Allow BuildConfig lookup when applicationId != namespace (#76)

Co-authored-by: dianaKhortiuk-frontegg <diana.khortiuk@frontegg.com>
Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>

Author: 3 people

android/build.gradle

@@ -62,6 +62,12 @@ android {
   kotlinOptions {
     jvmTarget = "17"
   }
+
+  testOptions {
+    unitTests.all {
+      useJUnit()
+    }
+  }
 }
 
 repositories {
@@ -81,6 +87,7 @@ dependencies {
   implementation 'io.reactivex.rxjava3:rxkotlin:3.0.1'
   implementation 'com.google.code.gson:gson:2.10.1'
   implementation 'com.frontegg.sdk:android:1.3.34'
+  testImplementation "junit:junit:4.13.2"
 }
 
 if (isNewArchitectureEnabled()) {

android/src/main/java/com/frontegg/reactnative/BuildConfigResolver.kt

@@ -0,0 +1,75 @@
+package com.frontegg.reactnative
+
+import android.content.Context
+import android.content.pm.PackageManager
+import android.util.Log
+
+/** Manifest meta-data name for the package that contains the host app [BuildConfig]. */
+const val BUILD_CONFIG_PACKAGE_META_DATA_NAME = "com.frontegg.reactnative.BUILD_CONFIG_PACKAGE"
+
+/**
+ * Ordered FQCN candidates for the host app [BuildConfig] class.
+ *
+ * @param applicationId Runtime application id ([Context.getPackageName]).
+ * @param manifestBuildConfigPackage Optional value from [BUILD_CONFIG_PACKAGE_META_DATA_NAME].
+ */
+fun buildConfigClassCandidates(
+    applicationId: String,
+    manifestBuildConfigPackage: String?,
+): List<String> {
+    val candidates = mutableListOf("$applicationId.BuildConfig")
+
+    val packageName = manifestBuildConfigPackage?.trim()?.takeIf { it.isNotEmpty() } ?: return candidates
+
+    val className =
+        if (packageName.endsWith(".BuildConfig")) packageName else "$packageName.BuildConfig"
+
+    if (className !in candidates) {
+        candidates.add(className)
+    }
+
+    return candidates
+}
+
+fun resolveBuildConfigClass(
+    applicationId: String,
+    manifestBuildConfigPackage: String?,
+): Class<*> {
+    val candidates = buildConfigClassCandidates(applicationId, manifestBuildConfigPackage)
+    var lastError: ClassNotFoundException? = null
+
+    for (className in candidates) {
+        try {
+            return Class.forName(className)
+        } catch (e: ClassNotFoundException) {
+            Log.w(TAG, "BuildConfig not found at $className, trying next candidate")
+            lastError = e
+        }
+    }
+
+    val hint =
+        if (manifestBuildConfigPackage.isNullOrBlank()) {
+            "If applicationId differs from your AGP namespace, add <meta-data " +
+                "android:name=\"$BUILD_CONFIG_PACKAGE_META_DATA_NAME\" " +
+                "android:value=\"your.namespace\" /> under <application>."
+        } else {
+            "Verify <meta-data android:name=\"$BUILD_CONFIG_PACKAGE_META_DATA_NAME\" /> " +
+                "points to the package that contains BuildConfig."
+        }
+
+    Log.e(TAG, "Could not load BuildConfig. Tried: ${candidates.joinToString()}. $hint")
+
+    throw lastError ?: ClassNotFoundException(
+        "No BuildConfig class found for applicationId=$applicationId"
+    )
+}
+
+fun Context.readBuildConfigPackageMetaData(): String? {
+    return try {
+        val appInfo = packageManager.getApplicationInfo(packageName, PackageManager.GET_META_DATA)
+        appInfo.metaData?.getString(BUILD_CONFIG_PACKAGE_META_DATA_NAME)
+    } catch (e: Exception) {
+        Log.w(TAG, "Failed to read $BUILD_CONFIG_PACKAGE_META_DATA_NAME from manifest", e)
+        null
+    }
+}

android/src/main/java/com/frontegg/reactnative/Utils.kt

@@ -15,9 +15,11 @@ interface ActivityProvider {
 val Context.fronteggConstants: FronteggConstants
     get() {
         val packageName = this.packageName
-        val className = "$packageName.BuildConfig"
         try {
-            val buildConfigClass = Class.forName(className)
+            val buildConfigClass = resolveBuildConfigClass(
+                packageName,
+                readBuildConfigPackageMetaData(),
+            )
 
             // Get the field from BuildConfig class
             val baseUrl = safeGetValueFromBuildConfig(buildConfigClass, "FRONTEGG_DOMAIN", "")
@@ -41,7 +43,6 @@ val Context.fronteggConstants: FronteggConstants
                 bundleId = this.packageName,
             )
         } catch (e: ClassNotFoundException) {
-            Log.e(TAG, "Class not found: $className")
             throw e
         }
     }

android/src/test/java/com/frontegg/reactnative/BuildConfigResolverTest.kt

@@ -0,0 +1,50 @@
+package com.frontegg.reactnative
+
+import org.junit.Assert.assertEquals
+import org.junit.Test
+
+class BuildConfigResolverTest {
+
+    @Test
+    fun buildConfigClassCandidates_usesApplicationIdWhenNoMetaData() {
+        assertEquals(
+            listOf("com.example.app.BuildConfig"),
+            buildConfigClassCandidates("com.example.app", null),
+        )
+    }
+
+    @Test
+    fun buildConfigClassCandidates_appendsMetaDataPackage() {
+        assertEquals(
+            listOf(
+                "com.healthie.app.flavor.BuildConfig",
+                "com.main.BuildConfig",
+            ),
+            buildConfigClassCandidates("com.healthie.app.flavor", "com.main"),
+        )
+    }
+
+    @Test
+    fun buildConfigClassCandidates_acceptsFullyQualifiedBuildConfigInMetaData() {
+        assertEquals(
+            listOf("com.example.app.BuildConfig", "com.main.BuildConfig"),
+            buildConfigClassCandidates("com.example.app", "com.main.BuildConfig"),
+        )
+    }
+
+    @Test
+    fun buildConfigClassCandidates_doesNotDuplicateWhenMetaDataMatchesApplicationId() {
+        assertEquals(
+            listOf("com.example.app.BuildConfig"),
+            buildConfigClassCandidates("com.example.app", "com.example.app"),
+        )
+    }
+
+    @Test
+    fun buildConfigClassCandidates_ignoresBlankMetaData() {
+        assertEquals(
+            listOf("com.example.app.BuildConfig"),
+            buildConfigClassCandidates("com.example.app", "   "),
+        )
+    }
+}

docs/setup.md

@@ -208,6 +208,18 @@ android {
 }
 ```
 
+### White-label apps (`applicationId` ≠ `namespace`)
+
+If your product flavors use different `applicationId` values but share one Java/Kotlin `namespace`, AGP generates `BuildConfig` under the **namespace** package, not under each flavor's `applicationId`. The SDK looks up `BuildConfig` by `applicationId` first; when that fails, add this under `<application>` in `android/app/src/main/AndroidManifest.xml` (use your shared namespace, without `.BuildConfig`):
+
+```xml
+<meta-data
+  android:name="com.frontegg.reactnative.BUILD_CONFIG_PACKAGE"
+  android:value="com.main" />
+```
+
+Apps where `applicationId` matches `namespace` do not need this entry.
+
 ### Enable Android AssetLinks
 
 To enable Android features like Magic Link authentication, password reset, account activation, and login with identity providers, follow the steps below.