Do not store webview if there is no corresponding serializer

packages/core/src/browser/shell/shell-layout-restorer.ts

@@ -32,9 +32,9 @@ import { ApplicationShell, applicationShellLayoutVersion, ApplicationShellLayout
 export interface StatefulWidget {
 
     /**
-     * Called on unload to store the inner state.
+     * Called on unload to store the inner state. Returns 'undefined' if the widget cannot be stored.
      */
-    storeState(): object;
+    storeState(): object | undefined;
 
     /**
      * Called when the widget got created by the storage service
@@ -205,14 +205,18 @@ export class ShellLayoutRestorer implements CommandContribution {
     private convertToDescription(widget: Widget): WidgetDescription | undefined {
         const desc = this.widgetManager.getDescription(widget);
         if (desc) {
-            let innerState = undefined;
             if (StatefulWidget.is(widget)) {
-                innerState = widget.storeState();
+                const innerState = widget.storeState();
+                return innerState ? {
+                    constructionOptions: desc,
+                    innerWidgetState: this.deflate(innerState)
+                } : undefined;
+            } else {
+                return {
+                    constructionOptions: desc,
+                    innerWidgetState: undefined
+                };
             }
-            return {
-                constructionOptions: desc,
-                innerWidgetState: innerState && this.deflate(innerState)
-            };
         }
     }
 
@@ -265,7 +269,7 @@ export class ShellLayoutRestorer implements CommandContribution {
     protected parse<T>(layoutData: string, parseContext: ShellLayoutRestorer.ParseContext): T {
         return JSON.parse(layoutData, (property: string, value) => {
             if (this.isWidgetsProperty(property)) {
-                const widgets: (Widget | undefined)[] = [];
+                const widgets = parseContext.filteredArray();
                 const descs = (value as WidgetDescription[]);
                 for (let i = 0; i < descs.length; i++) {
                     parseContext.push(async context => {
@@ -347,9 +351,22 @@ export class ShellLayoutRestorer implements CommandContribution {
     }
 
 }
+
 export namespace ShellLayoutRestorer {
+
     export class ParseContext {
         protected readonly toInflate: Inflate[] = [];
+        protected readonly toFilter: Widgets[] = [];
+
+        /**
+         * Returns an array, which will be filtered from undefined elements
+         * after resolving promises, that create widgets.
+         */
+        filteredArray(): Widgets {
+            const array: Widgets = [];
+            this.toFilter.push(array);
+            return array;
+        }
 
         push(toInflate: Inflate): void {
             this.toInflate.push(toInflate);
@@ -361,8 +378,20 @@ export namespace ShellLayoutRestorer {
                 pending.push(this.toInflate.pop()!(context));
             }
             await Promise.all(pending);
+
+            if (this.toFilter.length) {
+                this.toFilter.forEach(array => {
+                    for (let i = 0; i < array.length; i++) {
+                        if (array[i] === undefined) {
+                            array.splice(i--, 1);
+                        }
+                    }
+                });
+            }
         }
     }
+
+    export type Widgets = (Widget | undefined)[];
     export type Inflate = (context: InflateContext) => Promise<void>;
     export interface InflateContext extends ApplicationShellLayoutMigrationContext {
         readonly migrations: ApplicationShellLayoutMigration[];

packages/plugin-ext/src/hosted/browser/hosted-plugin.ts

@@ -197,19 +197,22 @@ export class HostedPluginSupport {
         this.taskProviderRegistry.onWillProvideTaskProvider(event => this.ensureTaskActivation(event));
         this.taskResolverRegistry.onWillProvideTaskResolver(event => this.ensureTaskActivation(event));
         this.fileService.onWillActivateFileSystemProvider(event => this.ensureFileSystemActivation(event));
+
         this.widgets.onDidCreateWidget(({ factoryId, widget }) => {
             if (factoryId === WebviewWidget.FACTORY_ID && widget instanceof WebviewWidget) {
                 const storeState = widget.storeState.bind(widget);
                 const restoreState = widget.restoreState.bind(widget);
+
                 widget.storeState = () => {
                     if (this.webviewRevivers.has(widget.viewType)) {
                         return storeState();
                     }
-                    return {};
+                    return undefined;
                 };
-                widget.restoreState = oldState => {
-                    if (oldState.viewType) {
-                        restoreState(oldState);
+
+                widget.restoreState = state => {
+                    if (state.viewType) {
+                        restoreState(state);
                         this.preserveWebview(widget);
                     } else {
                         widget.dispose();

packages/plugin-ext/src/main/browser/view/plugin-view-registry.ts

@@ -505,7 +505,10 @@ export class PluginViewRegistry implements FrontendApplicationContribution {
         const widgets = this.widgetManager.getWidgets(PLUGIN_VIEW_DATA_FACTORY_ID);
         for (const widget of widgets) {
             if (StatefulWidget.is(widget)) {
-                this.viewDataState.set(widget.id, widget.storeState());
+                const state = widget.storeState();
+                if (state) {
+                    this.viewDataState.set(widget.id, state);
+                }
             }
             widget.dispose();
         }
@@ -565,7 +568,10 @@ export class PluginViewRegistry implements FrontendApplicationContribution {
     protected storeViewDataStateOnDispose(viewId: string, widget: Widget & StatefulWidget): void {
         const dispose = widget.dispose.bind(widget);
         widget.dispose = () => {
-            this.viewDataState.set(viewId, widget.storeState());
+            const state = widget.storeState();
+            if (state) {
+                this.viewDataState.set(viewId, state);
+            }
             dispose();
         };
     }

packages/plugin-ext/src/main/browser/webviews-main.ts

@@ -34,7 +34,7 @@ export class WebviewsMainImpl implements WebviewsMain, Disposable {
 
     private readonly proxy: WebviewsExt;
     protected readonly shell: ApplicationShell;
-    protected readonly widgets: WidgetManager;
+    protected readonly widgetManager: WidgetManager;
     protected readonly pluginService: HostedPluginSupport;
     protected readonly viewColumnService: ViewColumnService;
     private readonly toDispose = new DisposableCollection();
@@ -43,7 +43,7 @@ export class WebviewsMainImpl implements WebviewsMain, Disposable {
         this.proxy = rpc.getProxy(MAIN_RPC_CONTEXT.WEBVIEWS_EXT);
         this.shell = container.get(ApplicationShell);
         this.viewColumnService = container.get(ViewColumnService);
-        this.widgets = container.get(WidgetManager);
+        this.widgetManager = container.get(WidgetManager);
         this.pluginService = container.get(HostedPluginSupport);
         this.toDispose.push(this.shell.onDidChangeActiveWidget(() => this.updateViewStates()));
         this.toDispose.push(this.shell.onDidChangeCurrentWidget(() => this.updateViewStates()));
@@ -61,7 +61,7 @@ export class WebviewsMainImpl implements WebviewsMain, Disposable {
         showOptions: WebviewPanelShowOptions,
         options: WebviewPanelOptions & WebviewOptions
     ): Promise<void> {
-        const view = await this.widgets.getOrCreateWidget<WebviewWidget>(WebviewWidget.FACTORY_ID, <WebviewWidgetIdentifier>{ id: panelId });
+        const view = await this.widgetManager.getOrCreateWidget<WebviewWidget>(WebviewWidget.FACTORY_ID, <WebviewWidgetIdentifier>{ id: panelId });
         this.hookWebview(view);
         view.viewType = viewType;
         view.title.label = title;
@@ -217,7 +217,7 @@ export class WebviewsMainImpl implements WebviewsMain, Disposable {
     }
 
     protected readonly updateViewStates = debounce(() => {
-        for (const widget of this.widgets.getWidgets(WebviewWidget.FACTORY_ID)) {
+        for (const widget of this.widgetManager.getWidgets(WebviewWidget.FACTORY_ID)) {
             if (widget instanceof WebviewWidget) {
                 this.updateViewState(widget);
             }
@@ -251,7 +251,7 @@ export class WebviewsMainImpl implements WebviewsMain, Disposable {
     }
 
     private async tryGetWebview(id: string): Promise<WebviewWidget | undefined> {
-        return this.widgets.getWidget<WebviewWidget>(WebviewWidget.FACTORY_ID, <WebviewWidgetIdentifier>{ id });
+        return this.widgetManager.getWidget<WebviewWidget>(WebviewWidget.FACTORY_ID, <WebviewWidgetIdentifier>{ id });
     }
 
 }