bugs for regexp.ReplaceAllString?

[wuceyang]

Go version

1.22.2

Output of go env in your module/workspace:

set GO111MODULE=on
set GOARCH=amd64
set GOBIN=
set GOCACHE=C:\Users\Administrator\AppData\Local\go-build
set GOENV=C:\Users\Administrator\AppData\Roaming\go\env  
set GOEXE=.exe
set GOEXPERIMENT=
set GOFLAGS=
set GOHOSTARCH=amd64
set GOHOSTOS=windows
set GOINSECURE=
set GOMODCACHE=C:\Users\Administrator\go\pkg\mod
set GONOPROXY=
set GONOSUMDB=
set GOOS=windows
set GOPATH=C:\Users\Administrator\go
set GOPRIVATE=
set GOPROXY=http://172.16.130.132:8081/repository/go-local/
set GOROOT=D:/Program Files/Go1.22.2
set AR=ar
set CC=gcc
set CXX=g++
set CGO_ENABLED=1
set GOMOD=D:\Work\Git\system-watcher-api\go.mod
set GOWORK=
set CGO_CFLAGS=-O2 -g
set CGO_CPPFLAGS=
set CGO_CXXFLAGS=-O2 -g
set CGO_FFLAGS=-O2 -g
set CGO_LDFLAGS=-O2 -g
set PKG_CONFIG=pkg-config
set GOGCCFLAGS=-m64 -mthreads -Wl,--no-gc-sections -fmessage-length=0 -ffile-prefix-map=C:\Users\ADMINI~1\AppData\Local\Temp\go-build2208406462=/tmp/go-build -gno-record-gcc-switches

What did you do?

when i rename uploaded filenames, codes below

package main
import (
    "fmt"
    "regexp"
)
func main () {
    var filename = "abc.123.txt"
    var pattern = regexp.MustCompile("^(.+?)\\.([^\\.]+)$")
    fmt.Println(pattern.ReplaceAllString(filename, "$1_.$2"))
}

What did you see happen?

output result: .txt

even when the codes like this

fmt.Println(pattern.ReplaceAllString(filename, "$1000.$2"))

the result unchanged

What did you expect to see?

it seems that golang can't get group no and strings
when i try this replacement in javascript and c#, the out is "abc.123000.txt", which is my expected result

[gabyhelp]

Related Issues and Documentation

• regex: ReplaceAllString and ReplaceAll broken group replacement #65000 (closed)
• Regex: Underscore (_) makes replace group not found #32885 (closed)
• regexp: issue parse string #68940 (closed)
• regexp: confusing ReplaceAllString result when using patterns like `$1_$2` #68712 (closed)
• regexp: Expand rules are confusing #40329
• regular expression sub-match not used in replace #42291 (closed)
• regexp: ReplaceAllString unexpected behavior with $ in src #69399 (closed)
• golang regex replace problem #29936 (closed)
• regexp: backreference to capturing group breaks if followed by underscore #39594
• strings: incorrect output #63596 (closed)

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[seankhliao]

https://go.dev/play/p/hIgPEsAiel1

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