[DAP] Send thread started/exited events

These events are needed to make sure that we don't list any stale
threads in the debugger, which produced some visual artifacts in LSP4E
(for instance, some threads still showing as available for resuming
after the program had completed).

plugins/org.eclipse.epsilon.eol.dap/src/org/eclipse/epsilon/eol/dap/EpsilonDebugAdapter.java

@@ -81,6 +81,8 @@
 import org.eclipse.lsp4j.debug.TerminateArguments;
 import org.eclipse.lsp4j.debug.TerminatedEventArguments;
 import org.eclipse.lsp4j.debug.Thread;
+import org.eclipse.lsp4j.debug.ThreadEventArguments;
+import org.eclipse.lsp4j.debug.ThreadEventArgumentsReason;
 import org.eclipse.lsp4j.debug.ThreadsResponse;
 import org.eclipse.lsp4j.debug.Variable;
 import org.eclipse.lsp4j.debug.VariablesArguments;
@@ -136,8 +138,8 @@ public void aboutToExecute(ModuleElement ast, IEolContext context) {
 				}
 
 				if (ast instanceof IEolModule) {
-					// Set up thread in our list if we don't have it yet
-					attachTo((IEolModule) ast);
+					ThreadState threadState = attachTo((IEolModule) ast);
+					sendThreadEvent(threadState.getThreadId(), ThreadEventArgumentsReason.STARTED);
 				}
 			}
 		}
@@ -171,7 +173,9 @@ public void finishedExecutingWithException(ModuleElement ast, EolRuntimeExceptio
 		protected void removeThreadFor(IEolModule module) {
 			synchronized (threads) {
 				for (Iterator<ThreadState> itThread = threads.values().iterator(); itThread.hasNext();) {
-					if (itThread.next().module == module) {
+					final ThreadState thread = itThread.next();
+					if (thread.module == module) {
+						sendThreadEvent(thread.getThreadId(), ThreadEventArgumentsReason.EXITED);
 						itThread.remove();
 					}
 				}
@@ -247,6 +251,10 @@ public ThreadState(int threadId, IEolModule module) {
 			}
 		}
 
+		public int getThreadId() {
+			return threadId;
+		}
+
 		@Override
 		public boolean isTerminated() {
 			return isTerminated;
@@ -286,19 +294,21 @@ protected BreakpointResult setBreakpoint(final String sourcePath, Integer localL
 		}
 	}
 
-	protected void attachTo(IEolModule module) {
+	protected ThreadState attachTo(IEolModule module) {
+		ThreadState thread;
 		synchronized (threads) {
-			for (ThreadState thread : threads.values()) {
-				if (thread.module == module) {
+			for (ThreadState t : threads.values()) {
+				if (t.module == module) {
 					// We already have attached to this module
-					return;
+					return t;
 				}
 			}
 
 			// Add a thread for this module
 			final int threadId = nextThread.getAndIncrement();
-			final ThreadState thread = new ThreadState(threadId, module);
+			thread = new ThreadState(threadId, module);
 			threads.put(threadId, thread);
+			sendThreadEvent(threadId, ThreadEventArgumentsReason.STARTED);
 			module.getContext().getExecutorFactory().setExecutionController(thread.debugger);
 		}
 
@@ -319,6 +329,8 @@ protected void attachTo(IEolModule module) {
 		module.getContext().setOutputStream(outStream);
 		final PrintStream errStream = createStream(module.getContext(), OutputEventArgumentsCategory.STDERR);
 		module.getContext().setErrorStream(errStream);
+
+		return thread;
 	}
 
 	public static final int FIRST_THREAD_ID = 1;
@@ -846,6 +858,16 @@ protected void sendStopped(int threadId, String reason) {
 		}
 	}
 
+	protected void sendThreadEvent(int threadId, String reason) {
+		if (client != null) {
+			ThreadEventArguments args = new ThreadEventArguments();
+			args.setReason(reason);
+			args.setThreadId(threadId);
+			client.thread(args);
+		}
+	}
+
+
 	public IEolModule getModule() {
 		return mainModule;
 	}

tests/org.eclipse.epsilon.eol.dap.test/src/org/eclipse/epsilon/eol/dap/test/AbstractEpsilonDebugAdapterTest.java

@@ -11,6 +11,7 @@
 
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertNotNull;
+import static org.junit.Assert.fail;
 
 import java.io.File;
 import java.io.IOException;
@@ -40,6 +41,8 @@
 import org.eclipse.lsp4j.debug.StackTraceArguments;
 import org.eclipse.lsp4j.debug.StackTraceResponse;
 import org.eclipse.lsp4j.debug.StoppedEventArguments;
+import org.eclipse.lsp4j.debug.ThreadEventArguments;
+import org.eclipse.lsp4j.debug.ThreadEventArgumentsReason;
 import org.eclipse.lsp4j.debug.ThreadsResponse;
 import org.eclipse.lsp4j.debug.Variable;
 import org.eclipse.lsp4j.debug.VariablesArguments;
@@ -63,6 +66,7 @@ protected class TestClient implements IDebugProtocolClient {
 		private ExitedEventArguments exitedArgs;
 
 		private List<OutputEventArguments> outputs = new ArrayList<>();
+		private List<ThreadEventArguments> threadEvents = new ArrayList<>();
 
 		@Override
 		public void stopped(StoppedEventArguments args) {
@@ -81,6 +85,11 @@ public void output(OutputEventArguments args) {
 			this.outputs.add(args);
 		}
 
+		@Override
+		public void thread(ThreadEventArguments args) {
+			this.threadEvents.add(args);
+		}
+
 		public StoppedEventArguments getStoppedArgs() {
 			return stoppedArgs;
 		}
@@ -92,7 +101,10 @@ public ExitedEventArguments getExitedArgs() {
 		public List<OutputEventArguments> getOutputs() {
 			return outputs;
 		}
-
+
+		public List<ThreadEventArguments> getThreadEvents() {
+			return threadEvents;
+		}
 	}
 
 	protected static final File BASE_RESOURCE_FOLDER = new File("../org.eclipse.epsilon.eol.dap.test/epsilon/");
@@ -262,4 +274,22 @@ protected Map<String, Variable> getVariablesFromTopStackFrame() throws Exception
 		return variablesByName;
 	}
 
+	protected void assertThreadStarted(int threadId) {
+		assertThreadEventWithReasonExists(threadId, ThreadEventArgumentsReason.STARTED);
+	}
+
+	protected void assertThreadExited(int threadId) {
+		assertThreadEventWithReasonExists(threadId, ThreadEventArgumentsReason.EXITED);
+	}
+
+	protected void assertThreadEventWithReasonExists(int threadId, final String reason) {
+		for (ThreadEventArguments ev : client.getThreadEvents()) {
+			if (ev.getThreadId() == threadId && reason.equals(ev.getReason())) {
+				return;
+			}
+		}
+
+		fail(String.format("Expected thread %d to have a %s event", threadId, reason));
+	}
+
 }

tests/org.eclipse.epsilon.eol.dap.test/src/org/eclipse/epsilon/eol/dap/test/eol/StandaloneEolTest.java

@@ -60,6 +60,7 @@ public void breakThenContinue() throws Exception {
 
 		// Wait for the client to be stopped at the breakpoint
 		assertStoppedBecauseOf(StoppedEventArgumentsReason.BREAKPOINT);
+		assertThreadStarted(EpsilonDebugAdapter.FIRST_THREAD_ID);
 		assertEquals("The debugger should mention the stopped thread",
 			(Integer) EpsilonDebugAdapter.FIRST_THREAD_ID, client.getStoppedArgs().getThreadId());
 
@@ -98,6 +99,7 @@ public void breakThenContinue() throws Exception {
 
 		// Execution should complete successfully
 		assertProgramCompletedSuccessfully();
+		assertThreadExited(EpsilonDebugAdapter.FIRST_THREAD_ID);
 
 		final String expected = "Hello Bob Someone"
 			+ System.lineSeparator()