fix: check_wire_collisions now detects wires that short two pins of the same component

Previously, the endpoint suppression logic skipped any wire where at least
one endpoint touched a pin, hiding the case where both endpoints are pins
of the same component (a direct pin-to-pin short through the body).

Replace the single endpoint_matches_pin loop with separate start_at_pin /
end_at_pin checks; suppress only when exactly one endpoint is at a pin.
Add regression test to cover this case.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

python/commands/schematic_analysis.py

@@ -654,19 +654,25 @@ def check_wire_collisions(schematic_path: Path) -> List[Dict[str, Any]]:
             if not _line_segment_intersects_aabb(sx, sy, ex, ey, bx1, by1, bx2, by2):
                 continue
 
-            # Check if either wire endpoint matches a pin of this symbol
-            endpoint_matches_pin = False
-            for px, py in sd["pin_set"]:
-                if (abs(sx - px) < pin_tolerance and abs(sy - py) < pin_tolerance):
-                    endpoint_matches_pin = True
-                    break
-                if (abs(ex - px) < pin_tolerance and abs(ey - py) < pin_tolerance):
-                    endpoint_matches_pin = True
-                    break
+            # Check which endpoints land on a pin of this symbol
+            start_at_pin = any(
+                abs(sx - px) < pin_tolerance and abs(sy - py) < pin_tolerance
+                for px, py in sd["pin_set"]
+            )
+            end_at_pin = any(
+                abs(ex - px) < pin_tolerance and abs(ey - py) < pin_tolerance
+                for px, py in sd["pin_set"]
+            )
 
-            if not endpoint_matches_pin:
-                sym = sd["sym"]
-                collisions.append({
+            # Suppress only when exactly ONE endpoint is at a pin: the wire arrives
+            # from elsewhere and terminates at this component (a valid connection).
+            # If BOTH endpoints match pins of this same component, the wire shorts
+            # two pins while traversing the body — that IS a collision.
+            if (start_at_pin or end_at_pin) and not (start_at_pin and end_at_pin):
+                continue
+
+            sym = sd["sym"]
+            collisions.append({
                     "wire": {
                         "start": {"x": sx, "y": sy},
                         "end": {"x": ex, "y": ey},

python/tests/test_schematic_analysis.py

@@ -415,6 +415,23 @@ class TestIntegrationCheckWireCollisions:
             "likely caused by reference-lookup always returning the first 'R?'"
         )
 
+    def test_wire_shorts_component_pins_detected_as_collision(self):
+        """Regression: a wire connecting pin1→pin2 of the same component
+        must be reported even though both endpoints land on pins."""
+        r_sexp = _make_resistor_sexp("R_short", 100.0, 100.0)
+        wire_sexp = (
+            '(wire (pts (xy 100 103.81) (xy 100 96.19))\n'
+            '  (stroke (width 0) (type default))\n'
+            '  (uuid "aaaaaaaa-0000-0000-0000-000000000001"))'
+        )
+        sch = _make_temp_schematic(r_sexp + "\n" + wire_sexp)
+        collisions = check_wire_collisions(sch)
+        assert len(collisions) == 1
+        w = collisions[0]["wire"]
+        assert w["start"]["x"] == pytest.approx(100.0)
+        assert w["start"]["y"] == pytest.approx(103.81)
+        assert collisions[0]["component"]["reference"] == "R_short"
+
 
 @pytest.mark.integration
 class TestIntegrationGetElementsInRegion: