fix: remove WebMessageListener before WebView.destroy() to prevent memory leaks (#431)

Author: evan-masseau

sdk/forms/src/main/java/com/klaviyo/forms/webview/KlaviyoWebViewClient.kt

@@ -11,6 +11,9 @@ import android.webkit.WebResourceResponse
 import android.webkit.WebView
 import android.webkit.WebViewClient as AndroidWebViewClient
 import androidx.core.net.toUri
+import androidx.webkit.WebViewCompat
+import androidx.webkit.WebViewFeature.WEB_MESSAGE_LISTENER
+import androidx.webkit.WebViewFeature.isFeatureSupported
 import com.klaviyo.core.Registry
 import com.klaviyo.core.config.Clock
 import com.klaviyo.core.utils.WeakReferenceDelegate
@@ -141,6 +144,18 @@ internal class KlaviyoWebViewClient() : AndroidWebViewClient(), WebViewClient, J
         webView?.let { webView ->
             Registry.threadHelper.runOnUiThread {
                 Registry.log.verbose("Clear IAF WebView reference")
+                val nativeBridge = Registry.get<NativeBridge>()
+
+                if (isFeatureSupported(WEB_MESSAGE_LISTENER)) {
+                    // Explicitly remove the listener: On some vendors' implementation of webview,
+                    // failure to remove the listener results in a memory leak.
+                    WebViewCompat.removeWebMessageListener(webView, nativeBridge.name)
+                } else {
+                    // For completeness, remove the JS interface if WEB_MESSAGE_LISTENER
+                    // is not supported, although [destroy] should clean this up internally
+                    webView.removeJavascriptInterface(nativeBridge.name)
+                }
+
                 webView.destroy()
                 this.webView = null
             }

sdk/forms/src/test/java/com/klaviyo/forms/webview/KlaviyoWebViewClientTest.kt

@@ -151,6 +151,9 @@ class KlaviyoWebViewClientTest : BaseTest() {
 
         mockkStatic(WebViewCompat::class)
         every { WebViewCompat.addWebMessageListener(any(), any(), any(), any()) } just runs
+        every { WebViewCompat.removeWebMessageListener(any(), any()) } just runs
+
+        every { anyConstructed<KlaviyoWebView>().removeJavascriptInterface(any()) } just runs
     }
 
     @After
@@ -345,6 +348,28 @@ class KlaviyoWebViewClientTest : BaseTest() {
         verifyDestroy()
     }
 
+    @Test
+    fun `destroyWebView removes WebMessageListener when supported`() {
+        val client = KlaviyoWebViewClient()
+        client.initializeWebView()
+        client.destroyWebView()
+
+        verify { WebViewCompat.removeWebMessageListener(any(), eq("MockNativeBridge")) }
+    }
+
+    @Test
+    fun `destroyWebView removes JavascriptInterface when WebMessageListener unsupported`() {
+        every { WebViewFeature.isFeatureSupported(WebViewFeature.WEB_MESSAGE_LISTENER) } returns false
+        every { anyConstructed<KlaviyoWebView>().addJavascriptInterface(any(), any()) } just runs
+
+        val client = KlaviyoWebViewClient()
+        client.initializeWebView()
+        client.destroyWebView()
+
+        verify { anyConstructed<KlaviyoWebView>().removeJavascriptInterface(eq("MockNativeBridge")) }
+        verify(inverse = true) { WebViewCompat.removeWebMessageListener(any(), any()) }
+    }
+
     @Test
     fun `verify detachWebView fails on a null webview`() {
         val client = KlaviyoWebViewClient()