[FIX] web: Pivot: handle __count__ measure

The former implementation of the Pivot view used __count__ as
magic field to display the number of records in groups. However,
in filters defined in xml, __count is used instead of __count__,
so it crashed when such filters were activated.

With the new views, we made those filters work by using __count.
However, if a user saved filters using __count__ at that time as
favorite, activating them in the new views produces a crash as
well.

This rev. adds a compatibility layer to ensure that the pivot
view handles both __count__ and __count measures uniformly.

addons/web/static/src/js/views/pivot/pivot_model.js

@@ -222,6 +222,17 @@ var PivotModel = AbstractModel.extend({
      * @returns {Deferred}
      */
     load: function (params) {
+        // In the preview implementation of the pivot view (a.k.a. version 2),
+        // the virtual field used to display the number of records was named
+        // __count__, whereas __count is actually the one used in xml. So
+        // basically, activating a filter specifying __count as measures crashed.
+        // Unfortunately, as __count__ was used in the JS, all filters saved as
+        // favorite at that time were saved with __count__, and not __count.
+        // So in order the make them still work with the new implementation, we
+        // simply rename __count__ into __count at this unique entry point.
+        var measures = _.map(params.measures, function (measure) {
+            return measure === '__count__' ? '__count' : measure;
+        });
         this.initialDomain = params.domain;
         this.initialRowGroupBys = params.rowGroupBys;
         this.fields = params.fields;
@@ -231,7 +242,7 @@ var PivotModel = AbstractModel.extend({
             context: _.extend({}, session.user_context, params.context),
             groupedBy: params.groupedBy,
             colGroupBys: params.colGroupBys,
-            measures: params.measures,
+            measures: measures,
             sorted_column: {},
         };
         this.defaultGroupedBy = params.groupedBy;

addons/web/static/tests/views/pivot_tests.js

@@ -859,4 +859,33 @@ QUnit.module('Views', {
         pivot.destroy();
     });
 
+    QUnit.test('pivot still handles __count__ measure', function (assert) {
+        // for retro-compatibility reasons, the pivot view still handles
+        // '__count__' measure.
+        assert.expect(2);
+
+        var pivot = createView({
+            View: PivotView,
+            model: "partner",
+            data: this.data,
+            arch: '<pivot></pivot>',
+            mockRPC: function (route, args) {
+                if (args.method === 'read_group') {
+                    assert.deepEqual(args.kwargs.fields, ['__count'],
+                        "should make a read_group with field __count");
+                }
+                return this._super(route, args);
+            },
+            viewOptions: {
+                context: {
+                    pivot_measures: ['__count__'],
+                },
+            },
+        });
+
+        var $countMeasure = pivot.$buttons.find('li[data-field=__count]');
+        assert.ok($countMeasure.hasClass('selected'), "The count measure should be activated");
+
+        pivot.destroy();
+    });
 });});