Strict null fixes for IEditorOpenHandler

src/vs/workbench/contrib/files/browser/explorerViewlet.ts

@@ -30,7 +30,7 @@ import { DelegatingEditorService } from 'vs/workbench/services/editor/browser/ed
 import { IEditorGroup, IEditorGroupsService } from 'vs/workbench/services/editor/common/editorGroupsService';
 import { IEditorService } from 'vs/workbench/services/editor/common/editorService';
 import { IEditorOptions } from 'vs/platform/editor/common/editor';
-import { IEditorInput } from 'vs/workbench/common/editor';
+import { IEditorInput, IEditor } from 'vs/workbench/common/editor';
 import { ViewletPanel } from 'vs/workbench/browser/parts/views/panelViewlet';
 import { KeyChord, KeyMod, KeyCode } from 'vs/base/common/keyCodes';
 import { Registry } from 'vs/platform/registry/common/platform';
@@ -183,7 +183,7 @@ export class ExplorerViewlet extends ViewContainerViewlet {
 			// We try to be smart and only use the delay if we recognize that the user action is likely to cause
 			// a new entry in the opened editors view.
 			const delegatingEditorService = this.instantiationService.createInstance(DelegatingEditorService);
-			delegatingEditorService.setEditorOpenHandler((group: IEditorGroup, editor: IEditorInput, options?: IEditorOptions) => {
+			delegatingEditorService.setEditorOpenHandler((group: IEditorGroup, editor: IEditorInput, options?: IEditorOptions): Promise<IEditor | null> => {
 				let openEditorsView = this.getOpenEditorsView();
 				if (openEditorsView) {
 					let delay = 0;
@@ -199,8 +199,8 @@ export class ExplorerViewlet extends ViewContainerViewlet {
 					openEditorsView.setStructuralRefreshDelay(delay);
 				}
 
-				const onSuccessOrError = (editor?: BaseEditor) => {
-					let openEditorsView = this.getOpenEditorsView();
+				const onSuccessOrError = (editor: BaseEditor | null) => {
+					const openEditorsView = this.getOpenEditorsView();
 					if (openEditorsView) {
 						openEditorsView.setStructuralRefreshDelay(0);
 					}

src/vs/workbench/services/editor/browser/editorService.ts

@@ -596,7 +596,7 @@ export class EditorService extends Disposable implements EditorServiceImpl {
 }
 
 export interface IEditorOpenHandler {
-	(group: IEditorGroup, editor: IEditorInput, options?: IEditorOptions | ITextEditorOptions): Promise<IEditor>;
+	(group: IEditorGroup, editor: IEditorInput, options?: IEditorOptions | ITextEditorOptions): Promise<IEditor | null>;
 }
 
 /**