Before this commit, Env was an indexed type, this means that one could
write env.anything, and it would accept it as a valid type. This is
actually quite dangerous, because we lose the typing advantages for all
keys that are properly defined.
For example, if a component is defined as:
class MyComponent extends Component<Props> {
...
}
Then Typescript will let it use anything from the environment, even if
it is wrong. So, most properly typed Typescript applications should use
instead a sub environment:
interface MyAppEnv extends Env {
someKey: someValue
}
Then, the component should be defined this way:
class MyComponent extends Component<Props, MyAppEnv> {
...
}
Before this commit, any typos in the environment accesses would not be
noticed by typescript.
In most cases, we just want Component<any, Env>. But since it was so
annoying to have always the type Env, we actually used
Component<any,any> everywhere.
With this commit, the generic types have a default (and their order is
swapped), so we can simply use Component in most cases, and
Component<Props> when we want to type the props.
It now takes two arguments: parent (optional, only for non-root
components) and props (optional). In the case of the root component,
the env is taken from the config (config.defaultEnv). If it doesn't
exists, the default env is created on the fly.
Closes#306
Géry Debongnie