rust-grep-regex/0001-regex-make-CRLF-hack-more-robust.patch

From 9d703110cfe01782d2d0b03a340f5983da215e68 Mon Sep 17 00:00:00 2001
From: Andrew Gallant <jamslam@gmail.com>
Date: Sat, 26 Jan 2019 12:25:21 -0500
Subject: [PATCH] regex: make CRLF hack more robust

This commit improves the CRLF hack to be more robust. In particular, in
addition to rewriting `$` as `(?:\r??$)`, we now strip `\r` from the end
of a match if and only if the regex has an ending line anchor required for
a match. This doesn't quite make the hack 100% correct, but should fix most
use cases in practice. An example of a regex that will still be incorrect
is `foo|bar$`, since the analysis isn't quite sophisticated enough to
determine that a `\r` can be safely stripped from any match. Even if we
fix that, regexes like `foo\r|bar$` still won't be handled correctly. Alas,
more work on this front should really be focused on enabling this in the
regex engine itself.

The specific cause of this bug was that grep-searcher was sneakily
stripping CRLF from matching lines when it really shouldn't have. We remove
that code now, and instead rely on better match semantics provided at a
lower level.

Fixes #1095
---
 src/config.rs  |   8 ++++
 src/crlf.rs    | 100 +++++++++++++++++++++++++++++++++++++++++++++++++
 src/matcher.rs |  57 ++++++++++++++++++++++++++--
 3 files changed, 162 insertions(+), 3 deletions(-)

diff --git a/src/config.rs b/src/config.rs
index f3d1f1c..efed9d4 100644
--- a/src/config.rs
+++ b/src/config.rs
@@ -160,6 +160,14 @@ impl ConfiguredHIR {
         non_matching_bytes(&self.expr)
     }
 
+    /// Returns true if and only if this regex needs to have its match offsets
+    /// tweaked because of CRLF support. Specifically, this occurs when the
+    /// CRLF hack is enabled and the regex is line anchored at the end. In
+    /// this case, matches that end with a `\r` have the `\r` stripped.
+    pub fn needs_crlf_stripped(&self) -> bool {
+        self.config.crlf && self.expr.is_line_anchored_end()
+    }
+
     /// Builds a regular expression from this HIR expression.
     pub fn regex(&self) -> Result<Regex, Error> {
         self.pattern_to_regex(&self.expr.to_string())
diff --git a/src/crlf.rs b/src/crlf.rs
index ff6b15b..838a28f 100644
--- a/src/crlf.rs
+++ b/src/crlf.rs
@@ -1,5 +1,105 @@
+use std::collections::HashMap;
+
+use grep_matcher::{Match, Matcher, NoError};
+use regex::bytes::Regex;
 use regex_syntax::hir::{self, Hir, HirKind};
 
+use config::ConfiguredHIR;
+use error::Error;
+use matcher::RegexCaptures;
+
+/// A matcher for implementing "word match" semantics.
+#[derive(Clone, Debug)]
+pub struct CRLFMatcher {
+    /// The regex.
+    regex: Regex,
+    /// A map from capture group name to capture group index.
+    names: HashMap<String, usize>,
+}
+
+impl CRLFMatcher {
+    /// Create a new matcher from the given pattern that strips `\r` from the
+    /// end of every match.
+    ///
+    /// This panics if the given expression doesn't need its CRLF stripped.
+    pub fn new(expr: &ConfiguredHIR) -> Result<CRLFMatcher, Error> {
+        assert!(expr.needs_crlf_stripped());
+
+        let regex = expr.regex()?;
+        let mut names = HashMap::new();
+        for (i, optional_name) in regex.capture_names().enumerate() {
+            if let Some(name) = optional_name {
+                names.insert(name.to_string(), i.checked_sub(1).unwrap());
+            }
+        }
+        Ok(CRLFMatcher { regex, names })
+    }
+}
+
+impl Matcher for CRLFMatcher {
+    type Captures = RegexCaptures;
+    type Error = NoError;
+
+    fn find_at(
+        &self,
+        haystack: &[u8],
+        at: usize,
+    ) -> Result<Option<Match>, NoError> {
+        let m = match self.regex.find_at(haystack, at) {
+            None => return Ok(None),
+            Some(m) => Match::new(m.start(), m.end()),
+        };
+        Ok(Some(adjust_match(haystack, m)))
+    }
+
+    fn new_captures(&self) -> Result<RegexCaptures, NoError> {
+        Ok(RegexCaptures::new(self.regex.capture_locations()))
+    }
+
+    fn capture_count(&self) -> usize {
+        self.regex.captures_len().checked_sub(1).unwrap()
+    }
+
+    fn capture_index(&self, name: &str) -> Option<usize> {
+        self.names.get(name).map(|i| *i)
+    }
+
+    fn captures_at(
+        &self,
+        haystack: &[u8],
+        at: usize,
+        caps: &mut RegexCaptures,
+    ) -> Result<bool, NoError> {
+        caps.strip_crlf(false);
+        let r = self.regex.captures_read_at(caps.locations(), haystack, at);
+        if !r.is_some() {
+            return Ok(false);
+        }
+
+        // If the end of our match includes a `\r`, then strip it from all
+        // capture groups ending at the same location.
+        let end = caps.locations().get(0).unwrap().1;
+        if end > 0 && haystack.get(end - 1) == Some(&b'\r') {
+            caps.strip_crlf(true);
+        }
+        Ok(true)
+    }
+
+    // We specifically do not implement other methods like find_iter or
+    // captures_iter. Namely, the iter methods are guaranteed to be correct
+    // by virtue of implementing find_at and captures_at above.
+}
+
+/// If the given match ends with a `\r`, then return a new match that ends
+/// immediately before the `\r`.
+pub fn adjust_match(haystack: &[u8], m: Match) -> Match {
+    if m.end() > 0 && haystack.get(m.end() - 1) == Some(&b'\r') {
+        m.with_end(m.end() - 1)
+    } else {
+        m
+    }
+}
+
 /// Substitutes all occurrences of multi-line enabled `$` with `(?:\r?$)`.
 ///
 /// This does not preserve the exact semantics of the given expression,
diff --git a/src/matcher.rs b/src/matcher.rs
index 831d573..b15d824 100644
--- a/src/matcher.rs
+++ b/src/matcher.rs
@@ -6,6 +6,7 @@ use grep_matcher::{
 use regex::bytes::{CaptureLocations, Regex};
 
 use config::{Config, ConfiguredHIR};
+use crlf::CRLFMatcher;
 use error::Error;
 use word::WordMatcher;
 
@@ -344,6 +345,11 @@ impl RegexMatcher {
 enum RegexMatcherImpl {
     /// The standard matcher used for all regular expressions.
     Standard(StandardMatcher),
+    /// A matcher that strips `\r` from the end of matches.
+    ///
+    /// This is only used when the CRLF hack is enabled and the regex is line
+    /// anchored at the end.
+    CRLF(CRLFMatcher),
     /// A matcher that only matches at word boundaries. This transforms the
     /// regex to `(^|\W)(...)($|\W)` instead of the more intuitive `\b(...)\b`.
     /// Because of this, the WordMatcher provides its own implementation of
@@ -358,6 +364,8 @@ impl RegexMatcherImpl {
     fn new(expr: &ConfiguredHIR) -> Result<RegexMatcherImpl, Error> {
         if expr.config().word {
             Ok(RegexMatcherImpl::Word(WordMatcher::new(expr)?))
+        } else if expr.needs_crlf_stripped() {
+            Ok(RegexMatcherImpl::CRLF(CRLFMatcher::new(expr)?))
         } else {
             Ok(RegexMatcherImpl::Standard(StandardMatcher::new(expr)?))
         }
@@ -379,6 +387,7 @@ impl Matcher for RegexMatcher {
         use self::RegexMatcherImpl::*;
         match self.matcher {
             Standard(ref m) => m.find_at(haystack, at),
+            CRLF(ref m) => m.find_at(haystack, at),
             Word(ref m) => m.find_at(haystack, at),
         }
     }
@@ -387,6 +396,7 @@ impl Matcher for RegexMatcher {
         use self::RegexMatcherImpl::*;
         match self.matcher {
             Standard(ref m) => m.new_captures(),
+            CRLF(ref m) => m.new_captures(),
             Word(ref m) => m.new_captures(),
         }
     }
@@ -395,6 +405,7 @@ impl Matcher for RegexMatcher {
         use self::RegexMatcherImpl::*;
         match self.matcher {
             Standard(ref m) => m.capture_count(),
+            CRLF(ref m) => m.capture_count(),
             Word(ref m) => m.capture_count(),
         }
     }
@@ -403,6 +414,7 @@ impl Matcher for RegexMatcher {
         use self::RegexMatcherImpl::*;
         match self.matcher {
             Standard(ref m) => m.capture_index(name),
+            CRLF(ref m) => m.capture_index(name),
             Word(ref m) => m.capture_index(name),
         }
     }
@@ -411,6 +423,7 @@ impl Matcher for RegexMatcher {
         use self::RegexMatcherImpl::*;
         match self.matcher {
             Standard(ref m) => m.find(haystack),
+            CRLF(ref m) => m.find(haystack),
             Word(ref m) => m.find(haystack),
         }
     }
@@ -425,6 +438,7 @@ impl Matcher for RegexMatcher {
         use self::RegexMatcherImpl::*;
         match self.matcher {
             Standard(ref m) => m.find_iter(haystack, matched),
+            CRLF(ref m) => m.find_iter(haystack, matched),
             Word(ref m) => m.find_iter(haystack, matched),
         }
     }
@@ -439,6 +453,7 @@ impl Matcher for RegexMatcher {
         use self::RegexMatcherImpl::*;
         match self.matcher {
             Standard(ref m) => m.try_find_iter(haystack, matched),
+            CRLF(ref m) => m.try_find_iter(haystack, matched),
             Word(ref m) => m.try_find_iter(haystack, matched),
         }
     }
@@ -451,6 +466,7 @@ impl Matcher for RegexMatcher {
         use self::RegexMatcherImpl::*;
         match self.matcher {
             Standard(ref m) => m.captures(haystack, caps),
+            CRLF(ref m) => m.captures(haystack, caps),
             Word(ref m) => m.captures(haystack, caps),
         }
     }
@@ -466,6 +482,7 @@ impl Matcher for RegexMatcher {
         use self::RegexMatcherImpl::*;
         match self.matcher {
             Standard(ref m) => m.captures_iter(haystack, caps, matched),
+            CRLF(ref m) => m.captures_iter(haystack, caps, matched),
             Word(ref m) => m.captures_iter(haystack, caps, matched),
         }
     }
@@ -481,6 +498,7 @@ impl Matcher for RegexMatcher {
         use self::RegexMatcherImpl::*;
         match self.matcher {
             Standard(ref m) => m.try_captures_iter(haystack, caps, matched),
+            CRLF(ref m) => m.try_captures_iter(haystack, caps, matched),
             Word(ref m) => m.try_captures_iter(haystack, caps, matched),
         }
     }
@@ -494,6 +512,7 @@ impl Matcher for RegexMatcher {
         use self::RegexMatcherImpl::*;
         match self.matcher {
             Standard(ref m) => m.captures_at(haystack, at, caps),
+            CRLF(ref m) => m.captures_at(haystack, at, caps),
             Word(ref m) => m.captures_at(haystack, at, caps),
         }
     }
@@ -509,6 +528,7 @@ impl Matcher for RegexMatcher {
         use self::RegexMatcherImpl::*;
         match self.matcher {
             Standard(ref m) => m.replace(haystack, dst, append),
+            CRLF(ref m) => m.replace(haystack, dst, append),
             Word(ref m) => m.replace(haystack, dst, append),
         }
     }
@@ -527,6 +547,9 @@ impl Matcher for RegexMatcher {
             Standard(ref m) => {
                 m.replace_with_captures(haystack, caps, dst, append)
             }
+            CRLF(ref m) => {
+                m.replace_with_captures(haystack, caps, dst, append)
+            }
             Word(ref m) => {
                 m.replace_with_captures(haystack, caps, dst, append)
             }
@@ -537,6 +560,7 @@ impl Matcher for RegexMatcher {
         use self::RegexMatcherImpl::*;
         match self.matcher {
             Standard(ref m) => m.is_match(haystack),
+            CRLF(ref m) => m.is_match(haystack),
             Word(ref m) => m.is_match(haystack),
         }
     }
@@ -549,6 +573,7 @@ impl Matcher for RegexMatcher {
         use self::RegexMatcherImpl::*;
         match self.matcher {
             Standard(ref m) => m.is_match_at(haystack, at),
+            CRLF(ref m) => m.is_match_at(haystack, at),
             Word(ref m) => m.is_match_at(haystack, at),
         }
     }
@@ -560,6 +585,7 @@ impl Matcher for RegexMatcher {
         use self::RegexMatcherImpl::*;
         match self.matcher {
             Standard(ref m) => m.shortest_match(haystack),
+            CRLF(ref m) => m.shortest_match(haystack),
             Word(ref m) => m.shortest_match(haystack),
         }
     }
@@ -572,6 +598,7 @@ impl Matcher for RegexMatcher {
         use self::RegexMatcherImpl::*;
         match self.matcher {
             Standard(ref m) => m.shortest_match_at(haystack, at),
+            CRLF(ref m) => m.shortest_match_at(haystack, at),
             Word(ref m) => m.shortest_match_at(haystack, at),
         }
     }
@@ -712,6 +739,9 @@ pub struct RegexCaptures {
     /// and the capturing groups must behave as if `(re)` is the `0`th capture
     /// group.
     offset: usize,
+    /// When enable, the end of a match has `\r` stripped from it, if one
+    /// exists.
+    strip_crlf: bool,
 }
 
 impl Captures for RegexCaptures {
@@ -720,8 +750,25 @@ impl Captures for RegexCaptures {
     }
 
     fn get(&self, i: usize) -> Option<Match> {
-        let actual = i.checked_add(self.offset).unwrap();
-        self.locs.pos(actual).map(|(s, e)| Match::new(s, e))
+        if !self.strip_crlf {
+            let actual = i.checked_add(self.offset).unwrap();
+            return self.locs.pos(actual).map(|(s, e)| Match::new(s, e));
+        }
+
+        // currently don't support capture offsetting with CRLF stripping
+        assert_eq!(self.offset, 0);
+        let m = match self.locs.pos(i).map(|(s, e)| Match::new(s, e)) {
+            None => return None,
+            Some(m) => m,
+        };
+        // If the end position of this match corresponds to the end position
+        // of the overall match, then we apply our CRLF stripping. Otherwise,
+        // we cannot assume stripping is correct.
+        if i == 0 || m.end() == self.locs.pos(0).unwrap().1 {
+            Some(m.with_end(m.end() - 1))
+        } else {
+            Some(m)
+        }
     }
 }
 
@@ -734,12 +781,16 @@ impl RegexCaptures {
         locs: CaptureLocations,
         offset: usize,
     ) -> RegexCaptures {
-        RegexCaptures { locs, offset }
+        RegexCaptures { locs, offset, strip_crlf: false }
     }
 
     pub(crate) fn locations(&mut self) -> &mut CaptureLocations {
         &mut self.locs
     }
+
+    pub(crate) fn strip_crlf(&mut self, yes: bool) {
+        self.strip_crlf = yes;
+    }
 }
 
 #[cfg(test)]
-- 
2.20.1