[FIX] web: grouped list multi edit with m2m

Before this commit, m2m fields were not updated when multi editing
in a grouped list.

Now, the fields are updated no matter how many levels of groupBys
are applied to the list.

Part of task 2078807

closes odoo/odoo#37589

Signed-off-by: Aaron Bohy (aab) <aab@odoo.com>

3 files changed, 13 insertions, 4 deletions

diff --git a/addons/web/static/src/js/views/basic/basic_model.js b/addons/web/static/src/js/views/basic/basic_model.js
index ce8d028d0af..d4e966440cb 100644
--- a/addons/web/static/src/js/views/basic/basic_model.js
+++ b/addons/web/static/src/js/views/basic/basic_model.js
@@ -3356,7 +3356,15 @@ var BasicModel = AbstractModel.extend({
         var viewType = view ? view.type : fieldInfo.viewType;
 
         var toFetch = {};
-        _.each(list.data, function (dataPoint) {
+
+        // flattens the list.data ids in a grouped case
+        let dataPointIds = list.data;
+        for (let i = 0; i < list.groupedBy.length; i++) {
+            dataPointIds = dataPointIds.reduce((acc, groupId) =>
+                acc.concat(this.localData[groupId].data), []);
+        }
+
+        dataPointIds.forEach(function (dataPoint) {
             var record = self.localData[dataPoint];
             if (typeof record.data[fieldName] === 'string'){
                 // in this case, the value is a local ID, which means that the
diff --git a/addons/web/static/src/js/views/list/list_controller.js b/addons/web/static/src/js/views/list/list_controller.js
index 611079ca3d5..fbd5e4a2af0 100644
--- a/addons/web/static/src/js/views/list/list_controller.js
+++ b/addons/web/static/src/js/views/list/list_controller.js
@@ -410,7 +410,7 @@ var ListController = BasicController.extend({
             if (validRecordIds.length > 0) {
                 const dialogOptions = {
                     confirm_callback: () => {
-                        this.model.saveRecords(recordId, validRecordIds, fieldName)
+                        this.model.saveRecords(this.handle, recordId, validRecordIds, fieldName)
                             .then(async () => {
                                 this._updateButtons('readonly');
                                 const state = this.model.get(this.handle);
diff --git a/addons/web/static/src/js/views/list/list_model.js b/addons/web/static/src/js/views/list/list_model.js
index 65526346c8e..9ba0b473a5a 100644
--- a/addons/web/static/src/js/views/list/list_model.js
+++ b/addons/web/static/src/js/views/list/list_model.js
@@ -37,15 +37,16 @@ odoo.define('web.ListModel', function (require) {
          * For a list of records, performs a write with all changes and fetches
          * all data.
          *
+         * @param {string} listDatapointId id of the parent list
          * @param {string} referenceRecordId the record datapoint used to
          *  generate the changes to apply to recordIds
          * @param {string[]} recordIds a list of record datapoint ids
          * @param {string} fieldName the field to write
          */
-        saveRecords: function (referenceRecordId, recordIds, fieldName) {
+        saveRecords: function (listDatapointId, referenceRecordId, recordIds, fieldName) {
             var self = this;
             var referenceRecord = this.localData[referenceRecordId];
-            var list = this.localData[referenceRecord.parentID];
+            var list = this.localData[listDatapointId];
             // generate all record values to ensure that we'll write something
             // (e.g. 2 records selected, edit a many2one in the first one, but
             // reset same value, we still want to save this value on the other