Address Apollo review deferred items (S2, I4, S5)

S2: Replace type() == list with isinstance() for list-to-dict conversion.

I4: Fix duplicate GraphViz port names when a pin appears in multiple
shorts. Port names now encode short column index (p{idx}j{col}) so
each cell in the shorts grid has a unique port. Edge generation in
gv_connector_shorts() updated to match.

S5: Add rendering tests for multi-pin loop edge chains and multi-short
port name uniqueness.

src/wireviz/wv_dataclasses.py

@@ -470,7 +470,7 @@ class Connector(TopLevelGraphicalComponent):
             self.show_pincount = self.style != "simple"
 
         # Convert short List to Short Dict
-        if type(self.shorts) == list:
+        if isinstance(self.shorts, list):
             self.shorts_hide_lable = True
             shDict = dict()
             for shIndex in range(0, len(self.shorts)):
@@ -479,7 +479,7 @@ class Connector(TopLevelGraphicalComponent):
             self.shorts = shDict
 
         # Convert loop List to loop Dict
-        if type(self.loops) == list:
+        if isinstance(self.loops, list):
             loDict = dict()
             for loIndex in range(0, len(self.loops)):
                 key = "AutoLO" + str(loIndex)

src/wireviz/wv_graphviz.py

@@ -303,10 +303,12 @@ def gv_pin_table(component) -> Table:
 
 
 def gv_short_row_part(pin, connector) -> List:
-    short_row = [] # Td("ADA"), Td("DAD")
-    for short, shPins in connector.shorts.items():
+    short_row = []
+    for sh_col, (short, shPins) in enumerate(connector.shorts.items()):
         if pin.id in shPins:
-            short_row.append(Td("", port=f"p{pin.index+1}j"))
+            # Port name encodes pin index + short column to stay unique
+            # when the same pin appears in multiple shorts.
+            short_row.append(Td("", port=f"p{pin.index+1}j{sh_col}"))
         else:
             short_row.append(Td(""))
     return short_row if len(short_row) > 0 else None
@@ -358,7 +360,7 @@ def gv_connector_loops(connector: Connector) -> List:
 def gv_connector_shorts(connector: Connector) -> List:
     short_edges = []
 
-    for short, shPins in connector.shorts.items():
+    for sh_col, (short, shPins) in enumerate(connector.shorts.items()):
         comp = getAddCompFromRef(short, connector)
         shColor = "#FFFFFF:#000000:#FFFFFF"
         if comp != None and comp.color != None:
@@ -366,10 +368,11 @@ def gv_connector_shorts(connector: Connector) -> List:
 
         for i in range(1, len(shPins)):
             # Convert pin IDs to 1-based port indices (same fix as loops).
+            # Port name includes short column index for uniqueness.
             idx_prev = connector.pin_objects[shPins[i - 1]].index + 1
             idx_curr = connector.pin_objects[shPins[i]].index + 1
-            head = f"{connector.designator}:p{idx_prev}j:c"
-            tail = f"{connector.designator}:p{idx_curr}j:c"
+            head = f"{connector.designator}:p{idx_prev}j{sh_col}:c"
+            tail = f"{connector.designator}:p{idx_curr}j{sh_col}:c"
             short_edges.append((head, tail, shColor))
     return short_edges
 

tests/test_resolve_pin.py

@@ -334,12 +334,13 @@ class TestRendering:
         graph = harness.create_graph()
         gv = graph.source
 
-        # Short should reference p1j and p2j (indices), not p10j and p20j
-        short_edges = re.findall(r"X1:p(\d+)j:c -- X1:p(\d+)j:c", gv)
+        # Short should reference p1j0 and p2j0 (index + column 0),
+        # not p10j0 and p20j0 (pin IDs)
+        short_edges = re.findall(r"X1:p(\d+)j\d+:c -- X1:p(\d+)j\d+:c", gv)
         assert len(short_edges) >= 1, f"Expected short edge, found none in:\n{gv}"
         idx_a, idx_b = short_edges[0]
         assert idx_a == "1" and idx_b == "2", (
-            f"Short ports should be p1j/p2j (indices), got p{idx_a}j/p{idx_b}j"
+            f"Short ports should be p1/p2 (indices), got p{idx_a}/p{idx_b}"
         )
 
     def test_sequential_pins_still_work(self):
@@ -357,6 +358,59 @@ class TestRendering:
         assert ":p1" in gv
         assert ":p2" in gv
 
+    def test_multi_pin_loop_renders_chain(self):
+        """S5: >2 pin loop produces correct edge chain (p1->p2, p2->p3)."""
+        import re
+        harness = self._make_harness()
+        harness.add_connector(
+            "X1",
+            pins=[10, 20, 30, 40],
+            pinlabels=["A", "B", "C", "D"],
+            loops=[["A", "B", "C"]],
+        )
+        harness.add_cable("W1", wirecount=1, colors=["BK"])
+        harness.connect("X1", "D", "W1", 1, None, None)
+        graph = harness.create_graph()
+        gv = graph.source
+
+        loop_edges = re.findall(r"X1:p(\d+)\w:\w -- X1:p(\d+)\w:\w", gv)
+        # 3-pin loop should produce 2 edges: p1->p2 and p2->p3
+        assert len(loop_edges) == 2, (
+            f"Expected 2 loop edges for 3-pin loop, got {len(loop_edges)}"
+        )
+        assert loop_edges[0] == ("1", "2")
+        assert loop_edges[1] == ("2", "3")
+
+    def test_pin_in_multiple_shorts_unique_ports(self):
+        """I4: pin in two shorts gets unique port names per column."""
+        import re
+        harness = self._make_harness()
+        harness.add_connector(
+            "X1",
+            pins=[1, 2, 3, 4],
+            shorts={"SH1": [1, 2], "SH2": [1, 3]},
+        )
+        harness.add_cable("W1", wirecount=1, colors=["BK"])
+        harness.connect("X1", 4, "W1", 1, None, None)
+        graph = harness.create_graph()
+        gv = graph.source
+
+        # SH1 edges should use column 0 (j0), SH2 should use column 1 (j1)
+        sh1_edges = re.findall(r"X1:p(\d+)j0:c -- X1:p(\d+)j0:c", gv)
+        sh2_edges = re.findall(r"X1:p(\d+)j1:c -- X1:p(\d+)j1:c", gv)
+        assert len(sh1_edges) >= 1, f"Expected SH1 edge (j0), found none in:\n{gv}"
+        assert len(sh2_edges) >= 1, f"Expected SH2 edge (j1), found none in:\n{gv}"
+        # SH1: pin 1 (idx 1) -> pin 2 (idx 2)
+        assert sh1_edges[0] == ("1", "2")
+        # SH2: pin 1 (idx 1) -> pin 3 (idx 3)
+        assert sh2_edges[0] == ("1", "3")
+
+        # Verify no duplicate port names in the HTML table
+        port_names = re.findall(r'PORT="(p\d+j\d+)"', gv)
+        assert len(port_names) == len(set(port_names)), (
+            f"Duplicate port names found: {port_names}"
+        )
+
 
 # --- Harness.connect() delegation ---