regexp: backreference to capturing group breaks if followed by underscore #39594
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ghost
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andybons
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This may be counter-intuitive, but if I interpret the documentation correctly, I think this is the way it is supposed to work:
So, the template in the example "$2_$1" is the same as "${2_}${1}", not "${2}_${1}". |
JavaScriptconsole.log('foo,bar'.replace(/(\w+),(\w+)/, '$2_$1'));Result is Perlmy $a = 'foo,bar';
$a =~ s/(\w+),(\w+)/\2_\1/;
warn $a;Result is Rubyputs 'foo,bar'.sub(/(\w+),(\w+)/, '\2_\1')Result is So, I propose to fix the behavior of Go. diff --git a/src/regexp/all_test.go b/src/regexp/all_test.go
index be7a2e7111..7d944d4844 100644
--- a/src/regexp/all_test.go
+++ b/src/regexp/all_test.go
@@ -227,6 +227,7 @@ var replaceTests = []ReplaceTest{
{"(a)(((b))){0}c", ".$1.", "xacxacx", "x.a.x.a.x"},
{"((a(b){0}){3}){5}(h)", "y caramb$2", "say aaaaaaaaaaaaaaaah", "say ay caramba"},
{"((a(b){0}){3}){5}h", "y caramb$2", "say aaaaaaaaaaaaaaaah", "say ay caramba"},
+ {"(Hello)_(World)", "$2_$1", "Hello_World!", "World_Hello!"},
}
var replaceLiteralTests = []ReplaceTest{
diff --git a/src/regexp/regexp.go b/src/regexp/regexp.go
index b547a2ab97..7bab7a5d81 100644
--- a/src/regexp/regexp.go
+++ b/src/regexp/regexp.go
@@ -981,12 +981,24 @@ func extract(str string) (name string, num int, rest string, ok bool) {
str = str[1:]
}
i := 0
- for i < len(str) {
- rune, size := utf8.DecodeRuneInString(str[i:])
- if !unicode.IsLetter(rune) && !unicode.IsDigit(rune) && rune != '_' {
- break
+ b := str[0]
+ if !brace && '0' <= b && b <= '9' {
+ i++
+ for i < len(str) {
+ rune, size := utf8.DecodeRuneInString(str[i:])
+ if !unicode.IsLetter(rune) && !unicode.IsDigit(rune) {
+ break
+ }
+ i += size
+ }
+ } else {
+ for i < len(str) {
+ rune, size := utf8.DecodeRuneInString(str[i:])
+ if !unicode.IsLetter(rune) && !unicode.IsDigit(rune) && rune != '_' {
+ break
+ }
+ i += size
}
- i += size
}
if i == 0 {
// empty name is not okay |
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What version of Go are you using (
go version)?Does this issue reproduce with the latest release?
Yes
What operating system and processor architecture are you using (
go env)?go envOutputWhat did you do?
Minimal case: Play
What did you expect to see?
I expect the pattern
"$2_$1"to work without needing to escape into"${2}_$1", as in python etc.The text was updated successfully, but these errors were encountered: