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Oxc Resolver

Rust port of enhanced-resolve.

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)

  1. 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:

Errors & Trouble Shooting

Options

The options are aligned with enhanced-resolve.

FieldDefaultDescription
alias[]A list of module alias configurations or an object which maps key to value
aliasFields[]A list of alias fields in description files
extensionAlias{}An object which maps extension to extension aliases
conditionNames[]A list of exports field condition names
descriptionFiles["package.json"]A list of description files to read from
enforceExtensionfalseEnforce that a extension from extensions must be used
exportsFields["exports"]A list of exports fields in description files
extensions[".js", ".json", ".node"]A list of extensions which should be tried for files
fallback[]Same as alias, but only used if default resolving fails
fileSystemThe file system which should be used
fullySpecifiedfalseRequest passed to resolve is already fully specified and extensions or main files are not resolved for it (they are still resolved for internal requests)
mainFields["main"]A list of main fields in description files
mainFiles["index"]A list of main files in directories
modules["node_modules"]A list of directories to resolve modules from, can be absolute path or folder name
resolveToContextfalseResolve to a context instead of a file
preferRelativefalsePrefer to resolve module requests as relative request and fallback to resolving as module
preferAbsolutefalsePrefer to resolve server-relative urls as absolute paths before falling back to resolve in roots
restrictions[]A list of resolve restrictions
roots[]A list of root paths
symlinkstrueWhether to resolve symlinks to their symlinked location

Unimplemented Options

FieldDefaultDescription
cachePredicatefunction() { return true };A function which decides whether a request should be cached or not. An object is passed to the function with path and request properties.
cacheWithContexttrueIf unsafe cache is enabled, includes request.context in the cache key
plugins[]A list of additional resolve plugins which should be applied
resolverundefinedA prepared Resolver to which the plugins are attached
unsafeCachefalseUse this cache object to unsafely cache the successful requests

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

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

Irrelevant tests

Sponsored By

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📖 License

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

Oxc partially copies code from the following projects.

ProjectLicense
webpack/enhanced-resolveMIT
dividab/tsconfig-pathsMIT
parcel-bundler/parcelMIT
tmccombs/json-comments-rsApache 2.0