fix(core): truncate excessively long lines in grep search output

[gundermanc]

Summary

This PR fixes a "too long message" error in the CLI by truncating excessively long lines in grep_search results.

Details

When grep_search finds matches in files with extremely long lines (e.g., minified JS, base64 strings, or large JSON blobs), the full line content was previously returned to the LLM and the UI. This could cause the CLI to hang or crash during rendering (specifically in wrap-ansi) and was inefficient for context usage.

This change enforces a MAX_LINE_LENGTH_TEXT_FILE (2000 characters) limit on lines formatted in grep-utils.ts. Lines exceeding this limit are truncated and appended with ... [truncated].

Related Issues

N/A (Verified via new unit test)

How to Validate

1. Run the new unit test: npm test -w @google/gemini-cli-core -- src/tools/grep.test.ts
2. Specifically, the test should truncate excessively long lines verifies the behavior.

Pre-Merge Checklist

• Updated relevant documentation and README (if needed)
• Added/updated tests (if needed)
• Noted breaking changes (if any)
• Validated on required platforms/methods:
  • MacOS
    • npm run
    • npx
    • Docker
    • Podman
    • Seatbelt
  • Windows
    • npm run
    • npx
    • Docker
  • Linux
    • npm run
    • npx
    • Docker

[github-actions]

Size Change: +271 B (0%)

Total Size: 26 MB

ℹ️ View Unchanged

Filename	Size	Change
./bundle/gemini.js	25.5 MB	+271 B (0%)
./bundle/node_modules/@google/gemini-cli-devtools/dist/client/main.js	221 kB	0 B
./bundle/node_modules/@google/gemini-cli-devtools/dist/src/_client-assets.js	227 kB	0 B
./bundle/node_modules/@google/gemini-cli-devtools/dist/src/index.js	11.5 kB	0 B
./bundle/node_modules/@google/gemini-cli-devtools/dist/src/types.js	132 B	0 B
./bundle/sandbox-macos-permissive-open.sb	890 B	0 B
./bundle/sandbox-macos-permissive-proxied.sb	1.31 kB	0 B
./bundle/sandbox-macos-restrictive-open.sb	3.36 kB	0 B
./bundle/sandbox-macos-restrictive-proxied.sb	3.56 kB	0 B
./bundle/sandbox-macos-strict-open.sb	4.82 kB	0 B
./bundle/sandbox-macos-strict-proxied.sb	5.02 kB	0 B

_{compressed-size-action}

[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 resolves an issue where grep_search results containing extremely long lines could cause the CLI to crash or hang, and inefficiently consume context. It introduces a mechanism to truncate these long lines, improving the stability and performance of the CLI when processing large or minified files.

Highlights

• Line Truncation Implemented: Excessively long lines in grep_search output are now truncated to prevent CLI crashes and improve context usage.
• New Constant Introduced: A MAX_LINE_LENGTH_TEXT_FILE constant (set to 2000 characters) defines the maximum length for lines before truncation.
• Enhanced Test Coverage: New unit tests were added for both GrepTool and RipGrepTool to specifically verify the line truncation behavior.

Changelog

• packages/core/src/tools/grep-utils.ts
  • Imported MAX_LINE_LENGTH_TEXT_FILE constant.
  • Added conditional logic to truncate llmContent lines exceeding MAX_LINE_LENGTH_TEXT_FILE and append ... [truncated].
• packages/core/src/tools/grep.test.ts
  • Added a new test case to verify that GrepTool correctly truncates excessively long lines.
• packages/core/src/tools/ripGrep.test.ts
  • Added a new test case to verify that RipGrepTool correctly truncates excessively long lines, including mocking spawn output.

Activity

• New unit tests were added to validate the truncation logic.
• The changes were validated on MacOS.

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[gemini-code-assist]

Code Review

This pull request addresses a crash caused by excessively long lines in grep search results by truncating them. The implementation is mostly correct, but it uses substring for truncation, which can incorrectly handle multi-byte Unicode characters, leading to potential data corruption. I've provided a suggestion to align with the repository's guidelines for safe string truncation.