Handle git grep output

Fixes #769

src/delta.rs

@@ -23,6 +23,7 @@ pub enum State {
     SubmoduleLog, // In a submodule section, with gitconfig diff.submodule = log
     SubmoduleShort(String), // In a submodule section, with gitconfig diff.submodule = short
     Blame(String, Option<String>), // In a line of `git blame` output (commit, repeat_blame_line).
+    Grep(String, Option<String>), // In a line of `git grep` output (file, repeat_grep_line).
     Unknown,
     // The following elements are created when a line is wrapped to display it:
     HunkZeroWrapped,  // Wrapped unchanged line
@@ -121,6 +122,7 @@ impl<'a> StateMachine<'a> {
                 || self.handle_submodule_short_line()?
                 || self.handle_hunk_line()?
                 || self.handle_blame_line()?
+                || self.handle_grep_line()?
                 || self.should_skip_line()
                 || self.emit_line_unchanged()?;
         }

src/handlers/file_meta.rs

@@ -210,7 +210,7 @@ fn get_file_extension_from_file_meta_line_file_path(path: &str) -> Option<&str>
 }
 
 /// Attempt to parse input as a file path and return extension as a &str.
-fn get_extension(s: &str) -> Option<&str> {
+pub fn get_extension(s: &str) -> Option<&str> {
     let path = Path::new(s);
     path.extension()
         .and_then(|e| e.to_str())

src/handlers/grep.rs

@@ -0,0 +1,310 @@
+use std::convert::{TryFrom, TryInto};
+
+use lazy_static::lazy_static;
+use regex::Regex;
+
+use crate::delta::{State, StateMachine};
+use crate::handlers;
+use crate::paint::BgShouldFill;
+use crate::utils;
+
+struct GrepOutputConfig {
+    render_context_header_as_hunk_header: bool,
+    highlight_hits: bool,
+}
+
+impl<'a> StateMachine<'a> {
+    /// If this is a line of git grep output then render it accordingly. If this
+    /// is the first grep line, then set the syntax-highlighter language.
+    pub fn handle_grep_line(&mut self) -> std::io::Result<bool> {
+        self.painter.emit()?;
+        let mut handled_line = false;
+
+        // TODO: It should be possible to eliminate some of the .clone()s and
+        // .to_owned()s.
+        let (_previous_file, repeat_grep_line, try_parse) = match &self.state {
+            State::Grep(file, repeat_grep_line) => {
+                (Some(file.as_str()), repeat_grep_line.clone(), true)
+            }
+            State::Unknown => (None, None, true),
+            _ => (None, None, false),
+        };
+        if try_parse {
+            if let Some(grep) = parse_git_grep_line(&self.line) {
+                let output_config = make_output_config();
+
+                // Emit syntax-highlighted code
+                // TODO: Determine the language less frequently, e.g. only when the file changes.
+                if let Some(lang) = handlers::file_meta::get_extension(grep.file)
+                    .or_else(|| self.config.default_language.as_deref())
+                {
+                    self.painter.set_syntax(Some(lang));
+                    self.painter.set_highlighter();
+                }
+                self.state = State::Grep(grep.file.to_owned(), repeat_grep_line);
+
+                match (
+                    &grep.line_type,
+                    output_config.render_context_header_as_hunk_header,
+                ) {
+                    // Emit context header line
+                    (LineType::ContextHeader, true) => handlers::hunk_header::write_hunk_header(
+                        grep.code,
+                        &[(grep.line_number.unwrap_or(0), 0)],
+                        &mut self.painter,
+                        &self.line,
+                        grep.file,
+                        self.config,
+                    )?,
+                    _ => {
+                        // Emit file & line-number
+                        let hit_marker = match (&grep.line_type, output_config.highlight_hits) {
+                            (LineType::Hit, true) => "• ",
+                            (LineType::NoHit, true) => "  ",
+                            _ => "",
+                        };
+                        let grep_line = match grep.line_number {
+                            Some(n) => {
+                                format!("{}{}:{:<3}:", hit_marker, grep.file, n)
+                            }
+                            None => format!("{}{}:", hit_marker, grep.file),
+                        };
+                        let style = self.config.file_style;
+                        write!(self.painter.writer, "{}", style.paint(grep_line))?;
+
+                        // Emit code line
+                        self.painter.syntax_highlight_and_paint_line(
+                            &format!("{}\n", grep.code),
+                            if matches!(&grep.line_type, LineType::Hit)
+                                && output_config.highlight_hits
+                            {
+                                self.config.plus_style
+                            } else {
+                                self.config.zero_style
+                            },
+                            self.state.clone(),
+                            BgShouldFill::default(),
+                        )
+                    }
+                }
+                handled_line = true
+            }
+        }
+        Ok(handled_line)
+    }
+}
+
+fn make_output_config() -> GrepOutputConfig {
+    match utils::parent_command_options() {
+        Some((longs, shorts)) if shorts.contains("-W") || longs.contains("--function-context") => {
+            // --function-context is in effect: i.e. the entire function is
+            // being displayed. In that case we don't render the first line
+            // as a header, since the second line is the true next line, and
+            // it will be more readable to have these displayed normally. We
+            // highlight hits, since these will be surrounded by non-hits.
+            GrepOutputConfig {
+                render_context_header_as_hunk_header: false,
+                highlight_hits: true,
+            }
+        }
+        Some((longs, shorts)) if shorts.contains("-p") || longs.contains("--show-function") => {
+            // --show-function is in effect, i.e. the function header is
+            // being displayed, along with hits within the function.
+            // Therefore we render the first line as a header, but we do not
+            // highlight hits, since all other lines are hits.
+            GrepOutputConfig {
+                render_context_header_as_hunk_header: true,
+                highlight_hits: false,
+            }
+        }
+        _ => GrepOutputConfig {
+            render_context_header_as_hunk_header: true,
+            highlight_hits: false,
+        },
+    }
+}
+
+#[derive(Debug, PartialEq)]
+pub struct GrepLine<'a> {
+    pub file: &'a str,
+    pub line_number: Option<usize>,
+    pub line_type: LineType,
+    pub code: &'a str,
+}
+
+#[derive(Debug, PartialEq)]
+pub enum LineType {
+    ContextHeader,
+    Hit,
+    NoHit,
+}
+
+// See tests for example grep lines
+lazy_static! {
+    static ref GREP_LINE_REGEX: Regex = Regex::new(
+        r"(?x)
+^
+(.+?\.[^-.=: ]+)         # 1. file name (TODO: it must have an extension)
+(?:
+    [-=:]([0-9]+)        # 2. optional line number
+)?
+([-=:])                  # 3. line-type marker
+(.*)                     # 4. code (i.e. line contents)
+$
+"
+    )
+    .unwrap();
+}
+
+pub fn parse_git_grep_line(line: &str) -> Option<GrepLine> {
+    let caps = GREP_LINE_REGEX.captures(line)?;
+    let file = caps.get(1).unwrap().as_str();
+    let line_number = caps.get(2).map(|m| m.as_str().parse().ok()).flatten();
+    let line_type = caps.get(3).map(|m| m.as_str()).try_into().ok()?;
+    let code = caps.get(4).unwrap().as_str();
+
+    Some(GrepLine {
+        file,
+        line_number,
+        line_type,
+        code,
+    })
+}
+
+impl TryFrom<Option<&str>> for LineType {
+    type Error = ();
+    fn try_from(from: Option<&str>) -> Result<Self, Self::Error> {
+        match from {
+            Some(marker) if marker == "=" => Ok(LineType::ContextHeader),
+            Some(marker) if marker == ":" => Ok(LineType::Hit),
+            Some(marker) if marker == "-" => Ok(LineType::NoHit),
+            _ => Err(()),
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::handlers::grep::{parse_git_grep_line, GrepLine, LineType};
+
+    #[test]
+    fn test_parse_grep_line() {
+        // git grep MinusPlus
+        assert_eq!(
+            parse_git_grep_line("src/config.rs:use crate::minusplus::MinusPlus;"),
+            Some(GrepLine {
+                file: "src/config.rs",
+                line_number: None,
+                line_type: LineType::Hit,
+                code: "use crate::minusplus::MinusPlus;",
+            })
+        );
+
+        // git grep -n MinusPlus    [with line numbers]
+        assert_eq!(
+            parse_git_grep_line("src/config.rs:21:use crate::minusplus::MinusPlus;"),
+            Some(GrepLine {
+                file: "src/config.rs",
+                line_number: Some(21),
+                line_type: LineType::Hit,
+                code: "use crate::minusplus::MinusPlus;",
+            })
+        );
+
+        // git grep -W MinusPlus    [with function context]
+        assert_eq!(
+            parse_git_grep_line("src/config.rs=pub struct Config {"), // hit
+            Some(GrepLine {
+                file: "src/config.rs",
+                line_number: None,
+                line_type: LineType::ContextHeader,
+                code: "pub struct Config {",
+            })
+        );
+        assert_eq!(
+            parse_git_grep_line("src/config.rs-    pub available_terminal_width: usize,"),
+            Some(GrepLine {
+                file: "src/config.rs",
+                line_number: None,
+                line_type: LineType::NoHit,
+                code: "    pub available_terminal_width: usize,",
+            })
+        );
+        assert_eq!(
+            parse_git_grep_line(
+                "src/config.rs:    pub line_numbers_style_minusplus: MinusPlus<Style>,"
+            ),
+            Some(GrepLine {
+                file: "src/config.rs",
+                line_number: None,
+                line_type: LineType::Hit,
+                code: "    pub line_numbers_style_minusplus: MinusPlus<Style>,",
+            })
+        );
+
+        // git grep -n -W MinusPlus [with line numbers and function context]
+        assert_eq!(
+            parse_git_grep_line("src/config.rs=57=pub struct Config {"),
+            Some(GrepLine {
+                file: "src/config.rs",
+                line_number: Some(57),
+                line_type: LineType::ContextHeader,
+                code: "pub struct Config {",
+            })
+        );
+        assert_eq!(
+            parse_git_grep_line("src/config.rs-58-    pub available_terminal_width: usize,"),
+            Some(GrepLine {
+                file: "src/config.rs",
+                line_number: Some(58),
+                line_type: LineType::NoHit,
+                code: "    pub available_terminal_width: usize,",
+            })
+        );
+        assert_eq!(
+            parse_git_grep_line(
+                "src/config.rs:95:    pub line_numbers_style_minusplus: MinusPlus<Style>,"
+            ),
+            Some(GrepLine {
+                file: "src/config.rs",
+                line_number: Some(95),
+                line_type: LineType::Hit,
+                code: "    pub line_numbers_style_minusplus: MinusPlus<Style>,",
+            })
+        );
+
+        // git grep -h MinusPlus    [no file names: TODO: handle this?]
+        //use crate::minusplus::MinusPlus;
+    }
+
+    #[test]
+    fn test_parse_grep_line_filenames() {
+        assert_eq!(
+            parse_git_grep_line("src/con-fig.rs:use crate::minusplus::MinusPlus;"),
+            Some(GrepLine {
+                file: "src/con-fig.rs",
+                line_number: None,
+                line_type: LineType::Hit,
+                code: "use crate::minusplus::MinusPlus;",
+            })
+        );
+        assert_eq!(
+            parse_git_grep_line("src/con-fig.rs-use crate::minusplus::MinusPlus;"),
+            Some(GrepLine {
+                file: "src/con-fig.rs",
+                line_number: None,
+                line_type: LineType::NoHit,
+                code: "use crate::minusplus::MinusPlus;",
+            })
+        );
+        assert_eq!(
+            parse_git_grep_line("de-lta.rs-            if self.source == Source::Unknown {"),
+            Some(GrepLine {
+                file: "de-lta.rs",
+                line_number: None,
+                line_type: LineType::NoHit,
+                code: "            if self.source == Source::Unknown {",
+            })
+        );
+    }
+}

src/handlers/hunk_header.rs

@@ -155,7 +155,7 @@ fn write_hunk_header_raw(
     Ok(())
 }
 
-fn write_hunk_header(
+pub fn write_hunk_header(
     code_fragment: &str,
     line_numbers: &[(usize, usize)],
     painter: &mut Painter,

src/handlers/mod.rs

@@ -7,6 +7,7 @@ pub mod draw;
 pub mod file_meta;
 pub mod file_meta_diff;
 pub mod file_meta_misc;
+pub mod grep;
 pub mod hunk;
 pub mod hunk_header;
 pub mod submodule;

src/paint.rs

@@ -623,6 +623,7 @@ impl<'p> Painter<'p> {
             State::HunkHeader(_, _) => true,
             State::HunkMinus(Some(_)) | State::HunkPlus(Some(_)) => false,
             State::Blame(_, _) => true,
+            State::Grep(_, _) => true,
             _ => panic!(
                 "should_compute_syntax_highlighting is undefined for state {:?}",
                 state