add Lib.extractOption

- abstracting out calcdata-to-global-trace-fallback
- use it in Drawing!
- use it in hover label style logic

- not super happy with the name
- not super happy about it being on Lib

Author: etpinard

src/components/drawing/index.js

@@ -443,12 +443,10 @@ drawing.tryColorscale = function(marker, prefix) {
 var TEXTOFFSETSIGN = {start: 1, end: -1, middle: 0, bottom: 1, top: -1};
 drawing.textPointStyle = function(s, trace, gd) {
     s.each(function(d) {
-        var p = d3.select(this),
-            text = d.tx || trace.text;
+        var p = d3.select(this);
+        var text = Lib.extractOption(d, trace, 'tx', 'text');
 
-        if(!text || Array.isArray(text)) {
-            // isArray test handles the case of (intentionally) missing
-            // or empty text within a text array
+        if(!text) {
             p.remove();
             return;
         }

src/components/fx/hover.js

@@ -1028,24 +1028,22 @@ function alignHoverText(hoverLabels, rotateLabels) {
 }
 
 function cleanPoint(d, hovermode) {
+    var index = d.index;
     var trace = d.trace || {};
     var cd0 = d.cd[0];
-    var cd = d.cd[d.index] || {};
+    var cd = d.cd[index] || {};
+
+    var getVal = Array.isArray(index) ?
+        function(calcKey, traceKey) {
+            return Lib.castOption(cd0, index, calcKey) ||
+                Lib.extractOption({}, trace, '', traceKey);
+        } :
+        function(calcKey, traceKey) {
+            return Lib.extractOption(cd, trace, calcKey, traceKey);
+        };
 
     function fill(key, calcKey, traceKey) {
-        var val;
-
-        if(cd[calcKey]) {
-            val = cd[calcKey];
-        } else if(cd0[calcKey]) {
-            var arr = cd0[calcKey];
-            if(Array.isArray(arr) && Array.isArray(arr[d.index[0]])) {
-                val = arr[d.index[0]][d.index[1]];
-            }
-        } else {
-            val = Lib.nestedProperty(trace, traceKey).get();
-        }
-
+        var val = getVal(calcKey, traceKey);
         if(val) d[key] = val;
     }
 

src/lib/index.js

@@ -437,6 +437,27 @@ lib.castOption = function(trace, ptNumber, astr, fn) {
     }
 };
 
+/** Extract option from calcdata item, correctly falling back to
+ *  trace value if not found.
+ *
+ *  @param {object} calcPt : calcdata[i][j] item
+ *  @param {object} trace : (full) trace object
+ *  @param {string} calcKey : calcdata key
+ *  @param {string} traceKey : aka trace attribute string
+ *  @return {any}
+ */
+lib.extractOption = function(calcPt, trace, calcKey, traceKey) {
+    var calcVal = calcPt[calcKey];
+    if(calcVal || calcVal === 0) return calcVal;
+
+    // fallback to trace value,
+    //   must check if value isn't itself an array
+    //   which means the trace attribute has a corresponding
+    //   calcdata key, but its value is falsy
+    var traceVal = lib.nestedProperty(trace, traceKey).get();
+    if(!Array.isArray(traceVal)) return traceVal;
+};
+
 /** Returns target as set by 'target' transform attribute
  *
  * @param {object} trace : full trace object