Overhaul extension registration (#21083)

This PR overhauls extension registration in order to make it more
modular.

The `extension` crate now contains an `ExtensionHostProxy` that can be
used to register various proxies that the extension host can use to
interact with the rest of the system.

There are now a number of different proxy traits representing the
various pieces of functionality that can be provided by an extension.
The respective crates that provide this functionality can implement
their corresponding proxy trait in order to register a proxy that the
extension host will use to register the bits of functionality provided
by the extension.

Release Notes:

- N/A

crates/context_servers/src/context_servers.rs

@@ -1,4 +1,5 @@
 pub mod client;
+mod extension_context_server;
 pub mod manager;
 pub mod protocol;
 mod registry;
@@ -19,6 +20,7 @@ pub const CONTEXT_SERVERS_NAMESPACE: &'static str = "context_servers";
 pub fn init(cx: &mut AppContext) {
     ContextServerSettings::register(cx);
     ContextServerFactoryRegistry::default_global(cx);
+    extension_context_server::init(cx);
 
     CommandPaletteFilter::update_global(cx, |filter, _cx| {
         filter.hide_namespace(CONTEXT_SERVERS_NAMESPACE);

crates/context_servers/src/extension_context_server.rs

@@ -0,0 +1,78 @@
+use std::sync::Arc;
+
+use extension::{Extension, ExtensionContextServerProxy, ExtensionHostProxy, ProjectDelegate};
+use gpui::{AppContext, Model};
+
+use crate::manager::ServerCommand;
+use crate::ContextServerFactoryRegistry;
+
+struct ExtensionProject {
+    worktree_ids: Vec<u64>,
+}
+
+impl ProjectDelegate for ExtensionProject {
+    fn worktree_ids(&self) -> Vec<u64> {
+        self.worktree_ids.clone()
+    }
+}
+
+pub fn init(cx: &mut AppContext) {
+    let proxy = ExtensionHostProxy::default_global(cx);
+    proxy.register_context_server_proxy(ContextServerFactoryRegistryProxy {
+        context_server_factory_registry: ContextServerFactoryRegistry::global(cx),
+    });
+}
+
+struct ContextServerFactoryRegistryProxy {
+    context_server_factory_registry: Model<ContextServerFactoryRegistry>,
+}
+
+impl ExtensionContextServerProxy for ContextServerFactoryRegistryProxy {
+    fn register_context_server(
+        &self,
+        extension: Arc<dyn Extension>,
+        id: Arc<str>,
+        cx: &mut AppContext,
+    ) {
+        self.context_server_factory_registry
+            .update(cx, |registry, _| {
+                registry.register_server_factory(
+                    id.clone(),
+                    Arc::new({
+                        move |project, cx| {
+                            log::info!(
+                                "loading command for context server {id} from extension {}",
+                                extension.manifest().id
+                            );
+
+                            let id = id.clone();
+                            let extension = extension.clone();
+                            cx.spawn(|mut cx| async move {
+                                let extension_project =
+                                    project.update(&mut cx, |project, cx| {
+                                        Arc::new(ExtensionProject {
+                                            worktree_ids: project
+                                                .visible_worktrees(cx)
+                                                .map(|worktree| worktree.read(cx).id().to_proto())
+                                                .collect(),
+                                        })
+                                    })?;
+
+                                let command = extension
+                                    .context_server_command(id.clone(), extension_project)
+                                    .await?;
+
+                                log::info!("loaded command for context server {id}: {command:?}");
+
+                                Ok(ServerCommand {
+                                    path: command.command,
+                                    args: command.args,
+                                    env: Some(command.env.into_iter().collect()),
+                                })
+                            })
+                        }
+                    }),
+                )
+            });
+    }
+}