dry: pull trace indices input -> list logic in helpers

- use it in Plotly.restyle and Plotly.animate
- call trace indices argument 'traces' consistently in
  restyle, update, and transition (to be consistent with the frame
  attribute 'traces').

src/plot_api/helpers.js

@@ -9,6 +9,7 @@
 
 'use strict';
 
+var isNumeric = require('fast-isnumeric');
 var m4FromQuat = require('gl-mat4/fromQuat');
 
 var Registry = require('../registry');
@@ -399,3 +400,15 @@ exports.swapXYData = function(trace) {
         trace.hoverinfo = hoverInfoParts.join('+');
     }
 };
+
+// coerce traceIndices input to array of trace indices
+exports.coerceTraceIndices = function(gd, traceIndices) {
+    if(isNumeric(traceIndices)) {
+        return [traceIndices];
+    }
+    else if(!Array.isArray(traceIndices) || !traceIndices.length) {
+        return gd.data.map(function(_, i) { return i; });
+    }
+
+    return traceIndices;
+};

src/plot_api/plot_api.js

@@ -1192,17 +1192,13 @@ Plotly.restyle = function restyle(gd, astr, val, traces) {
     });
 };
 
-function _restyle(gd, aobj, traces) {
+function _restyle(gd, aobj, _traces) {
     var fullLayout = gd._fullLayout,
         fullData = gd._fullData,
         data = gd.data,
         i;
 
-    // fill up traces
-    if(isNumeric(traces)) traces = [traces];
-    else if(!Array.isArray(traces) || !traces.length) {
-        traces = data.map(function(_, i) { return i; });
-    }
+    var traces = helpers.coerceTraceIndices(gd, _traces);
 
     // initialize flags
     var flags = {
@@ -2035,7 +2031,7 @@ function _relayout(gd, aobj) {
  *  integer or array of integers for the traces to alter (all if omitted)
  *
  */
-Plotly.update = function update(gd, traceUpdate, layoutUpdate, indices) {
+Plotly.update = function update(gd, traceUpdate, layoutUpdate, traces) {
     gd = helpers.getGraphDiv(gd);
     helpers.clearPromiseQueue(gd);
 
@@ -2049,7 +2045,7 @@ Plotly.update = function update(gd, traceUpdate, layoutUpdate, indices) {
     if(Object.keys(traceUpdate).length) gd.changed = true;
     if(Object.keys(layoutUpdate).length) gd.changed = true;
 
-    var restyleSpecs = _restyle(gd, traceUpdate, indices),
+    var restyleSpecs = _restyle(gd, traceUpdate, traces),
         restyleFlags = restyleSpecs.flags;
 
     var relayoutSpecs = _relayout(gd, layoutUpdate),
@@ -2286,7 +2282,7 @@ Plotly.animate = function(gd, frameOrGroupNameOrFrameList, animationOpts) {
                 Plots.transition(gd,
                     newFrame.frame.data,
                     newFrame.frame.layout,
-                    newFrame.frame.traces,
+                    helpers.coerceTraceIndices(gd, newFrame.frame.traces),
                     newFrame.frameOpts,
                     newFrame.transitionOpts
                 );

src/plots/plots.js

@@ -1348,27 +1348,18 @@ plots.computeFrame = function(gd, frameName) {
  *      an array of data objects following the normal Plotly data definition format
  * @param {Object} layout
  *      a layout object, following normal Plotly layout format
- * @param {Number[]} traceIndices
+ * @param {Number[]} traces
  *      indices of the corresponding traces specified in `data`
  * @param {Object} frameOpts
  *      options for the frame (i.e. whether to redraw post-transition)
  * @param {Object} transitionOpts
  *      options for the transition
  */
-plots.transition = function(gd, data, layout, traceIndices, frameOpts, transitionOpts) {
+plots.transition = function(gd, data, layout, traces, frameOpts, transitionOpts) {
     var i, traceIdx;
 
     var dataLength = Array.isArray(data) ? data.length : 0;
-
-    // Select which traces will be updated:
-    if(isNumeric(traceIndices)) traceIndices = [traceIndices];
-    else if(!Array.isArray(traceIndices) || !traceIndices.length) {
-        traceIndices = gd.data.map(function(v, i) { return i; });
-    }
-
-    if(traceIndices.length > dataLength) {
-        traceIndices = traceIndices.slice(0, dataLength);
-    }
+    var traceIndices = traces.slice(0, dataLength);
 
     var transitionedTraces = [];