Improve LSP configuration change notification (#878)

Author: matthewbastien

src/sourcekit-lsp/LanguageClientManager.ts

@@ -112,6 +112,13 @@ export class LanguageClientManager {
     // used by single server support to keep a record of the project folders
     // that are not at the root of their workspace
     public subFolderWorkspaces: vscode.Uri[];
+    /** Get the current state of the underlying LanguageClient */
+    public get state(): langclient.State {
+        if (!this.languageClient) {
+            return langclient.State.Stopped;
+        }
+        return this.languageClient.state;
+    }
 
     constructor(public workspaceContext: WorkspaceContext) {
         this.singleServerSupport = workspaceContext.swiftVersion.isGreaterThanOrEqual(
@@ -161,18 +168,40 @@ export class LanguageClientManager {
         }
         // on change config restart server
         const onChangeConfig = vscode.workspace.onDidChangeConfiguration(event => {
-            if (event.affectsConfiguration("swift.sourcekit-lsp")) {
-                vscode.window
-                    .showInformationMessage(
-                        "Changing LSP settings requires the language server be restarted.",
-                        "Ok"
-                    )
-                    .then(selected => {
-                        if (selected === "Ok") {
-                            this.restart();
-                        }
-                    });
+            if (!event.affectsConfiguration("swift.sourcekit-lsp")) {
+                return;
+            }
+            let message =
+                "Changing SourceKit-LSP settings requires the language server be restarted. Would you like to restart it now?";
+            let restartLSPButton = "Restart Language Server";
+            // Enabling/Disabling sourcekit-lsp shows a special notification
+            if (event.affectsConfiguration("swift.sourcekit-lsp.disable")) {
+                if (configuration.lsp.disable) {
+                    if (this.state === langclient.State.Stopped) {
+                        // Language client is already stopped
+                        return;
+                    }
+                    message =
+                        "You have disabled the Swift language server, but it is still running. Would you like to stop it now?";
+                    restartLSPButton = "Stop Language Server";
+                } else {
+                    if (this.state !== langclient.State.Stopped) {
+                        // Langauge client is already running
+                        return;
+                    }
+                    message =
+                        "You have enabled the Swift language server. Would you like to start it now?";
+                    restartLSPButton = "Start Language Server";
+                }
+            } else if (configuration.lsp.disable && this.state === langclient.State.Stopped) {
+                // Ignore configuration changes if SourceKit-LSP is disabled
+                return;
             }
+            vscode.window.showInformationMessage(message, restartLSPButton).then(selected => {
+                if (selected === restartLSPButton) {
+                    this.restart();
+                }
+            });
         });
 
         this.subscriptions.push(onChangeConfig);