Added checks for incorrect usage of innerHTML. Fixes #1370

[jimfb]

This PR adds checks to prevent the incorrect setting of inner html, to make it easier for developers to spot hazards in their code and avoid security holes. There have been several discussions about how best to handle the innerHTML issue ( most notably, the public discussion here: #1515 ), and the conclusion of these discussions was the creation of issue #1370, which is fixed by this commit.

[sophiebits]

Does anyone try to do this? I've never heard of anyone trying to…

[jimfb]

It's the intuitive thing to try, if you haven't read about dangerouslySetInnerHTML, so it's worth checking if for no other reason than to hint to the user where they might look for the supported function.

[sebmarkbage]

This == null check is already happening twice (now three). We still need the check once, so as long as these are within the block that only affects non-null values, I think we're fine adding invariants there.

[jimfb]

Added if-check outside call to invariant call, as per @sebmarkbage

[sebmarkbage]

We never throw strings because the stack is attached to the Error object. We also compress invariant error messages. So we should use the invariant module even if the first argument is false, although in this case it should be props == null.

[sebmarkbage]

Double space at the end here. One is enough. :)

There should also be a period. You can use the backticks it indicate what is code and what is period.

[jimfb]

Ready to merge?

[zpao]

This should be a warning, not an invariant. There's no reason to stop execution flow.

[jimfb]

Done.

[zpao]

Let's a get a better description in the summary here explaining the rational. It actually wasn't clear to me that we had settled on what we were doing with innerHTML.

[sebmarkbage]

Warnings should move into the __DEV__ block so that they never execute in prod.

We don't do that automatically, partially because we don't have good dead-code elimination but mostly because we don't know if there is extra work that can be removed in production rather than just this statement.

[jimfb]

Done.