fix and 🔒 category angular axis mocked range logic

- 🔪 useless axex.expand call in scatterpolar/calc, this
  is an artefact from an earlier angular dates attempt
- set mocked angular axis range using max of set 'period' and
  total categories length.
- more on period vs category in #2255

Author: etpinard

Diff for: src/plots/polar/polar.js

@@ -416,14 +416,15 @@ proto.updateAngularAxis = function(fullLayout, polarLayout) {
         _counteraxis: true,
 
         // don't use automargins routine for labels
-        automargin: false
+        automargin: false,
+
+        // don't pass through autorange logic
+        autorange: false
     });
 
     // Set the angular range in degrees to make auto-tick computation cleaner,
     // changing rotation/direction should not affect the angular tick labels.
     if(ax.type === 'linear') {
-        ax.autorange = false;
-
         if(isFullCircle(sector)) {
             ax.range = sector.slice();
         } else {
@@ -435,11 +436,18 @@ proto.updateAngularAxis = function(fullLayout, polarLayout) {
             ax.tick0 = rad2deg(ax.tick0);
             ax.dtick = rad2deg(ax.dtick);
         }
+
     }
     // Use tickval filter for category axes instead of tweaking
     // the range w.r.t sector, so that sectors that cross 360 can
     // show all their ticks.
     else if(ax.type === 'category') {
+        var period = angularLayout.period ?
+            Math.max(angularLayout.period, angularLayout._categories.length) :
+            angularLayout._categories.length;
+
+        ax.range = [0, period];
+
         ax._tickFilter = function(d) {
             return _this.isPtWithinSector({
                 r: _this.radialAxis.range[1],
@@ -449,7 +457,6 @@ proto.updateAngularAxis = function(fullLayout, polarLayout) {
     }
 
     setScale(ax, angularLayout, fullLayout);
-    doAutoRange(ax);
 
     // wrapper around c2rad from setConvertAngular
     // note that linear ranges are always set in degrees for Axes.doTicks

Diff for: src/traces/scatterpolar/calc.js

@@ -50,12 +50,6 @@ module.exports = function calc(gd, trace) {
     var ppad = calcMarkerSize(trace, len);
     Axes.expand(radialAxis, rArray, {ppad: ppad});
 
-    if(angularAxis.type !== 'linear') {
-        angularAxis.autorange = true;
-        Axes.expand(angularAxis, thetaArray);
-        delete angularAxis.autorange;
-    }
-
     calcColorscale(trace);
     arraysToCalcdata(cd, trace);
     calcSelection(cd, trace);

Diff for: test/jasmine/tests/polar_test.js

@@ -543,6 +543,65 @@ describe('Test relayout on polar subplots:', function() {
         .catch(fail)
         .then(done);
     });
+
+    it('should update axis ranges when extending traces', function(done) {
+        var gd = createGraphDiv();
+
+        function _assert(msg, exp) {
+            expect(gd._fullLayout.polar.radialaxis.autorange).toBe(true);
+
+            expect(gd.layout.polar.radialaxis.range)
+                .toBeCloseToArray(exp.rRange, 2, 'radial range in user layout - ' + msg);
+            expect(gd._fullLayout.polar.radialaxis.range)
+                .toBeCloseToArray(exp.rRange, 2, 'radial range in full layout - ' + msg);
+
+            expect(gd._fullLayout.polar._subplot.angularAxis.range)
+                .toBeCloseToArray([0, exp.period], 2, 'range in mocked angular axis - ' + msg);
+
+            expect(d3.selectAll('path.angulartick').size())
+                .toBe(exp.nTicks, '# of visible angular ticks - ' + msg);
+
+            expect([gd.calcdata[0][5].x, gd.calcdata[0][5].y])
+                .toBeCloseToArray(exp.sampleXY, -1, 'sample (x,y) px coords in calcdata - ' + msg);
+        }
+
+        Plotly.plot(gd, [{
+            type: 'scatterpolar',
+            r: [39, 28, 8, 7, 28, 39, 40, 30, 30, 30, 30],
+            theta: ['A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'A']
+        }])
+        .then(function() {
+            _assert('base', {
+                rRange: [0, 41.14],
+                period: 10,
+                nTicks: 10,
+                sampleXY: [-39, 0]
+            });
+            return Plotly.extendTraces(gd, {
+                r: [[-10, -5]],
+                theta: [['y', 'z']]
+            }, [0]);
+        })
+        .then(function() {
+            _assert('after extending trace', {
+                rRange: [-11.47, 41.47],
+                period: 12,
+                nTicks: 12,
+                sampleXY: [-43, 25]
+            });
+            return Plotly.relayout(gd, 'polar.angularaxis.period', 15);
+        })
+        .then(function() {
+            _assert('after angularaxis.period relayout', {
+                rRange: [-11.47, 41.47],
+                period: 15,
+                nTicks: 12,
+                sampleXY: [-25, 43]
+            });
+        })
+        .catch(fail)
+        .then(done);
+    });
 });
 
 describe('Test polar interactions:', function() {