rust-filepatterns: improve API and robustness for pattern files parsing

Within the next few patches we will be using this new API.

Differential Revision: https://phab.mercurial-scm.org/D7908

rust/hg-core/src/filepatterns.rs

@@ -1,380 +1,534 b''
 // filepatterns.rs
 //
 // Copyright 2019 Raphaël Gomès <[e-mail]>
 //
 // This software may be used and distributed according to the terms of the
 // GNU General Public License version 2 or any later version.
 
 //! Handling of Mercurial-specific patterns.
 
-use crate::{
-    utils::SliceExt, FastHashMap, LineNumber, PatternError, PatternFileError,
-};
+use crate::{utils::SliceExt, FastHashMap, PatternError};
 use lazy_static::lazy_static;
 use regex::bytes::{NoExpand, Regex};
 use std::fs::File;
 use std::io::Read;
 use std::path::{Path, PathBuf};
 use std::vec::Vec;
 
 lazy_static! {
     static ref RE_ESCAPE: Vec<Vec<u8>> = {
         let mut v: Vec<Vec<u8>> = (0..=255).map(|byte| vec![byte]).collect();
         let to_escape = b"()[]{}?*+-|^$\\.&~# \t\n\r\x0b\x0c";
         for byte in to_escape {
             v[*byte as usize].insert(0, b'\\');
         }
         v
     };
 }
 
 /// These are matched in order
 const GLOB_REPLACEMENTS: &[(&[u8], &[u8])] =
     &[(b"*/", b"(?:.*/)?"), (b"*", b".*"), (b"", b"[^/]*")];
 
+/// Appended to the regexp of globs
+const GLOB_SUFFIX: &[u8; 7] = b"(?:/|$)";
+
 #[derive(Debug, Copy, Clone, PartialEq, Eq)]
 pub enum PatternSyntax {
+    /// A regular expression
     Regexp,
     /// Glob that matches at the front of the path
     RootGlob,
     /// Glob that matches at any suffix of the path (still anchored at
     /// slashes)
     Glob,
+    /// a path relative to repository root, which is matched recursively
     Path,
+    /// A path relative to cwd
     RelPath,
+    /// an unrooted glob (*.rs matches Rust files in all dirs)
     RelGlob,
+    /// A regexp that needn't match the start of a name
     RelRegexp,
+    /// A path relative to repository root, which is matched non-recursively
+    /// (will not match subdirectories)
     RootFiles,
 }
 
 /// Transforms a glob pattern into a regex
 fn glob_to_re(pat: &[u8]) -> Vec<u8> {
     let mut input = pat;
     let mut res: Vec<u8> = vec![];
     let mut group_depth = 0;
 
     while let Some((c, rest)) = input.split_first() {
         input = rest;
 
         match c {
             b'*' => {
                 for (source, repl) in GLOB_REPLACEMENTS {
                     if let Some(rest) = input.drop_prefix(source) {
                         input = rest;
                         res.extend(*repl);
                         break;
                     }
                 }
             }
             b'?' => res.extend(b"."),
             b'[' => {
                 match input.iter().skip(1).position(|b| *b == b']') {
                     None => res.extend(b"\\["),
                     Some(end) => {
                         // Account for the one we skipped
                         let end = end + 1;
 
                         res.extend(b"[");
 
                         for (i, b) in input[..end].iter().enumerate() {
                             if *b == b'!' && i == 0 {
                                 res.extend(b"^")
                             } else if *b == b'^' && i == 0 {
                                 res.extend(b"\\^")
                             } else if *b == b'\\' {
                                 res.extend(b"\\\\")
                             } else {
                                 res.push(*b)
                             }
                         }
                         res.extend(b"]");
                         input = &input[end + 1..];
                     }
                 }
             }
             b'{' => {
                 group_depth += 1;
                 res.extend(b"(?:")
             }
             b'}' if group_depth > 0 => {
                 group_depth -= 1;
                 res.extend(b")");
             }
             b',' if group_depth > 0 => res.extend(b"|"),
             b'\\' => {
                 let c = {
                     if let Some((c, rest)) = input.split_first() {
                         input = rest;
                         c
                     } else {
                         c
                     }
                 };
                 res.extend(&RE_ESCAPE[*c as usize])
             }
             _ => res.extend(&RE_ESCAPE[*c as usize]),
         }
     }
     res
 }
 
 fn escape_pattern(pattern: &[u8]) -> Vec<u8> {
     pattern
         .iter()
         .flat_map(|c| RE_ESCAPE[*c as usize].clone())
         .collect()
 }
 
-fn parse_pattern_syntax(kind: &[u8]) -> Result<PatternSyntax, PatternError> {
+pub fn parse_pattern_syntax(
+    kind: &[u8],
+) -> Result<PatternSyntax, PatternError> {
     match kind {
-        b"re" => Ok(PatternSyntax::Regexp),
-        b"path" => Ok(PatternSyntax::Path),
-        b"relpath" => Ok(PatternSyntax::RelPath),
-        b"rootfilesin" => Ok(PatternSyntax::RootFiles),
-        b"relglob" => Ok(PatternSyntax::RelGlob),
-        b"relre" => Ok(PatternSyntax::RelRegexp),
-        b"glob" => Ok(PatternSyntax::Glob),
-        b"rootglob" => Ok(PatternSyntax::RootGlob),
+        b"re:" => Ok(PatternSyntax::Regexp),
+        b"path:" => Ok(PatternSyntax::Path),
+        b"relpath:" => Ok(PatternSyntax::RelPath),
+        b"rootfilesin:" => Ok(PatternSyntax::RootFiles),
+        b"relglob:" => Ok(PatternSyntax::RelGlob),
+        b"relre:" => Ok(PatternSyntax::RelRegexp),
+        b"glob:" => Ok(PatternSyntax::Glob),
+        b"rootglob:" => Ok(PatternSyntax::RootGlob),
         _ => Err(PatternError::UnsupportedSyntax(
             String::from_utf8_lossy(kind).to_string(),
         )),
     }
 }
 
 /// Builds the regex that corresponds to the given pattern.
 /// If within a `syntax: regexp` context, returns the pattern,
 /// otherwise, returns the corresponding regex.
-fn _build_single_regex(
-    syntax: PatternSyntax,
-    pattern: &[u8],
-    globsuffix: &[u8],
-) -> Vec<u8> {
+fn _build_single_regex(entry: &IgnorePattern) -> Vec<u8> {
+    let IgnorePattern {
+        syntax, pattern, ..
+    } = entry;
     if pattern.is_empty() {
         return vec![];
     }
     match syntax {
         PatternSyntax::Regexp => pattern.to_owned(),
         PatternSyntax::RelRegexp => {
             if pattern[0] == b'^' {
                 return pattern.to_owned();
             }
-            [b".*", pattern].concat()
+            [&b".*"[..], pattern].concat()
         }
         PatternSyntax::Path | PatternSyntax::RelPath => {
             if pattern == b"." {
                 return vec![];
             }
             [escape_pattern(pattern).as_slice(), b"(?:/|$)"].concat()
         }
         PatternSyntax::RootFiles => {
             let mut res = if pattern == b"." {
                 vec![]
             } else {
                 // Pattern is a directory name.
                 [escape_pattern(pattern).as_slice(), b"/"].concat()
             };
 
             // Anything after the pattern must be a non-directory.
             res.extend(b"[^/]+$");
             res
         }
         PatternSyntax::RelGlob => {
             let glob_re = glob_to_re(pattern);
             if let Some(rest) = glob_re.drop_prefix(b"[^/]*") {
-                [b".*", rest, globsuffix].concat()
+                [b".*", rest, GLOB_SUFFIX].concat()
             } else {
-                [b"(?:|.*/)", glob_re.as_slice(), globsuffix].concat()
+                [b"(?:|.*/)", glob_re.as_slice(), GLOB_SUFFIX].concat()
             }
         }
         PatternSyntax::Glob | PatternSyntax::RootGlob => {
-            [glob_to_re(pattern).as_slice(), globsuffix].concat()
+            [glob_to_re(pattern).as_slice(), GLOB_SUFFIX].concat()
         }
     }
 }
 
 const GLOB_SPECIAL_CHARACTERS: [u8; 7] =
     [b'*', b'?', b'[', b']', b'{', b'}', b'\\'];
 
+/// TODO support other platforms
+#[cfg(unix)]
+pub fn normalize_path_bytes(bytes: &[u8]) -> Vec<u8> {
+    if bytes.is_empty() {
+        return b".".to_vec();
+    }
+    let sep = b'/';
+
+    let mut initial_slashes = bytes.iter().take_while(|b| **b == sep).count();
+    if initial_slashes > 2 {
+        // POSIX allows one or two initial slashes, but treats three or more
+        // as single slash.
+        initial_slashes = 1;
+    }
+    let components = bytes
+        .split(|b| *b == sep)
+        .filter(|c| !(c.is_empty() || c == b"."))
+        .fold(vec![], |mut acc, component| {
+            if component != b".."
+                || (initial_slashes == 0 && acc.is_empty())
+                || (!acc.is_empty() && acc[acc.len() - 1] == b"..")
+            {
+                acc.push(component)
+            } else if !acc.is_empty() {
+                acc.pop();
+            }
+            acc
+        });
+    let mut new_bytes = components.join(&sep);
+
+    if initial_slashes > 0 {
+        let mut buf: Vec<_> = (0..initial_slashes).map(|_| sep).collect();
+        buf.extend(new_bytes);
+        new_bytes = buf;
+    }
+    if new_bytes.is_empty() {
+        b".".to_vec()
+    } else {
+        new_bytes
+    }
+}
+
 /// Wrapper function to `_build_single_regex` that short-circuits 'exact' globs
 /// that don't need to be transformed into a regex.
 pub fn build_single_regex(
-    kind: &[u8],
-    pat: &[u8],
-    globsuffix: &[u8],
+    entry: &IgnorePattern,
 ) -> Result<Vec<u8>, PatternError> {
-    let enum_kind = parse_pattern_syntax(kind)?;
-    if enum_kind == PatternSyntax::RootGlob
-        && !pat.iter().any(|b| GLOB_SPECIAL_CHARACTERS.contains(b))
+    let IgnorePattern {
+        pattern, syntax, ..
+    } = entry;
+    let pattern = match syntax {
+        PatternSyntax::RootGlob
+        | PatternSyntax::Path
+        | PatternSyntax::RelGlob
+        | PatternSyntax::RootFiles => normalize_path_bytes(&pattern),
+        _ => pattern.to_owned(),
+    };
+    if *syntax == PatternSyntax::RootGlob
+        && !pattern.iter().any(|b| GLOB_SPECIAL_CHARACTERS.contains(b))
     {
-        let mut escaped = escape_pattern(pat);
-        escaped.extend(b"(?:/|$)");
+        let mut escaped = escape_pattern(&pattern);
+        escaped.extend(GLOB_SUFFIX);
         Ok(escaped)
     } else {
-        Ok(_build_single_regex(enum_kind, pat, globsuffix))
+        let mut entry = entry.clone();
+        entry.pattern = pattern;
+        Ok(_build_single_regex(&entry))
     }
 }
 
 lazy_static! {
     static ref SYNTAXES: FastHashMap<&'static [u8], &'static [u8]> = {
         let mut m = FastHashMap::default();
 
         m.insert(b"re".as_ref(), b"relre:".as_ref());
         m.insert(b"regexp".as_ref(), b"relre:".as_ref());
         m.insert(b"glob".as_ref(), b"relglob:".as_ref());
         m.insert(b"rootglob".as_ref(), b"rootglob:".as_ref());
-        m.insert(b"include".as_ref(), b"include".as_ref());
-        m.insert(b"subinclude".as_ref(), b"subinclude".as_ref());
+        m.insert(b"include".as_ref(), b"include:".as_ref());
+        m.insert(b"subinclude".as_ref(), b"subinclude:".as_ref());
         m
     };
 }
 
-pub type PatternTuple = (Vec<u8>, LineNumber, Vec<u8>);
-type WarningTuple = (PathBuf, Vec<u8>);
+#[derive(Debug)]
+pub enum PatternFileWarning {
+    /// (file path, syntax bytes)
+    InvalidSyntax(PathBuf, Vec<u8>),
+    /// File path
+    NoSuchFile(PathBuf),
+}
 
 pub fn parse_pattern_file_contents<P: AsRef<Path>>(
     lines: &[u8],
     file_path: P,
     warn: bool,
-) -> (Vec<PatternTuple>, Vec<WarningTuple>) {
+) -> Result<(Vec<IgnorePattern>, Vec<PatternFileWarning>), PatternError> {
     let comment_regex = Regex::new(r"((?:^|[^\\])(?:\\\\)*)#.*").unwrap();
     let comment_escape_regex = Regex::new(r"\\#").unwrap();
-    let mut inputs: Vec<PatternTuple> = vec![];
-    let mut warnings: Vec<WarningTuple> = vec![];
+    let mut inputs: Vec<IgnorePattern> = vec![];
+    let mut warnings: Vec<PatternFileWarning> = vec![];
 
     let mut current_syntax = b"relre:".as_ref();
 
     for (line_number, mut line) in lines.split(|c| *c == b'\n').enumerate() {
         let line_number = line_number + 1;
 
         let line_buf;
         if line.contains(&b'#') {
             if let Some(cap) = comment_regex.captures(line) {
                 line = &line[..cap.get(1).unwrap().end()]
             }
             line_buf = comment_escape_regex.replace_all(line, NoExpand(b"#"));
             line = &line_buf;
         }
 
         let mut line = line.trim_end();
 
         if line.is_empty() {
             continue;
         }
 
         if let Some(syntax) = line.drop_prefix(b"syntax:") {
             let syntax = syntax.trim();
 
             if let Some(rel_syntax) = SYNTAXES.get(syntax) {
                 current_syntax = rel_syntax;
             } else if warn {
-                warnings
-                    .push((file_path.as_ref().to_owned(), syntax.to_owned()));
+                warnings.push(PatternFileWarning::InvalidSyntax(
+                    file_path.as_ref().to_owned(),
+                    syntax.to_owned(),
+                ));
             }
             continue;
         }
 
         let mut line_syntax: &[u8] = &current_syntax;
 
         for (s, rels) in SYNTAXES.iter() {
             if let Some(rest) = line.drop_prefix(rels) {
                 line_syntax = rels;
                 line = rest;
                 break;
             }
             if let Some(rest) = line.drop_prefix(&[s, &b":"[..]].concat()) {
                 line_syntax = rels;
                 line = rest;
                 break;
             }
         }
 
-        inputs.push((
-            [line_syntax, line].concat(),
+        inputs.push(IgnorePattern::new(
+            parse_pattern_syntax(&line_syntax).map_err(|e| match e {
+                PatternError::UnsupportedSyntax(syntax) => {
+                    PatternError::UnsupportedSyntaxInFile(
+                        syntax,
+                        file_path.as_ref().to_string_lossy().into(),
             line_number,
-            line.to_owned(),
+                    )
+                }
+                _ => e,
+            })?,
+            &line,
+            &file_path,
         ));
     }
-    (inputs, warnings)
+    Ok((inputs, warnings))
 }
 
 pub fn read_pattern_file<P: AsRef<Path>>(
     file_path: P,
     warn: bool,
-) -> Result<(Vec<PatternTuple>, Vec<WarningTuple>), PatternFileError> {
-    let mut f = File::open(file_path.as_ref())?;
+) -> Result<(Vec<IgnorePattern>, Vec<PatternFileWarning>), PatternError> {
+    let mut f = match File::open(file_path.as_ref()) {
+        Ok(f) => Ok(f),
+        Err(e) => match e.kind() {
+            std::io::ErrorKind::NotFound => {
+                return Ok((
+                    vec![],
+                    vec![PatternFileWarning::NoSuchFile(
+                        file_path.as_ref().to_owned(),
+                    )],
+                ))
+            }
+            _ => Err(e),
+        },
+    }?;
     let mut contents = Vec::new();
 
     f.read_to_end(&mut contents)?;
 
-    Ok(parse_pattern_file_contents(&contents, file_path, warn))
+    Ok(parse_pattern_file_contents(&contents, file_path, warn)?)
+}
+
+/// Represents an entry in an "ignore" file.
+#[derive(Debug, Eq, PartialEq, Clone)]
+pub struct IgnorePattern {
+    pub syntax: PatternSyntax,
+    pub pattern: Vec<u8>,
+    pub source: PathBuf,
 }
 
+impl IgnorePattern {
+    pub fn new(
+        syntax: PatternSyntax,
+        pattern: &[u8],
+        source: impl AsRef<Path>,
+    ) -> Self {
+        Self {
+            syntax,
+            pattern: pattern.to_owned(),
+            source: source.as_ref().to_owned(),
+        }
+    }
+}
+
+pub type PatternResult<T> = Result<T, PatternError>;
+
 #[cfg(test)]
 mod tests {
     use super::*;
+    use pretty_assertions::assert_eq;
 
     #[test]
     fn escape_pattern_test() {
-        let untouched = br#"!"%',/0123456789:;<=>@ABCDEFGHIJKLMNOPQRSTUVWXYZ_`abcdefghijklmnopqrstuvwxyz"#;
+        let untouched =
+            br#"!"%',/0123456789:;<=>@ABCDEFGHIJKLMNOPQRSTUVWXYZ_`abcdefghijklmnopqrstuvwxyz"#;
         assert_eq!(escape_pattern(untouched), untouched.to_vec());
         // All escape codes
         assert_eq!(
             escape_pattern(br#"()[]{}?*+-|^$\\.&~# \t\n\r\v\f"#),
             br#"\(\)\[\]\{\}\?\*\+\-\|\^\$\\\\\.\&\~\#\ \\t\\n\\r\\v\\f"#
                 .to_vec()
         );
     }
 
     #[test]
     fn glob_test() {
         assert_eq!(glob_to_re(br#"?"#), br#"."#);
         assert_eq!(glob_to_re(br#"*"#), br#"[^/]*"#);
         assert_eq!(glob_to_re(br#"**"#), br#".*"#);
         assert_eq!(glob_to_re(br#"**/a"#), br#"(?:.*/)?a"#);
         assert_eq!(glob_to_re(br#"a/**/b"#), br#"a/(?:.*/)?b"#);
         assert_eq!(glob_to_re(br#"[a*?!^][^b][!c]"#), br#"[a*?!^][\^b][^c]"#);
         assert_eq!(glob_to_re(br#"{a,b}"#), br#"(?:a|b)"#);
         assert_eq!(glob_to_re(br#".\*\?"#), br#"\.\*\?"#);
     }
 
     #[test]
     fn test_parse_pattern_file_contents() {
         let lines = b"syntax: glob\n*.elc";
 
         assert_eq!(
-            vec![(b"relglob:*.elc".to_vec(), 2, b"*.elc".to_vec())],
             parse_pattern_file_contents(lines, Path::new("file_path"), false)
+                .unwrap()
                 .0,
+            vec![IgnorePattern::new(
+                PatternSyntax::RelGlob,
+                b"*.elc",
+                Path::new("file_path")
+            )],
         );
 
         let lines = b"syntax: include\nsyntax: glob";
 
         assert_eq!(
             parse_pattern_file_contents(lines, Path::new("file_path"), false)
+                .unwrap()
                 .0,
             vec![]
         );
         let lines = b"glob:**.o";
         assert_eq!(
             parse_pattern_file_contents(lines, Path::new("file_path"), false)
+                .unwrap()
                 .0,
-            vec![(b"relglob:**.o".to_vec(), 1, b"**.o".to_vec())]
+            vec![IgnorePattern::new(
+                PatternSyntax::RelGlob,
+                b"**.o",
+                Path::new("file_path")
+            )]
+        );
+    }
+
+    #[test]
+    fn test_build_single_regex() {
+        assert_eq!(
+            build_single_regex(&IgnorePattern::new(
+                PatternSyntax::RelGlob,
+                b"rust/target/",
+                Path::new("")
+            ))
+            .unwrap(),
+            br"(?:|.*/)rust/target(?:/|$)".to_vec(),
         );
     }
 
     #[test]
     fn test_build_single_regex_shortcut() {
         assert_eq!(
-            br"(?:/|$)".to_vec(),
-            build_single_regex(b"rootglob", b"", b"").unwrap()
+            build_single_regex(&IgnorePattern::new(
+                PatternSyntax::RootGlob,
+                b"",
+                Path::new("")
+            ))
+            .unwrap(),
+            br"\.(?:/|$)".to_vec(),
         );
         assert_eq!(
+            build_single_regex(&IgnorePattern::new(
+                PatternSyntax::RootGlob,
+                b"whatever",
+                Path::new("")
+            ))
+            .unwrap(),
             br"whatever(?:/|$)".to_vec(),
-            build_single_regex(b"rootglob", b"whatever", b"").unwrap()
         );
         assert_eq!(
-            br"[^/]*\.o".to_vec(),
-            build_single_regex(b"rootglob", b"*.o", b"").unwrap()
+            build_single_regex(&IgnorePattern::new(
+                PatternSyntax::RootGlob,
+                b"*.o",
+                Path::new("")
+            ))
+            .unwrap(),
+            br"[^/]*\.o(?:/|$)".to_vec(),
         );
     }
 }

rust/hg-core/src/lib.rs

@@ -1,143 +1,169 b''
 // Copyright 2018-2020 Georges Racinet <[e-mail]>
 //           and Mercurial contributors
 //
 // This software may be used and distributed according to the terms of the
 // GNU General Public License version 2 or any later version.
 mod ancestors;
 pub mod dagops;
 pub use ancestors::{AncestorsIterator, LazyAncestors, MissingAncestors};
 mod dirstate;
 pub mod discovery;
 pub mod testing; // unconditionally built, for use from integration tests
 pub use dirstate::{
     dirs_multiset::{DirsMultiset, DirsMultisetIter},
     dirstate_map::DirstateMap,
     parsers::{pack_dirstate, parse_dirstate, PARENT_SIZE},
     status::{status, StatusResult},
     CopyMap, CopyMapIter, DirstateEntry, DirstateParents, EntryState,
     StateMap, StateMapIter,
 };
 mod filepatterns;
 pub mod matchers;
 pub mod revlog;
 pub use revlog::*;
 pub mod utils;
 
 use crate::utils::hg_path::{HgPathBuf, HgPathError};
 pub use filepatterns::{
-    build_single_regex, read_pattern_file, PatternSyntax, PatternTuple,
+    parse_pattern_syntax, read_pattern_file, IgnorePattern,
+    PatternFileWarning, PatternSyntax,
 };
 use std::collections::HashMap;
 use twox_hash::RandomXxHashBuilder64;
 
 pub type LineNumber = usize;
 
 /// Rust's default hasher is too slow because it tries to prevent collision
 /// attacks. We are not concerned about those: if an ill-minded person has
 /// write access to your repository, you have other issues.
 pub type FastHashMap<K, V> = HashMap<K, V, RandomXxHashBuilder64>;
 
 #[derive(Clone, Debug, PartialEq)]
 pub enum DirstateParseError {
     TooLittleData,
     Overflow,
     CorruptedEntry(String),
     Damaged,
 }
 
 impl From<std::io::Error> for DirstateParseError {
     fn from(e: std::io::Error) -> Self {
         DirstateParseError::CorruptedEntry(e.to_string())
     }
 }
 
 impl ToString for DirstateParseError {
     fn to_string(&self) -> String {
         use crate::DirstateParseError::*;
         match self {
             TooLittleData => "Too little data for dirstate.".to_string(),
             Overflow => "Overflow in dirstate.".to_string(),
             CorruptedEntry(e) => format!("Corrupted entry: {:?}.", e),
             Damaged => "Dirstate appears to be damaged.".to_string(),
         }
     }
 }
 
 #[derive(Debug, PartialEq)]
 pub enum DirstatePackError {
     CorruptedEntry(String),
     CorruptedParent,
     BadSize(usize, usize),
 }
 
 impl From<std::io::Error> for DirstatePackError {
     fn from(e: std::io::Error) -> Self {
         DirstatePackError::CorruptedEntry(e.to_string())
     }
 }
 #[derive(Debug, PartialEq)]
 pub enum DirstateMapError {
     PathNotFound(HgPathBuf),
     EmptyPath,
     InvalidPath(HgPathError),
 }
 
 impl ToString for DirstateMapError {
     fn to_string(&self) -> String {
         match self {
             DirstateMapError::PathNotFound(_) => {
                 "expected a value, found none".to_string()
             }
             DirstateMapError::EmptyPath => "Overflow in dirstate.".to_string(),
             DirstateMapError::InvalidPath(e) => e.to_string(),
         }
     }
 }
 
 pub enum DirstateError {
     Parse(DirstateParseError),
     Pack(DirstatePackError),
     Map(DirstateMapError),
     IO(std::io::Error),
 }
 
 impl From<DirstateParseError> for DirstateError {
     fn from(e: DirstateParseError) -> Self {
         DirstateError::Parse(e)
     }
 }
 
 impl From<DirstatePackError> for DirstateError {
     fn from(e: DirstatePackError) -> Self {
         DirstateError::Pack(e)
     }
 }
 
 #[derive(Debug)]
 pub enum PatternError {
+    Path(HgPathError),
     UnsupportedSyntax(String),
+    UnsupportedSyntaxInFile(String, String, usize),
+    TooLong(usize),
+    IO(std::io::Error),
 }
 
-#[derive(Debug)]
-pub enum PatternFileError {
-    IO(std::io::Error),
-    Pattern(PatternError, LineNumber),
+impl ToString for PatternError {
+    fn to_string(&self) -> String {
+        match self {
+            PatternError::UnsupportedSyntax(syntax) => {
+                format!("Unsupported syntax {}", syntax)
 }
-
-impl From<std::io::Error> for PatternFileError {
-    fn from(e: std::io::Error) -> Self {
-        PatternFileError::IO(e)
+            PatternError::UnsupportedSyntaxInFile(syntax, file_path, line) => {
+                format!(
+                    "{}:{}: unsupported syntax {}",
+                    file_path, line, syntax
+                )
+            }
+            PatternError::TooLong(size) => {
+                format!("matcher pattern is too long ({} bytes)", size)
+            }
+            PatternError::IO(e) => e.to_string(),
+            PatternError::Path(e) => e.to_string(),
+        }
     }
 }
 
 impl From<DirstateMapError> for DirstateError {
     fn from(e: DirstateMapError) -> Self {
         DirstateError::Map(e)
     }
 }
 
 impl From<std::io::Error> for DirstateError {
     fn from(e: std::io::Error) -> Self {
         DirstateError::IO(e)
     }
 }
+
+impl From<std::io::Error> for PatternError {
+    fn from(e: std::io::Error) -> Self {
+        PatternError::IO(e)
+    }
+}
+
+impl From<HgPathError> for PatternError {
+    fn from(e: HgPathError) -> Self {
+        PatternError::Path(e)
+    }
+}