[FIX] web: DebouncedField: notify changes only when changed

Before this rev., if you opened a form view with, e.g. a float
field, that is unset, and then click on edit, then save, it
actually saved the new value for the float field (being 0),
whereas it shouldn't do any RPC as nothing changed.

This is because the former code couldn't detect if the value "0"
in the input is there because the field is still unset or if the
user simply set it to 0.

addons/web/static/src/js/fields/basic_fields.js

@@ -91,6 +91,13 @@ var DebouncedField = AbstractField.extend({
     init: function () {
         this._super.apply(this, arguments);
 
+        // isDirty is used to detect that the user interacted at least once with
+        // the widget, so that we can prevent it from triggering a field_changed
+        // in commitChanges if the user didn't change anything (this is required
+        // as sometimes it is hard to detect that an unset value is still unset,
+        // e.g. if a numerical field contains the value 0, is it because it is
+        // still unset or because the user set it to 0?
+        this.isDirty = false;
         if (this.DEBOUNCE && this.mode === 'edit') {
             this._doDebouncedAction = _.debounce(this._doDebouncedAction.bind(this), this.DEBOUNCE);
         }
@@ -108,7 +115,7 @@ var DebouncedField = AbstractField.extend({
      * @override
      */
     commitChanges: function () {
-        if (this.mode === 'edit') {
+        if (this.isDirty && this.mode === 'edit') {
             this._setValue(this._getValue());
         }
     },
@@ -158,6 +165,7 @@ var DebouncedField = AbstractField.extend({
      * @private
      */
     _onInput: function () {
+        this.isDirty = true;
         this._doDebouncedAction();
     },
 });

addons/web/static/tests/fields/basic_fields_tests.js

@@ -438,6 +438,35 @@ QUnit.module('basic_fields', {
         list.destroy();
     });
 
+    QUnit.test('do not trigger a field_changed if they have not changed', function (assert) {
+        assert.expect(2);
+
+        this.data.partner.records[1].qux = undefined;
+        this.data.partner.records[1].int_field = undefined;
+        var form = createView({
+            View: FormView,
+            model: 'partner',
+            data: this.data,
+            arch:'<form string="Partners">' +
+                    '<sheet>' +
+                        '<field name="qux" widget="float" digits="[5,3]"/>' +
+                        '<field name="int_field"/>' +
+                    '</sheet>' +
+                '</form>',
+            res_id: 2,
+            mockRPC: function (route, args) {
+                assert.step(args.method);
+                return this._super.apply(this, arguments);
+            }
+        });
+
+        form.$buttons.find('.o_form_button_edit').click();
+        form.$buttons.find('.o_form_button_save').click();
+
+        assert.verifySteps(['read']); // should not have save as nothing changed
+
+        form.destroy();
+    });
 
     QUnit.module('FieldEmail');