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module: exports pattern support
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PR-URL: #34718
Backport-PR-URL: #35385
Reviewed-By: Jan Krems <jan.krems@gmail.com>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
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@guybedford @codebytere
guybedford authored and codebytere committed Oct 1, 2020
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102 changes: 69 additions & 33 deletions doc/api/esm.md
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Original file line number Diff line number Diff line change
Expand Up @@ -298,14 +298,14 @@ package. It is not a strong encapsulation since a direct require of any
absolute subpath of the package such as
`require('/path/to/node_modules/pkg/subpath.js')` will still load `subpath.js`.

#### Subpath exports
### Subpath exports

When using the `"exports"` field, custom subpaths can be defined along
with the main entry point by treating the main entry point as the
`"."` subpath:
> Stability: 1 - Experimental
<!-- eslint-skip -->
```js
When using the `"exports"` field, custom subpaths can be defined along with the
main entry point by treating the main entry point as the `"."` subpath:

```json
{
"main": "./main.js",
"exports": {
Expand All @@ -315,8 +315,7 @@ with the main entry point by treating the main entry point as the
}
```

Now only the defined subpath in `"exports"` can be imported by a
consumer:
Now only the defined subpath in `"exports"` can be imported by a consumer:

```js
import submodule from 'es-module-package/submodule';
Expand All @@ -330,30 +329,46 @@ 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

<!-- eslint-skip -->
```js
> 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 above, 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

Expand Down Expand Up @@ -1741,7 +1756,8 @@ 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
Expand Down Expand Up @@ -1775,29 +1791,43 @@ _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.
Expand All @@ -1809,8 +1839,12 @@ _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.
Expand All @@ -1819,16 +1853,18 @@ _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.
Expand Down
64 changes: 45 additions & 19 deletions lib/internal/modules/esm/resolve.js
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Original file line number Diff line number Diff line change
Expand Up @@ -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, './')) {
Expand All @@ -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);
}
Expand All @@ -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);
}

Expand All @@ -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)
Expand All @@ -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')
Expand Down Expand Up @@ -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;
Expand Down Expand Up @@ -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);
Expand All @@ -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;
Expand All @@ -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);
Expand All @@ -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 };
Expand All @@ -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;
Expand All @@ -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 };
}
}
}
Expand Down
3 changes: 3 additions & 0 deletions test/es-module/test-esm-exports.mjs
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Original file line number Diff line number Diff line change
Expand Up @@ -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) {
Expand Down
4 changes: 2 additions & 2 deletions test/fixtures/es-modules/pkgimports/package.json
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Original file line number Diff line number Diff line change
Expand Up @@ -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",
Expand Down
4 changes: 3 additions & 1 deletion test/fixtures/node_modules/pkgexports/package.json
View file

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