Add PathExt trait (#2823)

This PR adds a `PathExt` trait. It pulls in our existing `compact()`
function, as a method, and then adds a method, and testing, for
`icon_suffix()`. A test was added to fix:

- https://github.com/zed-industries/community/issues/1877

Release Notes:

- Fixed a bug where file icons would not be registered for files with
with `.` characters in their name
([#1877](https://github.com/zed-industries/community/issues/1877)).

crates/util/src/paths.rs

@@ -30,49 +30,47 @@ pub mod legacy {
     }
 }
 
-/// Compacts a given file path by replacing the user's home directory
-/// prefix with a tilde (`~`).
-///
-/// # Arguments
-///
-/// * `path` - A reference to a `Path` representing the file path to compact.
-///
-/// # Examples
-///
-/// ```
-/// use std::path::{Path, PathBuf};
-/// use util::paths::compact;
-/// let path: PathBuf = [
-///     util::paths::HOME.to_string_lossy().to_string(),
-///     "some_file.txt".to_string(),
-///  ]
-///  .iter()
-///  .collect();
-/// if cfg!(target_os = "linux") || cfg!(target_os = "macos") {
-///     assert_eq!(compact(&path).to_str(), Some("~/some_file.txt"));
-/// } else {
-///     assert_eq!(compact(&path).to_str(), path.to_str());
-/// }
-/// ```
-///
-/// # Returns
-///
-/// * A `PathBuf` containing the compacted file path. If the input path
-///   does not have the user's home directory prefix, or if we are not on
-///   Linux or macOS, the original path is returned unchanged.
-pub fn compact(path: &Path) -> PathBuf {
-    if cfg!(target_os = "linux") || cfg!(target_os = "macos") {
-        match path.strip_prefix(HOME.as_path()) {
-            Ok(relative_path) => {
-                let mut shortened_path = PathBuf::new();
-                shortened_path.push("~");
-                shortened_path.push(relative_path);
-                shortened_path
+pub trait PathExt {
+    fn compact(&self) -> PathBuf;
+    fn icon_suffix(&self) -> Option<&str>;
+}
+
+impl<T: AsRef<Path>> PathExt for T {
+    /// Compacts a given file path by replacing the user's home directory
+    /// prefix with a tilde (`~`).
+    ///
+    /// # Returns
+    ///
+    /// * A `PathBuf` containing the compacted file path. If the input path
+    ///   does not have the user's home directory prefix, or if we are not on
+    ///   Linux or macOS, the original path is returned unchanged.
+    fn compact(&self) -> PathBuf {
+        if cfg!(target_os = "linux") || cfg!(target_os = "macos") {
+            match self.as_ref().strip_prefix(HOME.as_path()) {
+                Ok(relative_path) => {
+                    let mut shortened_path = PathBuf::new();
+                    shortened_path.push("~");
+                    shortened_path.push(relative_path);
+                    shortened_path
+                }
+                Err(_) => self.as_ref().to_path_buf(),
             }
-            Err(_) => path.to_path_buf(),
+        } else {
+            self.as_ref().to_path_buf()
         }
-    } else {
-        path.to_path_buf()
+    }
+
+    fn icon_suffix(&self) -> Option<&str> {
+        let file_name = self.as_ref().file_name()?.to_str()?;
+
+        if file_name.starts_with(".") {
+            return file_name.strip_prefix(".");
+        }
+
+        self.as_ref()
+            .extension()
+            .map(|extension| extension.to_str())
+            .flatten()
     }
 }
 
@@ -279,4 +277,42 @@ mod tests {
             );
         }
     }
+
+    #[test]
+    fn test_path_compact() {
+        let path: PathBuf = [
+            HOME.to_string_lossy().to_string(),
+            "some_file.txt".to_string(),
+        ]
+        .iter()
+        .collect();
+        if cfg!(target_os = "linux") || cfg!(target_os = "macos") {
+            assert_eq!(path.compact().to_str(), Some("~/some_file.txt"));
+        } else {
+            assert_eq!(path.compact().to_str(), path.to_str());
+        }
+    }
+
+    #[test]
+    fn test_path_suffix() {
+        // No dots in name
+        let path = Path::new("/a/b/c/file_name.rs");
+        assert_eq!(path.icon_suffix(), Some("rs"));
+
+        // Single dot in name
+        let path = Path::new("/a/b/c/file.name.rs");
+        assert_eq!(path.icon_suffix(), Some("rs"));
+
+        // Multiple dots in name
+        let path = Path::new("/a/b/c/long.file.name.rs");
+        assert_eq!(path.icon_suffix(), Some("rs"));
+
+        // Hidden file, no extension
+        let path = Path::new("/a/b/c/.gitignore");
+        assert_eq!(path.icon_suffix(), Some("gitignore"));
+
+        // Hidden file, with extension
+        let path = Path::new("/a/b/c/.eslintrc.js");
+        assert_eq!(path.icon_suffix(), Some("eslintrc.js"));
+    }
 }