Add support for folder-specific settings (#2537)

This PR allows you to customize Zed's settings within a particular
folder by creating a `.zed/settings.json` file within that folder.

Todo

* [x] respect folder-specific settings for local projects
* [x] respect folder-specific settings in remote projects
* [x] pass a path when retrieving editor/language settings
* [x] pass a path when retrieving copilot settings
* [ ] update the `Setting` trait to make it clear which types of
settings are locally overridable

Release Notes:

* Added support for folder-specific settings. You can customize Zed's
settings within a particular folder by creating a `.zed` directory and a
`.zed/settings.json` file within that folder.

crates/editor/src/display_map.rs

@@ -272,12 +272,11 @@ impl DisplayMap {
     }
 
     fn tab_size(buffer: &ModelHandle<MultiBuffer>, cx: &mut ModelContext<Self>) -> NonZeroU32 {
-        let language_name = buffer
+        let language = buffer
             .read(cx)
             .as_singleton()
-            .and_then(|buffer| buffer.read(cx).language())
-            .map(|language| language.name());
-        language_settings(language_name.as_deref(), cx).tab_size
+            .and_then(|buffer| buffer.read(cx).language());
+        language_settings(language.as_deref(), None, cx).tab_size
     }
 
     #[cfg(test)]

crates/editor/src/editor.rs

@@ -3207,12 +3207,10 @@ impl Editor {
         snapshot: &MultiBufferSnapshot,
         cx: &mut ViewContext<Self>,
     ) -> bool {
-        let path = snapshot.file_at(location).map(|file| file.path().as_ref());
-        let language_name = snapshot
-            .language_at(location)
-            .map(|language| language.name());
-        let settings = all_language_settings(cx);
-        settings.copilot_enabled(language_name.as_deref(), path)
+        let file = snapshot.file_at(location);
+        let language = snapshot.language_at(location);
+        let settings = all_language_settings(file, cx);
+        settings.copilot_enabled(language, file.map(|f| f.path().as_ref()))
     }
 
     fn has_active_copilot_suggestion(&self, cx: &AppContext) -> bool {
@@ -7076,11 +7074,13 @@ impl Editor {
         };
 
         // If None, we are in a file without an extension
-        let file_extension = file_extension.or(self
+        let file = self
             .buffer
             .read(cx)
             .as_singleton()
-            .and_then(|b| b.read(cx).file())
+            .and_then(|b| b.read(cx).file());
+        let file_extension = file_extension.or(file
+            .as_ref()
             .and_then(|file| Path::new(file.file_name(cx)).extension())
             .and_then(|e| e.to_str())
             .map(|a| a.to_string()));
@@ -7091,7 +7091,7 @@ impl Editor {
             .get("vim_mode")
             == Some(&serde_json::Value::Bool(true));
         let telemetry_settings = *settings::get::<TelemetrySettings>(cx);
-        let copilot_enabled = all_language_settings(cx).copilot_enabled(None, None);
+        let copilot_enabled = all_language_settings(file, cx).copilot_enabled(None, None);
         let copilot_enabled_for_language = self
             .buffer
             .read(cx)

crates/editor/src/items.rs

@@ -1231,6 +1231,10 @@ mod tests {
             unimplemented!()
         }
 
+        fn worktree_id(&self) -> usize {
+            0
+        }
+
         fn is_deleted(&self) -> bool {
             unimplemented!()
         }

crates/editor/src/multi_buffer.rs

@@ -1377,8 +1377,14 @@ impl MultiBuffer {
         point: T,
         cx: &'a AppContext,
     ) -> &'a LanguageSettings {
-        let language = self.language_at(point, cx);
-        language_settings(language.map(|l| l.name()).as_deref(), cx)
+        let mut language = None;
+        let mut file = None;
+        if let Some((buffer, offset)) = self.point_to_buffer_offset(point, cx) {
+            let buffer = buffer.read(cx);
+            language = buffer.language_at(offset);
+            file = buffer.file();
+        }
+        language_settings(language.as_ref(), file, cx)
     }
 
     pub fn for_each_buffer(&self, mut f: impl FnMut(&ModelHandle<Buffer>)) {
@@ -2785,9 +2791,13 @@ impl MultiBufferSnapshot {
         point: T,
         cx: &'a AppContext,
     ) -> &'a LanguageSettings {
-        self.point_to_buffer_offset(point)
-            .map(|(buffer, offset)| buffer.settings_at(offset, cx))
-            .unwrap_or_else(|| language_settings(None, cx))
+        let mut language = None;
+        let mut file = None;
+        if let Some((buffer, offset)) = self.point_to_buffer_offset(point) {
+            language = buffer.language_at(offset);
+            file = buffer.file();
+        }
+        language_settings(language, file, cx)
     }
 
     pub fn language_scope_at<'a, T: ToOffset>(&'a self, point: T) -> Option<LanguageScope> {