ensure we mark discovery complete from cache

Author: jmcphers

src/vs/workbench/api/browser/positron/mainThreadLanguageRuntime.ts

@@ -1640,6 +1640,17 @@ export class MainThreadLanguageRuntime
 		this._proxy.$discoverLanguageRuntimes(disabledLanguageIds);
 	}
 
+	/**
+	 * Tell the extension host that initial discovery is over without asking
+	 * it to enumerate. Used by the warm-start fast path in
+	 * `RuntimeStartupService.discoverAllRuntimes`.
+	 *
+	 * (part of implementation of IRuntimeManager)
+	 */
+	markDiscoveryComplete(): void {
+		this._proxy.$markRuntimeDiscoveryComplete();
+	}
+
 	/**
 	 * Return a list of runtimes that are recommended for the current workspace.
 	 *

src/vs/workbench/api/common/positron/extHost.positron.protocol.ts

@@ -118,6 +118,7 @@ export interface ExtHostLanguageRuntimeShape {
 	$showProfileLanguageRuntime(handle: number): void;
 	$getLaunchInfo(handle: number): Promise<ILanguageRuntimeLaunchInfo | undefined>;
 	$discoverLanguageRuntimes(disabledLanguageIds: string[]): void;
+	$markRuntimeDiscoveryComplete(): void;
 	$recommendWorkspaceRuntimes(disabledLanguageIds: string[]): Promise<ILanguageRuntimeMetadata[]>;
 	$getDiscoveryRootSignature(languageId: string): Promise<IRuntimeRootSignature | undefined>;
 	$onDidRegisterLanguageRuntime(metadata: ILanguageRuntimeMetadata): void;

src/vs/workbench/api/common/positron/extHostLanguageRuntime.ts

@@ -1036,6 +1036,18 @@ export class ExtHostLanguageRuntime implements extHostProtocol.ExtHostLanguageRu
 		this._proxy.$completeLanguageRuntimeDiscovery();
 	}
 
+	/**
+	 * Set the discovery-complete flag without running an enumeration. Called
+	 * by the main thread on the warm-start fast path, where the discovery
+	 * cache has satisfied every manager and no real enumeration is needed.
+	 * Without this, late-registered runtime managers (those registered via
+	 * `registerLanguageRuntimeManager` after initial discovery) would never
+	 * see the flag flip and so would never self-discover.
+	 */
+	public $markRuntimeDiscoveryComplete(): void {
+		this._runtimeDiscoveryComplete = true;
+	}
+
 	/**
 	 * Notifies the extension host that the foreground session has changed.
 	 * This is forwarding the event from the main thread to the extension host.

src/vs/workbench/services/languageRuntime/common/languageRuntimeService.ts

@@ -969,6 +969,16 @@ export interface IRuntimeManager {
 	 */
 	discoverAllRuntimes(disabledLanguageIds: string[]): Promise<void>;
 
+	/**
+	 * Mark the manager's discovery-complete flag without running a real
+	 * enumeration. Used by the warm-start fast path: the discovery cache
+	 * already satisfied every bucket, so no manager needs to enumerate, but
+	 * the ext host still needs to know that initial discovery is over so
+	 * runtime managers registered later (via `registerLanguageRuntimeManager`)
+	 * self-trigger their own discovery.
+	 */
+	markDiscoveryComplete(): void;
+
 	/**
 	 * Recommend runtimes for this specific workspace.
 	 *

src/vs/workbench/services/runtimeStartup/common/runtimeStartup.ts

@@ -981,9 +981,15 @@ export class RuntimeStartupService extends Disposable implements IRuntimeStartup
 		if (managersNeedingFullDiscovery.length === 0) {
 			// Warm-start fast path. No manager has any work to do; transition
 			// straight to Complete. Mark every ext host's discovery flag true
-			// so the next rediscover invocation isn't fighting stale state.
+			// so the next rediscover invocation isn't fighting stale state, and
+			// signal each ext host that initial discovery is over so any
+			// runtime manager registered later (via the public
+			// `registerLanguageRuntimeManager` API) self-triggers its own
+			// discovery -- the IIFE inside the ext host is gated on a flag
+			// that, without this signal, would never flip on a warm start.
 			for (const manager of this._runtimeManagers) {
 				this._discoveryCompleteByExtHostId.set(manager.id, true);
+				manager.markDiscoveryComplete();
 			}
 			this.setStartupPhase(RuntimeStartupPhase.Complete);
 		} else {

src/vs/workbench/services/runtimeStartup/test/common/runtimeStartup.vitest.ts

@@ -83,6 +83,7 @@ function makeManager(opts: IManagerOptions): IRuntimeManager {
 	return {
 		id: opts.id,
 		discoverAllRuntimes: async () => { /* no-op for unit test */ },
+		markDiscoveryComplete: () => { /* no-op for unit test */ },
 		recommendWorkspaceRuntimes: async () => [],
 		managesRuntime: async (metadata) => ownsByPath.has(metadata.runtimePath),
 		validateMetadata: async (m) => m,