Quality: Map equality treats missing keys as equal when mapped value is null

[Nam0101]

✨ Code Quality

Problem

areMapsEqual compares values via next[key] without verifying key presence. If prev has {a: null} and next has {b: null} (same size, different keys), next[a] returns null, the value comparison passes, and the method incorrectly returns true. This can cause silent diffing errors (e.g., skipping updates when maps actually changed), leading to stale UI/state.

Severity: high
File: litho-core/src/main/java/com/facebook/litho/utils/MapDiffUtils.kt

Solution

Require key existence before value comparison:

@JvmStatic
fun <K, V> areMapsEqual(prev: Map<K, V>?, next: Map<K, V>?): Boolean {
if (prev === next) return true
if (prev == null || next == null) return false
if (prev.size != next.size) return false

return prev.all { (key, value) ->
next.containsKey(key) && equals(value, next[key])
}
}

Changes

• litho-core/src/main/java/com/facebook/litho/utils/MapDiffUtils.kt (modified)

Summary

Changelog

Test Plan

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🤖 About this PR

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1. Discovered by automated code analysis
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Closes #1079

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