[react-redux] DefaultProps support

I was trying to add connect to a component that has defaultProps and I had a hard time getting it right, even thought I could.

One thing I noticed while looking for ways to do it, is that there is an issue on the current tests: https://github.com/flow-typed/flow-typed/blob/master/definitions/npm/react-redux_v5.x.x/flow_v0.89.x-/test_connect.js#L10

That line should be passthroughWithDefaultProp: number, (not optional) because that component has passthroughWithDefaultProp as a defaultProp. When trying to use passthroughWithDefaultProp inside that component, even though that prop is always a number (guaranteed by defaultProp) Flow will complain that it can be a number or undefined, which is not ideal.

Also note that on this Flow documentation example foo is declared as number and not an options `number: https://flow.org/en/docs/react/hoc/#toc-exporting-wrapped-components

This try-flow link shows the problem I’m trying to point out: https://flow.org/try/#0PQKgBAAgZgNg9gdzCYAoVBLAtgBzgJwBdkwBDAZzACUBTUgY2KnzizAHJ87H2BudYMDABJAHb0CXRgC4wAV3IZRAczBwchDHFGkYYKATJgAJjShKaxk2dJyYhAAosc5dIQCeOGmCfryARjAAXjAAbwAfVDAwQTAAFQALDEpyBLg7K1E4YgAjb3VNbV0wPPpbcnyoMEIE71NzUUtrKFt7XxcAOiiwAA8AfllyQnwlZVRwgF9+VHoYCkoADTAaHsIaUWNKWgZCDoBhVjxG0UIAHnaAgD4w7qHSTXpm1sdnShDQ7uie2XZ2bonulwNjR8AAKACUN2i0ViIJY+E+YC4hDk+FE1SS5A6OFeHR6YAA1Bw+P9UADULEDvgpIRZAA5bLeNJIABi8CQCG07CYpAwegwVQQ3g8XjAGGIFDAAAN3INhqMpWAEOKEhi6jY7C8-G5PN4LgAmYJhSLRWVgIYjFTjKboWbzMAATWWq3Wm2o3F2B1w2nWZwN1w+0TuDyemouRsD0LNv1J0SBpjBkMjMKEWWW1IIAEJEcjUeiaslsbj3ITifxogDybEGWswMywGzEEquTy+XWQTQADQlOSt+xK2rorhYOAAN1G0vqzwuitBFW8jVWztIuBgNHBqFBpydwEusm2jA6AFE11hfacRTQ4FUHZdwdNYgApBTEVKICf1xtIFp8yjKmpGFk6IFFoOh6Di6hKiq6TEFKU5hq8Uo6qKFwAMwRiaYAAF5ypaYyTNMdrkJQABazprBsWwevshw+ic5yvKhAaAq6IIQlC0K5miGKFhBnRYaWvzlmAlYCEIR4ZgiW5kbu+7USeNBnvRl7XmAJF3rwQA

Here is how I made it work, but maybe there is a way to avoid having to use React.Config ourselves?:

import * as React from 'react';

type OwnProps = {|
  x: number
|};

type Props = {|
  ...OwnProps,
  // no state props
|};

class Comp extends React.Component<Props> {
  static defaultProps = { x: 3 };
  ...
}

type DefaultProps = {| x: number |};
type Config = React.Config<Props, DefaultProps>;
type OwnConfig = React.Config<OwnProps, DefaultProps>;

connect<Config, OwnConfig, _, _, _, _>()(Comp);

[AndrewSouthpaw]

Nice work @fabiomcosta, would you mind documenting this somewhere useful? Maybe in the react-redux libdef?

[jbrown215]

In the way Flow models react, Props should be the type of this.props and Config is the type of the Props with all defaultProps marked optional. The way you handled it in your example at the bottom of this issue is exactly correct!