gleam-lang/gleam

"Split alternative pattern" code action

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#4856 opened on Aug 16, 2025

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 (6 comments) (5 reactions) (0 assignees)Rust (21,417 stars) (960 forks)batch import
help wanted

Description

Sometimes code starts out as dealing with 2 patterns in the same way, but then later, something different has to happen for one or all of the cases. It could be nice if the language server provided a code action to split an alternative pattern into individual pattern matches.

Before:

case next() {
  Ok(response) -> response
  Error(MissingAccessToken) | Error(MissingRefreshToken) -> unauthorized()
  //  ^ split alternative patterns
}

After:

case next() {
  Ok(response) -> response
  Error(MissingAccessToken) -> unauthorized()
  Error(MissingRefreshToken) -> unauthorized()
}

To consider:

  • split The pattern on the selected pipe; That would make it more flexible, but would require more clicks to fully split a pattern.
  • Split out only the currently hovered alternative, leaving the rest in place

~ 💜

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.
3-5 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.
clear
Prerequisites
RustGleam language basics
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
65
Research direction
Examine the Gleam compiler's AST representation for alternative patterns, likely in the `compiler core` crate. Look at the language server code action implementations (e.g., in `src/ide.rs`) to understand how to add a new action. The issue suggests splitting the hovered pattern alternative into individual match arms, so you will need to modify the syntax tree accordingly. Check any comments in the issue for preferred implementation details.