gleam-lang/gleam

Formatter: Replace = symbols by : symbols where syntactically correct

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#2,979 opened on Apr 12, 2024

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

Description

I'm learning Gleam, and sometimes it's hard to remember to use = or : in some cases, especially for record expressions.

pub fn new(name: String) {
  Thing(
    name = name, // should have `:`
  )
}

A nice thing that elm-format does for Elm files, is to transform = to : (and the reverse) where appropriate. This is a time-saver and very nice for beginners. For instance, I have several times taught Elm to beginners, and when they would use the incorrect symbol, then save, the symbol would be fixed without them even noticing (or seeing an error message).

I don't know in how many places this kind of change could be applied, I think it could at least be done reliably in record expressions, maybe as well in type annotations.

Contributor guide

Tech stack
rust
Domain
toolingdeveloper experience
Issue type
feature
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.
fresh
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
clear
Prerequisites
Familiarity with Gleam syntaxUnderstanding of the formatter codebaseRust
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
60
Research direction
The formatter code is likely in the `src/formatter` directory of the Gleam compiler. The issue suggests a behavior similar to elm format, which automatically replaces `=` with `:` in record field assignments. Look at how record expressions are parsed and formatted, and identify where `=` is currently used incorrectly. Ensure that the substitution is only applied where syntactically correct, e.g., in record expressions and possibly type annotations. Check existing tests and comments in the issue for guidance.