Add system.fs_file_edit script for file splice operations with comprehensive benchmarks

[Copilot]

Implements a new system script system.fs_file_edit that provides file editing capabilities through a splice operation, similar to JavaScript's Array.splice() but for file lines.

What this adds

The new fs_file_edit tool allows AI agents to precisely edit files by:

• Inserting lines at a specific position without deleting existing content
• Deleting lines from a specific position without inserting new content
• Replacing lines by deleting and inserting in one operation

Usage

// Insert lines at position 3 without deleting
await runTool("fs_file_edit", {
    filename: "example.txt",
    insertLine: 3,
    deleteCount: 0,
    lines: ["new line 1", "new line 2"]
})

// Delete 2 lines starting at position 5
await runTool("fs_file_edit", {
    filename: "example.txt", 
    insertLine: 5,
    deleteCount: 2,
    lines: []
})

// Replace 1 line at position 2 with 3 new lines
await runTool("fs_file_edit", {
    filename: "example.txt",
    insertLine: 2, 
    deleteCount: 1,
    lines: ["replacement 1", "replacement 2", "replacement 3"]
})

Implementation details

• File: /packages/core/genaisrc/system.fs_file_edit.genai.mts
• Tool name: fs_file_edit (follows established fs_ naming convention)
• Parameters:
  • filename: Path relative to workspace root
  • insertLine: 1-based line number where to start the edit
  • deleteCount: Number of lines to delete (default: 0)
  • lines: Array of lines to insert (default: [])
• Validation: Comprehensive error handling for invalid line numbers, file boundaries, and missing files
• Security: Respects workspace boundaries like other file system tools

Testing & Benchmarks

• Added comprehensive test suite covering insert, delete, and replace operations
• Manual testing confirms tool loads correctly with CLI
• Integrates seamlessly with existing system (now 60 total tools)
• NEW: Added fs-file-edit-benchmark.genai.mts in samples/sample that provides comprehensive benchmarking with:
  • 10 test scenarios covering all file edit operations
  • Performance testing with large files
  • Error handling validation for edge cases
  • Structured test setup with sample files for reproducible testing

The benchmark script demonstrates proper usage patterns and validates tool reliability across different file editing scenarios, making it easier for developers to understand and test the fs_file_edit capabilities.

This enables more precise file editing for AI agents compared to full file rewrites, making it easier to implement targeted code changes and content modifications.

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[pelikhan]

@copilot rename tool to "fs_file_edit"

[Copilot]

@copilot rename tool to "fs_file_edit"

Done! Renamed the tool from "files_edit" to "fs_file_edit" to follow the established fs_ naming convention. Updated the script file, test file, and documentation. Commit: 13a038f

[pelikhan]

@copilot add genaiscript script in samples/sample that runs tests against file edit benchmarks

[Copilot]

@copilot add genaiscript script in samples/sample that runs tests against file edit benchmarks

Created fs-file-edit-benchmark.genai.mts in samples/sample/genaisrc that comprehensively tests the fs_file_edit tool with 10 benchmark scenarios covering insert, delete, replace, error handling, and performance testing. The script sets up test files and provides structured validation of all file splice operations. Commit: 7fb0fcc

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