Preview tab does not have a stable position (fixes #8245)

src/vs/workbench/common/editor/editorStacksModel.ts

@@ -251,8 +251,8 @@ export class EditorGroup implements IEditorGroup {
 				// Replace existing preview with this editor if we have a preview
 				if (this.preview) {
 					const indexOfPreview = this.indexOf(this.preview);
-					if (targetIndex >= indexOfPreview) {
-						targetIndex--;
+					if (targetIndex > indexOfPreview) {
+						targetIndex--; // accomodate for the fact that the preview editor closes
 					}
 
 					this.closeEditor(this.preview, !makeActive); // optimization to prevent multiple setActive() in one call

src/vs/workbench/parts/files/browser/editors/textFileEditor.ts

@@ -34,7 +34,6 @@ import {IMessageService, Severity, CancelAction} from 'vs/platform/message/commo
 import {IWorkbenchEditorService} from 'vs/workbench/services/editor/common/editorService';
 import {IModeService} from 'vs/editor/common/services/modeService';
 import {IThemeService} from 'vs/workbench/services/themes/common/themeService';
-import {IHistoryService} from 'vs/workbench/services/history/common/history';
 
 const LEGACY_EDITOR_VIEW_STATE_PREFERENCE_KEY = 'editorViewState'; // TODO@Ben migration
 const TEXT_EDITOR_VIEW_STATE_PREFERENCE_KEY = 'textEditorViewState';
@@ -56,7 +55,6 @@ export class TextFileEditor extends BaseTextEditor {
 		@ITelemetryService telemetryService: ITelemetryService,
 		@IFileService private fileService: IFileService,
 		@IViewletService private viewletService: IViewletService,
-		@IHistoryService private historyService: IHistoryService,
 		@IInstantiationService instantiationService: IInstantiationService,
 		@IWorkspaceContextService contextService: IWorkspaceContextService,
 		@IStorageService storageService: IStorageService,

src/vs/workbench/test/common/editor/editorStacksModel.test.ts

@@ -29,7 +29,7 @@ function create(): EditorStacksModel {
 	services.set(IWorkspaceContextService, new TestContextService());
 
 	const config = new TestConfigurationService();
-	config.setUserConfiguration('workbench', { editor: { openPositioning: 'right' }});
+	config.setUserConfiguration('workbench', { editor: { openPositioning: 'right' } });
 	services.set(IConfigurationService, config);
 
 	let inst = new InstantiationService(services);
@@ -644,7 +644,7 @@ suite('Editor Stacks Model', () => {
 
 		const config = new TestConfigurationService();
 		services.set(IConfigurationService, config);
-		config.setUserConfiguration('workbench', { editor: { openPositioning: 'left' }});
+		config.setUserConfiguration('workbench', { editor: { openPositioning: 'left' } });
 
 		let inst = new InstantiationService(services);
 
@@ -1177,7 +1177,7 @@ suite('Editor Stacks Model', () => {
 		const lifecycle = new TestLifecycleService();
 		services.set(ILifecycleService, lifecycle);
 		const config = new TestConfigurationService();
-		config.setUserConfiguration('workbench', { editor: { openPositioning: 'right' }});
+		config.setUserConfiguration('workbench', { editor: { openPositioning: 'right' } });
 		services.set(IConfigurationService, config);
 
 		let inst = new InstantiationService(services);
@@ -1221,7 +1221,7 @@ suite('Editor Stacks Model', () => {
 		const lifecycle = new TestLifecycleService();
 		services.set(ILifecycleService, lifecycle);
 		const config = new TestConfigurationService();
-		config.setUserConfiguration('workbench', { editor: { openPositioning: 'right' }});
+		config.setUserConfiguration('workbench', { editor: { openPositioning: 'right' } });
 		services.set(IConfigurationService, config);
 
 		let inst = new InstantiationService(services);
@@ -1303,7 +1303,7 @@ suite('Editor Stacks Model', () => {
 		const lifecycle = new TestLifecycleService();
 		services.set(ILifecycleService, lifecycle);
 		const config = new TestConfigurationService();
-		config.setUserConfiguration('workbench', { editor: { openPositioning: 'right' }});
+		config.setUserConfiguration('workbench', { editor: { openPositioning: 'right' } });
 		services.set(IConfigurationService, config);
 
 		let inst = new InstantiationService(services);
@@ -1353,7 +1353,7 @@ suite('Editor Stacks Model', () => {
 		const lifecycle = new TestLifecycleService();
 		services.set(ILifecycleService, lifecycle);
 		const config = new TestConfigurationService();
-		config.setUserConfiguration('workbench', { editor: { openPositioning: 'right' }});
+		config.setUserConfiguration('workbench', { editor: { openPositioning: 'right' } });
 		services.set(IConfigurationService, config);
 
 		let inst = new InstantiationService(services);
@@ -1395,7 +1395,7 @@ suite('Editor Stacks Model', () => {
 		const lifecycle = new TestLifecycleService();
 		services.set(ILifecycleService, lifecycle);
 		const config = new TestConfigurationService();
-		config.setUserConfiguration('workbench', { editor: { openPositioning: 'right' }});
+		config.setUserConfiguration('workbench', { editor: { openPositioning: 'right' } });
 		services.set(IConfigurationService, config);
 
 		let inst = new InstantiationService(services);
@@ -1716,4 +1716,21 @@ suite('Editor Stacks Model', () => {
 		assert.ok(events.changed[5].structural); // close
 		assert.equal(events.changed[5].editor, input1);
 	});
+
+	test('Preview tab does not have a stable position (https://github.com/Microsoft/vscode/issues/8245)', function () {
+		const model = create();
+
+		const group1 = model.openGroup('first');
+
+		const input1 = input();
+		const input2 = input();
+		const input3 = input();
+
+		group1.openEditor(input1, { pinned: true, active: true });
+		group1.openEditor(input2, { active: true });
+		group1.setActive(input1);
+
+		group1.openEditor(input3, { active: true });
+		assert.equal(group1.indexOf(input3), 1);
+	});
 });
\ No newline at end of file