Enhance: Bind extension to product flavor for robust type safety

This commit refactors flavor configuration in NiaFlavor.kt. The previous implementation relied on runtime type checks for ApplicationExtension and ApplicationProductFlavor, whereas the updated code leverages generics to explicitly bind the extension (E) to the product flavor (F). This change eliminates unnecessary runtime checks and enhances compile-time type safety. Additionally, the introduction of @JvmName(“configureFlavorsImpl”) resolves JVM signature clashes, streamlining our DSL and improving overall code clarity.

Author: laynepenney

build-logic/convention/src/main/kotlin/com/google/samples/apps/nowinandroid/NiaFlavor.kt

@@ -1,7 +1,6 @@
 package com.google.samples.apps.nowinandroid
 
 import com.android.build.api.dsl.ApplicationExtension
-import com.android.build.api.dsl.ApplicationProductFlavor
 import com.android.build.api.dsl.CommonExtension
 import com.android.build.api.dsl.ProductFlavor
 
@@ -19,11 +18,25 @@ enum class NiaFlavor(val dimension: FlavorDimension, val applicationIdSuffix: St
     prod(FlavorDimension.contentType),
 }
 
-fun configureFlavors(
-    commonExtension: CommonExtension<*, *, *, *, *, *>,
+fun <E : CommonExtension<*, *, *, F, *, *>, F : ProductFlavor> configureFlavors(
+    commonExtension: E,
     flavorConfigurationBlock: ProductFlavor.(flavor: NiaFlavor) -> Unit = {},
 ) {
-    commonExtension.apply {
+    when (commonExtension) {
+        is ApplicationExtension -> commonExtension.configureFlavors { nia ->
+            flavorConfigurationBlock(this, nia)
+            this.applicationIdSuffix = nia.applicationIdSuffix
+        }
+
+        else -> commonExtension.configureFlavors(flavorConfigurationBlock)
+    }
+}
+
+@JvmName("configureFlavorsImpl")
+private inline fun <E : CommonExtension<*, *, *, F, *, *>, F : ProductFlavor> E.configureFlavors(
+    crossinline flavorConfigurationBlock: F.(flavor: NiaFlavor) -> Unit = {},
+) {
+    apply {
         FlavorDimension.values().forEach { flavorDimension ->
             flavorDimensions += flavorDimension.name
         }
@@ -33,11 +46,6 @@ fun configureFlavors(
                 register(niaFlavor.name) {
                     dimension = niaFlavor.dimension.name
                     flavorConfigurationBlock(this, niaFlavor)
-                    if (this@apply is ApplicationExtension && this is ApplicationProductFlavor) {
-                        if (niaFlavor.applicationIdSuffix != null) {
-                            applicationIdSuffix = niaFlavor.applicationIdSuffix
-                        }
-                    }
                 }
             }
         }