Add test asserting display name setter is accessible on current IntelliJ build (#8809)

Follow-up to #8796.

Extracts the reflection lookup into a `@VisibleForTesting
getDisplaySetter()` method and adds a test asserting it returns
non-null. This serves as a regression guard: if JetBrains removes or
renames `setDisplayName` in a future build, the test will fail loudly
rather than the feature silently breaking for users (which was the
original failure mode in #8795).

Verified locally by running the test against the real SDK (passes), then
temporarily corrupting the method name to `setDisplayName_doesNotExist`
(fails with the expected assertion message).

I've reviewed the contributor guide and applied the relevant portions to
this PR.

Author: lukemmtt

src/io/flutter/run/LaunchState.java

@@ -60,6 +60,8 @@
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.List;
+import java.util.function.BiConsumer;
+import org.jetbrains.annotations.VisibleForTesting;
 
 /**
  * Launches a flutter app, showing it in the console.
@@ -168,20 +170,42 @@ protected RunContentDescriptor launch(@NotNull ExecutionEnvironment env) throws
     // The descriptor shows the run configuration name (e.g., `main.dart`) by default;
     // adding the device name will help users identify the instance when trying to operate a specific one.
     final String nameWithDeviceName = descriptor.getDisplayName() + " (" + device.deviceName() + ")";
-
-    try {
-      // RunContentDescriptor.setDisplayName() is protected, so we use reflection to call it.
-      final Method setDisplayName = RunContentDescriptor.class.getDeclaredMethod("setDisplayName", String.class);
-      setDisplayName.setAccessible(true);
-      setDisplayName.invoke(descriptor, nameWithDeviceName);
+    final BiConsumer<RunContentDescriptor, String> setter = getDisplaySetter();
+    if (setter != null) {
+      setter.accept(descriptor, nameWithDeviceName);
     }
-    catch (IllegalAccessException | InvocationTargetException | NoSuchMethodException e) {
-      FlutterUtils.info(LOG, "Error setting display name", e, true);
+    else {
+      FlutterUtils.info(LOG, "Could not find a way to set run tab display name", null, true);
     }
 
     return descriptor;
   }
 
+  /**
+   * Returns a function that sets the display name on a {@link RunContentDescriptor}, or null if unavailable.
+   * Uses reflection to call the protected {@code setDisplayName()} method.
+   * Exposed for testing to verify that the method is accessible on the current IntelliJ build.
+   */
+  @VisibleForTesting
+  @Nullable
+  static BiConsumer<RunContentDescriptor, String> getDisplaySetter() {
+    try {
+      final Method m = RunContentDescriptor.class.getDeclaredMethod("setDisplayName", String.class);
+      m.setAccessible(true);
+      return (descriptor, name) -> {
+        try {
+          m.invoke(descriptor, name);
+        }
+        catch (IllegalAccessException | InvocationTargetException e) {
+          FlutterUtils.info(LOG, "Error setting display name", e, true);
+        }
+      };
+    }
+    catch (NoSuchMethodException e) {
+      return null;
+    }
+  }
+
   private static Class classForName(String className) {
     try {
       return Class.forName(className);

testSrc/unit/io/flutter/run/LaunchStateTest.java

@@ -0,0 +1,21 @@
+/*
+ * Copyright 2026 The Chromium Authors. All rights reserved.
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+package io.flutter.run;
+
+import org.junit.Test;
+
+import static org.junit.Assert.assertNotNull;
+
+public class LaunchStateTest {
+
+  @Test
+  public void displaySetterIsAvailable() {
+    assertNotNull(
+      "setDisplayName not found on RunContentDescriptor — JetBrains may have removed or renamed it",
+      LaunchState.getDisplaySetter()
+    );
+  }
+}