module: exports pattern support

Backport-PR-URL: #35757
PR-URL: #34718
Reviewed-By: Jan Krems <jan.krems@gmail.com>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>

Author: guybedford

doc/api/esm.md

@@ -1038,7 +1038,8 @@ The resolver can throw the following errors:
 >       1. Set _mainExport_ to _exports_\[_"."_\].
 >    1. If _mainExport_ is not **undefined**, then
 >       1. Let _resolved_ be the result of **PACKAGE_TARGET_RESOLVE**(
->          _packageURL_, _mainExport_, _""_, **false**, _conditions_).
+>          _packageURL_, _mainExport_, _""_, **false**, **false**,
+>          _conditions_).
 >       1. If _resolved_ is not **null** or **undefined**, then
 >          1. Return _resolved_.
 > 1. Otherwise, if _exports_ is an Object and all keys of _exports_ start with
@@ -1072,29 +1073,43 @@ _isImports_, _conditions_)
 > 1. If _matchKey_ is a key of _matchObj_, and does not end in _"*"_, then
 >    1. Let _target_ be the value of _matchObj_\[_matchKey_\].
 >    1. Let _resolved_ be the result of **PACKAGE_TARGET_RESOLVE**(
->       _packageURL_, _target_, _""_, _isImports_, _conditions_).
+>       _packageURL_, _target_, _""_, **false**, _isImports_, _conditions_).
 >    1. Return the object _{ resolved, exact: **true** }_.
-> 1. Let _expansionKeys_ be the list of keys of _matchObj_ ending in _"/"_,
->    sorted by length descending.
+> 1. Let _expansionKeys_ be the list of keys of _matchObj_ ending in _"/"_
+>    or _"*"_, sorted by length descending.
 > 1. For each key _expansionKey_ in _expansionKeys_, do
+>    1. If _expansionKey_ ends in _"*"_ and _matchKey_ starts with but is
+>       not equal to the substring of _expansionKey_ excluding the last _"*"_
+>       character, then
+>       1. Let _target_ be the value of _matchObj_\[_expansionKey_\].
+>       1. Let _subpath_ be the substring of _matchKey_ starting at the
+>          index of the length of _expansionKey_ minus one.
+>       1. Let _resolved_ be the result of **PACKAGE_TARGET_RESOLVE**(
+>          _packageURL_, _target_, _subpath_, **true**, _isImports_,
+>          _conditions_).
+>       1. Return the object _{ resolved, exact: **true** }_.
 >    1. If _matchKey_ starts with _expansionKey_, then
 >       1. Let _target_ be the value of _matchObj_\[_expansionKey_\].
 >       1. Let _subpath_ be the substring of _matchKey_ starting at the
 >          index of the length of _expansionKey_.
 >       1. Let _resolved_ be the result of **PACKAGE_TARGET_RESOLVE**(
->          _packageURL_, _target_, _subpath_, _isImports_, _conditions_).
+>          _packageURL_, _target_, _subpath_, **false**, _isImports_,
+>          _conditions_).
 >       1. Return the object _{ resolved, exact: **false** }_.
 > 1. Return the object _{ resolved: **null**, exact: **true** }_.
 
-**PACKAGE_TARGET_RESOLVE**(_packageURL_, _target_, _subpath_, _internal_,
-_conditions_)
+**PACKAGE_TARGET_RESOLVE**(_packageURL_, _target_, _subpath_, _pattern_,
+_internal_, _conditions_)
 
 > 1. If _target_ is a String, then
->    1. If _subpath_ has non-zero length and _target_ does not end with _"/"_,
->       throw an _Invalid Module Specifier_ error.
+>    1. If _pattern_ is **false**, _subpath_ has non-zero length and _target_
+>       does not end with _"/"_, throw an _Invalid Module Specifier_ error.
 >    1. If _target_ does not start with _"./"_, then
 >       1. If _internal_ is **true** and _target_ does not start with _"../"_ or
 >          _"/"_ and is not a valid URL, then
+>          1. If _pattern_ is **true**, then
+>             1. Return **PACKAGE_RESOLVE**(_target_ with every instance of
+>                _"*"_ replaced by _subpath_, _packageURL_ + _"/"_)_.
 >          1. Return **PACKAGE_RESOLVE**(_target_ + _subpath_,
 >             _packageURL_ + _"/"_)_.
 >       1. Otherwise, throw an _Invalid Package Target_ error.
@@ -1106,8 +1121,12 @@ _conditions_)
 >    1. Assert: _resolvedTarget_ is contained in _packageURL_.
 >    1. If _subpath_ split on _"/"_ or _"\\"_ contains any _"."_, _".."_ or
 >       _"node_modules"_ segments, throw an _Invalid Module Specifier_ error.
->    1. Return the URL resolution of the concatenation of _subpath_ and
->       _resolvedTarget_.
+>    1. If _pattern_ is **true**, then
+>       1. Return the URL resolution of _resolvedTarget_ with every instance of
+>          _"*"_ replaced with _subpath_.
+>    1. Otherwise,
+>       1. Return the URL resolution of the concatenation of _subpath_ and
+>          _resolvedTarget_.
 > 1. Otherwise, if _target_ is a non-null Object, then
 >    1. If _exports_ contains any index property keys, as defined in ECMA-262
 >       [6.1.7 Array Index][], throw an _Invalid Package Configuration_ error.
@@ -1116,16 +1135,18 @@ _conditions_)
 >          then
 >          1. Let _targetValue_ be the value of the _p_ property in _target_.
 >          1. Let _resolved_ be the result of **PACKAGE_TARGET_RESOLVE**(
->             _packageURL_, _targetValue_, _subpath_, _internal_, _conditions_).
+>             _packageURL_, _targetValue_, _subpath_, _pattern_, _internal_,
+>             _conditions_).
 >          1. If _resolved_ is equal to **undefined**, continue the loop.
 >          1. Return _resolved_.
 >    1. Return **undefined**.
 > 1. Otherwise, if _target_ is an Array, then
 >    1. If _target.length is zero, return **null**.
 >    1. For each item _targetValue_ in _target_, do
 >       1. Let _resolved_ be the result of **PACKAGE_TARGET_RESOLVE**(
->          _packageURL_, _targetValue_, _subpath_, _internal_, _conditions_),
->          continuing the loop on any _Invalid Package Target_ error.
+>          _packageURL_, _targetValue_, _subpath_, _pattern_, _internal_,
+>          _conditions_), continuing the loop on any _Invalid Package Target_
+>          error.
 >       1. If _resolved_ is **undefined**, continue the loop.
 >       1. Return _resolved_.
 >    1. Return or throw the last fallback resolution **null** return or error.

doc/api/packages.md

@@ -181,17 +181,17 @@ Alternatively a project could choose to export entire folders:
   "exports": {
     ".": "./lib/index.js",
     "./lib": "./lib/index.js",
-    "./lib/": "./lib/",
+    "./lib/*": "./lib/*.js",
     "./feature": "./feature/index.js",
-    "./feature/": "./feature/",
+    "./feature/*": "./feature/*.js",
     "./package.json": "./package.json"
   }
 }
 ```
 
 As a last resort, package encapsulation can be disabled entirely by creating an
-export for the root of the package `"./": "./"`. This will expose every file in
-the package at the cost of disabling the encapsulation and potential tooling
+export for the root of the package `"./*": "./*"`. This will expose every file
+in the package at the cost of disabling the encapsulation and potential tooling
 benefits this provides. As the ES Module loader in Node.js enforces the use of
 [the full specifier path][], exporting the root rather than being explicit
 about entry is less expressive than either of the prior examples. Not only
@@ -254,29 +254,46 @@ import submodule from 'es-module-package/private-module.js';
 // Throws ERR_PACKAGE_PATH_NOT_EXPORTED
 ```
 
-Entire folders can also be mapped with package exports:
+### Subpath export patterns
+
+> Stability: 1 - Experimental
+
+Explicitly listing each exports subpath entry is recommended for packages with
+a small number of exports. But for packages that have very large numbers of
+subpaths this can start to cause package.json bloat and maintenance issues.
+
+For these use cases, subpath export patterns can be used instead:
 
 ```json
 // ./node_modules/es-module-package/package.json
 {
   "exports": {
-    "./features/": "./src/features/"
+    "./features/*": "./src/features/*.js"
   }
 }
 ```
 
-With the preceding, all modules within the `./src/features/` folder
-are exposed deeply to `import` and `require`:
+The left hand matching pattern must always end in `*`. All instances of `*` on
+the right hand side will then be replaced with this value, including if it
+contains any `/` separators.
 
 ```js
-import feature from 'es-module-package/features/x.js';
+import featureX from 'es-module-package/features/x';
 // Loads ./node_modules/es-module-package/src/features/x.js
+
+import featureY from 'es-module-package/features/y/y';
+// Loads ./node_modules/es-module-package/src/features/y/y.js
 ```
 
-When using folder mappings, ensure that you do want to expose every
-module inside the subfolder. Any modules which are not public
-should be moved to another folder to retain the encapsulation
-benefits of exports.
+This is a direct static replacement without any special handling for file
+extensions. In the previous example, `pkg/features/x.json` would be resolved to
+`./src/features/x.json.js` in the mapping.
+
+The property of exports being statically enumerable is maintained with exports
+patterns since the individual exports for a package can be determined by
+treating the right hand side target pattern as a `**` glob against the list of
+files within the package. Because `node_modules` paths are forbidden in exports
+targets, this expansion is dependent on only the files of the package itself.
 
 ### Package exports fallbacks
 

lib/internal/modules/esm/resolve.js

@@ -307,10 +307,11 @@ function throwInvalidPackageTarget(
 }
 
 const invalidSegmentRegEx = /(^|\\|\/)(\.\.?|node_modules)(\\|\/|$)/;
+const patternRegEx = /\*/g;
 
 function resolvePackageTargetString(
-  target, subpath, match, packageJSONUrl, base, internal, conditions) {
-  if (subpath !== '' && target[target.length - 1] !== '/')
+  target, subpath, match, packageJSONUrl, base, pattern, internal, conditions) {
+  if (subpath !== '' && !pattern && target[target.length - 1] !== '/')
     throwInvalidPackageTarget(match, target, packageJSONUrl, internal, base);
 
   if (!StringPrototypeStartsWith(target, './')) {
@@ -321,8 +322,12 @@ function resolvePackageTargetString(
         new URL(target);
         isURL = true;
       } catch {}
-      if (!isURL)
-        return packageResolve(target + subpath, packageJSONUrl, conditions);
+      if (!isURL) {
+        const exportTarget = pattern ?
+          StringPrototypeReplace(target, patternRegEx, subpath) :
+          target + subpath;
+        return packageResolve(exportTarget, packageJSONUrl, conditions);
+      }
     }
     throwInvalidPackageTarget(match, target, packageJSONUrl, internal, base);
   }
@@ -342,6 +347,9 @@ function resolvePackageTargetString(
   if (RegExpPrototypeTest(invalidSegmentRegEx, subpath))
     throwInvalidSubpath(match + subpath, packageJSONUrl, internal, base);
 
+  if (pattern)
+    return new URL(StringPrototypeReplace(resolved.href, patternRegEx,
+                                          subpath));
   return new URL(subpath, resolved);
 }
 
@@ -356,10 +364,10 @@ function isArrayIndex(key) {
 }
 
 function resolvePackageTarget(packageJSONUrl, target, subpath, packageSubpath,
-                              base, internal, conditions) {
+                              base, pattern, internal, conditions) {
   if (typeof target === 'string') {
     return resolvePackageTargetString(
-      target, subpath, packageSubpath, packageJSONUrl, base, internal,
+      target, subpath, packageSubpath, packageJSONUrl, base, pattern, internal,
       conditions);
   } else if (ArrayIsArray(target)) {
     if (target.length === 0)
@@ -371,8 +379,8 @@ function resolvePackageTarget(packageJSONUrl, target, subpath, packageSubpath,
       let resolved;
       try {
         resolved = resolvePackageTarget(
-          packageJSONUrl, targetItem, subpath, packageSubpath, base, internal,
-          conditions);
+          packageJSONUrl, targetItem, subpath, packageSubpath, base, pattern,
+          internal, conditions);
       } catch (e) {
         lastException = e;
         if (e.code === 'ERR_INVALID_PACKAGE_TARGET')
@@ -406,7 +414,7 @@ function resolvePackageTarget(packageJSONUrl, target, subpath, packageSubpath,
         const conditionalTarget = target[key];
         const resolved = resolvePackageTarget(
           packageJSONUrl, conditionalTarget, subpath, packageSubpath, base,
-          internal, conditions);
+          pattern, internal, conditions);
         if (resolved === undefined)
           continue;
         return resolved;
@@ -460,7 +468,7 @@ function packageExportsResolve(
   if (ObjectPrototypeHasOwnProperty(exports, packageSubpath)) {
     const target = exports[packageSubpath];
     const resolved = resolvePackageTarget(
-      packageJSONUrl, target, '', packageSubpath, base, false, conditions
+      packageJSONUrl, target, '', packageSubpath, base, false, false, conditions
     );
     if (resolved === null || resolved === undefined)
       throwExportsNotFound(packageSubpath, packageJSONUrl, base);
@@ -471,7 +479,13 @@ function packageExportsResolve(
   const keys = ObjectGetOwnPropertyNames(exports);
   for (let i = 0; i < keys.length; i++) {
     const key = keys[i];
-    if (key[key.length - 1] === '/' &&
+    if (key[key.length - 1] === '*' &&
+        StringPrototypeStartsWith(packageSubpath,
+                                  StringPrototypeSlice(key, 0, -1)) &&
+        packageSubpath.length >= key.length &&
+        key.length > bestMatch.length) {
+      bestMatch = key;
+    } else if (key[key.length - 1] === '/' &&
       StringPrototypeStartsWith(packageSubpath, key) &&
       key.length > bestMatch.length) {
       bestMatch = key;
@@ -480,12 +494,15 @@ function packageExportsResolve(
 
   if (bestMatch) {
     const target = exports[bestMatch];
-    const subpath = StringPrototypeSubstr(packageSubpath, bestMatch.length);
+    const pattern = bestMatch[bestMatch.length - 1] === '*';
+    const subpath = StringPrototypeSubstr(packageSubpath, bestMatch.length -
+      (pattern ? 1 : 0));
     const resolved = resolvePackageTarget(packageJSONUrl, target, subpath,
-                                          bestMatch, base, false, conditions);
+                                          bestMatch, base, pattern, false,
+                                          conditions);
     if (resolved === null || resolved === undefined)
       throwExportsNotFound(packageSubpath, packageJSONUrl, base);
-    return { resolved, exact: false };
+    return { resolved, exact: pattern };
   }
 
   throwExportsNotFound(packageSubpath, packageJSONUrl, base);
@@ -504,7 +521,7 @@ function packageImportsResolve(name, base, conditions) {
     if (imports) {
       if (ObjectPrototypeHasOwnProperty(imports, name)) {
         const resolved = resolvePackageTarget(
-          packageJSONUrl, imports[name], '', name, base, true, conditions
+          packageJSONUrl, imports[name], '', name, base, false, true, conditions
         );
         if (resolved !== null)
           return { resolved, exact: true };
@@ -513,7 +530,13 @@ function packageImportsResolve(name, base, conditions) {
         const keys = ObjectGetOwnPropertyNames(imports);
         for (let i = 0; i < keys.length; i++) {
           const key = keys[i];
-          if (key[key.length - 1] === '/' &&
+          if (key[key.length - 1] === '*' &&
+              StringPrototypeStartsWith(name,
+                                        StringPrototypeSlice(key, 0, -1)) &&
+              name.length >= key.length &&
+              key.length > bestMatch.length) {
+            bestMatch = key;
+          } else if (key[key.length - 1] === '/' &&
             StringPrototypeStartsWith(name, key) &&
             key.length > bestMatch.length) {
             bestMatch = key;
@@ -522,11 +545,14 @@ function packageImportsResolve(name, base, conditions) {
 
         if (bestMatch) {
           const target = imports[bestMatch];
-          const subpath = StringPrototypeSubstr(name, bestMatch.length);
+          const pattern = bestMatch[bestMatch.length - 1] === '*';
+          const subpath = StringPrototypeSubstr(name, bestMatch.length -
+            (pattern ? 1 : 0));
           const resolved = resolvePackageTarget(
-            packageJSONUrl, target, subpath, bestMatch, base, true, conditions);
+            packageJSONUrl, target, subpath, bestMatch, base, pattern, true,
+            conditions);
           if (resolved !== null)
-            return { resolved, exact: false };
+            return { resolved, exact: pattern };
         }
       }
     }

test/es-module/test-esm-exports.mjs

@@ -33,6 +33,9 @@ import fromInside from '../fixtures/node_modules/pkgexports/lib/hole.js';
       { default: 'self-cjs' } : { default: 'self-mjs' }],
     // Resolve self sugar
     ['pkgexports-sugar', { default: 'main' }],
+    // Path patterns
+    ['pkgexports/subpath/sub-dir1', { default: 'main' }],
+    ['pkgexports/features/dir1', { default: 'main' }]
   ]);
 
   if (isRequire) {

test/fixtures/es-modules/pkgimports/package.json

@@ -5,9 +5,9 @@
       "import": "./importbranch.js",
       "require": "./requirebranch.js"
     },
-    "#subpath/": "./sub/",
+    "#subpath/*": "./sub/*",
     "#external": "pkgexports/valid-cjs",
-    "#external/subpath/": "pkgexports/sub/",
+    "#external/subpath/*": "pkgexports/sub/*",
     "#external/invalidsubpath/": "pkgexports/sub",
     "#belowbase": "../belowbase",
     "#url": "some:url",