fix(core): resolve Windows line ending and path separation bugs across CLI

[muhammadusman586]

Summary for #20967

Fixes Windows cross-platform compatibility bugs where \r\n (CRLF) line endings
caused rendering artifacts and incorrect line counting, and where manual path
splitting by / broke filename extraction on Windows (which uses \).

Details

Root Cause:

1. Line Endings: Several files used .split('\n') to split text into lines.
   On Windows, line endings are \r\n, so splitting by \n alone leaves a
   trailing \r on each line, causing rendering artifacts in DiffRenderer and
   CodeColorizer, and incorrect line counts in fileUtils.ts.
2. Path Separation: A test file used filePath.split('/').pop() to extract
   filenames. On Windows, paths use \ as the separator, so this fails to
   extract the correct filename.

Fix:

1. Replaced .split('\n') with .split(/\r?\n/) in 4 locations across 3 files.
   The regex handles both Unix (\n) and Windows (\r\n) line endings.
2. Replaced filePath.split('/').pop() with path.basename(filePath) which is
   the idiomatic, platform-aware Node.js API for extracting filenames.

Impact: The CLI now correctly handles Windows line endings and paths in diff
rendering, code syntax highlighting, file content processing, and tests.

Files Changed

File	Change
packages/cli/src/ui/components/messages/DiffRenderer.tsx	.split('\n') → .split(/\r?\n/)
packages/cli/src/ui/utils/CodeColorizer.tsx	.split('\n') → .split(/\r?\n/) (2 locations)
packages/core/src/utils/fileUtils.ts	.split('\n') → .split(/\r?\n/)
packages/core/src/tools/read-many-files.test.ts	filePath.split('/').pop() → path.basename(filePath)

Related Issues

Fixes #20967

How to Validate

1. Line ending fix: Open a file with Windows CRLF line endings (\r\n) and
   verify:
   • Diff rendering in DiffRenderer shows clean output without trailing \r
     characters
   • Code syntax highlighting in CodeColorizer renders correctly
   • File line counting in fileUtils.ts returns accurate counts
2. Path separation fix: Run read-many-files tests on Windows — filename
   extraction should work correctly with backslash paths
3. Regression: Run
   npm test -w @google/gemini-cli-core -- src/tools/read-many-files.test.ts —
   all 31 tests pass

Pre-Merge Checklist

• Updated relevant documentation and README (if needed) - N/A
• Added/updated tests (if needed) - N/A (existing tests cover behavior; fix
  is in test file itself)
• Noted breaking changes (if any) - N/A (bug fix only)
• Validated on required platforms/methods:
  • MacOS
    • npm run
    • npx
    • Docker
    • Podman
    • Seatbelt
  • Windows
    • npm run
    • npx
    • Docker
  • Linux
    • npm run
    • npx
    • Docker

[gemini-code-assist]

Summary of Changes

Hello, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request significantly enhances the CLI's cross-platform compatibility, particularly for Windows environments. It resolves critical bugs related to how the application processes line endings and path separators, ensuring consistent and correct behavior in diff rendering, code highlighting, and file utility operations across different operating systems.

Highlights

• Windows Line Endings: Updated string splitting logic from ".split('\n')" to ".split(/\r?\n/)" in DiffRenderer.tsx, CodeColorizer.tsx, and fileUtils.ts to correctly handle both Unix (\n) and Windows (\r\n) line endings, resolving rendering artifacts and incorrect line counts.
• Path Separation: Replaced manual path splitting "filePath.split('/').pop()" with the platform-aware "path.basename(filePath)" in read-many-files.test.ts to ensure correct filename extraction on Windows, which uses \ as a path separator.

Changelog

• packages/cli/src/ui/components/messages/DiffRenderer.tsx
  • Updated line splitting to use a regex /\r?\n/ for robust handling of Windows and Unix line endings.
• packages/cli/src/ui/utils/CodeColorizer.tsx
  • Modified line splitting in two locations to use /\r?\n/ for accurate code highlighting regardless of line ending type.
• packages/core/src/tools/read-many-files.test.ts
  • Replaced a manual path splitting approach with path.basename() to correctly extract filenames in a platform-agnostic manner.
• packages/core/src/utils/fileUtils.ts
  • Adjusted line splitting logic to /\r?\n/ for accurate file content processing and line counting.
  • Removed an unnecessary eslint-disable comment.

Activity

• Addressed Windows cross-platform compatibility issues, specifically fixing bugs related to CRLF line endings and backslash path separators.
• Provided detailed validation steps for verifying the line ending and path separation fixes, including specific commands to run.
• Included a comprehensive pre-merge checklist, confirming validation on MacOS, Windows, and Linux across various execution methods.
• Fixed issue Resolve Windows line ending and path separation bugs across CLI components #20967.

Using Gemini Code Assist

The full guide for Gemini Code Assist can be found on our documentation page, here are some quick tips.

Invoking Gemini

You can request assistance from Gemini at any point by creating a comment using either /gemini <command> or @gemini-code-assist <command>. Below is a summary of the supported commands on the current page.

Feature	Command	Description
Code Review	/gemini review	Performs a code review for the current pull request in its current state.
Pull Request Summary	/gemini summary	Provides a summary of the current pull request in its current state.
Comment	@gemini-code-assist	Responds in comments when explicitly tagged, both in pull request comments and review comments.
Help	/gemini help	Displays a list of available commands.

Customization

To customize Gemini Code Assist for GitHub experience, repository maintainers can create a configuration file and/or provide a custom code review style guide (such as PEP-8 for Python) by creating and adding files to a .gemini/ folder in the base of the repository. Detailed instructions can be found here.

Limitations & Feedback

Gemini Code Assist may make mistakes. Please leave feedback on any instances where its feedback is incorrect or counter productive. You can react with 👍 and 👎 on @gemini-code-assist comments. If you're interested in giving your feedback about your experience with Gemini Code Assist for Github and other Google products, sign up here.

You can also get AI-powered code generation, chat, as well as code reviews directly in the IDE at no cost with the Gemini Code Assist IDE Extension.

Footnotes

1. Review the Privacy Notices, Generative AI Prohibited Use Policy, Terms of Service, and learn how to configure Gemini Code Assist in GitHub here. Gemini can make mistakes, so double check it and use code with caution. ↩

[gemini-code-assist]

Code Review

This pull request correctly addresses cross-platform compatibility issues on Windows by replacing platform-specific line splitting and path manipulation with platform-agnostic methods. The use of split(/\r?\n/) for line endings and path.basename() for extracting filenames is appropriate and resolves the described bugs. I have one concern regarding the removal of an ESLint disable comment, which could potentially cause CI failures.

[ruomengz]

Can we remove this?

[muhammadusman586]

Yes remove it, it was added by mistake.

[ruomengz]

Looks like this is still not removed.

[muhammadusman586]

Done! The .claude/worktrees/nervous-sutherland folder has been removed. Sorry for the delay on this!

[ruomengz]

Thanks for fixing!