feat: warn invalid platform folders (#5463)

* feat: handle empty platforms folder

* chore: shorter warning message

Co-authored-by: Igor Randjelovic <rigor789@gmail.com>

* fix: platformDirectoryItemCount variable name

* chore: explaining platformDirectoryItemCount check

Co-authored-by: Igor Randjelovic <rigor789@gmail.com>

Co-authored-by: Igor Randjelovic <rigor789@gmail.com>

lib/controllers/platform-controller.ts

@@ -143,6 +143,23 @@ export class PlatformController implements IPlatformController {
 		const hasPlatformDirectory = this.$fs.exists(
 			path.join(projectData.platformsDir, platformName)
 		);
+
+		if (hasPlatformDirectory) {
+			const platformDirectoryItemCount = this.$fs.readDirectory(
+				path.join(projectData.platformsDir, platformName)
+			).length;
+
+			// 5 is a magic number to approximate a valid platform folder
+			// any valid platform should contain at least 5 files
+			// we choose 5 to avoid false-positives due to system files like .DS_Store etc.
+			if (platformDirectoryItemCount <= 5) {
+				this.$logger.warn(
+					`The platforms/${platformName} folder appears to be invalid. If the build fails, run 'ns clean' and rebuild the app.`,
+					{ wrapMessageWithBorders: true }
+				);
+			}
+		}
+
 		const shouldAddNativePlatform =
 			!nativePrepare || !nativePrepare.skipNativePrepare;
 		const prepareInfo = this.$projectChangesService.getPrepareInfo(