emscripten-core/emscripten

file-packager js output not working with closure and --pre-js

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#12,701 opened on Nov 4, 2020

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good first bughelp wanted

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Description

I'm getting the following closure error when adding the output of file-packager using --pre-js:

ERROR - [JSC_VAR_MULTIPLY_DECLARED_ERROR] Variable Module declared more than once.

Using --preload-file instead works fine which leads me to believe this is a bug.

Commands for completeness:

file_packager.py testapp.resources.data --preload testapp/resources@resources --js-output=testapp.resources.js --use-preload-cache
em++ -s WASM=1 -DNDEBUG -O3 -s ENVIRONMENT=web -s MODULARIZE -s EXPORT_NAME=createModule -flto --closure 1 -s FORCE_FILESYSTEM --pre-js testapp.resources.js [...]

Contributor guide

Research direction
Investigate why the file packager output causes a duplicate Module declaration when used with pre js and Closure Compiler. Check if the issue is due to redefinition of Module or lack of proper modularization. Look at the generated JavaScript and compare with preload file path. Consider using MODULARIZE or renaming export.
Tech stack
cppjavascript
Domain
build systemtoolingweb dev
Issue type
Bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-2 days
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
Active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Mostly clear
Prerequisites
EmscriptenJavaScriptClosure Compiler
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
40