support os.File.WriteString

[luoliwoshang]

Summary

• implement os.File.WriteString by delegating to Write with an unsafe string-to-byte conversion
• add a regression demo under _demo/go/oswritestring that writes, closes, and verifies file contents

Details

• mirrors Go stdlib behavior for WriteString to avoid extra allocations
• demo checks byte count, closes the file, then validates content via os.ReadFile

Testing

• not run (demo added under _demo/go/oswritestring)

Issue

• Fixes support os.File.WriteString #1409

[gemini-code-assist]

Summary of Changes

Hello @luoliwoshang, 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 introduces the implementation of the os.File.WriteString method, which was previously a stub. The new implementation leverages an unsafe string-to-byte slice conversion to efficiently write string content to a file, mirroring the behavior of the Go standard library to minimize allocations. Additionally, a dedicated regression demo has been included to ensure the correct functionality and verification of this new feature.

Highlights

• os.File.WriteString Implementation: Implemented the WriteString method for os.File, which was previously a placeholder. It uses an unsafe conversion from string to byte slice to delegate to the Write method, aligning with Go's standard library for efficiency.
• New Regression Demo: Added a new demo under _demo/go/oswritestring to test and verify the functionality of the newly implemented os.File.WriteString. The demo creates a temporary file, writes content, closes it, and then reads and validates the content.

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[xgopilot]

Code Review Summary

This PR successfully implements os.File.WriteString with a clean, efficient implementation that matches Go's standard library approach. The code is correct and well-tested for the happy path.

Strengths:

• Zero-copy implementation using unsafe.Slice for optimal performance
• Proper demo with comprehensive validation (write, close, read-back verification)
• Clean resource management with defer os.Remove

Optional Enhancement:
Consider adding edge case coverage in the demo or a separate test for robustness (empty strings, large strings, multiple consecutive writes).

[xgopilot]

The demo validates the happy path well. For more robust testing, consider adding cases for:

• Empty string: f.WriteString("")
• Multiple consecutive writes to verify behavior
• Large strings (e.g., strings.Repeat("x", 10*1024*1024))

This would provide better confidence in edge case handling, especially since this enables previously disabled functionality.

[gemini-code-assist]

Code Review

This pull request correctly implements os.File.WriteString by delegating to os.File.Write using an efficient, allocation-free string-to-byte slice conversion with unsafe.Slice. The approach mirrors the Go standard library, which is excellent. The addition of a regression demo is also a great way to validate the new functionality. My only suggestion is to improve the error handling in the demo code for better diagnostics.

[gemini-code-assist]

While using panic is acceptable for a simple demo, it's generally better to use log.Fatalf for handling expected errors like I/O failures. This provides a cleaner error message without a full stack trace, which is more idiomatic for command-line applications and tests.

I'd recommend replacing all panic calls in this file with log.Fatalf. For example, this block could be changed to:

	if err != nil {
		log.Fatalf("Failed to create temp file: %v", err)
	}

This would require adding "log" to the imports.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 91.04%. Comparing base (01ee853) to head (cbe327a).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1554      +/-   ##
==========================================
+ Coverage   91.01%   91.04%   +0.03%     
==========================================
  Files          45       45              
  Lines       11958    11958              
==========================================
+ Hits        10883    10887       +4     
+ Misses        899      895       -4     
  Partials      176      176              

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