add and test aggregation back _index.

This necessitated a change in plots.js to prevent the supply defaults
step running twice with the second run acting on fullData rather then
userData.

src/plots/plots.js

@@ -1039,9 +1039,19 @@ plots.supplyTransformDefaults = function(traceIn, traceOut, layout) {
             _module = transformsRegistry[type],
             transformOut;
 
+        /*
+         * Supply defaults runs twice. First pass runs all supply defaults steps.
+         * If transforms exists another pass is run so any new traces generated
+         * in the transforms steps have their transform run. However if the
+         * transform does not have a 'transform' function (instead a calcFunction)
+         * than this second stage is unnecessary.
+         */
+        var isSecondStage = transformIn._module && transformIn._module === _module,
+            doSecondStage = _module && typeof _module.transform === 'function';
+
         if(!_module) Lib.warn('Unrecognized transform type ' + type + '.');
 
-        if(_module && _module.supplyDefaults) {
+        if(_module && _module.supplyDefaults && (!isSecondStage || doSecondStage)) {
             transformOut = _module.supplyDefaults(transformIn, traceOut, layout, traceIn);
             transformOut.type = type;
             transformOut._module = _module;

src/transforms/aggregate.js

@@ -164,7 +164,7 @@ exports.supplyDefaults = function(transformIn, traceOut) {
     }
 
     for(i = 0; i < aggregationsIn.length; i++) {
-        aggregationOut = {};
+        aggregationOut = {_index: i};
         var target = coercei('target');
         var func = coercei('func');
         var enabledi = coercei('enabled');
@@ -177,7 +177,7 @@ exports.supplyDefaults = function(transformIn, traceOut) {
             arrayAttrs[target] = 0;
             aggregationsOut[i] = aggregationOut;
         }
-        else aggregationsOut[i] = {enabled: false};
+        else aggregationsOut[i] = {enabled: false, _index: i};
     }
 
     // any array attributes we haven't yet covered, fill them with the default aggregation
@@ -186,7 +186,8 @@ exports.supplyDefaults = function(transformIn, traceOut) {
             aggregationsOut.push({
                 target: arrayAttrArray[i],
                 func: aggAttrs.func.dflt,
-                enabled: true
+                enabled: true,
+                _index: -1
             });
         }
     }

test/jasmine/tests/transform_aggregate_test.js

@@ -245,4 +245,40 @@ describe('aggregate', function() {
         expect(traceOut.marker.line.width).toBeCloseToArray([0.5, 0], 5);
         expect(traceOut.marker.color).toBeCloseToArray([Math.sqrt(1 / 3), 0], 5);
     });
+
+    it('links fullData aggregations to userData via _index', function() {
+        Plotly.newPlot(gd, [{
+            x: [1, 2, 3, 4, 5],
+            y: [2, 4, 6, 8, 10],
+            marker: {
+                size: [10, 10, 20, 20, 10],
+                color: ['red', 'green', 'blue', 'yellow', 'white']
+            },
+            transforms: [{
+                type: 'aggregate',
+                groups: 'marker.size',
+                aggregations: [
+                    {target: 'x', func: 'sum'},
+                    {target: 'x', func: 'avg'},
+                    {target: 'y', func: 'avg'},
+                ]
+            }]
+        }]);
+
+        var traceOut = gd._fullData[0];
+        var fullAggregation = traceOut.transforms[0];
+        var fullAggregations = fullAggregation.aggregations;
+        var enabledAggregations = fullAggregations.filter(function(agg) {
+            return agg.enabled;
+        });
+
+        expect(enabledAggregations[0].target).toEqual('x');
+        expect(enabledAggregations[0]._index).toEqual(0);
+
+        expect(enabledAggregations[1].target).toEqual('y');
+        expect(enabledAggregations[1]._index).toEqual(2);
+
+        expect(enabledAggregations[2].target).toEqual('marker.color');
+        expect(enabledAggregations[2]._index).toEqual(-1);
+    });
 });