Gracefully handle failure to parse hunk header

Fixes #765

4 files changed, 112 insertions, 71 deletions

diff --git a/src/handlers/hunk.rs b/src/handlers/hunk.rs
index a0bec617..e580dfa6 100644
--- a/src/handlers/hunk.rs
+++ b/src/handlers/hunk.rs
@@ -29,7 +29,7 @@ impl<'a> StateMachine<'a> {
     fn test_hunk_line(&self) -> bool {
         matches!(
             self.state,
-            State::HunkHeader(_, _, _)
+            State::HunkHeader(_, _, _, _)
                 | State::HunkZero(_)
                 | State::HunkMinus(_, _)
                 | State::HunkPlus(_, _)
@@ -59,8 +59,8 @@ impl<'a> StateMachine<'a> {
         {
             self.painter.paint_buffered_minus_and_plus_lines();
         }
-        if let State::HunkHeader(_, line, raw_line) = &self.state.clone() {
-            self.emit_hunk_header_line(line, raw_line)?;
+        if let State::HunkHeader(_, parsed_hunk_header, line, raw_line) = &self.state.clone() {
+            self.emit_hunk_header_line(parsed_hunk_header, line, raw_line)?;
         }
         self.state = match new_line_state(&self.line, &self.state) {
             Some(HunkMinus(diff_type, _)) => {
@@ -140,13 +140,13 @@ fn new_line_state(new_line: &str, prev_state: &State) -> Option<State> {
         HunkMinus(Unified, _)
         | HunkZero(Unified)
         | HunkPlus(Unified, _)
-        | HunkHeader(Unified, _, _) => Unified,
-        HunkHeader(Combined(Number(n), InMergeConflict::No), _, _) => {
+        | HunkHeader(Unified, _, _, _) => Unified,
+        HunkHeader(Combined(Number(n), InMergeConflict::No), _, _, _) => {
             Combined(Number(*n), InMergeConflict::No)
         }
         // The prefixes are specific to the previous line, but the number of merge parents remains
         // equal to the prefix length.
-        HunkHeader(Combined(Prefix(prefix), InMergeConflict::No), _, _) => {
+        HunkHeader(Combined(Prefix(prefix), InMergeConflict::No), _, _, _) => {
             Combined(Number(prefix.len()), InMergeConflict::No)
         }
         HunkMinus(Combined(Prefix(prefix), in_merge_conflict), _)
diff --git a/src/handlers/hunk_header.rs b/src/handlers/hunk_header.rs
index 3ecb86c8..84b5bf64 100644
--- a/src/handlers/hunk_header.rs
+++ b/src/handlers/hunk_header.rs
@@ -30,6 +30,12 @@ use crate::delta::{self, DiffType, InMergeConflict, MergeParents, State, StateMa
 use crate::paint::{self, BgShouldFill, Painter, StyleSectionSpecifier};
 use crate::style::DecorationStyle;
 
+#[derive(Clone, Default, Debug, PartialEq)]
+pub struct ParsedHunkHeader {
+    code_fragment: String,
+    line_numbers_and_hunk_lengths: Vec<(usize, usize)>,
+}
+
 impl<'a> StateMachine<'a> {
     #[inline]
     fn test_hunk_header_line(&self) -> bool {
@@ -45,39 +51,57 @@ impl<'a> StateMachine<'a> {
         if !self.test_hunk_header_line() {
             return Ok(false);
         }
-        let diff_type = match &self.state {
-            DiffHeader(Combined(MergeParents::Unknown, InMergeConflict::No)) => {
-                // https://git-scm.com/docs/git-diff#_combined_diff_format
-                let n_parents = self.line.chars().take_while(|c| c == &'@').count() - 1;
-                Combined(MergeParents::Number(n_parents), InMergeConflict::No)
-            }
-            DiffHeader(diff_type)
-            | HunkMinus(diff_type, _)
-            | HunkZero(diff_type)
-            | HunkPlus(diff_type, _) => diff_type.clone(),
-            Unknown => Unified,
-            _ => delta_unreachable(&format!(
-                "Unexpected state in handle_hunk_header: {:?}",
-                self.state
-            )),
-        };
-        self.state = HunkHeader(diff_type, self.line.clone(), self.raw_line.clone());
-        Ok(true)
+        let mut handled_line = false;
+        if let Some(parsed_hunk_header) = parse_hunk_header(&self.line) {
+            let diff_type = match &self.state {
+                DiffHeader(Combined(MergeParents::Unknown, InMergeConflict::No)) => {
+                    // https://git-scm.com/docs/git-diff#_combined_diff_format
+                    let n_parents = self.line.chars().take_while(|c| c == &'@').count() - 1;
+                    Combined(MergeParents::Number(n_parents), InMergeConflict::No)
+                }
+                DiffHeader(diff_type)
+                | HunkMinus(diff_type, _)
+                | HunkZero(diff_type)
+                | HunkPlus(diff_type, _) => diff_type.clone(),
+                Unknown => Unified,
+                _ => delta_unreachable(&format!(
+                    "Unexpected state in handle_hunk_header: {:?}",
+                    self.state
+                )),
+            };
+            self.state = HunkHeader(
+                diff_type,
+                parsed_hunk_header,
+                self.line.clone(),
+                self.raw_line.clone(),
+            );
+            handled_line = true;
+        }
+        Ok(handled_line)
     }
 
     /// Emit the hunk header, with any requested decoration.
-    pub fn emit_hunk_header_line(&mut self, line: &str, raw_line: &str) -> std::io::Result<bool> {
+    pub fn emit_hunk_header_line(
+        &mut self,
+        parsed_hunk_header: &ParsedHunkHeader,
+        line: &str,
+        raw_line: &str,
+    ) -> std::io::Result<bool> {
         self.painter.paint_buffered_minus_and_plus_lines();
         self.painter.set_highlighter();
         self.painter.emit()?;
 
-        let (code_fragment, line_numbers) = parse_hunk_header(line);
+        let ParsedHunkHeader {
+            code_fragment,
+            line_numbers_and_hunk_lengths,
+        } = parsed_hunk_header;
+
         if self.config.line_numbers {
             self.painter
                 .line_numbers_data
                 .as_mut()
                 .unwrap()
-                .initialize_hunk(&line_numbers, self.plus_file.to_string());
+                .initialize_hunk(line_numbers_and_hunk_lengths, self.plus_file.to_string());
         }
 
         if self.config.hunk_header_style.is_raw {
@@ -92,8 +116,8 @@ impl<'a> StateMachine<'a> {
             }
 
             write_hunk_header(
-                &code_fragment,
-                &line_numbers,
+                code_fragment,
+                line_numbers_and_hunk_lengths,
                 &mut self.painter,
                 line,
                 if self.plus_file == "/dev/null" {
@@ -132,25 +156,31 @@ lazy_static! {
 /// Given input like
 /// "@@ -74,15 +74,14 @@ pub fn delta("
 /// Return " pub fn delta(" and a vector of (line_number, hunk_length) tuples.
-fn parse_hunk_header(line: &str) -> (String, Vec<(usize, usize)>) {
-    let caps = HUNK_HEADER_REGEX.captures(line).unwrap();
-    let file_coordinates = &caps[1];
-    let line_numbers_and_hunk_lengths = HUNK_HEADER_FILE_COORDINATE_REGEX
-        .captures_iter(file_coordinates)
-        .map(|caps| {
-            (
-                caps[1].parse::<usize>().unwrap(),
-                caps.get(2)
-                    .map(|m| m.as_str())
-                    // Per the specs linked above, if the hunk length is absent then it is 1.
-                    .unwrap_or("1")
-                    .parse::<usize>()
-                    .unwrap(),
-            )
+fn parse_hunk_header(line: &str) -> Option<ParsedHunkHeader> {
+    if let Some(caps) = HUNK_HEADER_REGEX.captures(line) {
+        let file_coordinates = &caps[1];
+        let line_numbers_and_hunk_lengths = HUNK_HEADER_FILE_COORDINATE_REGEX
+            .captures_iter(file_coordinates)
+            .map(|caps| {
+                (
+                    caps[1].parse::<usize>().unwrap(),
+                    caps.get(2)
+                        .map(|m| m.as_str())
+                        // Per the specs linked above, if the hunk length is absent then it is 1.
+                        .unwrap_or("1")
+                        .parse::<usize>()
+                        .unwrap(),
+                )
+            })
+            .collect();
+        let code_fragment = caps[2].to_string();
+        Some(ParsedHunkHeader {
+            code_fragment,
+            line_numbers_and_hunk_lengths,
         })
-        .collect();
-    let code_fragment = &caps[2];
-    (code_fragment.to_string(), line_numbers_and_hunk_lengths)
+    } else {
+        None
+    }
 }
 
 fn write_hunk_header_raw(
@@ -177,7 +207,7 @@ fn write_hunk_header_raw(
 
 pub fn write_hunk_header(
     code_fragment: &str,
-    line_numbers: &[(usize, usize)],
+    line_numbers_and_hunk_lengths: &[(usize, usize)],
     painter: &mut Painter,
     line: &str,
     plus_file: &str,
@@ -193,7 +223,7 @@ pub fn write_hunk_header(
         "".to_string()
     };
 
-    let plus_line_number = line_numbers[line_numbers.len() - 1].0;
+    let plus_line_number = line_numbers_and_hunk_lengths[line_numbers_and_hunk_lengths.len() - 1].0;
     let file_with_line_number =
         paint_file_path_with_line_number(Some(plus_line_number), plus_file, config);
 
@@ -272,7 +302,12 @@ fn write_to_output_buffer(
         painter.syntax_highlight_and_paint_line(
             &line,
             StyleSectionSpecifier::Style(config.hunk_header_style),
-            delta::State::HunkHeader(DiffType::Unified, "".to_owned(), "".to_owned()),
+            delta::State::HunkHeader(
+                DiffType::Unified,
+                ParsedHunkHeader::default(),
+                "".to_owned(),
+                "".to_owned(),
+            ),
             BgShouldFill::No,
         );
         painter.output_buffer.pop(); // trim newline
@@ -287,9 +322,10 @@ pub mod tests {
 
     #[test]
     fn test_parse_hunk_header() {
-        let parsed = parse_hunk_header("@@ -74,15 +75,14 @@ pub fn delta(\n");
-        let code_fragment = parsed.0;
-        let line_numbers_and_hunk_lengths = parsed.1;
+        let ParsedHunkHeader {
+            code_fragment,
+            line_numbers_and_hunk_lengths,
+        } = parse_hunk_header("@@ -74,15 +75,14 @@ pub fn delta(\n").unwrap();
         assert_eq!(code_fragment, " pub fn delta(\n");
         assert_eq!(line_numbers_and_hunk_lengths[0], (74, 15),);
         assert_eq!(line_numbers_and_hunk_lengths[1], (75, 14),);
@@ -297,9 +333,10 @@ pub mod tests {
 
     #[test]
     fn test_parse_hunk_header_with_omitted_hunk_lengths() {
-        let parsed = parse_hunk_header("@@ -74 +75,2 @@ pub fn delta(\n");
-        let code_fragment = parsed.0;
-        let line_numbers_and_hunk_lengths = parsed.1;
+        let ParsedHunkHeader {
+            code_fragment,
+            line_numbers_and_hunk_lengths,
+        } = parse_hunk_header("@@ -74 +75,2 @@ pub fn delta(\n").unwrap();
         assert_eq!(code_fragment, " pub fn delta(\n");
         assert_eq!(line_numbers_and_hunk_lengths[0], (74, 1),);
         assert_eq!(line_numbers_and_hunk_lengths[1], (75, 2),);
@@ -307,9 +344,10 @@ pub mod tests {
 
     #[test]
     fn test_parse_hunk_header_added_file() {
-        let parsed = parse_hunk_header("@@ -1,22 +0,0 @@");
-        let code_fragment = parsed.0;
-        let line_numbers_and_hunk_lengths = parsed.1;
+        let ParsedHunkHeader {
+            code_fragment,
+            line_numbers_and_hunk_lengths,
+        } = parse_hunk_header("@@ -1,22 +0,0 @@").unwrap();
         assert_eq!(code_fragment, "",);
         assert_eq!(line_numbers_and_hunk_lengths[0], (1, 22),);
         assert_eq!(line_numbers_and_hunk_lengths[1], (0, 0),);
@@ -317,9 +355,10 @@ pub mod tests {
 
     #[test]
     fn test_parse_hunk_header_deleted_file() {
-        let parsed = parse_hunk_header("@@ -0,0 +1,3 @@");
-        let code_fragment = parsed.0;
-        let line_numbers_and_hunk_lengths = parsed.1;
+        let ParsedHunkHeader {
+            code_fragment,
+            line_numbers_and_hunk_lengths,
+        } = parse_hunk_header("@@ -0,0 +1,3 @@").unwrap();
         assert_eq!(code_fragment, "",);
         assert_eq!(line_numbers_and_hunk_lengths[0], (0, 0),);
         assert_eq!(line_numbers_and_hunk_lengths[1], (1, 3),);
@@ -327,9 +366,10 @@ pub mod tests {
 
     #[test]
     fn test_parse_hunk_header_merge() {
-        let parsed = parse_hunk_header("@@@ -293,11 -358,15 +358,16 @@@ dependencies =");
-        let code_fragment = parsed.0;
-        let line_numbers_and_hunk_lengths = parsed.1;
+        let ParsedHunkHeader {
+            code_fragment,
+            line_numbers_and_hunk_lengths,
+        } = parse_hunk_header("@@@ -293,11 -358,15 +358,16 @@@ dependencies =").unwrap();
         assert_eq!(code_fragment, " dependencies =");
         assert_eq!(line_numbers_and_hunk_lengths[0], (293, 11),);
         assert_eq!(line_numbers_and_hunk_lengths[1], (358, 15),);
@@ -338,9 +378,10 @@ pub mod tests {
 
     #[test]
     fn test_parse_hunk_header_cthulhu() {
-        let parsed = parse_hunk_header("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ -446,6 -446,6 -446,6 -446,6 -446,6 -446,6 -446,6 -446,6 -446,6 -446,6 -446,6 -446,6 -446,6 -446,6 -446,6 -446,6 -446,6 -446,6 -446,6 -446,6 -446,6 -446,6 -444,17 -446,6 -446,6 -446,6 -446,6 -446,6 -446,6 -446,6 -446,6 -446,6 -446,6 -446,6 -446,6 -446,6 -446,6 -446,6 -446,6 -446,6 -446,6 -446,6 -446,6 -446,6 -446,6 -446,6 -446,6 -446,6 -446,6 -446,6 -446,6 -446,6 -446,6 -446,6 -446,6 -446,6 -446,6 -446,6 -446,6 -446,6 -446,6 -446,6 -446,6 -446,6 -446,6 -446,6 +444,17 @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ int snd_soc_jack_add_gpios(struct snd_s");
-        let code_fragment = parsed.0;
-        let line_numbers_and_hunk_lengths = parsed.1;
+        let ParsedHunkHeader {
+            code_fragment,
+            line_numbers_and_hunk_lengths,
+        } = parse_hunk_header("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ -446,6 -446,6 -446,6 -446,6 -446,6 -446,6 -446,6 -446,6 -446,6 -446,6 -446,6 -446,6 -446,6 -446,6 -446,6 -446,6 -446,6 -446,6 -446,6 -446,6 -446,6 -446,6 -444,17 -446,6 -446,6 -446,6 -446,6 -446,6 -446,6 -446,6 -446,6 -446,6 -446,6 -446,6 -446,6 -446,6 -446,6 -446,6 -446,6 -446,6 -446,6 -446,6 -446,6 -446,6 -446,6 -446,6 -446,6 -446,6 -446,6 -446,6 -446,6 -446,6 -446,6 -446,6 -446,6 -446,6 -446,6 -446,6 -446,6 -446,6 -446,6 -446,6 -446,6 -446,6 -446,6 -446,6 +444,17 @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ int snd_soc_jack_add_gpios(struct snd_s").unwrap();
         assert_eq!(code_fragment, " int snd_soc_jack_add_gpios(struct snd_s");
         assert_eq!(line_numbers_and_hunk_lengths[0], (446, 6),);
         assert_eq!(line_numbers_and_hunk_lengths[1], (446, 6),);
diff --git a/src/handlers/merge_conflict.rs b/src/handlers/merge_conflict.rs
index 03dfb27a..1ff06fc3 100644
--- a/src/handlers/merge_conflict.rs
+++ b/src/handlers/merge_conflict.rs
@@ -40,7 +40,7 @@ impl<'a> StateMachine<'a> {
         }
 
         match self.state.clone() {
-            HunkHeader(Combined(merge_parents, InMergeConflict::No), _, _)
+            HunkHeader(Combined(merge_parents, InMergeConflict::No), _, _, _)
             | HunkMinus(Combined(merge_parents, InMergeConflict::No), _)
             | HunkZero(Combined(merge_parents, InMergeConflict::No))
             | HunkPlus(Combined(merge_parents, InMergeConflict::No), _) => {
diff --git a/src/handlers/submodule.rs b/src/handlers/submodule.rs
index 04e273e9..4578594a 100644
--- a/src/handlers/submodule.rs
+++ b/src/handlers/submodule.rs
@@ -18,7 +18,7 @@ impl<'a> StateMachine<'a> {
 
     #[inline]
     fn test_submodule_short_line(&self) -> bool {
-        matches!(self.state, State::HunkHeader(_, _, _))
+        matches!(self.state, State::HunkHeader(_, _, _, _))
             && self.line.starts_with("-Subproject commit ")
             || matches!(self.state, State::SubmoduleShort(_))
                 && self.line.starts_with("+Subproject commit ")
@@ -29,7 +29,7 @@ impl<'a> StateMachine<'a> {
             return Ok(false);
         }
         if let Some(commit) = get_submodule_short_commit(&self.line) {
-            if let State::HunkHeader(_, _, _) = self.state {
+            if let State::HunkHeader(_, _, _, _) = self.state {
                 self.state = State::SubmoduleShort(commit.to_owned());
             } else if let State::SubmoduleShort(minus_commit) = &self.state {
                 self.painter.emit()?;