fix: consider a value matching selected item label a known value (CP)

src/vaadin-combo-box-mixin.html

@@ -708,23 +708,31 @@
         }
       } else {
         const toLowerCase = (item) => item && item.toLowerCase && item.toLowerCase();
-        const itemsMatchedByLabel = this.filteredItems
-          && this.filteredItems.filter(item => toLowerCase(this._getItemLabel(item)) === toLowerCase(this._inputElementValue))
-          || [];
+
+        // Try to find an item whose label matches the input value. A matching item is searched from
+        // the filteredItems array (if available) and the selectedItem (if available).
+        const itemMatchingByLabel = [...(this.filteredItems || []), this.selectedItem].filter((item) => {
+          return toLowerCase(this._getItemLabel(item)) === toLowerCase(this._inputElementValue);
+        })[0];
+
         if (this.allowCustomValue
           // to prevent a repetitive input value being saved after pressing ESC and Tab.
-          && !itemsMatchedByLabel.length) {
+          && !itemMatchingByLabel) {
 
+          // An item matching by label was not found, but custom values are allowed.
+          // Dispatch a custom-value-set event with the input value.
           const e = new CustomEvent('custom-value-set', {detail: this._inputElementValue, composed: true, cancelable: true, bubbles: true});
           this.dispatchEvent(e);
           if (!e.defaultPrevented) {
             const customValue = this._inputElementValue;
             this._selectItemForValue(customValue);
             this.value = customValue;
           }
-        } else if (!this.allowCustomValue && !this.opened && itemsMatchedByLabel.length > 0) {
-          this.value = this._getItemValue(itemsMatchedByLabel[0]);
+        } else if (!this.allowCustomValue && !this.opened && itemMatchingByLabel) {
+          // An item matching by label was found, select it.
+          this.value = this._getItemValue(itemMatchingByLabel);
         } else {
+          // Revert the input value
           this._inputElementValue = this.selectedItem ? this._getItemLabel(this.selectedItem) : (this.value || '');
         }
       }

test/vaadin-combo-box.html

@@ -286,6 +286,36 @@
             comboBox.inputElement.blur();
             expect(spy).to.not.have.been.called;
           });
+
+          it('should not fire when the custom value equals the label of the selected item', () => {
+            const spy = sinon.spy();
+            comboBox.addEventListener('custom-value-set', spy);
+            comboBox.selectedItem = {
+              label: 'foo',
+              value: 'bar'
+            };
+
+            comboBox.open();
+            comboBox.inputElement.value = 'foo';
+            comboBox.close();
+
+            expect(spy.called).to.be.false;
+          });
+
+          it('should fire when the custom value equals the value of the selected item', () => {
+            const spy = sinon.spy();
+            comboBox.addEventListener('custom-value-set', spy);
+            comboBox.selectedItem = {
+              label: 'foo',
+              value: 'bar'
+            };
+
+            comboBox.open();
+            comboBox.inputElement.value = 'bar';
+            comboBox.close();
+
+            expect(spy.calledOnce).to.be.true;
+          });
         });
       });