jfmengels/elm-review-simplify

Simplify `if x then (_, True) else (_,False)` (and other conditionals that differ only by a boolean literal)

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#11 opened on Jul 17, 2021

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Description

Haven't put a ton of thought into how difficult it would be to implement as a rule, but I ran into it in my code today and noticed it wasn't caught by elm-review-simplify currently.

if bar then
    ( foo, True )
else
    ( foo, False )

can be simplified to just:

( foo, bar )

Honestly this could be extended to basically any two expressions that differ only by a Boolean between conditions, but it might be challenging to check for that.

E.g.

if bar then
    { a = foo, b = True }
else
    { a = foo, b = False }

if bar then
    func foo True
else
    func foo False

Off the top of my head, one could maybe descend into the two Node Expressions of an IfBlock and check for the presence of a boolean literal, then compare the ASTs for equality with the literal swapped?

Contributor guide

Research direction
Study the elm review AST module to understand how expressions are represented. Look for existing rules that traverse and compare AST nodes. Implement a rule that detects if else blocks where the two branches differ only by a boolean literal at the same position, then simplify by replacing the conditional with the common expression and the boolean from the condition.
Tech stack
None
Domain
developer 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.
Active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Clear
Prerequisites
Elmelm reviewAST manipulation
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
60