Request: Add support for changing a Array<?type> to a Array<type> via 'filter'

[oreqizer]

Let's say I have the following:

const maybeGet = (param: string): ?Object => param === "correct" ? { data: "data" } : null;

I want to fetch a bunch of those, that will give me Array<?Object>, then filter out those that don't match. That should produce Array<Object>. Say I want to do this:

function fetchStuff(params: Array<string>): Array<Object> {  // NOPE, Flow shouts at me
  const maybeObjs: Array<?Object> = params.map(maybeGet);

  return maybeObjs.filter(id => id);  // all nulls will get removed
}

Would it be possible to permit something like this? Maybe some other neat way of replicating this behavior?

Note:
I managed to do this via reduce:

function fetchStuff(params: Array<string>): Array<Object> {  // OK
  const maybeObjs: Array<?Object> = params.map(maybeGet);

  return maybeObjs.reduce((arr, obj) => {
    return obj ? arr.concat(obj) : arr;
  }, []);
}

but it's not really nice to do this all the time, when the filter verison is so much simpler.

[vkurchatkin]

This is possible already:

const arr: Array<?{}> = [null, {}, {}, null];
const arr1: Array<{}> = arr.filter(Boolean);

[gabro]

Isn't this the same topic as #1414?

[oreqizer]

ohhh thanks @vkurchatkin didn't try it that way. been using the id => id thing