introduce undefined target platform

src/vs/platform/extensionManagement/common/extensionGalleryService.ts

@@ -313,7 +313,7 @@ function getIsPreview(flags: string): boolean {
 }
 
 function getTargetPlatform(version: IRawGalleryExtensionVersion): TargetPlatform {
-	return version.targetPlatform ? toTargetPlatform(version.targetPlatform) : TargetPlatform.UNIVERSAL;
+	return version.targetPlatform ? toTargetPlatform(version.targetPlatform) : TargetPlatform.UNDEFINED;
 }
 
 function getAllTargetPlatforms(rawGalleryExtension: IRawGalleryExtension): TargetPlatform[] {
@@ -350,6 +350,11 @@ function isTargetPlatformCompatible(extensionTargetPlatform: TargetPlatform, all
 		return false;
 	}
 
+	// Compatible when extension target platform is not defined
+	if (extensionTargetPlatform === TargetPlatform.UNDEFINED) {
+		return true;
+	}
+
 	// Compatible when extension target platform is universal
 	if (extensionTargetPlatform === TargetPlatform.UNIVERSAL) {
 		return true;

src/vs/platform/extensionManagement/common/extensionManagement.ts

@@ -34,6 +34,7 @@ export const enum TargetPlatform {
 
 	UNIVERSAL = 'universal',
 	UNKNOWN = 'unknown',
+	UNDEFINED = 'undefined',
 }
 
 export function toTargetPlatform(targetPlatform: string): TargetPlatform {