having isComputed alongside to isRef and isReactive

[soundlake]

Hello devs.

import { isReactive, isRef, computed, ref } from 'vue';

const n = ref(0)
const double = computed(() => n.value * 2)

isReactive(double) // false
isRef(double) // false

I'd like to have a way to check if a value is computed. Especially since we have isRef and isReactive already, why not we have isComputed?

[skirtles-code]

isRef(double) will be true, not false:

• Playground

Though writing {{ isRef(double) }} directly in the template will yield false due to the automatic unwrapping.

isRef() should return true for all types of ref, whether they were created with ref(), computed(), toRef() or customRef().

Usually it doesn't matter what type of ref it is, just that it's a ref.

In cases where you need to know whether a ref is read/write or read-only you can use isReadonly().

That said, there are some rare use cases where detecting a computed is useful because it needs to be treated differently from other refs. e.g. When serialising data you'd typically want to skip computed refs because they're derived from other values. As far as I'm aware, there currently isn't an official way to achieve that, though it has been discussed previously, e.g. see #4165. It is relatively easy to implement in userland though.