Use more specific exception when @JsonDelegates throw an exception

This exception is thrown when the endpoint is created, not as a result of
a receiving a message. This is generally a coding error, so make this
exception the same as the other exceptions thrown by recursiveFindRpcMethods.

Included is adding additional tests to ensure coverage of some
previously missing uses cases.

Code cleanup done as part of #802

CHANGELOG.md

@@ -5,6 +5,7 @@
 Fixed issues: <https://github.com/eclipse-lsp4j/lsp4j/milestone/34?closed=1>
 
   * The exception handling around throwing `ResponseErrorException` has been improved to ensure that it is unwrapped to the expected `ResponseError` on the receiving side.
+  In addition, `@JsonDelegate`s that throw exceptions have their checked exceptions wrapped in the more narrow `IllegalStateException` instead of a `RuntimeException`.
     * See [#802](https://github.com/eclipse-lsp4j/lsp4j/issues/802) for detailed discussion.
 
 Breaking API changes:

org.eclipse.lsp4j.jsonrpc/src/main/java/org/eclipse/lsp4j/jsonrpc/services/GenericEndpoint.java

@@ -83,7 +83,7 @@ protected void recursiveFindRpcMethods(Object current, Set<Class<?>> visited, Se
 					LOG.fine("A delegate object is null, jsonrpc methods of '" + method + "' are ignored");
 				}
 			} catch (InvocationTargetException | IllegalAccessException e) {
-				throw new RuntimeException(e);
+				throw new IllegalStateException("An exception occurred while executing JsonDelegate method " + method, e);
 			}
 		});
 	}

org.eclipse.lsp4j.jsonrpc/src/test/java/org/eclipse/lsp4j/jsonrpc/test/annotations/impl/GenericEndpointTest.java

@@ -1,5 +1,5 @@
 /******************************************************************************
- * Copyright (c) 2016 TypeFox and others.
+ * Copyright (c) 2016, 2024 TypeFox and others.
  * 
  * This program and the accompanying materials are made available under the
  * terms of the Eclipse Public License v. 2.0 which is available at
@@ -42,6 +42,26 @@ public OtherThing doDelegate() {
 		}
 
 	}
+
+	public static class DelegateThrows {
+		@JsonDelegate
+		public OtherThing doDelegate() throws Exception {
+			throw new Exception("Exception in doDelegate");
+		}
+	}
+
+	public static class DuplicateNames1 {
+		@JsonNotification
+		public void duplicateName() {
+			Assert.fail("Should be unreachable");
+		}
+	}
+	public static class DuplicateNames2 {
+		@JsonNotification
+		public void duplicateName() {
+			Assert.fail("Should be unreachable");
+		}
+	}
 
 	public static class Bar {
 
@@ -79,7 +99,25 @@ public void testSimple() {
 
 		Assert.assertEquals(2, foo.calls);
 	}
-
+
+	@Test
+	public void testDelegateThrows() {
+		DelegateThrows delegateThrows = new DelegateThrows();
+		try {
+			new GenericEndpoint(delegateThrows);
+			Assert.fail("Find delegate methods did not have expected exception raised when FooThrows.doDelegate was called.");
+		} catch (IllegalStateException e) {
+			Throwable t = e;
+			do {
+				if ("Exception in doDelegate".equals(t.getMessage())) {
+					// test passes
+					break;
+				}
+			} while ((t = t.getCause()) != null);
+			Assert.assertNotNull("Failed to find excepted exception in cause chain", t);
+		}
+	}
+
 	@Test
 	public void testMultiServices() {
 		Foo foo = new Foo();
@@ -93,6 +131,18 @@ public void testMultiServices() {
 		Assert.assertEquals(1, bar.calls);
 	}
 
+	@Test
+	public void testDuplicateNamesGeneratesError() {
+		DuplicateNames1 duplicateNames1 = new DuplicateNames1();
+		DuplicateNames2 duplicateNames2 = new DuplicateNames2();
+		try {
+			new GenericEndpoint(Arrays.asList(duplicateNames1, duplicateNames2));
+			Assert.fail("Expected exception about duplicated names not thrown");
+		} catch (IllegalStateException e) {
+			// test passes
+		}
+	}
+
 	@Test
 	public void testUnexpectedParams() {
 		LogMessageAccumulator logMessages = new LogMessageAccumulator();