Support optional properties in objects about flow

[gcanti]

As for v0.4 this issue seems fixed:

/* @flow */

var x: {a?: string;} = {}; // ok!

[jwebcat]

I know this is an old issue but just in case someone else is curious about the comment of @romulof you have to type the object like so:

const config : Object = {
  baseURL: "apiUrl",
};

and no more error voila

[avikchaudhuri]

You can do b: null or b: undefined in the myThing literal to get by.

We may support optional property syntax in types, like so { a: ?any; b?: any } to let you omit properties, like you can omit arguments when parameters are declared optional. So that would typecheck your code as is.

[Raynos]

There is a difference between optional properties and nullable properties.

{ b?: String } means if the b property exist then enable that feature with the string argument.

{ b: String | null } means if the b property does not exist then default its value and use the feature.

One is for optional features, the other is for default values.

[gcanti]

+1

[samwgoldman]

Can this be closed?

[samwgoldman]

Closing. Please reopen if this is still an issue.

[romulof]

const config = {
  baseURL: apiUrl,
};

if (accessToken) { // <-- property `headers`. Property not found in object literal
  config.headers = {
    Authorization: `Bearer ${accessToken}`,
  };
}

Do I have to manually add type hints to config to suppress this error message?

[matthewchung74]

I know this is old, but am running into the case where I am checking a property that does not exist in a flow type.

var x: {a?: string;} = {}; // ok!
if (x.b ==="something") { 
  // do something
}

I think it would be helpful if this also gave an error.