[TypeScript] boolean optional prop is typed as foo?: boolean

[jacekkarczmarczyk]

Following code

// main.ts
import Vue from 'vue';
import { defineComponent } from '@vue/composition-api';

let bool = false;

Vue.extend({
  props: { foo: Boolean },
  mounted () {
    bool = this.foo; // No error
  },
});

defineComponent({
  props: { foo: Boolean },
  setup (props) {
    bool = props.foo; // <!--- Error
  },
});

throws a TS error:

  Type 'undefined' is not assignable to type 'boolean'.
    18 |   props: { foo: Boolean },
    19 |   setup (props) {
  > 20 |     bool = props.foo;
       |     ^
    21 |   },
    22 | });

[danielroe]

This looks like the correct behaviour to me.

[jacekkarczmarczyk]

This looks like the correct behaviour to me.

Doesn't look for me, if prop is not passed its value is bool: https://codepen.io/jkarczm/pen/VwKOEzp

[pikax]

Is not the correct behaviour, if Boolean is passed, it will be implicit converted to false if not provided

[jacekkarczmarczyk]

that can be closed i guess?