Optional boolean prop gives type `Ref<boolean | undefined>` which should be `Ref<boolean>` in vue

[jd-solanki]

SFC Playground: https://sfc.vuejs.org/#eNp9kN1qwzAMhV9F+KYbNDa7DW7H2AvsAXyTpkqTEv8gOy0j+N0npz9sHfTO50j6ZJ1ZfIQgTxOKWujY0hASRExT2Bo32OApwQyEHWToyFtYcevqXvr0Nlx9qYooJC5rdUExhEVCG8YmISsAvcwofmt1L4i1uBAr2wR5jN7xd+bSbq6FaEQNi1M83lK0EX1KIdZKxa4tq49RejoofkmaXBosSoy22pE/RyQGG7H+xVBsnpAqQrdHQnrGfGj9xy3YbFzmU25BPEYKY+MOGyPKMXx/611MEMiHCBvYYzc4/CpKL3fG3p/fa9h5P2LDMebty+vzZPu37Twvc5AzVMAifQf03c3Tilv+Bp9/APuhswM=

Here, we get show type as Ref<boolean> however in VS Code it is Ref<boolean | undefined> 🤔

[jmroon]

This is correct behavior if you have strictNullChecks on in typescript. Any optional property should be type | undefined.

The whole point of having strict on and having the property as optional is that you need to explicitly handle cases where it may be undefined. However, in the case of a boolean there's really no impact, since undefined is a falsy value anyways.

My guess is the SFC playground doesn't have strict mode on.

[xiaoxiangmoe]

Type definition for defineProps is in https://github.com/vuejs/core/blob/1fa3d9573051f549e6d381a5e88ec8d5d855e4c9/packages/runtime-core/src/apiSetupHelpers.ts#L61

Please create an issue in vuejs/core