net/http: serveError removes "Content-Encoding" which breaks our system (GODEBUG=httpservecontentkeepheaders=0)

[martinrode]

Go version

go version go1.23.2 darwin/arm64

Output of go env in your module/workspace:

GO111MODULE='on'
GOARCH='arm64'
GOBIN='/Users/martin/go/bin'
GOCACHE='/Users/martin/Library/Caches/go-build'
GOENV='/Users/martin/Library/Application Support/go/env'
GOEXE=''
GOEXPERIMENT=''
GOFLAGS=''
GOHOSTARCH='arm64'
GOHOSTOS='darwin'
GOINSECURE=''
GOMODCACHE='/Users/martin/go/pkg/mod'
GONOPROXY=''
GONOSUMDB=''
GOOS='darwin'
GOPATH='/Users/martin/go'
GOPRIVATE=''
GOPROXY='https://proxy.golang.org,direct'
GOROOT='/usr/local/go'
GOSUMDB='sum.golang.org'
GOTMPDIR=''
GOTOOLCHAIN='auto'
GOTOOLDIR='/usr/local/go/pkg/tool/darwin_arm64'
GOVCS=''
GOVERSION='go1.23.2'
GODEBUG=''
GOTELEMETRY='local'
GOTELEMETRYDIR='/Users/martin/Library/Application Support/go/telemetry'
GCCGO='gccgo'
GOARM64='v8.0'
AR='ar'
CC='clang'
CXX='clang++'
CGO_ENABLED='1'
GOMOD='/Users/martin/go/src/github.com/programmfabrik/fylr/go.mod'
GOWORK='/Users/martin/go/src/github.com/programmfabrik/go.work'
CGO_CFLAGS='-O2 -g'
CGO_CPPFLAGS=''
CGO_CXXFLAGS='-O2 -g'
CGO_FFLAGS='-O2 -g'
CGO_LDFLAGS='-O2 -g'
PKG_CONFIG='pkg-config'
GOGCCFLAGS='-fPIC -arch arm64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -ffile-prefix-map=/var/folders/4f/l31kb4n521d6g89qxrwcx69h0000gp/T/go-build1664119454=/tmp/go-build -gno-record-gcc-switches -fno-common'

What did you do?

We serve simple web pages using a compress handler (middleware).

This handler sets the header "Content-Encoding" to "gzip" if requested. If the served page ends up in a 404 and is served via net/http.serveError, the newly introduced deletion of http headers breaks the output of our system.

What did you see happen?

"Content-Encoding" header gets removed, but our content is still gzipped..

What did you expect to see?

I can see a reason why Cache-Control, Etag and Last-Modified makes sense to delete, but I don't see a reason to reset "Content-Encoding", but please remove the "Content-Encoding" from the list of deleted headers in net/http.serverError.

[seankhliao]

see the discussion on #66343

[gabyhelp]

Related Issues

• net/http: delete inappropriate headers in func Error #66343 (closed)
• net/http: ServeContent doesn't set Content-Length when Content-Encoding is set #19420 (closed)
• net/http: Server removes all explicitly set `Transfer-Encoding` headers #16063 (closed)
• net/http: include Content-Length header for 400 responses #61348 (closed)
• net/http: Transfer-Encoding header is missing in headers (http.Request) #27061 (closed)
• net/http: Support Transfer-Encoding: gzip #68543 (closed)

Related Code Changes

• net/http: keep Content-Encoding in Error, add GODEBUG for ServeContent
• net/http: remove misleading response headers on error
• net/http: set/override Content-Length for encoded range requests
• net/http: remove misleading response headers on error

_{(Emoji vote if this was helpful or unhelpful; more detailed feedback welcome in this discussion.)}

[martinrode]

I must object to closing this ticket. I described our problem in more detail here: #66343 (comment).

[martinrode]

Sorry, but I re-opened a new ticket (with improved reasoning). This change is a breaking change and really harms: #71138