Oxc Resolver

Rust port of enhanced-resolve.

• released on crates.io and npm.
• 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

Usage

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.

ESM

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"]
}

CJS

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"]
}

Cache

To support both CJS and ESM with the same cache:

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

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

Browser Field

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"]
}

Main Field

{
  "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).

Errors & Trouble Shooting

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

Options

The options are aligned with enhanced-resolve.

Unimplemented Options

Debugging

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.

NAPI

OXC_LOG=DEBUG your_program

Rolldown

RD_LOG='oxc_resolver' rolldown build

Rspack

RSPACK_PROFILE='TRACE=filter=oxc_resolver=trace&layer=logger' rspack build

Test

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

Sponsored By

📖 License

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

Oxc partially copies code from the following projects.