DiffViewer: prose files (Markdown, plain text) read plain, not as code

src/git/rows.rs

@@ -78,10 +78,29 @@ pub(super) fn washes(kind: LineKind, colors: &Palette) -> (Option<Hsla>, Hsla) {
     }
 }
 
-/// A line's code, colored as code, its changed words washed.
-pub(super) fn code(line: &DiffLine, colors: &Palette, cx: &App) -> StyledText {
+/// Extensions of prose and plain text.
+const PROSE: [&str; 13] = [
+    "md", "markdown", "mdown", "mkd", "txt", "text", "rst", "adoc", "asciidoc", "org", "csv",
+    "tsv", "log",
+];
+
+/// Whether `path` holds prose, read plain rather than as code.
+pub(super) fn prose(path: &str) -> bool {
+    let name = path.rsplit_once('/').map_or(path, |(_, name)| name);
+    match name.rsplit_once('.') {
+        Some((stem, ext)) if !stem.is_empty() => PROSE.contains(&ext.to_ascii_lowercase().as_str()),
+        _ => true,
+    }
+}
+
+/// A line's text, colored as code unless prose, changed words washed.
+pub(super) fn code(line: &DiffLine, colors: &Palette, prose: bool, cx: &App) -> StyledText {
     let (_, word) = washes(line.kind, colors);
-    let mut styles: Vec<(Range<usize>, HighlightStyle)> = code_colors(&line.text, cx);
+    let mut styles: Vec<(Range<usize>, HighlightStyle)> = if prose {
+        Vec::new()
+    } else {
+        code_colors(&line.text, cx)
+    };
     styles.extend(line.words.iter().map(|range| {
         (
             range.clone(),
@@ -108,6 +127,23 @@ pub(super) fn spoken(line: &DiffLine) -> SharedString {
 
 #[cfg(test)]
 mod tests {
+    #[test]
+    fn prose_reads_plain_and_code_reads_as_code() {
+        for path in [
+            "docs/README.md",
+            "notes.MARKDOWN",
+            "LICENSE",
+            ".gitignore",
+            "a/b.txt",
+            "data.csv",
+        ] {
+            assert!(super::prose(path), "{path}");
+        }
+        for path in ["src/main.rs", "web/app.js", "a.md/b.py", "Cargo.toml"] {
+            assert!(!super::prose(path), "{path}");
+        }
+    }
+
     #[test]
     fn a_line_speaks_its_number_change_and_text() {
         let stretches = super::super::diff::diff("a\nb\n", "a\nc\n", 1);

src/git/viewer.rs

@@ -9,7 +9,7 @@ use gpui::{
 use super::{
     badges::DiffStat,
     diff::{DiffLine, LineKind, Stretch, diff, side_numbers},
-    rows::{Place, Shown, code, shown, spoken, washes},
+    rows::{Place, Shown, code, prose, shown, spoken, washes},
 };
 use crate::{
     buttons::{Button, ButtonVariant, SegmentedControl},
@@ -194,6 +194,7 @@ impl RenderOnce for DiffViewer {
             .len()
             .max(2);
         let (id, on_open) = (self.id.clone(), self.on_open.clone());
+        let prose = prose(&self.path);
         let (button, button_height) = (
             self.hunk_action.is_some(),
             theme.control_height(ControlSize::Sm),
@@ -269,7 +270,9 @@ impl RenderOnce for DiffViewer {
                         .when_some(wash, |side, wash| side.bg(wash))
                         .child(number(shown))
                         .children(line.map(|(_, line)| {
-                            div().whitespace_nowrap().child(code(line, &colors, cx))
+                            div()
+                                .whitespace_nowrap()
+                                .child(code(line, &colors, prose, cx))
                         }));
                     match line {
                         Some((place, line)) => {
@@ -328,7 +331,7 @@ impl RenderOnce for DiffViewer {
                                             .flex_1()
                                             .min_w_0()
                                             .overflow_hidden()
-                                            .child(code(line, &colors, cx)),
+                                            .child(code(line, &colors, prose, cx)),
                                     )
                                     .into_any_element()
                             }