Merge branch 'fix/release-build-jni-keep-rules'

Release builds aborted on the first callback of every test: R8 renamed the
IperfCallback implementation and its methods, so the JNI GetMethodID lookups
resolved nothing. Adds the keep rules, and makes the native side report a
failed lookup instead of aborting the process on the next JNI call.

Debug builds do not minify, so every on-device check until now passed while the
shipping artifact was broken. Found by running the release APK during release
preparation.

Verified with the release APK on an XQ-AS72: clean run at 806 Mbits/sec,
matching the server's own figure.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

android/app/build.gradle.kts

@@ -37,6 +37,13 @@ android {
             // TODO: Add your own signing config for the release build.
             // Signing with the debug keys for now, so `flutter run --release` works.
             signingConfig = signingConfigs.getByName("debug")
+
+            // proguard-rules.pro keeps the names JNI resolves at runtime.
+            // Without it a release build aborts on the first callback.
+            proguardFiles(
+                getDefaultProguardFile("proguard-android-optimize.txt"),
+                "proguard-rules.pro",
+            )
         }
     }
 

android/app/proguard-rules.pro

@@ -0,0 +1,21 @@
+# JNI reaches these by name. R8 renames by default, so without these rules a
+# release build resolves nothing: GetMethodID("onOutput", ...) returns NULL,
+# raises NoSuchMethodError, and the next JNI call aborts the process with
+#   NoSuchMethodError: no non-static method "Lp0;.onOutput(Ljava/lang/String;)V"
+# Debug builds do not minify, so this only ever appears in release.
+
+# The plugin object holds the native method declarations and is looked up from
+# C by its fully qualified name (Java_com_novoyuuparosk_iperf3gui_IperfRunner_*).
+-keep class com.novoyuuparosk.iperf3gui.IperfRunner { *; }
+
+# The callback interface and everything implementing it: iperf_jni.c resolves
+# onOutput/onError/onComplete by name on the concrete object's class, so the
+# implementors' method names must survive too, not just the interface's.
+-keep interface com.novoyuuparosk.iperf3gui.IperfRunner$IperfCallback { *; }
+-keep class * implements com.novoyuuparosk.iperf3gui.IperfRunner$IperfCallback { *; }
+
+# Belt and braces for any future native method: keep the name of any class
+# declaring one, and the native methods themselves.
+-keepclasseswithmembernames,includedescriptorclasses class * {
+    native <methods>;
+}

android/app/src/main/cpp/iperf_jni.c

@@ -86,6 +86,21 @@ struct iperf_run_state {
  * iperf_run_client() and cleared after it returns. */
 static struct iperf_run_state *g_current_state = NULL;
 
+/* Resolve a method ID, clearing the exception a failed lookup leaves behind.
+ *
+ * GetMethodID raises NoSuchMethodError on failure, and any further JNI call
+ * made while an exception is pending aborts the process. Returning NULL and
+ * clearing lets the caller fail on its own terms. */
+static jmethodID resolve_method(JNIEnv *env, jclass cls,
+                                const char *name, const char *sig) {
+    jmethodID mid = (*env)->GetMethodID(env, cls, name, sig);
+    if ((*env)->ExceptionCheck(env)) {
+        (*env)->ExceptionClear(env);
+        return NULL;
+    }
+    return mid;
+}
+
 /* Helper: invoke the output callback via CallVoidMethod */
 static void signal_output(JNIEnv *env, struct iperf_run_state *state,
                           const char *msg) {
@@ -272,13 +287,25 @@ Java_com_novoyuuparosk_iperf3gui_IperfRunner_runIperfLive(
 
     /* Resolve callback method IDs up front so failures can be reported. */
     jclass callback_cls = (*env)->GetObjectClass(env, callback);
-    jmethodID mid_output = (*env)->GetMethodID(
+    jmethodID mid_output = resolve_method(
             env, callback_cls, "onOutput", "(Ljava/lang/String;)V");
-    jmethodID mid_error = (*env)->GetMethodID(
+    jmethodID mid_error = resolve_method(
             env, callback_cls, "onError", "(Ljava/lang/String;)V");
-    jmethodID mid_complete = (*env)->GetMethodID(
+    jmethodID mid_complete = resolve_method(
             env, callback_cls, "onComplete", "()V");
 
+    /* If the names did not resolve there is no way to report anything: the
+     * reporting path is the thing that is missing. Bail out loudly instead.
+     *
+     * In practice this means R8 renamed the callback in a release build and
+     * android/app/proguard-rules.pro has stopped covering it. */
+    if (!mid_output || !mid_error || !mid_complete) {
+        LOGE("Callback methods did not resolve (onOutput=%p onError=%p "
+             "onComplete=%p) — check the -keep rules for IperfCallback",
+             mid_output, mid_error, mid_complete);
+        return;
+    }
+
     /* Report a startup failure directly on the callback object and finish,
      * so Dart's completer always resolves instead of waiting for a timeout. */
     #define FAIL_EARLY(msg) do {                                              \