Update esm loader hooks API

dist-raw/node-esm-default-get-format.js

@@ -0,0 +1,83 @@
+// Copied from https://raw.githubusercontent.com/nodejs/node/v15.3.0/lib/internal/modules/esm/get_format.js
+// Then modified to suite our needs.
+// Formatting is intentionally bad to keep the diff as small as possible, to make it easier to merge
+// upstream changes and understand our modifications.
+
+'use strict';
+const {
+  RegExpPrototypeExec,
+  StringPrototypeStartsWith,
+} = require('./node-primordials');
+const { extname } = require('path');
+const { getOptionValue } = require('./node-options');
+
+const experimentalJsonModules = getOptionValue('--experimental-json-modules');
+const experimentalSpeciferResolution =
+  getOptionValue('--experimental-specifier-resolution');
+const experimentalWasmModules = getOptionValue('--experimental-wasm-modules');
+const { getPackageType } = require('./node-esm-resolve-implementation.js').createResolve({tsExtensions: [], jsExtensions: []});
+const { URL, fileURLToPath } = require('url');
+const { ERR_UNKNOWN_FILE_EXTENSION } = require('./node-errors').codes;
+
+const extensionFormatMap = {
+  '__proto__': null,
+  '.cjs': 'commonjs',
+  '.js': 'module',
+  '.mjs': 'module'
+};
+
+const legacyExtensionFormatMap = {
+  '__proto__': null,
+  '.cjs': 'commonjs',
+  '.js': 'commonjs',
+  '.json': 'commonjs',
+  '.mjs': 'module',
+  '.node': 'commonjs'
+};
+
+if (experimentalWasmModules)
+  extensionFormatMap['.wasm'] = legacyExtensionFormatMap['.wasm'] = 'wasm';
+
+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 [ , mime ] = RegExpPrototypeExec(
+      /^([^/]+\/[^;,]+)(?:[^,]*?)(;base64)?,/,
+      parsed.pathname,
+    ) || [ null, 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:') {
+    const ext = extname(parsed.pathname);
+    let format;
+    if (ext === '.js') {
+      format = getPackageType(parsed.href) === 'module' ? 'module' : 'commonjs';
+    } else {
+      format = extensionFormatMap[ext];
+    }
+    if (!format) {
+      if (experimentalSpeciferResolution === 'node') {
+        process.emitWarning(
+          'The Node.js specifier resolution in ESM is experimental.',
+          'ExperimentalWarning');
+        format = legacyExtensionFormatMap[ext];
+      } else {
+        throw new ERR_UNKNOWN_FILE_EXTENSION(ext, fileURLToPath(url));
+      }
+    }
+    return { format: format || null };
+  }
+  return { format: null };
+}
+exports.defaultGetFormat = defaultGetFormat;

esm.mjs

@@ -6,6 +6,7 @@ const require = createRequire(fileURLToPath(import.meta.url));
 const esm = require('./dist/esm');
 export const {
   resolve,
+  load,
   getFormat,
   transformSource,
 } = esm.registerAndCreateEsmHooks();

package.json

@@ -69,7 +69,8 @@
     "test-local": "npm run lint-fix && npm run build-tsc && npm run build-pack && npm run test-spec --",
     "coverage-report": "nyc report --reporter=lcov",
     "prepare": "npm run clean && npm run build-nopack",
-    "api-extractor": "api-extractor run --local --verbose"
+    "api-extractor": "api-extractor run --local --verbose",
+    "esm-usage-example": "npm run build-tsc && cd esm-usage-example && node --experimental-specifier-resolution node --loader ../esm.mjs ./index"
   },
   "engines": {
     "node": ">=12.0.0"

src/esm.ts

@@ -12,6 +12,7 @@ import { normalizeSlashes } from './util';
 const {
   createResolve,
 } = require('../dist-raw/node-esm-resolve-implementation');
+const { defaultGetFormat } = require('../dist-raw/node-esm-default-get-format');
 
 // Note: On Windows, URLs look like this: file:///D:/dev/@TypeStrong/ts-node-examples/foo.ts
 
@@ -28,7 +29,12 @@ export function registerAndCreateEsmHooks(opts?: RegisterOptions) {
     preferTsExts: tsNodeInstance.options.preferTsExts,
   });
 
-  return { resolve, getFormat, transformSource };
+  // The hooks API changed in node version X so we need to check for backwards compatibility
+  // TODO: When the new API is released, change to the correct node version here
+  const newHooksAPI = parseInt(process.versions.node.split('.')[0], 10) >= 17;
+  return newHooksAPI
+    ? { resolve, load }
+    : { resolve, getFormat, transformSource };
 
   function isFileUrlOrNodeStyleSpecifier(parsed: UrlWithStringQuery) {
     // We only understand file:// URLs, but in node, the specifier can be a node-style `./foo` or `foo`
@@ -72,6 +78,35 @@ export function registerAndCreateEsmHooks(opts?: RegisterOptions) {
     );
   }
 
+  async function load(
+    url: string,
+    context: {},
+    defaultLoad: typeof load
+  ): Promise<{ format: Format; source: string | Buffer }> {
+    const { format } = await getFormat(url, context, defaultGetFormat);
+
+    const { source: rawSource } = await defaultLoad(
+      url,
+      { format },
+      defaultLoad
+    );
+
+    const defaultTransformSource: typeof transformSource = async (
+      source,
+      _context,
+      _defaultTransformSource
+    ) => ({ source });
+    const { source } = await transformSource(
+      rawSource,
+      { url, format },
+      defaultTransformSource
+    );
+    return {
+      format,
+      source,
+    };
+  }
+
   type Format = 'builtin' | 'commonjs' | 'dynamic' | 'json' | 'module' | 'wasm';
   async function getFormat(
     url: string,