fix render: write content length in Data.Render

[dengaleev]

This PR fixes an issue where the Content-Length header is not set correctly for large data written by ResponseWriter.Write. According to the Go documentation, the Content-Length header is automatically added only for small data sizes. For larger data, it is necessary to explicitly set the Content-Length header to ensure proper behavior.

[dengaleev]

Hi, @appleboy

Could you check this pull request?

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 99.00%. Comparing base (3dc1cd6) to head (c4e549a).
Report is 104 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #4206      +/-   ##
==========================================
- Coverage   99.21%   99.00%   -0.22%     
==========================================
  Files          42       44       +2     
  Lines        3182     3405     +223     
==========================================
+ Hits         3157     3371     +214     
- Misses         17       24       +7     
- Partials        8       10       +2     

Flag	Coverage Δ
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--ldflags="-checklinkname=0" -tags "sonic avx"	98.99% <100.00%> (?)
-tags go_json	98.99% <100.00%> (?)
-tags nomsgpack	98.98% <100.00%> (?)
go-1.18	?
go-1.19	?
go-1.20	?
go-1.21	?
go-1.23	99.00% <100.00%> (?)
go-1.24	99.00% <100.00%> (?)
macos-latest	99.00% <100.00%> (-0.22%)	⬇️
ubuntu-latest	99.00% <100.00%> (-0.22%)	⬇️

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[appleboy]

I will take it.

[Copilot]

Pull Request Overview

This PR fixes an issue with the Content-Length header in Data.Render to ensure that it is set correctly for both large and empty data responses.

• Updated Data.Render to explicitly set the Content-Length header using strconv.Itoa(len(r.Data)).
• Added tests in render_test.go to verify the header for various data sizes, including zero-length.

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
render/render_test.go	Added tests to validate the Content-Length header for different data sizes.
render/data.go	Modified Render to set the Content-Length header based on the data length.

[Copilot]

The condition 'if len(r.Data) > 0' prevents setting the Content-Length header when the data length is 0, causing test failures for zero-length responses. Consider removing the condition so the header is always set to strconv.Itoa(len(r.Data)).

Suggested change

	if len(r.Data) > 0 {
	w.Header().Set("Content-Length", strconv.Itoa(len(r.Data)))
	}
	w.Header().Set("Content-Length", strconv.Itoa(len(r.Data)))