The Node.js Loaders Team maintains and actively develops the ECMAScript Modules Loaders implementation in Node.js core.
This team is spun off from the Modules team. We aim to implement the use cases that went unfulfilled by the initial ES modules implementation that can be achieved via loaders.
Before extending into new frontiers, we need to improve the loaders API enough that users can do just about everything they could do in CommonJS with ESM + loaders. (Outside of loaders scope, but related to the goal of parity between CommonJS and ESM, is finishing and stabilizing --experimental-vm-modules
.)
-
Finish nodejs/node#37468 / nodejs/node#35524, simplifying the hooks to
resolve
,load
andglobalPreloadCode
. -
Refactor the internal Node ESMLoader hooks into
resolve
andload
. Node’s internal loader already has no-ops fortransformSource
andgetGlobalPreloadCode
, so all this really entails is wrapping the internalgetFormat
andgetSource
with one functionload
(getFormat
is used internally outside ESMLoader, so they cannot merely be merged). nodejs/node#37468 -
Refactor Node’s internal ESM loader to move its exception on unknown file types from within
resolve
(on detection of unknown extensions) to withinload
(if the resolved extension has no defined translator). nodejs/node#37468 -
Implement chaining as described in the design, where the
default<hookName>
becomesnext
and references the next registered hook in the chain. nodejs/node#42623 -
Have loaders apply to subsequent loaders. https://github.com/nodejs/loaders/blob/main/doc/design/proposal-ambient-loaders.md, nodejs/node#43772
-
Move loaders off thread. nodejs/modules#351 (comment). nodejs/node#43658, nodejs/node#44710
-
Provide a way to register loaders from application code, such as
import { register } from 'node:module'
. nodejs/node#46826, nodejs/node#48559. -
Replace
globalPreload
hook with newinitialize
hook; updateregister
to preserve the communications channel from that hook so that we continue to provide a way to communicate between loaders code and application code. See nodejs#124 (comment) and nodejs#147. nodejs/node#48842. -
Remove
globalPreload
hook. nodejs/node#49144. -
Support loading source when the return value of
load
hasformat: 'commonjs'
. See nodejs/node#34753 (comment) and https://github.com/nodejs/loaders-test/blob/835506a638c6002c1b2d42ab7137db3e7eda53fa/coffeescript-loader/loader.js#L45-L50. nodejs/node#47999. -
Unflag
import.meta.resolve
. nodejs/node#49028.
-
Provide a way to register loaders via configuration, for example via adding support for
.env
files to Node.js or havingnode
read configuration from a new field inpackage.json
or other configuration file. See nodejs/node#46826, #98, nodejs/node#43973 (comment). nodejs/node#48890. -
Integrated support for external formats.
- Phase 1: Support identifying external modules (eg
typescript
); see nodejs/node#49704. - Phase 2: Support guided remediation via package manager search (eg
npm search … typescript
). - Phase 3: Automatically configure Node.
- Phase 1: Support identifying external modules (eg
-
First-class support for import maps that doesn’t require a custom loader.
-
Add helper/utility functions to reduce boilerplate in user-defined hooks.
-
Start with helpers for retrieving the closest parent
package.json
associated with a specifier string; and for retrieving thepackage.json
for a particular package by name (which is not necessarily the same result). -
Potentially include all the functions that make up the ESM resolution algorithm as defined in the spec. Create helper functions for each of the functions defined in that psuedocode:
esmResolve
,packageImportsResolve
,packageResolve
,esmFileFormat
,packageSelfResolve
,readPackageJson
,packageExportsResolve
,lookupPackageScope
,packageTargetResolve
,packageImportsExportsResolve
,patternKeyCompare
. (Not necessarily all with these exact names, but corresponding to these functions from the spec.) -
Follow up with similar helper functions that make up what happens within Node’s internal
load
. (Definitions to come.)
-
-
Helper/utility functions to allow access to the CommonJS named exports discovery algorithm (
cjs-module-lexer
). -
Hooks for customizing the REPL, including transpilation and tab completion. Support users pasting TypeScript (or CoffeeScript or whatever) into the REPL and having just as good an experience as with plain JavaScript.
- Support top-level
await
in the REPL API, if possible.
- Support top-level
-
Allow customizing string inputs:
--eval
CLI flag,Worker
constructor, stdin, etc. -
Hooks for customizing the stack trace (in other words, a hook version of
Error.prepareStackTrace
). This would allow transpiled languages to improve the output. -
Hooks for customizing filesystem calls, for allowing things like virtual filesystems or archives treated as volumes.
-
Inherit configuration blob to worker threads and child processes.