Display an error for dependency cycles

Previously, dependency cycles that were created during node expansion
would cause the application to quit (due to an uncaught exception). Now,
we'll throw a proper error to the UI. We also make an attempt to 'blame'
the most relevant node in the UI.

tests/inference/test_execution.py

@@ -234,6 +234,7 @@ class TestExecution:
 
         try:
             client.run(g)
+            assert False, "Should have raised an error"
         except Exception as e:
             assert 'prompt_id' in e.args[0], f"Did not get back a proper error message: {e}"
 
@@ -298,6 +299,35 @@ class TestExecution:
         else:
             client.run(g)
 
+    def test_cycle_error(self, client: ComfyClient, builder: GraphBuilder):
+        g = builder
+        input1 = g.node("StubImage", content="BLACK", height=512, width=512, batch_size=1)
+        input2 = g.node("StubImage", content="WHITE", height=512, width=512, batch_size=1)
+        mask = g.node("StubMask", value=0.5, height=512, width=512, batch_size=1)
+
+        lazy_mix1 = g.node("TestLazyMixImages", image1=input1.out(0), mask=mask.out(0))
+        lazy_mix2 = g.node("TestLazyMixImages", image1=lazy_mix1.out(0), image2=input2.out(0), mask=mask.out(0))
+        g.node("SaveImage", images=lazy_mix2.out(0))
+
+        # When the cycle exists on initial submission, it should raise a validation error
+        with pytest.raises(urllib.error.HTTPError):
+            client.run(g)
+
+    def test_dynamic_cycle_error(self, client: ComfyClient, builder: GraphBuilder):
+        g = builder
+        input1 = g.node("StubImage", content="BLACK", height=512, width=512, batch_size=1)
+        input2 = g.node("StubImage", content="WHITE", height=512, width=512, batch_size=1)
+        generator = g.node("TestDynamicDependencyCycle", input1=input1.out(0), input2=input2.out(0))
+        g.node("SaveImage", images=generator.out(0))
+
+        # When the cycle is in a graph that is generated dynamically, it should raise a runtime error
+        try:
+            client.run(g)
+            assert False, "Should have raised an error"
+        except Exception as e:
+            assert 'prompt_id' in e.args[0], f"Did not get back a proper error message: {e}"
+            assert e.args[0]['node_id'] == generator.id, "Error should have been on the generator node"
+
     def test_custom_is_changed(self, client: ComfyClient, builder: GraphBuilder):
         g = builder
         # Creating the nodes in this specific order previously caused a bug

tests/inference/testing_nodes/testing-pack/specific_tests.py

@@ -1,5 +1,6 @@
 import torch
 from .tools import VariantSupport
+from comfy.graph_utils import GraphBuilder
 
 class TestLazyMixImages:
     @classmethod
@@ -191,6 +192,35 @@ class TestCustomValidation3:
             result = input1 * input2
         return (result,)
 
+class TestDynamicDependencyCycle:
+    @classmethod
+    def INPUT_TYPES(cls):
+        return {
+            "required": {
+                "input1": ("IMAGE",),
+                "input2": ("IMAGE",),
+            },
+        }
+
+    RETURN_TYPES = ("IMAGE",)
+    FUNCTION = "dynamic_dependency_cycle"
+
+    CATEGORY = "Testing/Nodes"
+
+    def dynamic_dependency_cycle(self, input1, input2):
+        g = GraphBuilder()
+        mask = g.node("StubMask", value=0.5, height=512, width=512, batch_size=1)
+        mix1 = g.node("TestLazyMixImages", image1=input1, mask=mask.out(0))
+        mix2 = g.node("TestLazyMixImages", image1=mix1.out(0), image2=input2, mask=mask.out(0))
+
+        # Create the cyle
+        mix1.set_input("image2", mix2.out(0))
+
+        return {
+            "result": (mix2.out(0),),
+            "expand": g.finalize(),
+        }
+
 TEST_NODE_CLASS_MAPPINGS = {
     "TestLazyMixImages": TestLazyMixImages,
     "TestVariadicAverage": TestVariadicAverage,
@@ -198,6 +228,7 @@ TEST_NODE_CLASS_MAPPINGS = {
     "TestCustomValidation1": TestCustomValidation1,
     "TestCustomValidation2": TestCustomValidation2,
     "TestCustomValidation3": TestCustomValidation3,
+    "TestDynamicDependencyCycle": TestDynamicDependencyCycle,
 }
 
 TEST_NODE_DISPLAY_NAME_MAPPINGS = {
@@ -207,4 +238,5 @@ TEST_NODE_DISPLAY_NAME_MAPPINGS = {
     "TestCustomValidation1": "Custom Validation 1",
     "TestCustomValidation2": "Custom Validation 2",
     "TestCustomValidation3": "Custom Validation 3",
+    "TestDynamicDependencyCycle": "Dynamic Dependency Cycle",
 }