Always pull force flag from component

[marvinhagemeister]

The way MobX works is that every observed component returns false from shouldComponentUpdate unless props have changed. They than trigger the child renders themselves via direct forceUpdate calls.

Our issue was that we only set the force flag sort-of globally during a render and would ignore any children that have been enqueued via forceUpdate in the same render cycle. This PR addresses that by ensuring that the force flag is always the one from the current component.

Tasks:

• Add a test case

Fixes #1983
Size -24 B 💯

[coveralls]

Coverage increased (+1.3%) to 99.767% when pulling c3b9cd6 on force-mobx into 02f8473 on master.

[JoviDeCroock]

Great work! I wanted to dig into this later too hehe beat me to it! Hero! 💯

[cristianbote]

Wow! 😁

[andrewiggins]

@marvinhagemeister Woo! Love it when we can save bytes and fix bugs :)

In src/components.js:132 you clear the force flag: component._force = false. Should this be somewhere else that guarentees the flag is always cleared even for children of whose _force flag is true.

In the UT that you added, do we also need to clear the components _force flag? What I'm thinking happens is that both Inner and Outer queue up a rerender, but renderComponent is only called with Outer, because Inner's _dirty flag is set to false when Outer's rerender is processed. Since Inner never goes into renderComponent (the condition on src/component.js:198 prevents it).

I took a stab at this but wanted to drop a message here so someone can look at it in case I forget.

[marvinhagemeister]

@andrewiggins Good catch! That's something I didn't think of. Maybe we just need to reset the flag at the end of diff(), once a component has finished rendering instead of in renderComponent