Expose context server settings to extensions (#20555)

This PR exposes context server settings to extensions.

Extensions can use `ContextServerSettings::for_project` to get the
context server settings for the current project.

The `experimental.context_servers` setting has been removed and replaced
with the `context_servers` setting (which is now an object instead of an
array).

Release Notes:

- N/A

---------

Co-authored-by: Max Brunsfeld <maxbrunsfeld@gmail.com>

crates/extension_api/src/settings.rs

@@ -1,34 +1,56 @@
 //! Provides access to Zed settings.
 
-#[path = "../wit/since_v0.1.0/settings.rs"]
+#[path = "../wit/since_v0.2.0/settings.rs"]
 mod types;
 
-use crate::{wit, Result, SettingsLocation, Worktree};
+use crate::{wit, Project, Result, SettingsLocation, Worktree};
 use serde_json;
 pub use types::*;
 
 impl LanguageSettings {
     /// Returns the [`LanguageSettings`] for the given language.
     pub fn for_worktree(language: Option<&str>, worktree: &Worktree) -> Result<Self> {
-        let location = SettingsLocation {
-            worktree_id: worktree.id(),
-            path: worktree.root_path(),
-        };
-        let settings_json = wit::get_settings(Some(&location), "language", language)?;
-        let settings: Self = serde_json::from_str(&settings_json).map_err(|err| err.to_string())?;
-        Ok(settings)
+        get_settings("language", language, Some(worktree.id()))
     }
 }
 
 impl LspSettings {
     /// Returns the [`LspSettings`] for the given language server.
     pub fn for_worktree(language_server_name: &str, worktree: &Worktree) -> Result<Self> {
-        let location = SettingsLocation {
-            worktree_id: worktree.id(),
-            path: worktree.root_path(),
-        };
-        let settings_json = wit::get_settings(Some(&location), "lsp", Some(language_server_name))?;
-        let settings: Self = serde_json::from_str(&settings_json).map_err(|err| err.to_string())?;
-        Ok(settings)
+        get_settings("lsp", Some(language_server_name), Some(worktree.id()))
     }
 }
+
+impl ContextServerSettings {
+    /// Returns the [`ContextServerSettings`] for the given context server.
+    pub fn for_project(context_server_id: &str, project: &Project) -> Result<Self> {
+        let global_setting: Self = get_settings("context_servers", Some(context_server_id), None)?;
+
+        for worktree_id in project.worktree_ids() {
+            let settings = get_settings(
+                "context_servers",
+                Some(context_server_id),
+                Some(worktree_id),
+            )?;
+            if settings != global_setting {
+                return Ok(settings);
+            }
+        }
+
+        Ok(global_setting)
+    }
+}
+
+fn get_settings<T: serde::de::DeserializeOwned>(
+    settings_type: &str,
+    settings_name: Option<&str>,
+    worktree_id: Option<u64>,
+) -> Result<T> {
+    let location = worktree_id.map(|worktree_id| SettingsLocation {
+        worktree_id,
+        path: String::new(),
+    });
+    let settings_json = wit::get_settings(location.as_ref(), settings_type, settings_name)?;
+    let settings: T = serde_json::from_str(&settings_json).map_err(|err| err.to_string())?;
+    Ok(settings)
+}