make middlewares work before auto redirection

[unbyte]

What it solves

Currently if enable RedirectTrailingSlash or RedirectFixedPath, gin will skip any global middlewares and redirect directly. It leads to some problems. For example, recording the path that caused the redirection (logger), adding some external headers to response (handler), or even rewrite target path.

Feature

• call global middlewares before auto redirection

• add AutoRedirect API on engine to set handlers used before auto redirection. It's like NoMethod and NoRoute, and will be called just before redirect.

may related: #1004 , #2458
close #2458

[codecov]

Codecov Report

Merging #2477 (51ef7a6) into master (d062a6a) will increase coverage by 0.13%.
The diff coverage is 100.00%.

❗ Current head 51ef7a6 differs from pull request most recent head 5f94d6f. Consider uploading reports for the commit 5f94d6f to get more accurate results

@@            Coverage Diff             @@
##           master    #2477      +/-   ##
==========================================
+ Coverage   98.60%   98.73%   +0.13%     
==========================================
  Files          41       41              
  Lines        3084     3088       +4     
==========================================
+ Hits         3041     3049       +8     
+ Misses         30       27       -3     
+ Partials       13       12       -1     

Flag	Coverage Δ
go-1.13	98.73% <100.00%> (∅)
go-1.14	98.57% <100.00%> (∅)
go-1.15	98.57% <100.00%> (∅)
go-1.16	98.57% <100.00%> (-0.04%)	⬇️
go-1.17	98.47% <100.00%> (-0.04%)	⬇️
macos-latest	98.73% <100.00%> (+0.13%)	⬆️
nomsgpack	98.71% <100.00%> (+0.13%)	⬆️
ubuntu-latest	98.73% <100.00%> (+0.13%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
gin.go	99.13% <100.00%> (-0.04%)	⬇️
context.go	97.81% <0.00%> (-0.09%)	⬇️
tree.go	100.00% <0.00%> (ø)
debug.go	100.00% <0.00%> (+8.33%)	⬆️

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[unbyte]

@thinkerou PTAL, I think this feature will be very helpful, but I don't know if there is still something to consider when adding such feature ❤

[knusbaum]

👍
I'm hitting this problem too.
I'm not able to attach headers to outgoing redirects since the middleware does handle those at the moment.

[betabandido]

Right now gin-contrib/cors middleware fails to work when a redirect occurs (due to RedirectTrailingSlash). But, it seems to me that being a same-domain redirect, gin (together with the CORS middleware) should support this use case. Is there any reason not to?

[giancarlosisasi]

👀

[unbyte]

@appleboy Hi, I have updated this PR to adapt to the latest master branch.

Sadly we have encountered the problem this PR solved again recently😥. When could it be merged?

[Arekusei]

any updates?

[appleboy]

@unbyte Please fix the conflicts.

[unbyte]

@appleboy fixed.

[dungmv]

any updates

[WhaleFell]

any updates?

[userwerk]

We are running into the same issue. Any chance this will make it into the next release @appleboy?