Fixed nested themes not being republished on outer theme changes

[Andarist]

What:

This fixes a bug when having nested ThemeProviders and updating outer theme the change is not reaching the StyledComponent

<ThemeProvider theme={{}}>
	<ThemeProvider theme={{}}>
		<StyledComponent>
	</ThemeProvider>
</ThemeProvider>

Why:

This is a bug fix.

How:
Using publish in the nested ThemeProviders subscriptions.

Checklist:

• Documentation - N/A
• Tests
• Code complete

[emmatown]

emotion-theming is basically the same as styled-components' theming so I think this bug might also exist in styled-components.

I also checked and it seems like this would also happen in glamorous too.

cc @kentcdodds @mxstbr

Edit: Just reproduced it with glamorous and styled-components.

[Andarist]

Nice catch! I've sent out PRs to both, still need to sit down to write a test and port it to all 3 repos.

Those ThemeProviders are basically the same in all packages, wouldn't it make sense to join forces and have a single ThemeProvider package to maintain?

[codecov]

Codecov Report

Merging #497 into master will increase coverage by <.01%.
The diff coverage is 100%.

Impacted Files	Coverage Δ
packages/emotion-theming/src/theme-provider.js	100% <100%> (ø)	⬆️

[emmatown]

@Andarist There's been an effort to do that in https://github.com/cssinjs/theming but it isn't the exact API we need, it's not as performant and no one has been particularly motivated to change it.

[Andarist]

@mitchellhamilton I've added a test so the PR is ready to merge (I think 😄 )

There's been an effort to do that in https://github.com/cssinjs/theming but it isn't the exact API we need, it's not as performant and no one has been particularly motivated to change it.

That's a bummer, seems really sad having to reimplement this fix in every lib when their codebases around this component is 90+% the same.

[emmatown]

Thanks!!