The Node.js Loaders Team maintains and actively develops the ECMAScript Modules Loaders implementation in Node.js core.
History
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 module customization hooks; to provide hooks that are sufficiently powerful to allow the sunset of CommonJS monkey-patching; and to improve the ES modules implementation to reach parity with CommonJS.
Synchronous version of the module customization hooks so that the hooks can be used in the require path on the main thread, per design.
Goal: Parity with CommonJS
Synchronize the ESM loader, to hopefully close the startup performance gap with CommonJS and allow more predictable async activity on startup (for example, no async_hooks activity will precede user code). Tracking issue.
Implement import.meta.main, matching other runtimes. Tracking issue.
Other Improvements
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 the package.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.
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.
Loaders Team
Purpose
The Node.js Loaders Team maintains and actively develops the ECMAScript Modules Loaders implementation in Node.js core.
History
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 module customization hooks; to provide hooks that are sufficiently powerful to allow the sunset of CommonJS monkey-patching; and to improve the ES modules implementation to reach parity with CommonJS.
Project
Resources
Use cases
Design
Project board
Meeting minutes
Status
Goal: Sunset Monkey-Patching
requirepath on the main thread, per design.Goal: Parity with CommonJS
Synchronize the ESM loader, to hopefully close the startup performance gap with CommonJS and allow more predictable async activity on startup (for example, no
async_hooksactivity will precede user code). Tracking issue.Implement
import.meta.main, matching other runtimes. Tracking issue.Other Improvements
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.jsonassociated with a specifier string; and for retrieving thepackage.jsonfor 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.
awaitin the REPL API, if possible.Allow customizing string inputs:
--evalCLI flag,Workerconstructor, 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.