Stop infinite looping when errors occur in /world/Error()

Content.Tests/DMProject/Tests/Builtins/world_error_infinite_loop.dm

@@ -0,0 +1,19 @@
+//RUNTIME ERROR, RETURN TRUE
+var/error_loop_count = 0
+
+/world/Error()
+	error_loop_count++
+	if(error_loop_count > 1)
+		world.log << "this is a test failure"
+		return
+	TestProc()	
+
+/proc/SubError()
+	CRASH("we're doing an error!")
+
+/proc/TestProc()
+	SubError()
+
+/proc/RunTest()
+	TestProc()
+	return error_loop_count == 1

OpenDreamRuntime/DreamManager.cs

@@ -435,7 +435,7 @@ public ClientObjectReference GetClientReference(DreamObjectAtom atom) {
         }
     }
 
-    public void HandleException(Exception e, string msg = "", string file = "", int line = 0) {
+    public void HandleException(Exception e, string msg = "", string file = "", int line = 0, bool inWorldError = false) {
         if (string.IsNullOrEmpty(msg)) { // Just print the C# exception if we don't override the message
             msg = e.Message;
         }
@@ -452,8 +452,12 @@ public void HandleException(Exception e, string msg = "", string file = "", int
         obj.Desc = new DreamValue(msg);
         obj.Line = new DreamValue(line);
         obj.File = new DreamValue(file);
-
-        WorldInstance.SpawnProc("Error", usr: null, new DreamValue(obj));
+        if (!inWorldError) // if an error occurs in /world/Error(), don't call it again
+            WorldInstance.SpawnProc("Error", usr: null, new DreamValue(obj));
+        else {
+            _sawmill.Error("CRITICAL: An error occurred in /world/Error()");
+            WriteWorldLog(msg);
+        }
     }
 
     public void OptionalException<T>(WarningCode code, string exceptionText) where T : Exception {

OpenDreamRuntime/DreamThread.cs

@@ -479,7 +479,14 @@ private void HandleException(Exception exception) {
                 line = source.Item2;
             }
 
-            dreamMan.HandleException(exception, msg, file, line);
+            bool inWorldError = _current?.Proc?.OwningType == dreamMan.WorldInstance.ObjectDefinition.TreeEntry && _current.Proc.Name == "Error";
+            if (!inWorldError && _stack.Count > 0) {
+                //if we're not directly in /world.Error, check the stack
+                var top = _stack.ElementAt(_stack.Count - 1); //only the top of the stack can be /world/Error
+                inWorldError = top.Proc?.OwningType == dreamMan.WorldInstance.ObjectDefinition.TreeEntry && top.Proc?.Name == "Error";
+            }
+
+            dreamMan.HandleException(exception, msg, file, line, inWorldError: inWorldError);
             IoCManager.Resolve<IDreamDebugManager>().HandleException(this, exception);
         }