Reset forced minimum tick spacing on every calc pass

setConvert cleared ax._minDtick / ax._forceTick0 so each calc pass would
start over, but the cleanup never had any effect: setConvert runs while
supplyDefaults builds the new _fullLayout, where the keys do not exist
yet, and relinkPrivateKeys then copies the old values back onto it.

Axes.minDtick treats 0 as "forcing cancelled", so the 0 written by
whichever figure was drawn first survived every later update and vetoed
the forcing for every figure after it. Reacting from a scatter to a box
plot lost the one-tick-per-box spacing, while newPlot of the same figure
kept it.

Move the reset into ax.clearCalc, the axis' own per-calc-pass reset,
which doCalcdata runs for every axis before any cross-trace calc.

Author: jayesh-keychain

src/plots/cartesian/set_convert.js

@@ -58,7 +58,7 @@ function isValidCategory(v) {
  * Creates/updates these conversion functions, and a few more utilities
  * like cleanRange, and makeCalcdata
  *
- * also clears ._minDtick, ._forceTick0
+ * also creates ax.clearCalc, which clears ._minDtick, ._forceTick0
  */
 module.exports = function setConvert(ax, fullLayout) {
     fullLayout = fullLayout || {};
@@ -952,6 +952,12 @@ module.exports = function setConvert(ax, fullLayout) {
 
     // should skip if not category nor multicategory
     ax.clearCalc = function() {
+        // for bar charts and box plots: reset forced minimum tick spacing.
+        // this has to happen here rather than in setConvert, as the values
+        // are relinked onto the new fullLayout after supplyDefaults runs
+        delete ax._minDtick;
+        delete ax._forceTick0;
+
         var group = ax._matchGroup;
         if(group) {
             var categories = null;
@@ -1024,8 +1030,4 @@ module.exports = function setConvert(ax, fullLayout) {
     // even though it won't be needed by this axis
     ax._separators = fullLayout.separators;
     ax._numFormat = locale ? locale.numberFormat : numberFormat;
-
-    // and for bar charts and box plots: reset forced minimum tick spacing
-    delete ax._minDtick;
-    delete ax._forceTick0;
 };

test/jasmine/tests/axes_test.js

@@ -8303,6 +8303,45 @@ describe('more react tests', function() {
             expect(gd._fullLayout.xaxis.range).toBeCloseToArray([-0.173, 2]);
         }).then(done, done.fail);
     });
+
+    it('should not carry over the forced minimum tick spacing of the previous figure', function(done) {
+        var layout = {width: 700, height: 400};
+
+        var scatterFig = {
+            data: [{y: [1, 2, 3]}],
+            layout: layout
+        };
+
+        // one box per integer position - each box forces a tick of its own
+        var boxFig = {
+            data: [{
+                type: 'box',
+                x: [1, 1, 2, 2, 3, 3],
+                y: [1, 2, 3, 4, 5, 6]
+            }],
+            layout: layout
+        };
+
+        function getXLabels() {
+            return gd._fullLayout.xaxis._vals.map(function(d) { return d.text; });
+        }
+
+        Plotly.newPlot(gd, boxFig)
+        .then(function() {
+            expect(getXLabels()).toEqual(['1', '2', '3']);
+
+            // scatter cancels the forcing for its own figure only
+            return Plotly.newPlot(gd, scatterFig);
+        })
+        .then(function() {
+            return Plotly.react(gd, boxFig);
+        })
+        .then(function() {
+            expect(gd._fullLayout.xaxis._minDtick).toBe(1);
+            expect(getXLabels()).toEqual(['1', '2', '3']);
+        })
+        .then(done, done.fail);
+    });
 });
 
 describe('category preservation tests on gd passed to Plotly.react()', function() {

test/jasmine/tests/plot_api_test.js

@@ -1649,7 +1649,8 @@ describe('Test plot api', function () {
                     return Plotly.restyle(gd, { x0: 12.3 });
                 })
                 .then(function () {
-                    checkTicks('x', ['12', '12.5'], 'switched to numeric');
+                    // a single box forces one tick at its own position
+                    checkTicks('x', ['12.3'], 'switched to numeric');
                     expect(gd._fullLayout.xaxis.type).toBe('linear');
                 })
                 .then(done, done.fail);