[FIX] web: pivot unload filter, reset, load another filter

On a pivot view with a default filter which has column and row groupbys
Remove the filter
Collapse all columns and rows
Activate another Filter from favorite which has a column groupby at least

Before this commit, the columns were not displayed in the DOM, though RPC's
and internal data were actually correct
This was because we considered the changes had been done "in place"
taking the old tree to build the new one for the columns
when really, we should have recomputed the column tree

After this commit, the columns display the group we want

OPW 1935155

closes odoo/odoo#31247

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

@@ -277,8 +277,10 @@ var PivotModel = AbstractModel.extend({
                 self._updateMainGroupBys(old_row, self.data.main_row);
             }
 
-            self._updateTree(old_col.root, self.data.main_col.root);
-            self._updateMainGroupBys(old_col, self.data.main_col);
+            if (!('pivot_column_groupby' in (params.context || {}))) {
+                self._updateTree(old_col.root, self.data.main_col.root);
+                self._updateMainGroupBys(old_col, self.data.main_col);
+            }
         });
     },
     /**

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

@@ -899,6 +899,95 @@ QUnit.module('Views', {
         pivot.destroy();
     });
 
+    QUnit.test('Unload Filter, reset display, load another filter', function (assert) {
+        assert.expect(18);
+
+        var pivot = createView({
+            View: PivotView,
+            model: "partner",
+            data: this.data,
+            arch: '<pivot>' +
+                        '<field name="foo" type="measure"/>' +
+                '</pivot>',
+            viewOptions: {
+                context: {
+                    pivot_measures: ['foo'],
+                    pivot_column_groupby: ['customer'],
+                    pivot_row_groupby: ['product_id'],
+                },
+            },
+        });
+
+        // Check Columns
+        assert.strictEqual(pivot.$('thead .o_pivot_header_cell_opened').length, 1,
+            'The column should be grouped');
+        assert.strictEqual(pivot.$('thead tr:contains("First")').length, 1,
+            'There should be a column "First"');
+        assert.strictEqual(pivot.$('thead tr:contains("Second")').length, 1,
+            'There should be a column "Second"');
+
+        // Check Rows
+        assert.strictEqual(pivot.$('tbody .o_pivot_header_cell_opened').length, 1,
+            'The row should be grouped');
+        assert.strictEqual(pivot.$('tbody tr:contains("xphone")').length, 1,
+            'There should be a row "xphone"');
+        assert.strictEqual(pivot.$('tbody tr:contains("xpad")').length, 1,
+            'There should be a row "xpad"');
+
+        // Equivalent to unload the filter
+        var reloadParams = {
+            context: {},
+        };
+        pivot.reload(reloadParams);
+        // collapse all headers
+        pivot.$('.o_pivot_header_cell_opened').click();
+        pivot.$('.o_pivot_header_cell_opened').click();
+
+        // Check Columns
+        assert.strictEqual(pivot.$('thead .o_pivot_header_cell_closed').length, 1,
+            'The column should not be grouped');
+        assert.strictEqual(pivot.$('thead tr:contains("First")').length, 0,
+            'There should not be a column "First"');
+        assert.strictEqual(pivot.$('thead tr:contains("Second")').length, 0,
+            'There should not be a column "Second"');
+
+        // Check Rows
+        assert.strictEqual(pivot.$('tbody .o_pivot_header_cell_closed').length, 1,
+            'The row should not be grouped');
+        assert.strictEqual(pivot.$('tbody tr:contains("xphone")').length, 0,
+            'There should not be a row "xphone"');
+        assert.strictEqual(pivot.$('tbody tr:contains("xpad")').length, 0,
+            'There should not be a row "xpad"');
+
+        // Equivalent to load another filter
+        reloadParams = {
+            context: {
+                pivot_measures: ['foo'],
+                pivot_column_groupby: ['customer'],
+                pivot_row_groupby: ['product_id'],
+            },
+        };
+        pivot.reload(reloadParams);
+
+        // Check Columns
+        assert.strictEqual(pivot.$('thead .o_pivot_header_cell_opened').length, 1,
+            'The column should be grouped');
+        assert.strictEqual(pivot.$('thead tr:contains("First")').length, 1,
+            'There should be a column "First"');
+        assert.strictEqual(pivot.$('thead tr:contains("Second")').length, 1,
+            'There should be a column "Second"');
+
+        // Check Rows
+        assert.strictEqual(pivot.$('tbody .o_pivot_header_cell_opened').length, 1,
+            'The row should be grouped');
+        assert.strictEqual(pivot.$('tbody tr:contains("xphone")').length, 1,
+            'There should be a row "xphone"');
+        assert.strictEqual(pivot.$('tbody tr:contains("xpad")').length, 1,
+            'There should be a row "xpad"');
+
+        pivot.destroy();
+    });
+
     QUnit.test('correctly uses pivot_ keys from the context', function (assert) {
         assert.expect(7);