Moar Warnings

[sebmarkbage]

Warn if accessing .type on a factory

This was an important convenience as an upgrade path but shouldn't be necessary if you're using best-practice of calling createFactory in the consuming component.

Warn if using Maps as children

We're not sure if this is the way we want to support this API. It creates two ways of doing things. It may conflict with a model that lazily flattens all children into iterable flat lists.

It is convenient to avoid needing to explicitly redefine the key of Maps. However, this use case isn't as common as having an iterable where the key is on the value, not the key.

I'm also not comfortable with the feature testing that we're doing. It seems potentially fragile.

We still support other iterables though.

cc @leebyron

Warn if getDOMNode or isMounted is accessed in render

This is an anti-pattern that can be easily avoided by putting the logic in componentDidMount and componentDidUpdate instead.

Otherwise creates a dependency on stale data inside render without enforcing a two-pass render.

[leebyron]

I'm also not comfortable with the feature testing that we're doing. It seems potentially fragile.

The testing we are doing is pretty close to the spec, so it should be robust. The spec describes all uses of @@Iterable properties as having the same function object value as the default iteration function property (values for Array and Set, entries for Map)