sindresorhus/eslint-plugin-unicorn

`explicit-length-check`: ignore variables with non-array properties?

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#1,266 opened on May 12, 2021

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Description

if (
  dimensions.width &&
  dimensions.height &&
  dimensions.length // violation reported by unicorn/explicit-length-check
) { }

In this example, packagingData.dimensions is an object, and length could be a string.

As a heuristic to avoid false positives with detecting length or size on variables that are not actually arrays, could we ignore variables that have non-array properties? For example, an array does not have a width property, so if we see that used, we would assume dimensions is not an array, and ignore it.

Contributor guide

Tech stack
javascriptnodejs
Domain
tooling
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.
half day
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
JavaScriptESLint rule APIAST basics
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
45
Research direction
Investigate the current implementation of the `explicit length check` rule in `rules/explicit length check.js`. Understand how it detects violations and consider adding logic to check if the variable has other property accesses that are not typical for arrays (e.g., `.width`, `.height`). Review any existing tests to ensure the heuristic does not introduce false negatives. The issue suggests using a heuristic: if a variable has non array properties, ignore it. Implement this and add appropriate tests.