Clip scattercarpet traces with clipPath of ref'ed carpet

src/traces/scattercarpet/plot.js

@@ -37,6 +37,6 @@ module.exports = function plot(gd, plotinfoproxy, data, layer) {
         // separately to all scattercarpet traces, but that would require
         // lots of reorganization of scatter traces that is otherwise not
         // necessary. That makes this a potential optimization.
-        Drawing.setClipUrl(node, carpet._clipPathId, gd);
+        Drawing.setClipUrl(node, data[i][0].carpet._clipPathId, gd);
     }
 };

test/image/mocks/scattercarpet-on-two-carpets.json

@@ -0,0 +1,66 @@
+{
+  "data": [
+    {
+      "type": "carpet",
+      "a": [ 4, 4, 4, 4.5, 4.5, 4.5, 5, 5, 5, 6, 6, 6 ],
+      "b": [ 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3 ],
+      "y": [ 2, 3.5, 4, 3, 4.5, 5, 5.5, 6.5, 7.5, 8, 8.5, 10 ],
+      "aaxis": {
+        "tickprefix": "a = ",
+        "ticksuffix": "m",
+        "smoothing": 1,
+        "minorgridcount": 9
+      },
+      "baxis": {
+        "tickprefix": "b = ",
+        "ticksuffix": "Pa",
+        "smoothing": 1,
+        "minorgridcount": 9
+      },
+      "carpet": "c0"
+    },
+    {
+      "type": "carpet",
+      "a": [ 4, 4, 4, 4.5, 4.5, 4.5, 5, 5, 5, 6, 6, 6 ],
+      "b": [ 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3 ],
+      "y": [ 22, 23.5, 24, 23, 24.5, 25, 25.5, 26.5, 27.5, 28, 28.5, 30 ],
+      "aaxis": {
+        "tickprefix": "a = ",
+        "ticksuffix": "m",
+        "smoothing": 1,
+        "minorgridcount": 9
+      },
+      "baxis": {
+        "tickprefix": "b = ",
+        "ticksuffix": "Pa",
+        "smoothing": 1,
+        "minorgridcount": 9
+      },
+      "carpet": "c1"
+    },
+    {
+      "type": "scattercarpet",
+      "a": [ 4, 4.5, 5, 6 ],
+      "b": [ 2.5, 2.5, 2.5, 2.5 ],
+      "line": {
+        "shape": "spline",
+        "smoothing": 1,
+        "color": "blue"
+      },
+      "mode": "lines",
+      "carpet": "c0"
+    },
+    {
+      "type": "scattercarpet",
+      "a": [ 4, 4.5, 5, 6 ],
+      "b": [ 2.5, 2.5, 2.5, 2.5 ],
+      "line": {
+        "shape": "spline",
+        "smoothing": 1,
+        "color": "red"
+      },
+      "mode": "lines",
+      "carpet": "c1"
+    }
+  ]
+}