fix(telemetry): replace JSON.stringify with safeJsonStringify in file exporters

[gsquared94]

Summary

Fix FileSpanExporter.export() crash caused by TypeError: Converting circular structure to JSON when writing OTel spans to a telemetry outfile.

Details

OTel ReadableSpan objects contain circular references through their internal span processor chain (BatchSpanProcessor2 → BindOnceFuture → _that). The FileExporter.serialize() method used JSON.stringify(data, null, 2) which does not handle circular references.

Replaced JSON.stringify with the existing safeJsonStringify utility from packages/core/src/utils/safeJsonStringify.ts, which uses a WeakSet to detect and replace circular references with [Circular].

Also added GEMINI.md updates with a mandatory pre-PR checklist to enforce development workflow compliance.

Related Issues

Fixes #19228

How to Validate

1. Run the new unit tests:

   npm test -w @google/gemini-cli-core -- src/telemetry/file-exporters.test.ts

2. Enable file-based telemetry and verify spans are written without crash:

   { "telemetry": { "enabled": true, "target": "local", "otlpEndpoint": "", "outfile": ".gemini/telemetry.log" } }

   GEMINI_DEV_TRACING=true gemini

3. Verify circular references appear as [Circular] in the output file.

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

[gemini-code-assist]

Summary of Changes

Hello @gsquared94, 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 addresses a critical bug where the telemetry file exporters would crash when attempting to serialize OpenTelemetry objects containing circular references. The solution involves integrating a pre-existing safe JSON stringification utility, which detects and handles these circular structures, thereby preventing application failures. The changes are thoroughly validated with new unit tests, and the project's development guidelines have been updated to include a mandatory pre-PR checklist to improve overall code quality and adherence to best practices.

Highlights

• Telemetry Crash Fix: Resolved a TypeError: Converting circular structure to JSON crash that occurred when OpenTelemetry spans with circular references were written to a telemetry outfile.
• Safe JSON Serialization: Replaced JSON.stringify with the existing safeJsonStringify utility in FileExporter.serialize() to gracefully handle circular references by replacing them with [Circular].
• New Unit Tests: Added comprehensive unit tests for FileSpanExporter, FileLogExporter, and FileMetricExporter to ensure correct serialization, including handling of circular references, and proper error reporting.
• Development Workflow Enhancement: Introduced a mandatory pre-PR checklist in GEMINI.md to enforce development workflow compliance and ensure consistent quality before pull request creation.

Changelog

• GEMINI.md
  • Added a new section for mandatory pre-PR checklist under 'Development Conventions'.
• packages/core/src/telemetry/file-exporters.test.ts
  • Introduced new unit tests for FileSpanExporter, FileLogExporter, and FileMetricExporter.
• packages/core/src/telemetry/file-exporters.ts
  • Imported safeJsonStringify utility.
  • Replaced JSON.stringify with safeJsonStringify in the serialize method to prevent crashes from circular references.

Activity

• The author has added new unit tests to cover the changes.
• The author has validated the fix by enabling file-based telemetry and verifying spans are written without crashing, and that circular references appear as [Circular] in the output.
• The author has checked off the 'Added/updated tests' item in the pre-merge checklist.

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[gemini-code-assist]

Code Review

This pull request effectively addresses the TypeError: Converting circular structure to JSON by integrating safeJsonStringify into the file exporters. The addition of comprehensive unit tests, including specific cases for circular references, thoroughly validates the fix and ensures the robustness of the telemetry export mechanism. The changes are well-implemented and directly resolve the identified issue.