fix: do not support recursive resolution

It will return `undefined` if the import is recursive.

.changeset/metal-planets-end.md

@@ -0,0 +1,8 @@
+---
+'resolve.imports': patch
+---
+
+Do not support recursive resolution.
+
+There is no spec for it.
+It will return `undefined` if the import is recursive.

packages/resolve.imports/README.md

@@ -4,7 +4,13 @@
 [![NPM downloads][downloads-image]][downloads-url]
 [![Codecov][codecov-image]][codecov-url]
 
-Resolves files based on the [imports] field within the specified `package.json`.
+[subpath-imports] field resolver without file-system reliance.
+
+It uses a new logic differs from [resolve.exports] which also handles:
+
+- [File extensions](#subpath-imports) ([issue in `resolve.exports`][file-extensions-issue])
+- [Array patterns](#array-patterns) ([issue in `resolve.exports`][array-patterns-issue])
+- [Subpath patterns with extensions](#subpath-imports) ([issue in `resolve.exports`][subpath-patterns-issue])
 
 ## Install
 
@@ -24,11 +30,125 @@ rush add -p resolve.imports
 
 ## Usage
 
+Here is the API:
+
+`resolve(pjson: Record, entry: string, options?: { conditions?: string[] }): string | undefined`:
+
+- `pjson` is the package.json object.
+- `entry` is the entry to resolve.
+- `options` is optional. It contains:
+  - `conditions` is the conditions to resolve. It is used for [subpath imports][subpath-imports].
+
+It returns either a `string`, `string[]` (for [array pattern](#array-patterns)) or `undefined`.
+
+Note that it does not support recursive resolution. i.e.:
+
+```ts
+import { resolve } from 'resolve.imports';
+
+const pjson = {
+  "imports": {
+    "#internal/*.js": "#another-internal/*.js",
+    "#another-internal/*.js": "./src/another-internal/*.js"
+  }
+}
+
+resolve(pjson, '#internal/foo.js') //=> undefined
+```
+
+It is not supported because I can't find such use case in the spec.
+If you have such use case, please open an issue.
+
+### Subpath imports
+
+[Subpath imports][subpath-imports] are supported:
+
+Using [chalk] as an example:
+
+```ts
+import { resolve } from 'resolve.imports';
+
+const chalkPackageJson = {
+  "imports": {
+    "#ansi-styles": "./source/vendor/ansi-styles/index.js",
+    "#supports-color": {
+      "node": "./source/vendor/supports-color/index.js",
+      "default": "./source/vendor/supports-color/browser.js"
+    }
+  }
+}
+
+resolve(chalkPackageJson, '#ansi-styles') //=> `./source/vendor/ansi-styles/index.js`
+resolve(chalkPackageJson, '#supports-color') //=> `./source/vendor/supports-color/browser.js`
+resolve(chalkPackageJson, '#supports-color', { conditions: ['node'] }) //=> `./source/vendor/supports-color/index.js`
+resolve(chalkPackageJson, '#supports-color', { conditions: ['default']}) //=> `./source/vendor/supports-color/browser.js`
+```
+
+### File extensions
+
+[File extensions][file-extensions-issue] are supported:
+
 ```ts
 import { resolve } from 'resolve.imports';
 
-// `path = './source/vendored/ansi-styles/index.js'`
-const path = resolve(packageJsonContent, '#ansi-styles', { conditions: ['imports', 'node', 'default'] });
+const pjson = {
+  imports: {
+    '#internal/a.js': './src/internal/a.js',
+}
+
+resolve(pjson, '#internal/a.js') //=> `./src/internal/a.js`
+```
+
+### Array patterns
+
+```ts
+import { resolve } from 'resolve.imports';
+
+const pjson = {
+  imports: {
+    '#internal/*.js': ['./src/internal/*.js', './src/internal2/*.js']
+}
+
+resolve(pjson, '#internal/a.js') //=> ['./src/internal/foo.js', './src/internal2/foo.js']
+```
+
+### Subpath patterns
+
+[Subpath patterns][subpath-patterns] are supported:
+
+```ts
+import { resolve } from 'resolve.imports';
+
+const pjson = {
+  "imports": {
+    "#internal/*.js": "./src/internal/*.js"
+  }
+}
+
+resolve(pjson, '#internal/foo.js') //=> `./src/internal/foo.js`
+```
+
+### Nested conditions
+
+[Nested conditions](https://nodejs.org/api/packages.html#nested-conditions) are supported:
+
+```ts
+import { resolve } from 'resolve.imports';
+
+const pjson = {
+  "imports": {
+    '#feature': {
+      "node": {
+        "import": "./feature-node.mjs",
+        "require": "./feature-node.cjs"
+      },
+      "default": "./feature.mjs"
+    }
+  }
+}
+
+resolve(pjson, '#feature') //=> `./feature.mjs`
+resolve(pjson, '#feature', { conditions: ['node', 'import']}) //=> `./feature-node.mjs`
 ```
 
 This is used by [@repobuddy/jest] to resolve ESM packages correctly.
@@ -41,10 +161,15 @@ This is used by [@repobuddy/jest] to resolve ESM packages correctly.
 - [@node-loader/import-maps](https://github.com/node-loader/node-loader-import-maps)
 
 [@repobuddy/jest]: https://github.com/repobuddy/jest
+[array-patterns-issue]: https://github.com/lukeed/resolve.exports/issues/17
+[chalk]: https://github.com/chalk/chalk
 [codecov-image]: https://codecov.io/gh/cyberuni/resolve.imports/branch/main/graph/badge.svg
 [codecov-url]: https://codecov.io/gh/cyberuni/resolve.imports
 [downloads-image]: https://img.shields.io/npm/dm/resolve.imports.svg?style=flat
 [downloads-url]: https://npmjs.org/package/resolve.imports
-[imports]: https://nodejs.org/api/packages.html#subpath-imports
+[file-extensions-issue]: https://github.com/lukeed/resolve.exports/issues/22
 [npm-image]: https://img.shields.io/npm/v/resolve.imports.svg?style=flat
 [npm-url]: https://npmjs.org/package/resolve.imports
+[subpath-imports]: https://nodejs.org/api/packages.html#subpath-imports
+[subpath-patterns-issue]: https://github.com/lukeed/resolve.exports/issues/16
+[subpath-patterns]: https://nodejs.org/api/packages.html#subpath-patterns

packages/resolve.imports/ts/index.spec.ts

@@ -100,6 +100,31 @@ describe('no * pattern', () => {
     )
     expect(r).toBe('./node.mjs')
   })
+
+  it('works with explicit file path', () => {
+    const pkg = {
+      imports: {
+        '#internal/a.js': './src/internal/a.js',
+        '#internal/b.js': {
+          import: './src/internal/b.mjs',
+          require: './src/internal/b.cjs',
+          default: './src/browser/b.mjs'
+        },
+        '#internal/c.js': {
+          node: {
+            import: './src/internal/c.mjs',
+            require: './src/internal/c.cjs',
+          },
+          default: './src/browser/c.mjs'
+        }
+      }
+    }
+    expect(resolve(pkg, '#internal/a.js')).toBe('./src/internal/a.js')
+    expect(resolve(pkg, '#internal/b.js')).toBe('./src/browser/b.mjs')
+    expect(resolve(pkg, '#internal/b.js', { conditions: ['import'] })).toBe('./src/internal/b.mjs')
+    expect(resolve(pkg, '#internal/c.js')).toBe('./src/browser/c.mjs')
+    expect(resolve(pkg, '#internal/c.js', { conditions: ['node', 'require'] })).toBe('./src/internal/c.cjs')
+  })
 })
 
 describe(`subpath patterns`, () => {
@@ -209,4 +234,18 @@ describe(`subpath patterns`, () => {
     )
     expect(r).toBe('./src/internal/foo/foo.js')
   })
+
+  // Do not see any spec for this.
+  // So do not support it for now to avoid deviating from spec.
+  it('does not support recursive references', () => {
+    const pkg = {
+      imports: {
+        '#internal/*.js': '#internal/*.js',
+        '#a': '#b',
+        '#b': './b.js',
+      }
+    }
+    expect(resolve(pkg, '#a')).toBeUndefined()
+    expect(resolve(pkg, '#internal/foo.js')).toBeUndefined()
+  })
 })

packages/resolve.imports/ts/index.ts

@@ -18,7 +18,7 @@ export function resolve(pkg: any, entry: string, options?: ResolveOptions) {
 
   const matched = pkg.imports[entry]
   if (matched) {
-    return lookupReplacer(matched, options?.conditions?.slice())
+    return noRecursive(lookupReplacer(matched, options?.conditions?.slice()))
   }
 
   for (const key in pkg.imports) {
@@ -28,7 +28,9 @@ export function resolve(pkg: any, entry: string, options?: ResolveOptions) {
     if (entry.startsWith(prefix)) {
       const replacer = lookupReplacer(pkg.imports[key], options?.conditions?.slice())
 
-      if (replacer) return Array.isArray(replacer) ? replacer.map(replacePattern) : replacePattern(replacer)
+      if (replacer) return noRecursive(
+        Array.isArray(replacer) ? replacer.map(replacePattern) : replacePattern(replacer)
+      )
     }
 
     function replacePattern(replacer: string) {
@@ -51,3 +53,8 @@ function lookupReplacer(map: ImportMap, conditions?: string[]): string | string[
   }
   return map.default as any
 }
+
+function noRecursive(value: string | string[] | undefined): string | string[] | undefined {
+  if (Array.isArray(value)) return value.map(noRecursive) as string[]
+  return value?.startsWith('#') ? undefined : value
+}