Hunk highlighting test and refactoring

- New command-line option --syntax highlight to select which category
  of hunk lines to be syntax highlighted. --highlight-removed is now
  deprecated.
- New hunk highlighting test tests syntax highlighting and background colors
- Refactor: construction of style modifiers for config struct
- Refactor: compute minus and plus foreground style sections separately
- Refactor: foreground style logic
- Refactor: rearrange style modifier construction for config
- Refactor: change variable name: => highlight_minus_lines
- Refactor: clean up --color-only config implementation

1 files changed, 62 insertions, 33 deletions

diff --git a/src/paint.rs b/src/paint.rs
index 9f220ae0..b702ebe9 100644
--- a/src/paint.rs
+++ b/src/paint.rs
@@ -9,12 +9,13 @@ use syntect::parsing::{SyntaxReference, SyntaxSet};
 use crate::bat::assets::HighlightingAssets;
 use crate::bat::terminal::to_ansi_color;
 use crate::config;
+use crate::delta::State;
 use crate::edits;
 use crate::paint::superimpose_style_sections::superimpose_style_sections;
 use crate::style;
 
-const ANSI_CSI_ERASE_IN_LINE: &str = "\x1b[K";
-const ANSI_SGR_RESET: &str = "\x1b[0m";
+pub const ANSI_CSI_ERASE_IN_LINE: &str = "\x1b[K";
+pub const ANSI_SGR_RESET: &str = "\x1b[0m";
 
 pub struct Painter<'a> {
     pub minus_lines: Vec<String>,
@@ -63,13 +64,30 @@ impl<'a> Painter<'a> {
     }
 
     pub fn paint_buffered_lines(&mut self) {
-        let (minus_line_syntax_style_sections, plus_line_syntax_style_sections) =
-            Self::get_syntax_style_sections(
-                &self.minus_lines,
-                &self.plus_lines,
-                &mut self.highlighter,
-                self.config,
-            );
+        let minus_fixed_foreground_style = self.get_fixed_foreground_style(
+            self.config.minus_foreground_style_modifier,
+            self.config
+                .lines_to_be_syntax_highlighted
+                .contains(State::HunkMinus as usize),
+        );
+        let plus_fixed_foreground_style = self.get_fixed_foreground_style(
+            self.config.plus_foreground_style_modifier,
+            self.config
+                .lines_to_be_syntax_highlighted
+                .contains(State::HunkPlus as usize),
+        );
+        let minus_line_syntax_style_sections = Self::get_syntax_style_sections_for_lines(
+            &self.minus_lines,
+            &mut self.highlighter,
+            minus_fixed_foreground_style,
+            self.config,
+        );
+        let plus_line_syntax_style_sections = Self::get_syntax_style_sections_for_lines(
+            &self.plus_lines,
+            &mut self.highlighter,
+            plus_fixed_foreground_style,
+            self.config,
+        );
         let (minus_line_diff_style_sections, plus_line_diff_style_sections) =
             Self::get_diff_style_sections(&self.minus_lines, &self.plus_lines, self.config);
         // TODO: lines and style sections contain identical line text
@@ -99,6 +117,22 @@ impl<'a> Painter<'a> {
         self.plus_lines.clear();
     }
 
+    fn get_fixed_foreground_style(
+        &self,
+        foreground_style_modifier: Option<StyleModifier>,
+        should_syntax_highlight: bool,
+    ) -> Option<Style> {
+        match (
+            foreground_style_modifier,
+            should_syntax_highlight,
+            self.config.theme,
+        ) {
+            (Some(style_modifier), _, _) => Some(self.config.no_style.apply(style_modifier)),
+            (_, true, Some(_)) => None,
+            _ => Some(self.config.no_style),
+        }
+    }
+
     /// Superimpose background styles and foreground syntax
     /// highlighting styles, and write colored lines to output buffer.
     pub fn paint_lines(
@@ -161,44 +195,33 @@ impl<'a> Painter<'a> {
         Ok(())
     }
 
-    /// Perform syntax highlighting for minus and plus lines in buffer.
-    fn get_syntax_style_sections<'m, 'p>(
-        minus_lines: &'m [String],
-        plus_lines: &'p [String],
+    fn get_syntax_style_sections_for_lines<'s>(
+        lines: &'s [String],
         highlighter: &mut HighlightLines,
+        fixed_style: Option<Style>,
         config: &config::Config,
-    ) -> (Vec<Vec<(Style, &'m str)>>, Vec<Vec<(Style, &'p str)>>) {
-        let mut minus_line_sections = Vec::new();
-        for line in minus_lines.iter() {
-            minus_line_sections.push(Painter::get_line_syntax_style_sections(
-                &line,
-                highlighter,
-                &config,
-                config.highlight_removed,
-            ));
-        }
-        let mut plus_line_sections = Vec::new();
-        for line in plus_lines.iter() {
-            plus_line_sections.push(Painter::get_line_syntax_style_sections(
+    ) -> Vec<Vec<(Style, &'s str)>> {
+        let mut line_sections = Vec::new();
+        for line in lines.iter() {
+            line_sections.push(Painter::get_line_syntax_style_sections(
                 &line,
                 highlighter,
+                fixed_style,
                 &config,
-                true,
             ));
         }
-        (minus_line_sections, plus_line_sections)
+        line_sections
     }
 
     pub fn get_line_syntax_style_sections(
         line: &'a str,
         highlighter: &mut HighlightLines,
+        fixed_style: Option<Style>,
         config: &config::Config,
-        should_syntax_highlight: bool,
     ) -> Vec<(Style, &'a str)> {
-        if should_syntax_highlight && config.theme.is_some() {
-            highlighter.highlight(line, &config.syntax_set)
-        } else {
-            vec![(config.no_style, line)]
+        match fixed_style {
+            Some(fixed_style) => vec![(fixed_style, line)],
+            None => highlighter.highlight(line, &config.syntax_set),
         }
     }
 
@@ -249,6 +272,12 @@ pub fn paint_text_foreground(text: &str, color: Color, true_color: bool) -> Stri
     to_ansi_color(color, true_color).paint(text).to_string()
 }
 
+#[allow(dead_code)]
+pub fn paint_text_background(text: &str, color: Color, true_color: bool) -> String {
+    let style = ansi_term::Style::new().on(to_ansi_color(color, true_color));
+    style.paint(text).to_string()
+}
+
 // See
 // https://en.wikipedia.org/wiki/ANSI_escape_code#8-bit
 pub fn ansi_color_name_to_number(name: &str) -> Option<u8> {