[sim] Make SimDevice callbacks synchronous (#2861)

Asynchronous callbacks are more efficient but pose synchronization challenges;
other sim callbacks are synchronous but SimDevice ones were not.

wpilibj/src/test/java/edu/wpi/first/wpilibj/simulation/SimDeviceSimTest.java

@@ -12,20 +12,77 @@ import org.junit.jupiter.api.Test;
 import edu.wpi.first.hal.SimBoolean;
 import edu.wpi.first.hal.SimDevice;
 
+import java.util.concurrent.atomic.AtomicInteger;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertFalse;
 import static org.junit.jupiter.api.Assertions.assertTrue;
 
 class SimDeviceSimTest {
   @Test
   void testBasic() {
-    SimDevice dev = SimDevice.create("test");
-    SimBoolean devBool = dev.createBoolean("bool", false, false);
+    try (SimDevice dev = SimDevice.create("test")) {
+      SimBoolean devBool = dev.createBoolean("bool", false, false);
 
-    SimDeviceSim sim = new SimDeviceSim("test");
-    SimBoolean simBool = sim.getBoolean("bool");
+      SimDeviceSim sim = new SimDeviceSim("test");
+      SimBoolean simBool = sim.getBoolean("bool");
 
-    assertFalse(simBool.get());
-    simBool.set(true);
-    assertTrue(devBool.get());
+      assertFalse(simBool.get());
+      simBool.set(true);
+      assertTrue(devBool.get());
+    }
+  }
+
+  @Test
+  void testDeviceCreatedCallback() {
+    AtomicInteger callback1Counter = new AtomicInteger(0);
+    AtomicInteger callback2Counter = new AtomicInteger(0);
+
+    try (SimDevice otherdev = SimDevice.create("testnotDC");
+        SimDevice dev1 = SimDevice.create("testDC1")) {
+      SimDeviceSim sim = new SimDeviceSim("testDC1");
+      try (
+          CallbackStore callback1 = sim.registerDeviceCreatedCallback("testDC", (name, handle) -> {
+            callback1Counter.addAndGet(1);
+          }, false);
+          CallbackStore callback2 = sim.registerDeviceCreatedCallback("testDC", (name, handle) -> {
+            callback2Counter.addAndGet(1);
+          }, true)) {
+        assertEquals(0, callback1Counter.get(), "Callback 1 called early");
+        assertEquals(1, callback2Counter.get(), "Callback 2 called early or not initalized with existing devices");
+
+        SimDevice dev2 = SimDevice.create("testDC2");
+        dev2.close();
+
+        assertEquals(1, callback1Counter.get(), "Callback 1 called either more than once or not at all");
+        assertEquals(2, callback2Counter.get(), "Callback 2 called either more or less than twice");
+      }
+
+      SimDevice dev3 = SimDevice.create("testDC3");
+      dev3.close();
+
+      assertEquals(1, callback1Counter.get(), "Callback 1 called after closure");
+      assertEquals(2, callback2Counter.get(), "Callback 2 called after closure");
+    }
+  }
+
+  @Test
+  void testDeviceFreedCallback() {
+    AtomicInteger counter = new AtomicInteger(0);
+
+    SimDevice dev1 = SimDevice.create("testDF1");
+    SimDeviceSim sim = new SimDeviceSim("testDF1");
+    try (CallbackStore callback = sim.registerDeviceFreedCallback("testDF", (name, handle) -> {
+      counter.addAndGet(1);
+    }, false)) {
+      assertEquals(0, counter.get(), "Callback called early");
+      dev1.close();
+      assertEquals(1, counter.get(), "Callback called either more than once or not at all");
+    }
+
+    SimDevice dev2 = SimDevice.create("testDF2");
+    dev2.close();
+
+    assertEquals(1, counter.get(), "Callback called after closure");
   }
 }