Add a setting for custom associations between languages and files (#9290)

Closes #5178

Release Notes:

- Added a `file_types` setting that can be used to associate languages
with file names and file extensions. For example, to interpret all `.c`
files as C++, and files called `MyLockFile` as TOML, add the following
to `settings.json`:

    ```json
    {
      "file_types": {
        "C++": ["c"],
        "TOML": ["MyLockFile"]
      }
    }
    ```

As with most zed settings, this can be configured on a per-directory
basis by including a local `.zed/settings.json` file in that directory.

---------

Co-authored-by: Marshall <marshall@zed.dev>

crates/settings/src/settings.rs

@@ -8,7 +8,7 @@ use util::asset_str;
 
 pub use keymap_file::KeymapFile;
 pub use settings_file::*;
-pub use settings_store::{Settings, SettingsJsonSchemaParams, SettingsStore};
+pub use settings_store::{Settings, SettingsJsonSchemaParams, SettingsLocation, SettingsStore};
 
 #[derive(RustEmbed)]
 #[folder = "../../assets"]

crates/settings/src/settings_store.rs

@@ -86,9 +86,8 @@ pub trait Settings: 'static + Send + Sync {
         });
     }
 
-    /// path is a (worktree ID, Path)
     #[track_caller]
-    fn get<'a>(path: Option<(usize, &Path)>, cx: &'a AppContext) -> &'a Self
+    fn get<'a>(path: Option<SettingsLocation>, cx: &'a AppContext) -> &'a Self
     where
         Self: Sized,
     {
@@ -120,6 +119,12 @@ pub trait Settings: 'static + Send + Sync {
     }
 }
 
+#[derive(Clone, Copy)]
+pub struct SettingsLocation<'a> {
+    pub worktree_id: usize,
+    pub path: &'a Path,
+}
+
 pub struct SettingsJsonSchemaParams<'a> {
     pub staff_mode: bool,
     pub language_names: &'a [String],
@@ -168,7 +173,7 @@ trait AnySettingValue: 'static + Send + Sync {
         custom: &[DeserializedSetting],
         cx: &mut AppContext,
     ) -> Result<Box<dyn Any>>;
-    fn value_for_path(&self, path: Option<(usize, &Path)>) -> &dyn Any;
+    fn value_for_path(&self, path: Option<SettingsLocation>) -> &dyn Any;
     fn set_global_value(&mut self, value: Box<dyn Any>);
     fn set_local_value(&mut self, root_id: usize, path: Arc<Path>, value: Box<dyn Any>);
     fn json_schema(
@@ -234,7 +239,7 @@ impl SettingsStore {
     ///
     /// Panics if the given setting type has not been registered, or if there is no
     /// value for this setting.
-    pub fn get<T: Settings>(&self, path: Option<(usize, &Path)>) -> &T {
+    pub fn get<T: Settings>(&self, path: Option<SettingsLocation>) -> &T {
         self.setting_values
             .get(&TypeId::of::<T>())
             .unwrap_or_else(|| panic!("unregistered setting type {}", type_name::<T>()))
@@ -659,10 +664,10 @@ impl<T: Settings> AnySettingValue for SettingValue<T> {
         Ok(DeserializedSetting(Box::new(value)))
     }
 
-    fn value_for_path(&self, path: Option<(usize, &Path)>) -> &dyn Any {
-        if let Some((root_id, path)) = path {
+    fn value_for_path(&self, path: Option<SettingsLocation>) -> &dyn Any {
+        if let Some(SettingsLocation { worktree_id, path }) = path {
             for (settings_root_id, settings_path, value) in self.local_values.iter().rev() {
-                if root_id == *settings_root_id && path.starts_with(settings_path) {
+                if worktree_id == *settings_root_id && path.starts_with(settings_path) {
                     return value;
                 }
             }
@@ -1010,7 +1015,10 @@ mod tests {
             .unwrap();
 
         assert_eq!(
-            store.get::<UserSettings>(Some((1, Path::new("/root1/something")))),
+            store.get::<UserSettings>(Some(SettingsLocation {
+                worktree_id: 1,
+                path: Path::new("/root1/something"),
+            })),
             &UserSettings {
                 name: "John Doe".to_string(),
                 age: 31,
@@ -1018,7 +1026,10 @@ mod tests {
             }
         );
         assert_eq!(
-            store.get::<UserSettings>(Some((1, Path::new("/root1/subdir/something")))),
+            store.get::<UserSettings>(Some(SettingsLocation {
+                worktree_id: 1,
+                path: Path::new("/root1/subdir/something")
+            })),
             &UserSettings {
                 name: "Jane Doe".to_string(),
                 age: 31,
@@ -1026,7 +1037,10 @@ mod tests {
             }
         );
         assert_eq!(
-            store.get::<UserSettings>(Some((1, Path::new("/root2/something")))),
+            store.get::<UserSettings>(Some(SettingsLocation {
+                worktree_id: 1,
+                path: Path::new("/root2/something")
+            })),
             &UserSettings {
                 name: "John Doe".to_string(),
                 age: 42,
@@ -1034,7 +1048,10 @@ mod tests {
             }
         );
         assert_eq!(
-            store.get::<MultiKeySettings>(Some((1, Path::new("/root2/something")))),
+            store.get::<MultiKeySettings>(Some(SettingsLocation {
+                worktree_id: 1,
+                path: Path::new("/root2/something")
+            })),
             &MultiKeySettings {
                 key1: "a".to_string(),
                 key2: "b".to_string(),