Fix duplicate edges (#139)

* fix duplicate edge creation

* more extensive testing

* test for groups

* nitpick

Author: PythonFZ

pyproject.toml

@@ -1,6 +1,6 @@
 [project]
 name = "znflow"
-version = "0.2.6"
+version = "0.2.7"
 description = "A general purpose framework for building and running computational graphs."
 authors = [
     { name = "Fabian Zills", email = "fzills@icp.uni-stuttgart.de" },
@@ -17,6 +17,7 @@ dev = [
     "attrs>=25.1.0",
     "dask>=2025.2.0",
     "distributed>=2025.2.0",
+    "ipykernel>=6.30.1",
     "pydantic>=2.10.6",
     "pytest>=8.3.4",
     "pytest-cov>=6.0.0",

tests/test_edges.py

@@ -0,0 +1,107 @@
+import dataclasses
+
+import znflow
+
+
+@dataclasses.dataclass
+class Node(znflow.Node):
+    a: int
+    b: int
+    c: int | None = None
+
+
+def test_no_duplicate_edges():
+    """Test that connections don't create duplicate edges."""
+    project = znflow.DiGraph()
+
+    with project:
+        a = Node(a=1, b=2)
+        b = Node(a=3, b=4)
+        _ = Node(a=a.c, b=b.c)
+
+    # Should have 3 nodes
+    assert len(project.nodes) == 3
+
+    # Should have 2 unique edges: a.c -> c.a and b.c -> c.b
+    assert len(project.edges) == 2
+
+    # Verify the edges are what we expect
+    edge_descriptions = {
+        f"{d['u_attr']}->{d['v_attr']}" for _, _, d in project.edges(data=True)
+    }
+    assert edge_descriptions == {"c->a", "c->b"}
+
+
+def test_multiple_connections_same_nodes():
+    """Test that multiple different connections between same nodes work."""
+
+    @dataclasses.dataclass
+    class MultiNode(znflow.Node):
+        x: int | None = None
+        y: int | None = None
+        z: int | None = None
+
+    project = znflow.DiGraph()
+
+    with project:
+        a = MultiNode()
+        _ = MultiNode(x=a.x, y=a.y)
+
+    # Should have 2 edges: a.x -> b.x and a.y -> b.y
+    assert len(project.edges) == 2
+
+    # Verify the edges are what we expect
+    edge_descriptions = {
+        f"{d['u_attr']}->{d['v_attr']}" for _, _, d in project.edges(data=True)
+    }
+    assert edge_descriptions == {"x->x", "y->y"}
+
+
+def test_no_duplicate_edges_group():
+    project = znflow.DiGraph()
+
+    with project.group("group"):
+        a = Node(a=1, b=2)
+        b = Node(a=3, b=4)
+        _ = Node(a=a.c, b=b.c)
+
+    with project:
+        pass
+
+    with project.group("other-group"):
+        pass
+
+    # Should have 3 nodes
+    assert len(project.nodes) == 3
+
+    # Should have 2 unique edges: a.c -> c.a and b.c -> c.b
+    assert len(project.edges) == 2
+
+    edge_descriptions = {
+        f"{d['u_attr']}->{d['v_attr']}" for _, _, d in project.edges(data=True)
+    }
+    assert edge_descriptions == {"c->a", "c->b"}
+
+
+def test_no_duplicate_edges_iterable():
+    project = znflow.DiGraph()
+
+    with project.group("subgraph"):
+        a = Node(a=1, b=2)
+        b = Node(a=3, b=4)
+        c = Node(a=5, b=6)
+        _ = Node(a=[a.a], b=[b.b, c.c])
+
+    with project:
+        pass
+
+    with project.group("other-subgraph"):
+        pass
+
+    assert len(project.nodes) == 4
+    assert len(project.edges) == 3
+
+    edge_descriptions = {
+        f"{d['u_attr']}->{d['v_attr']}" for _, _, d in project.edges(data=True)
+    }
+    assert edge_descriptions == {"a->a", "b->b", "c->b"}