chore(bind): return 413 status code when error is http.MaxBytesError

[ItalyPaleAle]

Re-do of #3841 which had ended up in a bad state

The Go standard library includes a method http.MaxBytesReader that allows limiting the request body. For example, users can create a middleware like:

func MiddlewareMaxBodySize(c *gin.Context) {
	// Limit request body to 100 bytes
	c.Request.Body = http.MaxBytesReader(c.Writer, c.Request.Body, 100)
	c.Next()
}

When the body exceeds the limit, reading from the request body returns an error of type http.MaxBytesError.

This PR makes sure that when the error is of kind http.MaxBytesError, Gin returns the correct status code 413 (Request Entity Too Large) instead of a generic 400 (Bad Request).

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 98.92%. Comparing base (3dc1cd6) to head (4de0ae4).
Report is 123 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #4227      +/-   ##
==========================================
- Coverage   99.21%   98.92%   -0.30%     
==========================================
  Files          42       44       +2     
  Lines        3182     3432     +250     
==========================================
+ Hits         3157     3395     +238     
- Misses         17       26       +9     
- Partials        8       11       +3     

Flag	Coverage Δ
	?
--ldflags="-checklinkname=0" -tags sonic	98.85% <83.33%> (?)
-tags go_json	98.85% <83.33%> (?)
-tags nomsgpack	98.90% <100.00%> (?)
go-1.18	?
go-1.19	?
go-1.20	?
go-1.21	?
go-1.23	98.92% <100.00%> (?)
go-1.24	98.92% <100.00%> (?)
macos-latest	98.92% <100.00%> (-0.30%)	⬇️
ubuntu-latest	98.92% <100.00%> (-0.30%)	⬇️

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[ItalyPaleAle]

The test is failing when using "sonic avx" as tags, but I can't repro the error locally... Any advice?

[appleboy]

Please rebase the master branch

[Copilot]

Pull Request Overview

This PR ensures that when a binding error is due to http.MaxBytesError, Gin responds with HTTP 413 instead of 400.
Key changes:

• Update MustBindWith in context.go to detect http.MaxBytesError and return 413
• Add TestContextBindRequestTooLarge and adjust related tests in context_test.go
• Simplify URL concatenation in gin_test.go

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

File	Description
context.go	Detect http.MaxBytesError in MustBindWith and set 413
context_test.go	Replace buffer usage, add test for oversized request binding
gin_test.go	Simplify HTTP GET calls by string concatenation

[ItalyPaleAle]

Please rebase the master branch

Done, thanks

[Copilot]

Pull Request Overview

This PR changes Gin’s binding behavior to return a 413 (Request Entity Too Large) status code when the error from reading the request body is of type http.MaxBytesError. In addition, it updates several tests to use strings.NewReader for constructing request bodies and adds a new test (TestContextBindRequestTooLarge) to verify the new behavior.

Reviewed Changes

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

File	Description
context_test.go	Updates to use strings.NewReader for request bodies and addition of a new test for 413.
context.go	Updates MustBindWith to handle http.MaxBytesError, returning HTTP 413 instead of 400.

[appleboy]

@ItalyPaleAle testing error. Please help to take a look.

[ItalyPaleAle]

@ItalyPaleAle testing error. Please help to take a look.

I cannot repro locally. Looks like tests pass on other platforms, but fail when the sonic tag is used. Maybe this is caused by an incompatibility with the sonic library?

[appleboy]

[ItalyPaleAle]

But the test passes when NOT using sonic: https://github.com/gin-gonic/gin/actions/runs/15143597508/job/42624844475?pr=4227 must be a bug in the sonic library

I can disable this test when sonic is used?

[ItalyPaleAle]

This feature won't work when using go-json or sonic due to bugs upstream:

goccy/go-json#485
bytedance/sonic#800

In those cases, gin will continue to return a 400 response. Tests should pass now

[appleboy]

@ItalyPaleAle Thanks for your effort.