regexp.ReplaceAllString is removing the accents of a normalized string

[esdrasbeleza]

What version of Go are you using (go version)?

$ go version
go1.16.3 darwin/amd64

Does this issue reproduce with the latest release?

Yes.

What operating system and processor architecture are you using (go env)?

go env Output

$ go env
GO111MODULE=""
GOARCH="amd64"
GOBIN=""
GOCACHE="/Users/esdrasbeleza/Library/Caches/go-build"
GOENV="/Users/esdrasbeleza/Library/Application Support/go/env"
GOEXE=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="darwin"
GOINSECURE=""
GOMODCACHE="/Users/esdrasbeleza/go/pkg/mod"
GONOPROXY=""
GONOSUMDB=""
GOOS="darwin"
GOPATH="/Users/esdrasbeleza/go"
GOPRIVATE=""
GOPROXY="https://proxy.golang.org,direct"
GOROOT="/usr/local/Cellar/go/1.16.3/libexec"
GOSUMDB="sum.golang.org"
GOTMPDIR=""
GOTOOLDIR="/usr/local/Cellar/go/1.16.3/libexec/pkg/tool/darwin_amd64"
GOVCS=""
GOVERSION="go1.16.3"
GCCGO="gccgo"
AR="ar"
CC="clang"
CXX="clang++"
CGO_ENABLED="1"
GOMOD="/Users/esdrasbeleza/dev/array/monorepo/golang/go.mod"
CGO_CFLAGS="-g -O2"
CGO_CPPFLAGS=""
CGO_CXXFLAGS="-g -O2"
CGO_FFLAGS="-g -O2"
CGO_LDFLAGS="-g -O2"
PKG_CONFIG="pkg-config"
GOGCCFLAGS="-fPIC -arch x86_64 -m64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -fdebug-prefix-map=/var/folders/v_/4ltj2w9n2l525tl1n_shy5vm0000gn/T/go-build3161634107=/tmp/go-build -gno-record-gcc-switches -fno-common"

What did you do?

I'm implementing a solution that requires me to use a regexp to remove some special chars from a string.
The string is supposed to be normalized before the removal happens.
I was able to reproduce it in playground.

What did you expect to see?

My regexp operation is supposed to replace all characters that are not an Unicode letter, number, dash, underline or space with an empty string, like Bákè123 -_.

What did you see instead?

ReplaceAllString is also replacing my letters with accents with the same letters without accents, so I see Bake123 -_.

[ianlancetaylor]

The regexp package always works in terms of UTF-8 encoded code points. It doesn't work in terms of normalized strings. It doesn't support the kind of operation that you need. Sorry.