11'use strict' ;
2+
23const {
34 RegExpPrototypeExec,
45 ObjectPrototypeHasOwnProperty,
56 PromisePrototypeThen,
67 PromiseResolve,
8+ StringPrototypeIncludes,
79 StringPrototypeCharCodeAt,
810 StringPrototypeSlice,
911} = primordials ;
1012const { basename, relative } = require ( 'path' ) ;
1113const { getOptionValue } = require ( 'internal/options' ) ;
1214const {
1315 extensionFormatMap,
16+ getFormatOfExtensionlessFile,
1417 mimeToFormat,
1518} = require ( 'internal/modules/esm/formats' ) ;
1619
1720const experimentalNetworkImports =
1821getOptionValue ( '--experimental-network-imports' ) ;
22+ const defaultTypeFlag = getOptionValue ( '--experimental-default-type' ) ;
23+ // The next line is where we flip the default to ES modules someday.
24+ const defaultType = defaultTypeFlag === 'module' ? 'module' : 'commonjs' ;
1925const { getPackageType, getPackageScopeConfig } = require ( 'internal/modules/esm/resolve' ) ;
2026const { fileURLToPath } = require ( 'internal/url' ) ;
2127const { ERR_UNKNOWN_FILE_EXTENSION } = require ( 'internal/errors' ) . codes ;
@@ -66,6 +72,18 @@ function extname(url) {
6672return '' ;
6773}
6874
75+ /**
76+ * Determine whether the given file URL is under a `node_modules` folder.
77+ * This function assumes that the input has already been verified to be a `file:` URL,
78+ * and is a file rather than a folder.
79+ * @param {URL } url
80+ */
81+ function underNodeModules ( url ) {
82+ if ( url . protocol !== 'file:' ) { return false ; } // We determine module types for other protocols based on MIME header
83+
84+ return StringPrototypeIncludes ( url . pathname , '/node_modules/' ) ;
85+ }
86+
6987/**
7088 * @param {URL } url
7189 * @param {{parentURL: string} } context
@@ -74,8 +92,37 @@ function extname(url) {
7492 */
7593function getFileProtocolModuleFormat ( url , context , ignoreErrors ) {
7694const ext = extname ( url ) ;
95+
7796if ( ext === '.js' ) {
78- return getPackageType ( url ) === 'module' ? 'module' : 'commonjs' ;
97+ const packageType = getPackageType ( url ) ;
98+ if ( packageType !== 'none' ) {
99+ return packageType ;
100+ }
101+ // The controlling `package.json` file has no `type` field.
102+ if ( defaultType === 'module' ) {
103+ // An exception to the type flag making ESM the default everywhere is that package scopes under `node_modules`
104+ // should retain the assumption that a lack of a `type` field means CommonJS.
105+ return underNodeModules ( url ) ? 'commonjs' : 'module' ;
106+ }
107+ return 'commonjs' ;
108+ }
109+
110+ if ( ext === '' ) {
111+ const packageType = getPackageType ( url ) ;
112+ if ( defaultType === 'commonjs' ) { // Legacy behavior
113+ if ( packageType === 'none' || packageType === 'commonjs' ) {
114+ return 'commonjs' ;
115+ }
116+ // If package type is `module`, fall through to the error case below
117+ } else { // Else defaultType === 'module'
118+ if ( underNodeModules ( url ) ) { // Exception for package scopes under `node_modules`
119+ return 'commonjs' ;
120+ }
121+ if ( packageType === 'none' || packageType === 'module' ) {
122+ return getFormatOfExtensionlessFile ( url ) ;
123+ } // Else packageType === 'commonjs'
124+ return 'commonjs' ;
125+ }
79126}
80127
81128const format = extensionFormatMap [ ext ] ;
@@ -89,12 +136,10 @@ function getFileProtocolModuleFormat(url, context, ignoreErrors) {
89136const config = getPackageScopeConfig ( url ) ;
90137const fileBasename = basename ( filepath ) ;
91138const relativePath = StringPrototypeSlice ( relative ( config . pjsonPath , filepath ) , 1 ) ;
92- suggestion = 'Loading extensionless files is not supported inside of ' +
93- '"type":"module" package.json contexts. The package.json file ' +
94- `${ config . pjsonPath } +
95- `changing ${ filepath } +
96- 'field of package.json can point to a file with an extension, for example ' +
97- `{"type":"module","bin":{"${ fileBasename } ${ relativePath } ;
139+ suggestion = 'Loading extensionless files is not supported inside of "type":"module" package.json contexts ' +
140+ `without --experimental-default-type=module. The package.json file ${ config . pjsonPath } +
141+ `context. Try changing ${ filepath } +
142+ `to a file with an extension, for example {"type":"module","bin":{"${ fileBasename } ${ relativePath } ;
98143}
99144throw new ERR_UNKNOWN_FILE_EXTENSION ( ext , filepath , suggestion ) ;
100145}
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