printer: fix \r\n line terminator handling

This fixes a bug where it was assumed that 'is_suffix' when CRLF
handling was enabled mean that '\r\n' was present. But that's not the
case, and it is intentional that 'is_suffix' only looks for '\n'. (Which
is why #1803 wasn't taken, which tries to fix this by changing
'is_suffix'.)

Fixes #1765, Closes #1803

CHANGELOG.md

@@ -47,6 +47,8 @@ Bug fixes:
   Clarify that CLI invocation must always be valid, regardless of config file.
 * [BUG #1741](https://github.com/BurntSushi/ripgrep/issues/1741):
   Fix stdin detection when using PowerShell in UNIX environments.
+* [BUG #1765](https://github.com/BurntSushi/ripgrep/issues/1765):
+  Fix panic when `--crlf` is used in some cases.
 * [BUG #1816](https://github.com/BurntSushi/ripgrep/issues/1816):
   Add documentation for glob alternate syntax, e.g., `{a,b,..}`.
 * [BUG #1847](https://github.com/BurntSushi/ripgrep/issues/1847):

crates/printer/src/standard.rs

@@ -1474,7 +1474,10 @@ impl<'a, M: Matcher, W: WriteColor> StandardImpl<'a, M, W> {
         let lineterm = self.searcher.line_terminator();
         if lineterm.is_suffix(&buf[*line]) {
             let mut end = line.end() - 1;
-            if lineterm.is_crlf() && buf[end - 1] == b'\r' {
+            if lineterm.is_crlf()
+                && end > 0
+                && buf.get(end - 1) == Some(&b'\r')
+            {
                 end -= 1;
             }
             *line = line.with_end(end);
@@ -1547,11 +1550,12 @@ impl<'a, M: Matcher, W: WriteColor> StandardImpl<'a, M, W> {
 
 #[cfg(test)]
 mod tests {
-    use grep_regex::RegexMatcher;
+    use grep_matcher::LineTerminator;
+    use grep_regex::{RegexMatcher, RegexMatcherBuilder};
     use grep_searcher::SearcherBuilder;
-    use termcolor::NoColor;
+    use termcolor::{Ansi, NoColor};
 
-    use super::{Standard, StandardBuilder};
+    use super::{ColorSpecs, Standard, StandardBuilder};
 
     const SHERLOCK: &'static str = "\
 For the Doctor Watsons of this world, as opposed to the Sherlock
@@ -1576,6 +1580,10 @@ and exhibited clearly, with a label attached.\
         String::from_utf8(printer.get_mut().get_ref().to_owned()).unwrap()
     }
 
+    fn printer_contents_ansi(printer: &mut Standard<Ansi<Vec<u8>>>) -> String {
+        String::from_utf8(printer.get_mut().get_ref().to_owned()).unwrap()
+    }
+
     #[test]
     fn reports_match() {
         let matcher = RegexMatcher::new("Sherlock").unwrap();
@@ -3388,4 +3396,21 @@ and xxx clearly, with a label attached.
 ";
         assert_eq_printed!(expected, got);
     }
+
+    #[test]
+    fn regression_search_empty_with_crlf() {
+        let matcher =
+            RegexMatcherBuilder::new().crlf(true).build(r"x?").unwrap();
+        let mut printer = StandardBuilder::new()
+            .color_specs(ColorSpecs::default_with_color())
+            .build(Ansi::new(vec![]));
+        SearcherBuilder::new()
+            .line_terminator(LineTerminator::crlf())
+            .build()
+            .search_reader(&matcher, &b"\n"[..], printer.sink(&matcher))
+            .unwrap();
+
+        let got = printer_contents_ansi(&mut printer);
+        assert!(!got.is_empty());
+    }
 }

tests/regression.rs

@@ -867,6 +867,16 @@ use B;
     eqnice!("2\n", cmd.stdout());
 });
 
+// See: https://github.com/BurntSushi/ripgrep/issues/1765
+rgtest!(r1765, |dir: Dir, mut cmd: TestCommand| {
+    dir.create("test", "\n");
+    // We need to add --color=always here to force the failure, since the bad
+    // code path is only triggered when colors are enabled.
+    cmd.args(&[r"x?", "--crlf", "--color", "always"]);
+
+    assert!(!cmd.stdout().is_empty());
+});
+
 rgtest!(r1866, |dir: Dir, mut cmd: TestCommand| {
     dir.create("test", "foobar\nfoobar\nfoo quux");
     cmd.args(&[