strategy for loading a standard JavaScript module
 translators.set('module', async function moduleStrategy(url) {
-  const source = `${await readFileAsync(new URL(url))}`;
+  const source = `${await getSource(url)}`;
   debug(`Translating StandardModule ${url}`);
   const { ModuleWrap, callbackMap } = internalBinding('module_wrap');
   const module = new ModuleWrap(stripShebang(source), url);
@@ -112,26 +141,32 @@ translators.set('builtin', async function builtinStrategy(url) {
 translators.set('json', async function jsonStrategy(url) {
   debug(`Translating JSONModule ${url}`);
   debug(`Loading JSONModule ${url}`);
-  const pathname = fileURLToPath(url);
-  const modulePath = isWindows ?
-    StringPrototype.replace(pathname, winSepRegEx, '\\') : pathname;
-  let module = CJSModule._cache[modulePath];
-  if (module && module.loaded) {
-    const exports = module.exports;
-    return createDynamicModule([], ['default'], url, (reflect) => {
-      reflect.exports.default.set(exports);
-    });
+  const pathname = url.startsWith('file:') ? fileURLToPath(url) : null;
+  let modulePath;
+  let module;
+  if (pathname) {
+    modulePath = isWindows ?
+      StringPrototype.replace(pathname, winSepRegEx, '\\') : pathname;
+    module = CJSModule._cache[modulePath];
+    if (module && module.loaded) {
+      const exports = module.exports;
+      return createDynamicModule([], ['default'], url, (reflect) => {
+        reflect.exports.default.set(exports);
+      });
+    }
   }
-  const content = await readFileAsync(pathname, 'utf-8');
-  // A require call could have been called on the same file during loading and
-  // that resolves synchronously. To make sure we always return the identical
-  // export, we have to check again if the module already exists or not.
-  module = CJSModule._cache[modulePath];
-  if (module && module.loaded) {
-    const exports = module.exports;
-    return createDynamicModule(['default'], url, (reflect) => {
-      reflect.exports.default.set(exports);
-    });
+  const content = `${await getSource(url)}`;
+  if (pathname) {
+    // A require call could have been called on the same file during loading and
+    // that resolves synchronously. To make sure we always return the identical
+    // export, we have to check again if the module already exists or not.
+    module = CJSModule._cache[modulePath];
+    if (module && module.loaded) {
+      const exports = module.exports;
+      return createDynamicModule(['default'], url, (reflect) => {
+        reflect.exports.default.set(exports);
+      });
+    }
   }
   try {
     const exports = JsonParse(stripBOM(content));
@@ -144,10 +179,12 @@ translators.set('json', async function jsonStrategy(url) {
     // parse error instead of just manipulating the original error message.
     // That would allow to add further properties and maybe additional
     // debugging information.
-    err.message = pathname + ': ' + err.message;
+    err.message = errPath(url) + ': ' + err.message;
     throw err;
   }
-  CJSModule._cache[modulePath] = module;
+  if (pathname) {
+    CJSModule._cache[modulePath] = module;
+  }
   return createDynamicModule([], ['default'], url, (reflect) => {
     debug(`Parsing JSONModule ${url}`);
     reflect.exports.default.set(module.exports);
@@ -156,14 +193,13 @@ translators.set('json', async function jsonStrategy(url) {
 
 // Strategy for loading a wasm module
 translators.set('wasm', async function(url) {
-  const pathname = fileURLToPath(url);
-  const buffer = await readFileAsync(pathname);
+  const buffer = await getSource(url);
   debug(`Translating WASMModule ${url}`);
   let compiled;
   try {
     compiled = await WebAssembly.compile(buffer);
   } catch (err) {
-    err.message = pathname + ': ' + err.message;
+    err.message = errPath(url) + ': ' + err.message;
     throw err;
   }