make caching more robust; fixes #69534

src/vs/workbench/api/electron-browser/mainThreadDebugService.ts

@@ -285,6 +285,12 @@ export class MainThreadDebugService implements MainThreadDebugServiceShape, IDeb
 
 	// dto helpers
 
+	public $sessionCached(sessionID: string) {
+		// remember that the EH has cached the session and we do not have to send it again
+		this._sessions.add(sessionID);
+	}
+
+
 	getSessionDto(session: undefined): undefined;
 	getSessionDto(session: IDebugSession): IDebugSessionDto;
 	getSessionDto(session: IDebugSession | undefined): IDebugSessionDto | undefined;
@@ -294,7 +300,7 @@ export class MainThreadDebugService implements MainThreadDebugServiceShape, IDeb
 			if (this._sessions.has(sessionID)) {
 				return sessionID;
 			} else {
-				this._sessions.add(sessionID);
+				// this._sessions.add(sessionID); 	// #69534: see $sessionCached above
 				return {
 					id: sessionID,
 					type: session.configuration.type,

src/vs/workbench/api/node/extHost.protocol.ts

@@ -636,6 +636,7 @@ export type DebugSessionUUID = string;
 
 export interface MainThreadDebugServiceShape extends IDisposable {
 	$registerDebugTypes(debugTypes: string[]): void;
+	$sessionCached(sessionID: string): void;
 	$acceptDAMessage(handle: number, message: DebugProtocol.ProtocolMessage): void;
 	$acceptDAError(handle: number, name: string, message: string, stack: string): void;
 	$acceptDAExit(handle: number, code: number, signal: string): void;

src/vs/workbench/api/node/extHostDebugService.ts

@@ -794,19 +794,23 @@ export class ExtHostDebugService implements ExtHostDebugServiceShape {
 			if (typeof dto === 'string') {
 				return this._debugSessions.get(dto);
 			} else {
-				const folder = await this.getFolder(dto.folderUri);
-				const debugSession = new ExtHostDebugSession(this._debugServiceProxy, dto.id, dto.type, dto.name, folder, dto.configuration);
-				this._debugSessions.set(debugSession.id, debugSession);
-				return debugSession;
+				let ds = this._debugSessions.get(dto.id);
+				if (!ds) {
+					const folder = await this.getFolder(dto.folderUri);
+					ds = new ExtHostDebugSession(this._debugServiceProxy, dto.id, dto.type, dto.name, folder, dto.configuration);
+					this._debugSessions.set(ds.id, ds);
+					this._debugServiceProxy.$sessionCached(ds.id);
+				}
+				return ds;
 			}
 		}
 		return undefined;
 	}
 
-	private async getFolder(_folderUri: UriComponents | undefined): Promise<vscode.WorkspaceFolder | undefined> {
+	private getFolder(_folderUri: UriComponents | undefined): Promise<vscode.WorkspaceFolder | undefined> {
 		if (_folderUri) {
 			const folderURI = URI.revive(_folderUri);
-			return await this._workspaceService.resolveWorkspaceFolder(folderURI);
+			return this._workspaceService.resolveWorkspaceFolder(folderURI);
 		}
 		return undefined;
 	}