Allow extensions to define more of the methods in the LspAdapter trait (#9554)

Our goal is to extract Svelte support into an extension, since we've
seen problems with the Tree-sitter Svelte parser crashing due to bugs in
the external scanner. In order to do this, we need a couple more
capabilities in LSP extensions:

* [x] `initialization_options` - programmatically controlling the JSON
initialization params sent to the language server
* [x] `prettier_plugins` - statically specifying a list of prettier
plugins that apply for a given language.
* [x] `npm_install_package`

Release Notes:

- N/A

---------

Co-authored-by: Marshall <marshall@zed.dev>
Co-authored-by: Marshall Bowers <elliott.codes@gmail.com>

crates/extension/src/extension_lsp_adapter.rs

@@ -92,4 +92,37 @@ impl LspAdapter for ExtensionLspAdapter {
     async fn installation_test_binary(&self, _: PathBuf) -> Option<LanguageServerBinary> {
         None
     }
+
+    async fn initialization_options(
+        self: Arc<Self>,
+        delegate: &Arc<dyn LspAdapterDelegate>,
+    ) -> Result<Option<serde_json::Value>> {
+        let delegate = delegate.clone();
+        let json_options = self
+            .extension
+            .call({
+                let this = self.clone();
+                |extension, store| {
+                    async move {
+                        let resource = store.data_mut().table().push(delegate)?;
+                        let options = extension
+                            .call_language_server_initialization_options(
+                                store,
+                                &this.config,
+                                resource,
+                            )
+                            .await?
+                            .map_err(|e| anyhow!("{}", e))?;
+                        anyhow::Ok(options)
+                    }
+                    .boxed()
+                }
+            })
+            .await?;
+        Ok(if let Some(json_options) = json_options {
+            serde_json::from_str(&json_options)?
+        } else {
+            None
+        })
+    }
 }

crates/extension/src/wasm_host.rs

@@ -307,6 +307,46 @@ impl wit::ExtensionImports for WasmState {
             .map_err(|err| err.to_string()))
     }
 
+    async fn npm_package_installed_version(
+        &mut self,
+        package_name: String,
+    ) -> wasmtime::Result<Result<Option<String>, String>> {
+        async fn inner(
+            this: &mut WasmState,
+            package_name: String,
+        ) -> anyhow::Result<Option<String>> {
+            this.host
+                .node_runtime
+                .npm_package_installed_version(&this.host.work_dir, &package_name)
+                .await
+        }
+
+        Ok(inner(self, package_name)
+            .await
+            .map_err(|err| err.to_string()))
+    }
+
+    async fn npm_install_package(
+        &mut self,
+        package_name: String,
+        version: String,
+    ) -> wasmtime::Result<Result<(), String>> {
+        async fn inner(
+            this: &mut WasmState,
+            package_name: String,
+            version: String,
+        ) -> anyhow::Result<()> {
+            this.host
+                .node_runtime
+                .npm_install_packages(&this.host.work_dir, &[(&package_name, &version)])
+                .await
+        }
+
+        Ok(inner(self, package_name, version)
+            .await
+            .map_err(|err| err.to_string()))
+    }
+
     async fn latest_github_release(
         &mut self,
         repo: String,