loader: introduce --experimental-raw-imports flag and implementation

Author: efekrskl

lib/internal/modules/esm/assert.js

@@ -8,6 +8,7 @@ const {
   ObjectValues,
 } = primordials;
 const { validateString } = require('internal/validators');
+const { getOptionValue } = require('internal/options');
 
 const {
   ERR_IMPORT_ATTRIBUTE_TYPE_INCOMPATIBLE,
@@ -32,6 +33,12 @@ const formatTypeMap = {
   'wasm': kImplicitTypeAttribute, // It's unclear whether the HTML spec will require an type attribute or not for Wasm; see https://github.com/WebAssembly/esm-integration/issues/42
 };
 
+const experimentalFormatTypeMap = {
+  '__proto__': null,
+  'bytes': 'bytes',
+  'text': 'text',
+};
+
 /**
  * The HTML spec disallows the default type to be explicitly specified
  * (for now); so `import './file.js'` is okay but
@@ -42,6 +49,17 @@ const supportedTypeAttributes = ArrayPrototypeFilter(
   ObjectValues(formatTypeMap),
   (type) => type !== kImplicitTypeAttribute);
 
+function getExperimentalFormatType(format) {
+  const type = experimentalFormatTypeMap[format];
+  if (type === undefined) {
+    return undefined;
+  }
+  if (!getOptionValue('--experimental-raw-imports')) {
+    return undefined;
+  }
+  return type;
+}
+
 
 /**
  * Test a module's import attributes.
@@ -60,7 +78,7 @@ function validateAttributes(url, format,
       throw new ERR_IMPORT_ATTRIBUTE_UNSUPPORTED(keys[i], importAttributes[keys[i]], url);
     }
   }
-  const validType = formatTypeMap[format];
+  const validType = formatTypeMap[format] ?? getExperimentalFormatType(format);
 
   switch (validType) {
     case undefined:
@@ -101,7 +119,9 @@ function handleInvalidType(url, type) {
   validateString(type, 'type');
 
   // `type` might not have been one of the types we understand.
-  if (!ArrayPrototypeIncludes(supportedTypeAttributes, type)) {
+  if (!ArrayPrototypeIncludes(supportedTypeAttributes, type) &&
+      !(ObjectPrototypeHasOwnProperty(experimentalFormatTypeMap, type) &&
+        getOptionValue('--experimental-raw-imports'))) {
     throw new ERR_IMPORT_ATTRIBUTE_UNSUPPORTED('type', type, url);
   }
 

lib/internal/modules/esm/get_format.js

@@ -78,6 +78,25 @@ const protocolHandlers = {
   'node:'() { return 'builtin'; },
 };
 
+function getFormatFromImportAttributes(importAttributes) {
+  if (
+    !getOptionValue('--experimental-raw-imports') ||
+    !importAttributes ||
+    !ObjectPrototypeHasOwnProperty(importAttributes, 'type') ||
+    typeof importAttributes.type !== 'string'
+  ) {
+    return undefined;
+  }
+
+  switch (importAttributes.type) {
+    case 'text':
+    case 'bytes':
+      return importAttributes.type;
+    default:
+      return undefined;
+  }
+}
+
 /**
  * Determine whether the given ambiguous source contains CommonJS or ES module syntax.
  * @param {string | Buffer | undefined} [source]
@@ -238,10 +257,15 @@ function getFileProtocolModuleFormat(url, context = { __proto__: null }, ignoreE
 
 /**
  * @param {URL} url
- * @param {{parentURL: string}} context
+ * @param {{parentURL: string, importAttributes?: Record<string, string>}} context
  * @returns {Promise<string> | string | undefined} only works when enabled
  */
 function defaultGetFormatWithoutErrors(url, context) {
+  const format = getFormatFromImportAttributes(context?.importAttributes);
+  if (format !== undefined) {
+    return format;
+  }
+
   const protocol = url.protocol;
   if (!ObjectPrototypeHasOwnProperty(protocolHandlers, protocol)) {
     return null;
@@ -251,10 +275,15 @@ function defaultGetFormatWithoutErrors(url, context) {
 
 /**
  * @param {URL} url
- * @param {{parentURL: string}} context
+ * @param {{parentURL: string, importAttributes?: Record<string, string>}} context
  * @returns {Promise<string> | string | undefined} only works when enabled
  */
 function defaultGetFormat(url, context) {
+  const format = getFormatFromImportAttributes(context?.importAttributes);
+  if (format !== undefined) {
+    return format;
+  }
+
   const protocol = url.protocol;
   if (!ObjectPrototypeHasOwnProperty(protocolHandlers, protocol)) {
     return null;

lib/internal/modules/esm/load.js

@@ -91,7 +91,10 @@ function defaultLoad(url, context = kEmptyObject) {
 
     if (format == null) {
       // Now that we have the source for the module, run `defaultGetFormat` to detect its format.
-      format = defaultGetFormat(urlInstance, context);
+      format = defaultGetFormat(urlInstance, {
+        __proto__: context,
+        importAttributes,
+      });
 
       if (format === 'commonjs') {
         // For backward compatibility reasons, we need to discard the source in
@@ -155,7 +158,10 @@ function defaultLoadSync(url, context = kEmptyObject) {
     }
 
     // Now that we have the source for the module, run `defaultGetFormat` to detect its format.
-    format ??= defaultGetFormat(urlInstance, context);
+    format ??= defaultGetFormat(urlInstance, {
+      __proto__: context,
+      importAttributes,
+    });
 
     // For backward compatibility reasons, we need to let go through Module._load
     // again.

lib/internal/modules/esm/translators.js

@@ -642,3 +642,23 @@ translators.set('module-typescript', function(url, translateContext, parentURL)
   translateContext.source = stripTypeScriptModuleTypes(stringify(source), url);
   return FunctionPrototypeCall(translators.get('module'), this, url, translateContext, parentURL);
 });
+
+// Strategy for loading source as text.
+translators.set('text', function textStrategy(url, translateContext) {
+  let { source } = translateContext;
+  assertBufferSource(source, true, 'load');
+  source = stringify(source);
+  return new ModuleWrap(url, undefined, ['default'], function() {
+    this.setExport('default', source);
+  });
+});
+
+// Strategy for loading source as raw bytes.
+translators.set('bytes', function bytesStrategy(url, translateContext) {
+  let { source } = translateContext;
+  assertBufferSource(source, false, 'load');
+  source = new Uint8Array(Buffer.from(source));
+  return new ModuleWrap(url, undefined, ['default'], function() {
+    this.setExport('default', source);
+  });
+});

src/node_options.cc

@@ -632,6 +632,11 @@ EnvironmentOptionsParser::EnvironmentOptionsParser() {
   AddAlias("--loader", "--experimental-loader");
   AddOption("--experimental-modules", "", NoOp{}, kAllowedInEnvvar);
   AddOption("--experimental-wasm-modules", "", NoOp{}, kAllowedInEnvvar);
+  AddOption("--experimental-raw-imports",
+            "experimental support for raw source imports with import "
+            "attributes",
+            &EnvironmentOptions::experimental_raw_imports,
+            kAllowedInEnvvar);
   AddOption("--experimental-import-meta-resolve",
             "experimental ES Module import.meta.resolve() parentURL support",
             &EnvironmentOptions::experimental_import_meta_resolve,

src/node_options.h

@@ -134,6 +134,7 @@ class EnvironmentOptions : public Options {
   std::string localstorage_file;
   bool experimental_global_navigator = true;
   bool experimental_global_web_crypto = true;
+  bool experimental_raw_imports = false;
   bool experimental_import_meta_resolve = false;
   std::string input_type;  // Value of --input-type
   bool entry_is_url = false;