Re: [pbs-devel] [PATCH pathpatterns] match_list: added `matches_path()` function, which matches only the path

[Wolfgang Bumiller <w.bumiller@proxmox.com>]

On Fri, Aug 11, 2023 at 10:26:22AM +0200, Wolfgang Bumiller wrote:
> On Wed, Aug 09, 2023 at 12:19:12PM +0200, Gabriel Goller wrote:
> > Added `matches_path()` function, which only matches against the path and returns
> > an error if a file_mode pattern is found/needed in the matching list. This is
> > useful when we want to check if a file is excluded before running `stat()` on
> > the file to get the file_mode (which could fail).
> > 
> > Signed-off-by: Gabriel Goller <g.goller@proxmox.com>
> > ---
> >  src/match_list.rs | 159 +++++++++++++++++++++++++++++++++++++++++++++-
> >  1 file changed, 158 insertions(+), 1 deletion(-)
> > 
> > diff --git a/src/match_list.rs b/src/match_list.rs
> > index c5b14e0..acad328 100644
> > --- a/src/match_list.rs
> > +++ b/src/match_list.rs
> > @@ -1,6 +1,6 @@
> >  //! Helpers for include/exclude lists.
> > -
> >  use bitflags::bitflags;
> > +use std::fmt;
> >  
> >  use crate::PatternFlag;
> >  
> > @@ -39,6 +39,17 @@ impl Default for MatchFlag {
> >      }
> >  }
> >  
> > +#[derive(Debug, PartialEq)]
> > +pub struct FileModeRequiredForMatching;
> 
> Let's shorten this to just `FileModeRequired` ;-)
> 
> > +
> > +impl fmt::Display for FileModeRequiredForMatching {
> > +    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
> > +        write!(f, "File mode is required for matching")
> > +    }
> > +}
> > +
> > +impl std::error::Error for FileModeRequiredForMatching {}
> > +
> >  /// A pattern entry. (Glob patterns or literal patterns.)
> >  // Note:
> >  // For regex we'd likely use the POSIX extended REs via `regexec(3)`, since we're targetting
> > @@ -304,12 +315,32 @@ impl MatchEntry {
> >  
> >          self.matches_path_exact(path)
> >      }
> > +
> > +    /// Check whether the path contains a matching suffix. Returns an error if a file mode is required.
> > +    pub fn matches_path<T: AsRef<[u8]>>(
> > +        &self,
> > +        path: T,
> > +    ) -> Result<bool, FileModeRequiredForMatching> {
> > +        self.matches_path_do(path.as_ref())
> > +    }
> > +
> > +    fn matches_path_do(&self, path: &[u8]) -> Result<bool, FileModeRequiredForMatching> {
> > +        if !self.flags.contains(MatchFlag::ANY_FILE_TYPE) {
> > +            return Err(FileModeRequiredForMatching);
> > +        }
> > +
> > +        Ok(self.matches_path_suffix_do(path))
> > +    }
> >  }
> >  
> >  #[doc(hidden)]
> >  pub trait MatchListEntry {
> >      fn entry_matches(&self, path: &[u8], file_mode: Option<u32>) -> Option<MatchType>;
> >      fn entry_matches_exact(&self, path: &[u8], file_mode: Option<u32>) -> Option<MatchType>;
> > +    fn entry_matches_path(
> > +        &self,
> > +        path: &[u8],
> > +    ) -> Result<Option<MatchType>, FileModeRequiredForMatching>;
> 
> >  }
> >  
> >  impl MatchListEntry for &'_ MatchEntry {
> > @@ -328,6 +359,21 @@ impl MatchListEntry for &'_ MatchEntry {
> >              None
> >          }
> >      }
> > +
> > +    fn entry_matches_path(
> > +        &self,
> > +        path: &[u8],
> > +    ) -> Result<Option<MatchType>, FileModeRequiredForMatching> {
> > +        if let Ok(b) = self.matches_path(path) {
> 
> This can just use `?`, it's the exact same error type after all.
> (Also `if let Ok` is generally best avoided since the 'else' branch
> discards the error, and if not, it's often a case like this where it can
> juse use '?' ;-) ).
> 
> Effectively this could be as short as
> 
>     Ok(self.matches_path(path)?.then(|| self.match_type()))
> 
> > +            if b {
> 
> As an additional hint: when you nest ifs around things you can match,
> you can just include both cases in the patterns:
>     match self.matches_path(path) {
>         Ok(true) => Ok(Some(self.match_type())),
>         Ok(false) => Ok(None),
>         Err(err) => Err(err),
>         // where this Err() case already tells you that you can use '?' instead
>     }
> 
> > +                Ok(Some(self.match_type()))
> > +            } else {
> > +                Ok(None)
> > +            }
> > +        } else {
> > +            Err(FileModeRequiredForMatching)
> > +        }
> > +    }
> >  }
> >  
> >  impl MatchListEntry for &'_ &'_ MatchEntry {
> > @@ -346,6 +392,21 @@ impl MatchListEntry for &'_ &'_ MatchEntry {
> >              None
> >          }
> >      }
> > +
> > +    fn entry_matches_path(
> > +        &self,
> > +        path: &[u8],
> > +    ) -> Result<Option<MatchType>, FileModeRequiredForMatching> {
> 
> same
> 
> > +        if let Ok(b) = self.matches_path(path) {
> > +            if b {
> > +                Ok(Some(self.match_type()))
> > +            } else {
> > +                Ok(None)
> > +            }
> > +        } else {
> > +            Err(FileModeRequiredForMatching)
> > +        }
> > +    }
> >  }
> >  
> >  /// This provides [`matches`](MatchList::matches) and [`matches_exact`](MatchList::matches_exact)
> > @@ -374,6 +435,20 @@ pub trait MatchList {
> >      }
> >  
> >      fn matches_exact_do(&self, path: &[u8], file_mode: Option<u32>) -> Option<MatchType>;
> > +
> > +    /// Check whether this list contains anything exactly matching the path, returns error if
> > +    /// `file_mode` is required for exact matching.
> > +    fn matches_path<T: AsRef<[u8]>>(
> > +        &self,
> > +        path: T,
> > +    ) -> Result<Option<MatchType>, FileModeRequiredForMatching> {
> > +        self.matches_path_do(path.as_ref())
> > +    }
> > +
> > +    fn matches_path_do(
> > +        &self,
> > +        path: &[u8],
> > +    ) -> Result<Option<MatchType>, FileModeRequiredForMatching>;
> >  }
> >  
> >  impl<'a, T> MatchList for T
> > @@ -408,6 +483,24 @@ where
> >  
> >          None
> >      }
> > +
> > +    fn matches_path_do(
> > +        &self,
> > +        path: &[u8],
> > +    ) -> Result<Option<MatchType>, FileModeRequiredForMatching> {
> 
> Given the amount of tiny match helpers we run through with those 2
> traits already I wonder if we should just make a breaking change here
> instead and only have the versions with the `Result` while users (or
> defaulted helpers in the trait) just pass `file_mode.unwrap_or(!0)`
> (since a mode of 0 should match anything ;-) ).

(of s/of 0/of !0/` of course)