René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Support for Attributes?","articleBody":"I'm now happy with Fable's reflection, which allows me to do what [pydantic](https://github.com/samuelcolvin/pydantic) does in the python world.\r\n\r\nHowever I want to step further. I want to allow syntax sugars in the configuration, but get the same syntax tree.\r\n\r\n```F#\r\ntype github_url= { url: string;  [\u003cDefault(\"main\")\u003e] branch: string}\r\n\r\ntype myconfig = \r\n{\r\n   [\u003cAllowSingular\u003e] author: string array\r\n   url : github_url\r\n    ...\r\n}\r\n```\r\n\r\nBy using attributes, I want to control JSON deserialization, to parse into the same results for\r\n\r\n```json\r\n{\r\n    \"author\" :  [\"fable\"],\r\n    \"url\" : { \"name\": \"xxx/xxx\", \"branch\", \"main\" },\r\n    ...\r\n}\r\n```\r\n\r\nand \r\n\r\n\r\n```json\r\n{ \r\n    \"author\":  \"fable\",\r\n    \"url\": \"xxx/xxx\"\r\n}\r\n```\r\n\r\nIs the use of attributes possible in Fable?","author":{"url":"https://github.com/thautwarm","@type":"Person","name":"thautwarm"},"datePublished":"2022-01-16T03:46:15.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":5},"url":"https://github.com/48/Fable.Python/issues/48"}