Fix crash when ordering categories by value with null coordinates

draftlogs/7855_fix.md

@@ -0,0 +1 @@
+- Fix crash when ordering categories by value (e.g. `sum descending`) with `null` coordinates [[#7855](https://github.com/plotly/plotly.js/pull/7855)]

src/plots/plots.js

@@ -3188,6 +3188,10 @@ function sortAxisCategoriesByValue(axList, gd) {
                         catIndex = cdi.p;
                         if(catIndex === undefined) catIndex = cdi[axLetter];
 
+                        // Skip points whose position is not a valid category
+                        // (e.g. a null/NaN coordinate maps to BADNUM)
+                        if(!(catIndex + 1)) continue;
+
                         value = cdi.s;
                         if(value === undefined) value = cdi.v;
                         if(value === undefined) value = isX ? cdi.y : cdi.x;

test/jasmine/tests/calcdata_test.js

@@ -1215,6 +1215,21 @@ describe('calculated data and points', function() {
                 })
                 .then(done, done.fail);
             });
+
+            it('does not throw when a category coordinate is null and ordering by value', function(done) {
+                Plotly.newPlot(gd, [{
+                    type: 'bar',
+                    x: ['a', null, 'b'],
+                    y: [3, 5, 7]
+                }], {
+                    xaxis: {type: 'category', categoryorder: 'sum descending'}
+                })
+                .then(function() {
+                    // the null point is dropped, remaining categories are ordered by value
+                    expect(gd._fullLayout.xaxis._categories).toEqual(['b', 'a']);
+                })
+                .then(done, done.fail);
+            });
         });
     });