useExplicitLengthCheck ruins multi-line conditions that have single-line comments

Environment information

CLI:
  Version:                      2.3.3
  Color support:                true

Platform:
  CPU Architecture:             aarch64
  OS:                           macos

Environment:
  BIOME_LOG_PATH:               unset
  BIOME_LOG_PREFIX_NAME:        unset
  BIOME_CONFIG_PATH:            unset
  BIOME_THREADS:                unset
  NO_COLOR:                     unset
  TERM:                         screen-256color
  JS_RUNTIME_VERSION:           v22.20.0
  JS_RUNTIME_NAME:              node
  NODE_PACKAGE_MANAGER:         unset

Biome Configuration:
  Status:                       Not set
  Path:                         unset

Workspace:
  Open Documents:               0

Rule name

lint/style/useExplicitLengthCheck

Playground link

https://biomejs.dev/playground/?lintRules=useExplicitLengthCheck&analyzerFixMode=safeAndUnsafeFixes&code=ZgB1AG4AYwB0AGkAbwBuACAAdQBzAGUAUQB1AGUAcgB5AEEAcwBzAGkAcwB0AGEAbgB0ACgAKQAgAHsACgAgACAAaQBmACAAKAAKACAAIAAgACAAIQBzAGgAbwB3AFQAaABpAG4AawBpAG4AZwAgACYAJgAgAC8ALwAgAHcAaABpAGwAZQAgAGkAdAAnAHMAIAB0AGgAaQBuAGsAaQBuAGcAIAB0AGgAZQByAGUAIABpAHMAIABoAG8AcABlACAAdABvACAAZwBlAHQAIABzAHUAZwBnAGUAcwB0AGkAbwBuAHMACgAgACAAIAAgACEAYwBvAG0AbQBlAG4AdABzAD8ALgBsAGUAbgBnAHQAaAAKACAAIAApACAAewAKACAAIAAgACAAYwBvAG4AcwBvAGwAZQAuAGwAbwBnACgAKQA7AAoAIAAgAH0ACgB9AAoA

Expected result

Minimal JS to reproduce the issue:

function useQueryAssistant() {
  if (
    !showThinking && // while it's thinking there is hope to get suggestions
    !comments?.length
  ) {
    console.log();
  }
}

If you apply unsafe writes:

yarn exec biome lint ./test.ts --only=lint/style/useExplicitLengthCheck --write --unsafe

It will break the multi-line condition by joining it with a single-line comment:

function useQueryAssistant() {
  if (
    !showThinking && // while it's thinking there is hope to get suggestionscomments?.length === 0
  ) {
    console.log();
  }
}

Code of Conduct

I agree to follow Biome's Code of Conduct

Actually the same issue happens with the useSimplifiedLogicExpression rule:

if (
-  !showRequestSizeWarning ||
-  !query.metrics // context was too large to count tokens
+  !(showRequestSizeWarning &&query.metrics // context was too large to count tokens) // context was too large to count tokens
) {/* ... */}

I'm not seeing this behavior for either of those rules in the playground.

I'm not seeing this behavior for either of those rules in the playground.

See the suggested unsafe fix in the console tab.
And Biome actually applies this change when I run the following command:

biome lint ./test.ts --only=lint/style/useExplicitLengthCheck --write --unsafe

@GeneZharov

Hello @GeneZharov, please provide a minimal reproduction. You can use one of the following options:

Provide a link to our playground, if it's applicable.
Provide a link to GitHub repository. To easily create a reproduction, you can use our interactive CLI via npm create @biomejs/biome-reproduction

Issues marked with S-Needs repro will be closed if they have no activity within 3 days.

Update dependency @biomejs/biome to v2.5.14 (#24)

Update dependency @biomejs/biome to v2.5.14 (#45)

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useExplicitLengthCheck ruins multi-line conditions that have single-line comments #7984

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useExplicitLengthCheck ruins multi-line conditions that have single-line comments #7984

Description

Environment information

Rule name

Playground link

Expected result

Code of Conduct

Activity

GeneZharov commented on Nov 4, 2025

dyc3 commented on Nov 4, 2025

GeneZharov commented on Nov 4, 2025

github-actions commented on Nov 4, 2025

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