Adopt welcome view for lightweight mode

package.json

@@ -328,7 +328,14 @@
           "when": "extensionActivated"
         }
       ]
-    }
+    },
+    "viewsWelcome": [
+      {
+        "view": "javaProjectExplorer",
+        "contents": "No projects are listed because the Java Language Server is currently running in [LightWeight Mode](https://aka.ms/vscode-java-lightweight). To show projects, click on the button to switch to Standard Mode.\n[Switch to Standard Mode](command:java.server.mode.switch?%5B%22Standard%22,true%5D)",
+        "when": "java:serverMode == LightWeight"
+      }
+    ]
   },
   "scripts": {
     "compile": "tsc -p . && webpack --config webpack.config.js",

src/commands.ts

@@ -54,13 +54,9 @@ export namespace Commands {
 
     export const JAVA_GETPACKAGEDATA = "java.getPackageData";
 
-    export const JAVA_PROJECT_SWITCH_SERVER_MODE = "java.project.switch.server.mode";
-
     /**
      * command from VS Code Java to switch the language server mode
      */
-    export const JAVA_SWITCH_SERVER_MODE = "java.server.mode.switch";
-
     export const JAVA_RESOLVEPATH = "java.resolvePath";
 
     export const JAVA_PROJECT_GETMAINMETHOD = "java.project.getMainMethod";

src/extension.ts

@@ -2,7 +2,7 @@
 // Licensed under the MIT license.
 
 import { commands, Event, Extension, ExtensionContext, extensions, Uri } from "vscode";
-import { dispose as disposeTelemetryWrapper, initializeFromJsonFile, instrumentOperation, instrumentOperationAsVsCodeCommand } from "vscode-extension-telemetry-wrapper";
+import { dispose as disposeTelemetryWrapper, initializeFromJsonFile, instrumentOperation } from "vscode-extension-telemetry-wrapper";
 import { Commands } from "./commands";
 import { Context } from "./constants";
 import { contextManager } from "./contextManager";
@@ -63,13 +63,6 @@ async function activateExtension(_operationId: string, context: ExtensionContext
     contextManager.setContextValue(Context.EXTENSION_ACTIVATED, true);
 
     initExpService(context);
-
-    context.subscriptions.push(instrumentOperationAsVsCodeCommand(Commands.JAVA_PROJECT_SWITCH_SERVER_MODE, async () => {
-        if (isSwitchingServer()) {
-            return;
-        }
-        await commands.executeCommand(Commands.JAVA_SWITCH_SERVER_MODE, "Standard" /*mode*/);
-    }));
 }
 
 // determine if the add dependency shortcut will show or not
@@ -96,15 +89,25 @@ export function isStandardServerReady(): boolean {
         return true;
     }
 
-    if (serverMode !== "Standard") {
+    if (serverMode !== LanguageServerMode.Standard) {
         return false;
     }
 
     return true;
 }
 
+export function isLightWeightMode(): boolean {
+    return serverMode === LanguageServerMode.LightWeight;
+}
+
 export function isSwitchingServer(): boolean {
-    return serverMode === "Hybrid";
+    return serverMode === LanguageServerMode.Hybrid;
 }
 
 let serverMode: string | undefined;
+
+const enum LanguageServerMode {
+    LightWeight = "LightWeight",
+    Standard = "Standard",
+    Hybrid = "Hybrid",
+}

src/views/dependencyDataProvider.ts

@@ -10,13 +10,12 @@ import { instrumentOperation, instrumentOperationAsVsCodeCommand } from "vscode-
 import { Commands } from "../commands";
 import { newJavaClass, newPackage } from "../explorerCommands/new";
 import { createJarFile } from "../exportJarFileCommand";
-import { isStandardServerReady, isSwitchingServer } from "../extension";
+import { isLightWeightMode, isSwitchingServer } from "../extension";
 import { Jdtls } from "../java/jdtls";
 import { INodeData, NodeKind } from "../java/nodeData";
 import { Settings } from "../settings";
 import { DataNode } from "./dataNode";
 import { ExplorerNode } from "./explorerNode";
-import { LightWeightNode } from "./lightWeightNode";
 import { explorerNodeCache } from "./nodeCache/explorerNodeCache";
 import { ProjectNode } from "./projectNode";
 import { WorkspaceNode } from "./workspaceNode";
@@ -97,18 +96,16 @@ export class DependencyDataProvider implements TreeDataProvider<ExplorerNode> {
     }
 
     public async getChildren(element?: ExplorerNode): Promise<ExplorerNode[]> {
+        if (isLightWeightMode()) {
+            return [];
+        }
+
         if (isSwitchingServer()) {
             await new Promise<void>((resolve: () => void): void => {
                 extensions.getExtension("redhat.java")!.exports.onDidServerModeChange(resolve);
             });
         }
 
-        if (!isStandardServerReady()) {
-            return [
-                new LightWeightNode(),
-            ];
-        }
-
         if (!this._rootItems || !element) {
             return this.getRootNodes();
         } else {