google/closure-compiler

Add an @pure annotation

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#2395 opened on Mar 31, 2017

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 (5 comments) (0 reactions) (0 assignees)Java (7,176 stars) (1,197 forks)batch import
feathelp wanted

Description

I'd like to have an annotation to declare an intent that a function will not have side effects. In the presence of this annotation, I'd like the compiler to warn me if the function has side effects.

In a lot of code, you have simple helper methods that are intended to be side-effect free. It's very easy for a side effect to be accidentally introduced at a later time. I'd like to have a warning issued for this so the developer can correct it.

Contributor guide

Tech stack
javajavascript
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.
4
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
over 1 week
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
stale
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
mostly clear
Prerequisites
JavaScriptJavaClosure Compiler internalsside effect analysis
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
25
Research direction
Review the Closure Compiler's existing annotation system (e.g., @const, @param) and the side effect analysis pass (likely in the 'JSDocInfoParser' and 'CheckSideEffects' classes). Examine the 5 comments on the issue for any maintainer suggestions or prior attempts. Propose a concrete syntax for @pure and define what constitutes a side effect in the JavaScript context. Implement the annotation parsing and integrate with the warning system.