settings ui: Create settings key trait (#37489)

This PR separates out the associated constant `KEY` from the `Settings`
trait into a new trait `SettingsKey`. This allows for the key trait to
be derived using attributes to specify the path so that the new
`SettingsUi` derive macro can use the same attributes to determine top
level settings paths thereby removing the need to duplicate the path in
both `Settings::KEY` and `#[settings_ui(path = "...")]`

Co-authored-by: Ben Kunkle <ben@zed.dev>

Release Notes:

- N/A

---------

Co-authored-by: Ben Kunkle <ben@zed.dev>

crates/workspace/src/workspace_settings.rs

@@ -6,7 +6,7 @@ use collections::HashMap;
 use gpui::App;
 use schemars::JsonSchema;
 use serde::{Deserialize, Serialize};
-use settings::{Settings, SettingsSources, SettingsUi};
+use settings::{Settings, SettingsKey, SettingsSources, SettingsUi};
 
 #[derive(Deserialize)]
 pub struct WorkspaceSettings {
@@ -118,7 +118,8 @@ pub enum RestoreOnStartupBehavior {
     LastSession,
 }
 
-#[derive(Clone, Default, Serialize, Deserialize, JsonSchema, SettingsUi)]
+#[derive(Clone, Default, Serialize, Deserialize, JsonSchema, SettingsUi, SettingsKey)]
+#[settings_key(None)]
 pub struct WorkspaceSettingsContent {
     /// Active pane styling settings.
     pub active_pane_modifiers: Option<ActivePanelModifiers>,
@@ -223,7 +224,8 @@ pub struct TabBarSettings {
     pub show_tab_bar_buttons: bool,
 }
 
-#[derive(Clone, Default, Serialize, Deserialize, JsonSchema, SettingsUi)]
+#[derive(Clone, Default, Serialize, Deserialize, JsonSchema, SettingsUi, SettingsKey)]
+#[settings_key(key = "tab_bar")]
 pub struct TabBarSettingsContent {
     /// Whether or not to show the tab bar in the editor.
     ///
@@ -282,8 +284,6 @@ pub struct CenteredLayoutSettings {
 }
 
 impl Settings for WorkspaceSettings {
-    const KEY: Option<&'static str> = None;
-
     type FileContent = WorkspaceSettingsContent;
 
     fn load(sources: SettingsSources<Self::FileContent>, _: &mut App) -> Result<Self> {
@@ -373,8 +373,6 @@ impl Settings for WorkspaceSettings {
 }
 
 impl Settings for TabBarSettings {
-    const KEY: Option<&'static str> = Some("tab_bar");
-
     type FileContent = TabBarSettingsContent;
 
     fn load(sources: SettingsSources<Self::FileContent>, _: &mut App) -> Result<Self> {