fix types for task API props (microsoft#236735)

fix microsoft#231858

Author: meganrogge

src/vs/workbench/api/common/extHostTypes.ts

@@ -2343,7 +2343,9 @@ export class ShellExecution implements vscode.ShellExecution {
 				throw illegalArgument('command');
 			}
 			this._command = arg0;
-			this._args = arg1 as (string | vscode.ShellQuotedString)[];
+			if (arg1) {
+				this._args = arg1;
+			}
 			this._options = arg2;
 		} else {
 			if (typeof arg0 !== 'string') {
@@ -2380,7 +2382,7 @@ export class ShellExecution implements vscode.ShellExecution {
 		return this._args;
 	}
 
-	set args(value: (string | vscode.ShellQuotedString)[]) {
+	set args(value: (string | vscode.ShellQuotedString)[] | undefined) {
 		this._args = value || [];
 	}
 

src/vscode-dts/vscode.d.ts

@@ -8668,12 +8668,12 @@ declare module 'vscode' {
 		/**
 		 * The shell command. Is `undefined` if created with a full command line.
 		 */
-		command: string | ShellQuotedString;
+		command: string | ShellQuotedString | undefined;
 
 		/**
 		 * The shell args. Is `undefined` if created with a full command line.
 		 */
-		args: Array<string | ShellQuotedString>;
+		args: Array<string | ShellQuotedString> | undefined;
 
 		/**
 		 * The shell options used when the command line is executed in a shell.