What is import-meta-resolve?
The import-meta-resolve package provides utilities for resolving module specifiers in the same way that Node.js does for ES modules. It allows developers to programmatically resolve specifiers from the context of a specific file or URL, which can be useful for tooling that needs to understand module resolution, bundlers, and other development tools.
What are import-meta-resolve's main functionalities?
Resolving module specifiers
This feature allows you to resolve the full path of a module specifier from a specific context, typically the URL of the importing module. The code sample demonstrates how to use the resolve function to find the full path of 'some-module' as if it were being imported from the current module.
import { resolve } from 'import-meta-resolve';
(async () => {
const resolved = await resolve('some-module', import.meta.url);
console.log(resolved);
})();
Other packages similar to import-meta-resolve
resolve
The 'resolve' package is a popular Node.js module resolution algorithm that can be used programmatically. It is similar to import-meta-resolve but does not specifically target ES module resolution semantics. It is more general-purpose and can resolve CommonJS modules as well.
enhanced-resolve
This package is used internally by webpack to resolve module paths. It is highly configurable and can handle complex resolution scenarios, including loaders and plugin systems. While it offers more features than import-meta-resolve, it is also more complex and tailored to webpack's ecosystem.
import-meta-resolve
Resolve things like Node.js.
Contents
What is this?
This package is a ponyfill for import.meta.resolve
.
It supports everything you need to resolve files just like modern Node does:
import maps, export maps, loading CJS and ESM projects, all of that!
When to use this?
As of Node.js 18.2, import.meta.resolve
is still behind an experimental flag.
This package can be used to do what it does in Node 14–18.
Install
This package is ESM only.
In Node.js (version 14.14+, 16.0+, or 18.0+), install with npm:
npm install import-meta-resolve
Use
import {resolve} from 'import-meta-resolve'
console.log(await resolve('./index.js', import.meta.url))
console.log(await resolve('builtins', import.meta.url))
console.log(await resolve('@eslint/eslintrc', import.meta.url))
console.log(await resolve('tape/lib/test', import.meta.url))
console.log(await resolve('fs', import.meta.url))
API
This package exports the identifiers resolve
and moduleResolve
.
There is no default export.
resolve(specifier, parent)
Match import.meta.resolve
except that parent
is required (you can pass
import.meta.url
).
Parameters
specifier
(string
)
— /example.js
, ./example.js
, ../example.js
, some-package
, fs
, etcparent
(string
, example: import.meta.url
)
— full URL (to a file) that specifier
is resolved relative from
Returns
Returns a promise that resolves to a full file:
, data:
, or node:
URL
(string
) to the found thing.
moduleResolve(specifier, parent, conditions, preserveSymlinks)
The “Resolver Algorithm Specification” as detailed in the Node docs
(which is sync and slightly lower-level than resolve
).
Parameters
specifier
(string
)
— /example.js
, ./example.js
, ../example.js
, some-package
, fs
, etcparent
(URL
, example: import.meta.url
)
— full URL (to a file) that specifier
is resolved relative fromconditions
(Set<string>
, default: new Set('node', 'import')
)
— conditionspreserveSymlinks
(boolean
, default: false
)
— keep symlinks instead of resolving them
Returns
A URL object (URL
) to the found thing.
Algorithm
The algorithm for resolve
matches how Node handles import.meta.resolve
, with
a couple of differences.
The algorithm for moduleResolve
matches the Resolver Algorithm
Specification as detailed in the Node docs (which is sync and slightly
lower-level than resolve
).
Differences to Node
parent
defaulting to import.meta.url
cannot be ponyfilled: you have to
explicitly pass it- No support for CLI flags:
--experimental-specifier-resolution
,
--experimental-json-modules
, --experimental-wasm-modules
,
--experimental-policy
, --experimental-network-imports
, --no-addons
,
--input-type
, --preserve-symlinks
,
--preserve-symlinks-main
, nor --conditions
work - No attempt is made to add a suggestion based on how things used to work in
CJS before to not-found errors
- Prototypal methods are not guarded: Node protects for example
String#slice
or so from being tampered with, whereas this doesn’t
Errors
ERR_INVALID_MODULE_SPECIFIER
— when specifier
is invalid (example: '#'
)ERR_INVALID_PACKAGE_CONFIG
— when a package.json
is invalid (example: invalid JSON)ERR_INVALID_PACKAGE_TARGET
— when a package.json
exports
or imports
is invalid (example: when it
does not start with './'
)ERR_MODULE_NOT_FOUND
— when specifier
cannot be found in parent
(example: 'some-missing-package'
)ERR_NETWORK_IMPORT_DISALLOWED
— thrown when trying to resolve a local file or builtin from a remote file
(node:fs
relative to 'https://example.com'
)ERR_PACKAGE_IMPORT_NOT_DEFINED
— when a local import is not defined in an import map (example: '#local'
when not defined)ERR_PACKAGE_PATH_NOT_EXPORTED
— when an export is not defined in an export map (example: 'tape/index.js'
,
which is not in its export map)ERR_UNSUPPORTED_DIR_IMPORT
— when attempting to import a directory (example: './lib/'
)ERR_UNKNOWN_FILE_EXTENSION
— when somehow reading a file that has an unexpected extensions ('./readme.md'
)ERR_INVALID_ARG_VALUE
— when conditions
is incorrectERR_UNSUPPORTED_ESM_URL_SCHEME
— when an unexpected protocol is found ('xss:alert(1)'
)
Types
This package is fully typed with TypeScript.
It exports the additional types ErrnoException
.
Compatibility
This package is at least compatible with all maintained versions of Node.js.
As of now, that is Node.js 14.14+, 16.0+, and 18.0+.
Contribute
Yes please!
See How to Contribute to Open Source.
License
MIT © Titus Wormer