Add `ValidationUtils` and update ProGuard rules

This commit introduces a new `ValidationUtils.kt` file with email validation logic.
It also updates the ProGuard rules in `consumer-rules.pro` to keep runtime visible annotations and fields for `EventBus`.
Additionally, a `.gitignore` file is added to the `mylibrary` module to ignore the `build` directory, and the release build type in `app/build.gradle.kts` is now debuggable.

app/build.gradle.kts

@@ -43,6 +43,7 @@ android {
             applicationIdSuffix = NiaBuildType.DEBUG.applicationIdSuffix
         }
         release {
+            isDebuggable = true
             isMinifyEnabled = true
             applicationIdSuffix = NiaBuildType.RELEASE.applicationIdSuffix
             proguardFiles(getDefaultProguardFile("proguard-android-optimize.txt"), "proguard-rules.pro")

app/mylibrary/consumer-rules.pro

@@ -8,7 +8,7 @@
 }
 
 
--keepattributes *Annotation*
+-keepattributes RuntimeVisibleAnnotations
 
 -keep @interface com.example.mylibrary.OnEvent
 
@@ -23,6 +23,7 @@
 
 -whyareyoukeeping class com.example.mylibrary.EventBus {
  <methods>;
+<fields>;
 }
 
 

app/mylibrary/src/main/java/com/example/mylibrary/Worker.kt

@@ -31,4 +31,3 @@ object WorkerLoader {
         worker.doWork()
     }
 }
-

app/src/main/kotlin/com/google/samples/apps/nowinandroid/MainActivity.kt

@@ -103,6 +103,8 @@ class MainActivity : ComponentActivity() {
         runner.process(task1) // This will be executed.
 
 
+        isEmailValid("ajeshr@google.com")
+
 
         // We keep this as a mutable state, so that we can track changes inside the composition.
         // This allows us to react to dark/light mode changes.
@@ -234,4 +236,4 @@ class ImportantBackgroundTask {
     fun execute() {
         Log.e("ImportantBackgroundTask", "✅ Executing the important background task... ✅")
     }
-}
+}

app/src/main/kotlin/com/google/samples/apps/nowinandroid/ValidationUtils.kt

@@ -0,0 +1,33 @@
+/*
+ * Copyright 2025 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.google.samples.apps.nowinandroid
+
+import android.util.Log
+
+// A top-level function not inside a class
+fun isEmailValid(email: String): Boolean {
+    Log.e("crash", "nothing to crash")
+    return email.contains("@")
+}
+
+fun isSomethingElse(email: String): Boolean {
+    Log.e("crash", "nothing to crash")
+    return email.contains("@")
+}
+
+
+