Multi-type prop validation is not consistent

[aphofstede]

Vue.js version

2.0.1

Reproduction Link

https://jsfiddle.net/alexman/f7sb0rd3/9/

Steps to reproduce

Create a component with a prop of type [String, Boolean] and instantiate it with a boolean value or shorthand prop notation. (<my-component my-prop></my-component>)

What is Expected?

Booleans are accepted and passed to the validator as a boolean value.

What is actually happening?

You'll see that it will not validate booleans / shorthand prop notation.
Defining it reversed, [Boolean, String], does seem to work as expected except for not being able to pass false as a value.

Observations

I noticed validateProp() does the following "magic", which doesn't seem to take the option of an array of types into account?

  if (getType(prop.type) === 'Boolean') {
    if (absent && !hasOwn(prop, 'default')) {
      value = false
    } else if (value === '' || value === hyphenate(key)) {
      value = true
    }
  }

[defcc]

getType func seems not to deal with multi-type props, it just returns the first type

I will try to make a pr

[posva]

I'm not sure to understand the issue. Were you expecting the value to be cast as a Boolean? Although you said it was either a String or a Boolean?. Why would using the order to specify what the prop should be cast to be non-consistent?

[aphofstede]

Not consistent: Because the behaviour differs between type: [Boolean, String] and type: [String, Boolean].
About expectations: Using just the type: Boolean does some magic to convert the eventual value to a boolean type. With multiple allowed types, when the caller passes a "boolean'able" value, I would expect value to be a boolean type also (which is then passed to the custom validator). If it cannot be resolved to a boolean but conforms to another type in the array of allowed types (and after it passes custom validation) -> also valid. Otherwise -> invalid.

[posva]

What do you mean by magic? Do you refer when there's no value?
I'd say it's normal to differ because types are differents (order in array matters)

[aphofstede]

I referred to the piece of code mentioned in "Observations" above.
Why does the order matter? I interpret it as "any of X, Y, Z"

[posva]

I'll share the rest of the team.