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| author | Russ Cox <rsc@golang.org> | 2021-10-07 09:56:29 -0400 |
|---|---|---|
| committer | Russ Cox <rsc@golang.org> | 2021-10-11 15:28:50 +0000 |
| commit | 702e33717486cb8331db17304f2369ef641da61f (patch) | |
| tree | a024631a5c2497d89ad7da56979025fe2ac8bf0a /src/regexp/regexp.go | |
| parent | 34f7b1f841cc450cc3aba42019e613fd03a84fce (diff) | |
| download | go-git-702e33717486cb8331db17304f2369ef641da61f.tar.gz | |
regexp: document and implement that invalid UTF-8 bytes are the same as U+FFFD
What should it mean to run a regexp match on invalid UTF-8 bytes?
The coherent behavior options are:
1. Invalid UTF-8 does not match any character classes,
nor a U+FFFD literal (nor \x{fffd}).
2. Each byte of invalid UTF-8 is treated identically to a U+FFFD in the input,
as a utf8.DecodeRune loop might.
RE2 uses Rule 1.
Because it works byte at a time, it can also provide \C to match any
single byte of input, which matches invalid UTF-8 as well.
This provides the nice property that a match for a regexp without \C
is guaranteed to be valid UTF-8.
Unfortunately, today Go has an incoherent mix of these two, although
mostly Rule 2. This is a deviation from RE2, and it gives up the nice
property, but we probably can't correct that at this point.
In particular .* already matches entire inputs today, valid UTF-8 or
not, and I doubt we can break that.
This CL adopts Rule 2 officially, fixing the few places that deviate from it.
Fixes #48749.
Change-Id: I96402527c5dfb1146212f568ffa09dde91d71244
Reviewed-on: https://go-review.googlesource.com/c/go/+/354569
Trust: Russ Cox <rsc@golang.org>
Run-TryBot: Russ Cox <rsc@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Rob Pike <r@golang.org>
Diffstat (limited to 'src/regexp/regexp.go')
| -rw-r--r-- | src/regexp/regexp.go | 8 |
1 files changed, 7 insertions, 1 deletions
diff --git a/src/regexp/regexp.go b/src/regexp/regexp.go index bfcf7910cf..af7259c9bf 100644 --- a/src/regexp/regexp.go +++ b/src/regexp/regexp.go @@ -20,6 +20,8 @@ // or any book about automata theory. // // All characters are UTF-8-encoded code points. +// Following utf8.DecodeRune, each byte of an invalid UTF-8 sequence +// is treated as if it encoded utf8.RuneError (U+FFFD). // // There are 16 methods of Regexp that match a regular expression and identify // the matched text. Their names are matched by this regular expression: @@ -276,7 +278,11 @@ func minInputLen(re *syntax.Regexp) int { case syntax.OpLiteral: l := 0 for _, r := range re.Rune { - l += utf8.RuneLen(r) + if r == utf8.RuneError { + l++ + } else { + l += utf8.RuneLen(r) + } } return l case syntax.OpCapture, syntax.OpPlus: |