[IMP] web: list: add expand attrs

When this attribute is set to true on the <tree> root node, in a
grouped list view, first level groups are automatically opened.

Part of task 1915702

addons/web/static/src/js/views/basic/basic_model.js

@@ -4323,8 +4323,11 @@ var BasicModel = AbstractModel.extend({
                         self.localData[newGroup.id] = newGroup;
                     } else if (!newGroup.openGroupByDefault || openGroupCount >= self.OPEN_GROUP_LIMIT) {
                         newGroup.isOpen = false;
+                    } else if ('__fold' in group) {
+                        newGroup.isOpen = !group.__fold;
                     } else {
-                        newGroup.isOpen = '__fold' in group ? !group.__fold : true;
+                        // open the group iff it is a first level group
+                        newGroup.isOpen = !self.localData[newGroup.parentID].parentID;
                     }
                     list.data.push(newGroup.id);
                     list.count += newGroup.count;

addons/web/static/src/js/views/list/list_view.js

@@ -54,6 +54,7 @@ var ListView = BasicView.extend({
         this.rendererParams.addCreateLineInGroups = this.rendererParams.editable && this.controllerParams.activeActions.create;
 
         this.loadParams.limit = this.loadParams.limit || 80;
+        this.loadParams.openGroupByDefault = !!JSON.parse(this.arch.attrs.expand || "0");
         this.loadParams.type = 'list';
     },
 

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

@@ -4065,6 +4065,60 @@ QUnit.module('Views', {
         delete widgetRegistry.map.asyncWidget;
     });
 
+    QUnit.test('grouped list with expand attribute', async function (assert) {
+        assert.expect(6);
+
+        var list = await createView({
+            View: ListView,
+            model: 'foo',
+            data: this.data,
+            arch: '<tree expand="1"><field name="foo"/></tree>',
+            groupBy: ['bar'],
+            mockRPC: function (route, args) {
+                assert.step(args.method || route);
+                return this._super.apply(this, arguments);
+            }
+        });
+
+        assert.containsN(list, '.o_group_header', 2);
+        assert.containsN(list, '.o_data_row', 4);
+
+        assert.verifySteps([
+            'read_group',
+            '/web/dataset/search_read',
+            '/web/dataset/search_read',
+        ]);
+
+        list.destroy();
+    });
+
+    QUnit.test('grouped list (two levels) with expand attribute', async function (assert) {
+        // the expand attribute only opens the first level groups
+        assert.expect(5);
+
+        var list = await createView({
+            View: ListView,
+            model: 'foo',
+            data: this.data,
+            arch: '<tree expand="1"><field name="foo"/></tree>',
+            groupBy: ['bar', 'int_field'],
+            mockRPC: function (route, args) {
+                assert.step(args.method || route);
+                return this._super.apply(this, arguments);
+            }
+        });
+
+        assert.containsN(list, '.o_group_header', 6);
+
+        assert.verifySteps([
+            'read_group', // global
+            'read_group', // first group
+            'read_group', // second group
+        ]);
+
+        list.destroy();
+    });
+
     QUnit.test('editable grouped lists', async function (assert) {
         assert.expect(4);
 

doc/reference/views.rst

@@ -221,6 +221,9 @@ root can have the following attributes:
     corresponding attribute to ``false``
 ``limit``
     the default size of a page. It should be a positive integer
+``expand``
+    when the list view is grouped, automatically open the first level of groups
+    if set to true (default: false)
 
 Possible children elements of the list view are:
 

odoo/addons/base/rng/tree_view.rng

@@ -42,6 +42,14 @@
                     </rng:choice>
                 </rng:attribute>
             </rng:optional>
+            <rng:optional>
+                <rng:attribute name="expand">
+                    <rng:choice>
+                        <rng:value>1</rng:value>
+                        <rng:value>0</rng:value>
+                    </rng:choice>
+                </rng:attribute>
+            </rng:optional>
             <rng:zeroOrMore>
                 <rng:choice>
                     <rng:ref name="control"/>