Rust port of enhanced-resolve.

• Released on crates.io and npm.
• Implements the ESM and CommonJS module resolution algorithm specification.
• Built-in tsconfig-paths-webpack-plugin
  • support extending tsconfig defined in tsconfig.extends
  • support paths alias defined in tsconfig.compilerOptions.paths
  • support project references defined tsconfig.references
  • support template variable ${configDir} for substitution of config files directory path
• Supports in-memory file system via the FileSystem trait.
• Contains tracing instrumentation.

See index.d.ts for resolveSync and ResolverFactory API.

Quick example:

import assert from 'assert';
import path from 'path';
import resolve, { ResolverFactory } from './index.js';

// `resolve`
assert(resolve.sync(process.cwd(), './index.js').path, path.join(cwd, 'index.js'));

// `ResolverFactory`
const resolver = new ResolverFactory();
assert(resolver.sync(process.cwd(), './index.js').path, path.join(cwd, 'index.js'));

See https://stackblitz.com/edit/oxc-resolver for usage example.

See docs.rs/oxc_resolver.

• For node.js, yarn pnp should work without any configuration, given the following conditions:
  • the program is called with the yarn command, where the value process.versions.pnp is set.
  • .pnp.cjs manifest file exists in the closest directory, searched from the current working directory,
  • no multi-project setup, per second bullet point in FIND_PNP_MANIFEST

An absolute path to a directory where the specifier is resolved against.

For CommonJS modules, it is the __dirname variable that contains the absolute path to the folder containing current module.

For ECMAScript modules, it is the value of import.meta.url.

Behavior is undefined when given a path to a file.

The string passed to require or import, i.e. require("specifier") or import "specifier"

• Error: Package subpath '.' is not defined by "exports" in - occurs when resolving without conditionNames.

The following usages apply to both Rust and Node.js; the code snippets are written in JavaScript.

To handle the exports field in package.json, ESM and CJS need to be differentiated.

Per ESM Resolution algorithm

defaultConditions is the conditional environment name array, ["node", "import"].

This means when the caller is an ESM import (import "module"), resolve options should be

{
  "conditionNames": ["node", "import"]
}

Per CJS Resolution algorithm

LOAD_PACKAGE_EXPORTS(X, DIR)

5. let MATCH = PACKAGE_EXPORTS_RESOLVE(pathToFileURL(DIR/NAME), "." + SUBPATH, package.json "exports", ["node", "require"]) defined in the ESM resolver.

This means when the caller is a CJS require (require("module")), resolve options should be

{
  "conditionNames": ["node", "require"]
}

To support both CJS and ESM with the same cache:

const esmResolver = new ResolverFactory({
  conditionNames: ['node', 'import'],
});

const cjsResolver = esmResolver.cloneWithOptions({
  conditionNames: ['node', 'require'],
});

From this non-standard spec:

The browser field is provided to JavaScript bundlers or component tools when packaging modules for client side use.

The option is

{
  "aliasFields": ["browser"]
}

{
  "mainFields": ["module", "main"]
}

Quoting esbuild's documentation:

• main - This is the standard field for all packages that are meant to be used with node. The name main is hard-coded in to node's module resolution logic itself. Because it's intended for use with node, it's reasonable to expect that the file path in this field is a CommonJS-style module.
• module - This field came from a proposal for how to integrate ECMAScript modules into node. Because of this, it's reasonable to expect that the file path in this field is an ECMAScript-style module. This proposal wasn't adopted by node (node uses "type": "module" instead) but it was adopted by major bundlers because ECMAScript-style modules lead to better tree shaking, or dead code removal.
• browser - This field came from a proposal that allows bundlers to replace node-specific files or modules with their browser-friendly versions. It lets you specify an alternate browser-specific entry point. Note that it is possible for a package to use both the browser and module field together (see the note below).

The following options are aligned with enhanced-resolve, and is implemented for Rust crate usage.

See index.d.ts for Node.js usage.

The following environment variable emits tracing information for the oxc_resolver::resolve function.

e.g.

2024-06-11T07:12:20.003537Z DEBUG oxc_resolver: options: ResolveOptions { ... }, path: "...", specifier: "...", ret: "..."
    at /path/to/oxc_resolver-1.8.1/src/lib.rs:212
    in oxc_resolver::resolve with path: "...", specifier: "..."

The input values are options, path and specifier, the returned value is ret.

OXC_LOG=DEBUG your_program

RD_LOG='oxc_resolver' rolldown build

Tests are ported from

• enhanced-resolve
• tsconfig-path and parcel-resolver for tsconfig-paths

Test cases are located in ./src/tests, fixtures are located in ./tests

• alias.test.js
• browserField.test.js
• dependencies.test.js
• exportsField.test.js
• extension-alias.test.js
• extensions.test.js
• fallback.test.js
• fullSpecified.test.js
• identifier.test.js (see unit test in crates/oxc_resolver/src/request.rs)
• importsField.test.js
• incorrect-description-file.test.js (need to add ctx.fileDependencies)
• missing.test.js
• path.test.js (see unit test in crates/oxc_resolver/src/path.rs)
• plugins.test.js
• pnp.test.js
• resolve.test.js
• restrictions.test.js (partially done, regex is not supported yet)
• roots.test.js
• scoped-packages.test.js
• simple.test.js
• symlink.test.js

Irrelevant tests

• CachedInputFileSystem.test.js
• SyncAsyncFileSystemDecorator.test.js
• forEachBail.test.js
• getPaths.test.js
• pr-53.test.js
• unsafe-cache.test.js
• yield.test.js

oxc_resolver is free and open-source software licensed under the MIT License.

Oxc partially copies code from the following projects.