feat(syntax): add support for hidden_file_extensions (#3613)

* feat(syntax): add support for hidden_file_extensions

CHANGELOG.md

@@ -5,6 +5,7 @@
 
 ## Features
 
+- Added support for `hidden_file_extensions` from `.sublime-syntax` files, see #3613 (@Matei02355)
 - Add word wrapping mode via `--wrap=word`, see #3597 (@veeceey)
 - Implement `--unbuffered` mode for streaming input, allowing partial lines to display immediately (e.g. `tail -f | bat -u`). Closes #3555, see #3583 (@mainnebula)
 - Added an initial `flake.nix` for a ready made development environment; see #3578 (@vorburger)

src/assets.rs

@@ -262,6 +262,24 @@ impl HighlightingAssets {
             .map(|syntax| SyntaxReferenceInSet { syntax, syntax_set }))
     }
 
+    fn find_syntax_by_hidden_file_name(
+        &self,
+        file_name: &OsStr,
+    ) -> Result<Option<SyntaxReferenceInSet<'_>>> {
+        let Some(hidden_file_extension) = file_name
+            .to_str()
+            .and_then(|name| name.strip_prefix('.'))
+            .filter(|name| !name.is_empty())
+        else {
+            return Ok(None);
+        };
+
+        // syntect stores `hidden_file_extensions` in the same extension list as
+        // regular file extensions, but dotfiles must be queried without the
+        // leading period.
+        self.find_syntax_by_extension(Some(OsStr::new(hidden_file_extension)))
+    }
+
     fn find_syntax_by_token(&self, token: &str) -> Result<Option<SyntaxReferenceInSet<'_>>> {
         let syntax_set = self.get_syntax_set()?;
         Ok(syntax_set
@@ -275,6 +293,9 @@ impl HighlightingAssets {
         ignored_suffixes: &IgnoredSuffixes,
     ) -> Result<Option<SyntaxReferenceInSet<'_>>> {
         let mut syntax = self.find_syntax_by_extension(Some(file_name))?;
+        if syntax.is_none() {
+            syntax = self.find_syntax_by_hidden_file_name(file_name)?;
+        }
         if syntax.is_none() {
             syntax =
                 ignored_suffixes.try_with_stripped_suffix(file_name, |stripped_file_name| {
@@ -661,6 +682,55 @@ mod tests {
         );
     }
 
+    #[cfg(feature = "build-assets")]
+    #[test]
+    fn syntax_detection_hidden_file_extensions() {
+        let source_dir = TempDir::new().expect("creation of temporary source directory");
+        let cache_dir = TempDir::new().expect("creation of temporary cache directory");
+        let syntax_dir = source_dir.path().join("syntaxes");
+
+        std::fs::create_dir_all(&syntax_dir).expect("creation of syntax directory succeeds");
+        std::fs::write(
+            syntax_dir.join("HiddenFileExtension.sublime-syntax"),
+            r#"%YAML 1.2
+---
+name: Hidden File Extension
+hidden_file_extensions:
+  - testrc
+scope: source.hiddenfileextension
+
+contexts:
+  main:
+    - match: .
+      scope: source.hiddenfileextension
+"#,
+        )
+        .expect("custom syntax can be written");
+
+        build(
+            source_dir.path(),
+            false,
+            false,
+            cache_dir.path(),
+            env!("CARGO_PKG_VERSION"),
+        )
+        .expect("custom assets can be built");
+
+        let test = SyntaxDetectionTest {
+            assets: HighlightingAssets::from_cache(cache_dir.path())
+                .expect("custom syntax cache can be loaded"),
+            syntax_mapping: SyntaxMapping::new(),
+            temp_dir: TempDir::new().expect("creation of temporary directory"),
+        };
+
+        assert_eq!(test.syntax_for_file(".testrc"), "Hidden File Extension");
+        assert_eq!(
+            test.syntax_for_stdin_with_content(".testrc", b""),
+            "Hidden File Extension"
+        );
+        assert!(test.syntax_is_same_for_inputkinds(".testrc", ""));
+    }
+
     #[cfg(unix)]
     #[test]
     fn syntax_detection_for_symlinked_file() {