fix: resolve default view for markdown files on first startup

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

@@ -125,7 +125,7 @@ export class EditorResolverService extends Disposable implements IEditorResolver
 		let resource = EditorResourceAccessor.getCanonicalUri(untypedEditor, { supportSideBySide: SideBySideEditor.PRIMARY });
 
 		// If it was resolved before we await for the extensions to activate and then proceed with resolution or else the backing extensions won't be registered
-		if (this.cache && resource && this.resourceMatchesCache(resource)) {
+		if (this.cache && resource && (this.resourceMatchesCache(resource) || this.resourceMatchesUserAssociation(resource))) {
 			await this.extensionService.whenInstalledExtensionsRegistered();
 		}
 
@@ -825,6 +825,22 @@ export class EditorResolverService extends Disposable implements IEditorResolver
 		this.storageService.store(EditorResolverService.cacheStorageID, JSON.stringify(Array.from(cacheStorage)), StorageScope.PROFILE, StorageTarget.MACHINE);
 	}
 
+	/**
+	 * Checks if a resource matches any user-configured editor association that
+	 * points to a non-default editor. This ensures that on first startup (when
+	 * the cache is empty), we still wait for extensions to register before
+	 * resolving the editor, so that user-configured custom editors are available.
+	 */
+	private resourceMatchesUserAssociation(resource: URI): boolean {
+		const userAssociations = this.getAllUserAssociations();
+		for (const association of userAssociations) {
+			if (association.filenamePattern && association.viewType !== DEFAULT_EDITOR_ASSOCIATION.id && globMatchesResource(association.filenamePattern, resource)) {
+				return true;
+			}
+		}
+		return false;
+	}
+
 	private resourceMatchesCache(resource: URI): boolean {
 		if (!this.cache) {
 			return false;

src/vs/workbench/services/editor/test/browser/editorResolverService.test.ts

@@ -12,7 +12,8 @@ import { EditorPart } from '../../../../browser/parts/editor/editorPart.js';
 import { DiffEditorInput } from '../../../../common/editor/diffEditorInput.js';
 import { EditorResolverService } from '../../browser/editorResolverService.js';
 import { IEditorGroupsService } from '../../common/editorGroupsService.js';
-import { IEditorResolverService, ResolvedStatus, RegisteredEditorPriority } from '../../common/editorResolverService.js';
+import { IEditorResolverService, ResolvedStatus, RegisteredEditorPriority, editorsAssociationsSettingId } from '../../common/editorResolverService.js';
+import { TestConfigurationService } from '../../../../../platform/configuration/test/common/testConfigurationService.js';
 import { createEditorPart, ITestInstantiationService, TestFileEditorInput, TestServiceAccessor, workbenchInstantiationService } from '../../../../test/browser/workbenchTestServices.js';
 
 suite('EditorResolverService', () => {
@@ -455,4 +456,69 @@ suite('EditorResolverService', () => {
 
 		registeredSingleEditor.dispose();
 	});
+
+	test('User-configured editor association resolves on first startup with empty cache #244597', async () => {
+		const CUSTOM_EDITOR_INPUT_ID = 'testCustomEditorInput';
+
+		// Set up a configuration with a user-configured editor association
+		const instantiationService = workbenchInstantiationService({
+			configurationService: () => new TestConfigurationService({
+				[editorsAssociationsSettingId]: {
+					'*.md': 'CUSTOM_MD_EDITOR'
+				}
+			})
+		}, disposables);
+
+		const part = await createEditorPart(instantiationService, disposables);
+		instantiationService.stub(IEditorGroupsService, part);
+
+		const editorResolverService = instantiationService.createInstance(EditorResolverService);
+		disposables.add(editorResolverService);
+
+		// Register both the default text editor and the custom markdown editor with 'option' priority
+		// (matching how markdown preview is registered in package.json)
+		const defaultEditor = editorResolverService.registerEditor('*',
+			{
+				id: 'default',
+				label: 'Default Editor',
+				detail: 'Default',
+				priority: RegisteredEditorPriority.default
+			},
+			{},
+			{
+				createEditorInput: ({ resource }, group) => ({ editor: new TestFileEditorInput(URI.parse(resource.toString()), TEST_EDITOR_INPUT_ID) })
+			}
+		);
+
+		const customEditor = editorResolverService.registerEditor('*.md',
+			{
+				id: 'CUSTOM_MD_EDITOR',
+				label: 'Markdown Preview',
+				detail: 'Markdown Preview Details',
+				priority: RegisteredEditorPriority.option
+			},
+			{},
+			{
+				createEditorInput: ({ resource }, group) => ({ editor: new TestFileEditorInput(URI.parse(resource.toString()), CUSTOM_EDITOR_INPUT_ID) })
+			}
+		);
+
+		// Resolve a .md file - should use the custom editor due to user association
+		const resultingResolution = await editorResolverService.resolveEditor(
+			{ resource: URI.file('test.md') },
+			part.activeGroup
+		);
+		assert.ok(resultingResolution);
+		assert.notStrictEqual(typeof resultingResolution, 'number');
+		if (resultingResolution !== ResolvedStatus.ABORT && resultingResolution !== ResolvedStatus.NONE) {
+			assert.strictEqual(resultingResolution.editor.typeId, CUSTOM_EDITOR_INPUT_ID,
+				'Should resolve to custom editor when user has configured editor association');
+			resultingResolution.editor.dispose();
+		} else {
+			assert.fail('Expected editor to resolve successfully');
+		}
+
+		defaultEditor.dispose();
+		customEditor.dispose();
+	});
 });