gleam-lang/gleam

Lift literal expressions to top-level constants in JavaScript code generation

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#4,090 opened on Dec 17, 2024

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 (7 comments) (0 reactions) (0 assignees)Rust (21,417 stars) (960 forks)batch import
help wanted

Description

  1. make a massive list in gleam

you can use gleam csv package to turn a csv file to gleam list then do io.debug(parssed_csv)

  1. make the list be let list = [ // here will be the long list ]

  2. do some computation to the data for me it was getting a specific element from the list

  3. change the list from let list = to const list

(make sure its a process that would take 1 or more seconds so you can notice the difference visually)

i noticed this in a lustre application i needed to get the element number 34 from list number 77 this took 4 seconds just by changing the list to const it was instant

( the version this happened on was 1.5 iirc it good to test if it still happens now )

Contributor guide

Tech stack
javascriptrust
Domain
backendperformance
Issue type
performance
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.
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
Gleam compiler internalsRust programmingJavaScript code generation
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
35
Research direction
Investigate the JavaScript code generation module in the Gleam compiler, likely in `src/codegen/javascript.rs`. Identify where literal expressions (e.g., large lists) are emitted as local variables and modify them to become top level constants. Consider using a constant pool to hoist large literals. The issue discussion suggests this optimization is straightforward and has been proposed before. There are no linked PRs yet.