google/closure-compiler

Add an Option To Prevent Rewriting Import/Require Statements for Specific Modules

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#1382 opened on Jan 10, 2016

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 (10 comments) (5 reactions) (0 assignees)Java (7,176 stars) (1,197 forks)batch import
help wanted

Description

When working with module systems, there needs to be some way to designate that certain import statements are intended to be runtime imports rather than compile time. This will only apply to CommonJS modules currently until such a time as the compiler recognizes and rewrites the WhatWG Loader Import Statements. See

The consensus around this discussion seems to be that this should be a flag, rather than an annotation.

The flag should meet the following criteria:

  • The same flag should work for ES6 and CommonJS modules
  • It MUST take into account all of the following cases:
    • The --module flags are used and thus both the import and export statements are provided to the compiler as input but divided into separate outputs for runtime loading
    • The export statement is not provided to the compiler and is therefore external code. This covers core NodeJS module imports.

Contributor guide

Tech stack
javascriptnodejs
Domain
build systemdeveloper experience
Issue type
feature
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
4
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
over 1 week
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
stale
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
mostly clear
Prerequisites
understanding of CommonJSES6 modulesclosure compiler flags
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
30
Research direction
The issue requests a flag to prevent rewriting imports for specific modules. Look at the linked discussion in the closure compiler Google Group and issue #1380 for prior context. Examine how the existing module flag handles imports/exports and how external module imports (like Node.js core modules) are currently treated. The proposed flag should work for both CommonJS and ES6 modules and needs to be implemented in the compiler's pass that rewrites import statements. Consider any existing annotations or options that could be extended.