rust-regex: fix issues with regex anchoring and performance
It turns out that the way I tried to work around `regex`'s behavior difference
with `re2` and Python's `re` was 1) buggy and 2) much more complicated than
needed.
In a few words:
`regex` adds `.*` on either side of patterns when no start or end anchor is
present. My previous workaround put `^` or `$` for every pattern, which is
wrong even without the other 2 bugs on top of it.
Using `^(?:<patterns>)` right at the end of the `regex` path fixes the issue.
I've opened an issue to get a build option instead:
https://github.com/rust-lang/regex/issues/675
Differential Revision: https://phab.mercurial-scm.org/D8506
--- a/rust/hg-core/src/filepatterns.rs Thu May 07 16:56:03 2020 -0400
+++ b/rust/hg-core/src/filepatterns.rs Thu May 07 23:52:08 2020 +0200
@@ -176,9 +176,7 @@
return vec![];
}
match syntax {
- // The `regex` crate adds `.*` to the start and end of expressions
- // if there are no anchors, so add them.
- PatternSyntax::Regexp => [b"^", &pattern[..], b"$"].concat(),
+ PatternSyntax::Regexp => pattern.to_owned(),
PatternSyntax::RelRegexp => {
// The `regex` crate accepts `**` while `re2` and Python's `re`
// do not. Checking for `*` correctly triggers the same error all
@@ -196,15 +194,14 @@
}
PatternSyntax::RootFiles => {
let mut res = if pattern == b"." {
- vec![b'^']
+ vec![]
} else {
// Pattern is a directory name.
- [b"^", escape_pattern(pattern).as_slice(), b"/"].concat()
+ [escape_pattern(pattern).as_slice(), b"/"].concat()
};
// Anything after the pattern must be a non-directory.
res.extend(b"[^/]+$");
- res.push(b'$');
res
}
PatternSyntax::RelGlob => {
@@ -216,7 +213,7 @@
}
}
PatternSyntax::Glob | PatternSyntax::RootGlob => {
- [b"^", glob_to_re(pattern).as_slice(), GLOB_SUFFIX].concat()
+ [glob_to_re(pattern).as_slice(), GLOB_SUFFIX].concat()
}
PatternSyntax::Include | PatternSyntax::SubInclude => unreachable!(),
}
@@ -654,7 +651,7 @@
Path::new("")
))
.unwrap(),
- Some(br"^[^/]*\.o(?:/|$)".to_vec()),
+ Some(br"[^/]*\.o(?:/|$)".to_vec()),
);
}
}
--- a/rust/hg-core/src/matchers.rs Thu May 07 16:56:03 2020 -0400
+++ b/rust/hg-core/src/matchers.rs Thu May 07 23:52:08 2020 +0200
@@ -347,7 +347,9 @@
) -> PatternResult<impl Fn(&HgPath) -> bool + Sync> {
use std::io::Write;
- let mut escaped_bytes = vec![];
+ // The `regex` crate adds `.*` to the start and end of expressions if there
+ // are no anchors, so add the start anchor.
+ let mut escaped_bytes = vec![b'^', b'(', b'?', b':'];
for byte in pattern {
if *byte > 127 {
write!(escaped_bytes, "\\x{:x}", *byte).unwrap();
@@ -355,6 +357,7 @@
escaped_bytes.push(*byte);
}
}
+ escaped_bytes.push(b')');
// Avoid the cost of UTF8 checking
//