## Problem/Motivation Found by the #3582974 coverage sweep. `InputDefinition::fromDataDefinition()` mishandles plain (non-config) typed-data definitions in two ways: 1. **Unlabeled definitions crash.** Typed-data labels are optional, but the factory passes `$definition->getLabel()` (NULL) straight into the `InputDefinition` constructor, whose `$label` parameter is `string|TranslatableMarkup` — a `TypeError`. 2. **List item definitions lose their type.** For a plain `ListDataDefinition`, the recursive item conversion reads `$definition->toArray()['type']`, which is not set on item definitions ("Undefined array key" warning), so the resulting item `InputDefinition` has a NULL data type. Reproduction (kernel): ```php $list = ListDataDefinition::create('string')->setLabel('Tags'); $definition = InputDefinition::fromDataDefinition($list); // TypeError from the item's NULL label; with a label set, the item's // data type comes out NULL instead of 'string'. ``` The config-schema path (`fromConfigSchema()`) is unaffected — covered green by `InputDefinitionFactoryTest`. ## Proposed resolution - Fall back to a generated label (e.g. the data type or property name) when `getLabel()` is NULL, matching the `create()` factory's placeholder pattern. - Resolve the item data type from `$definition->getItemDefinition()->getDataType()` instead of the `toArray()` array, and guard the `type` read generally. - Restore the `testFromDataDefinitionList` kernel test (written during #3582974, pulled from that MR to keep it green): ```php public function testFromDataDefinitionList(): void { $list = ListDataDefinition::create('string')->setLabel('Tags'); $definition = InputDefinition::fromDataDefinition($list); $this->assertInstanceOf(ListInputDefinition::class, $definition); $this->assertSame('string', $definition->getItemDefinition()->getDataType()); } ``` ## AI usage (if applicable) - [x] **AI Assisted Issue:** This issue was generated with AI assistance, but was reviewed and refined by the creator. - [ ] **AI Assisted Code:** This code was mainly generated by a human, with AI autocompleting or parts AI generated, but under full human supervision. - [x] **AI Generated Code:** This code was mainly generated by an AI with human guidance, and reviewed, tested, and refined by a human. - [ ] **Vibe Coded:** This code was generated by an AI and has only been functionally tested.