Only call nodeSort for non-circular Sankey

Author: adamreeve

src/traces/sankey/render.js

@@ -40,7 +40,7 @@ function sankeyModel(layout, d, traceIndex) {
         right: d3Sankey.sankeyRight,
         center: d3Sankey.sankeyCenter
     }[trace.node.align];
-    var input_sort = trace.node.sort == 'input';
+    var input_sort = trace.node.sort === 'input';
 
     var width = layout.width * (domain.x[1] - domain.x[0]);
     var height = layout.height * (domain.y[1] - domain.y[0]);
@@ -49,6 +49,10 @@ function sankeyModel(layout, d, traceIndex) {
     var links = calcData._links;
     var circular = calcData.circular;
 
+    if(circular && input_sort) {
+        Lib.error('Circular Sankey diagrams do not support the "input" node.sort mode; falling back to the default sort.');
+    }
+
     // Select Sankey generator
     var sankey;
     if(circular) {
@@ -68,10 +72,14 @@ function sankeyModel(layout, d, traceIndex) {
           return d.pointNumber;
       })
       .nodeAlign(nodeAlign)
-      .nodeSort(input_sort ? null : undefined)
       .nodes(nodes)
       .links(links);
 
+    // d3-sankey-circular does not support the nodeSort method
+    if(!circular) {
+        sankey.nodeSort(input_sort ? null : undefined);
+    }
+
     var graph = sankey();
 
     if(sankey.nodePadding() < nodePad) {