testing: persist empty history filter (microsoft#154573)

Fixes microsoft#150120

Author: connor4312

src/vs/workbench/contrib/testing/browser/testingExplorerFilter.ts

@@ -35,7 +35,7 @@ const testFilterDescriptions: { [K in TestFilterTerm]: string } = {
 export class TestingExplorerFilter extends BaseActionViewItem {
 	private input!: SuggestEnabledInputWithHistory;
 	private wrapper!: HTMLDivElement;
-	private readonly history: StoredValue<string[]> = this.instantiationService.createInstance(StoredValue, {
+	private readonly history: StoredValue<{ values: string[]; lastValue: string } | string[]> = this.instantiationService.createInstance(StoredValue, {
 		key: 'testing.filterHistory2',
 		scope: StorageScope.WORKSPACE,
 		target: StorageTarget.USER
@@ -65,9 +65,12 @@ export class TestingExplorerFilter extends BaseActionViewItem {
 		const wrapper = this.wrapper = dom.$('.testing-filter-wrapper');
 		container.appendChild(wrapper);
 
-		const history = this.history.get([]);
-		if (history.length) {
-			this.state.setText(history[history.length - 1]);
+		let history = this.history.get({ lastValue: '', values: [] });
+		if (history instanceof Array) {
+			history = { lastValue: '', values: history };
+		}
+		if (history.lastValue) {
+			this.state.setText(history.lastValue);
 		}
 
 		const input = this.input = this._register(this.instantiationService.createInstance(ContextScopedSuggestEnabledInputWithHistory, {
@@ -94,7 +97,7 @@ export class TestingExplorerFilter extends BaseActionViewItem {
 				value: this.state.text.value,
 				placeholderText: localize('testExplorerFilter', "Filter (e.g. text, !exclude, @tag)"),
 			},
-			history
+			history: history.values
 		}));
 		this._register(attachSuggestEnabledInputBoxStyler(input, this.themeService));
 
@@ -145,12 +148,7 @@ export class TestingExplorerFilter extends BaseActionViewItem {
 	 * Persists changes to the input history.
 	 */
 	public saveState() {
-		const history = this.input.getHistory();
-		if (history.length) {
-			this.history.store(history);
-		} else {
-			this.history.delete();
-		}
+		this.history.store({ lastValue: this.input.getValue(), values: this.input.getHistory() });
 	}
 
 	/**