[FIX] web: pass context of changed field to onchange RPC

When a field with an onchange is changed, if there is a context
defined on the field in the arch, this context must be added to
the context sent with the onchange RPC.

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

@@ -861,12 +861,15 @@ var BasicModel = AbstractModel.extend({
         var self = this;
         var onchange_spec = this._buildOnchangeSpecs(record);
         var idList = record.data.id ? [record.data.id] : [];
-        var context = this._getContext(record);
-        var currentData = this._generateOnChangeData(record);
-
+        var options = {};
         if (fields.length === 1) {
             fields = fields[0];
+            // if only one field changed, add its context to the RPC context
+            options.fieldName = fields;
         }
+        var context = this._getContext(record, options);
+        var currentData = this._generateOnChangeData(record);
+
         return self._rpc({
                 model: record.model,
                 method: 'onchange',

addons/web/static/test/views/form_tests.js

@@ -2507,6 +2507,40 @@ QUnit.module('Views', {
         form.destroy();
     });
 
+    QUnit.test('context of onchanges contains the context of changed fields', function (assert) {
+        assert.expect(2);
+
+        this.data.partner.onchanges = {
+            foo: function () {},
+        };
+        var form = createView({
+            View: FormView,
+            model: 'partner',
+            data: this.data,
+            arch: '<form>' +
+                    '<group>' +
+                        '<field name="foo" context="{\'test\': 1}"/>' +
+                        '<field name="int_field" context="{\'int_ctx\': 1}"/>' +
+                    '</group>' +
+                '</form>',
+            mockRPC: function (route, args) {
+                if (args.method === 'onchange') {
+                    assert.strictEqual(args.args[4].test, 1,
+                        "the context of the field triggering the onchange should be given");
+                    assert.strictEqual(args.args[4].int_ctx, undefined,
+                        "the context of other fields should not be given");
+                }
+                return this._super.apply(this, arguments);
+            },
+            res_id: 2,
+        });
+
+        form.$buttons.find('.o_form_button_edit').click();
+        form.$('.o_form_input:first').val('coucou').trigger('input');
+
+        form.destroy();
+    });
+
     QUnit.test('navigation with tab key in form view', function (assert) {
         assert.expect(2);