feat(android): log build warnings if res files have invalid names

- Restored old behavior (before Titanium 9.0.0) where we used to rename invalid "res" files into valid names.
  * No longer post-fixing MD5 hash to res files anymore (which was the old behavior).
- TIMOB-27718: Now log a build warning for every "res" file name that is invalid.

android/cli/commands/_build.js

@@ -2606,7 +2606,10 @@ AndroidBuilder.prototype.copyResources = function copyResources(next) {
 				let isDrawable = false;
 
 				if (m && m.length >= 4 && m[3]) {
-					const destFilename = m[3].toLowerCase();
+					const destFilename = m[3];
+					const destLowerCaseFilename = destFilename.toLowerCase();
+					const extMatch = destLowerCaseFilename.match(drawableExtRegExp);
+					const origExt = extMatch && extMatch[1] || '';
 
 					destDir = path.join(
 						_t.buildAppMainResDir,
@@ -2615,11 +2618,30 @@ AndroidBuilder.prototype.copyResources = function copyResources(next) {
 
 					if (splashScreenRegExp.test(filename)) {
 						// we have a splash screen image
-						const extMatch = destFilename.match(drawableExtRegExp);
-						const origExt = extMatch && extMatch[1] || '';
 						to = path.join(destDir, 'background' + origExt);
 					} else {
-						to = path.join(destDir, filename);
+						// We have a drawable image file. (Rename it if it contains invalid characters.)
+						let warningMessages = [];
+						if (destFilename.includes('/') || destFilename.includes('\\')) {
+							warningMessages.push(__('- Files cannot be put into subdirectories.'));
+						}
+						let destFilteredFilename = destLowerCaseFilename.replace(drawableExtRegExp, '');
+						destFilteredFilename = destFilteredFilename.replace(/[^a-z0-9_]/g, '_') + origExt;
+						if (destFilteredFilename !== destFilename) {
+							warningMessages.push(__('- Names must contain only lowercase a-z, 0-9, or underscore.'));
+						}
+						if (/^\d/.test(destFilteredFilename)) {
+							warningMessages.push(__('- Names cannot start with a number.'));
+							destFilteredFilename = '_' + destFilteredFilename;
+						}
+						if (warningMessages.length > 0) {
+							_t.logger.warn(__(`Invalid "res" file: ${path.relative(_t.projectDir, from)}`));
+							for (const nextMessage of warningMessages) {
+								_t.logger.warn(nextMessage);
+							}
+							_t.logger.warn(__(`- Titanium will rename to: ${destFilteredFilename}`));
+						}
+						to = path.join(destDir, destFilteredFilename);
 					}
 					isDrawable = true;
 				} else if (m = relPath.match(relSplashScreenRegExp)) {

android/titanium/src/java/org/appcelerator/titanium/util/TiUIHelper.java

@@ -905,17 +905,33 @@ private static String getResourceKeyForImage(String url)
 		}
 
 		// This is a "res" drawable references. Remove file extension since Android strips them off in built app.
-		// Note: Periods are not legal characters in resource names. So, it's okay to strip off the 1st one found.
-		int index = path.indexOf('.');
+		final String NINE_PATCH_EXTENSION = ".9.png";
 		String pathWithoutExtension = path;
+		int index = -1;
+		if (path.toLowerCase().endsWith(NINE_PATCH_EXTENSION)) {
+			index = path.length() - NINE_PATCH_EXTENSION.length();
+		} else {
+			index = path.lastIndexOf('.');
+			if ((index >= 0) && (path.indexOf('/', index) >= 0)) {
+				index = -1;
+			}
+		}
 		if (index > 0) {
 			pathWithoutExtension = path.substring(0, index);
 		} else if (index == 0) {
 			pathWithoutExtension = null;
 		}
 
-		// If we've extracted a valid "res" path, then store it for fast access later.
+		// Handle extracted "res" file path.
 		if ((pathWithoutExtension != null) && !pathWithoutExtension.isEmpty()) {
+			// If "res" file path is invalid, then make it valid.
+			// Must be all lower-case, can only contain letters/number, and cannot start with a number.
+			pathWithoutExtension = pathWithoutExtension.toLowerCase().replaceAll("[^a-z0-9_]", "_");
+			if (Character.isDigit(pathWithoutExtension.charAt(0))) {
+				pathWithoutExtension = "_" + pathWithoutExtension;
+			}
+
+			// Add "res" path to dictionary for fast access later.
 			TiUIHelper.resourceImageKeys.put(url, pathWithoutExtension);
 		}