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Fixed an issue with nested contexts unwinding when server rendering. Issue #12984 #12985

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merged 8 commits into from Jun 11, 2018
Merged

Fixed an issue with nested contexts unwinding when server rendering. Issue #12984 #12985

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8ff3f62
Fixed an issue with nested contexts unwinding when server rendering. …
ericsoderberghp Jun 5, 2018
27bb329
Fixed an issue with search direction and stricter false checking
ericsoderberghp Jun 5, 2018
8d38f45
Use decrement infix operator
ericsoderberghp Jun 5, 2018
037c4d5
Streamlined existence checks
ericsoderberghp Jun 5, 2018
e69904c
Streamlined assignment. Removed redundant comment. Use null for array…
ericsoderberghp Jun 6, 2018
731c686
Made prettier
ericsoderberghp Jun 6, 2018
6d31d3a
Relaxed type checking and improved comment
ericsoderberghp Jun 6, 2018
5114a3e
Improve test coverage
gaearon Jun 11, 2018
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28 changes: 28 additions & 0 deletions packages/react-dom/src/__tests__/ReactDOMServerIntegrationNewContext-test.js
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Expand Up @@ -191,5 +191,33 @@ describe('ReactDOMServerIntegration', () => {
expect(e.querySelector('#theme').textContent).toBe('light');
expect(e.querySelector('#language').textContent).toBe('english');
});

itRenders(
'nested context unwinding',
async render => {
const Theme = React.createContext('dark');
const Language = React.createContext('french');

const App = () => (
<div>
<Theme.Provider value="light">
<Language.Provider>
<Theme.Provider value="dark">
<Theme.Consumer>
{theme => <div id="theme1">{theme}</div>}
</Theme.Consumer>
</Theme.Provider>
<Theme.Consumer>
{theme => <div id="theme2">{theme}</div>}
</Theme.Consumer>
</Language.Provider>
</Theme.Provider>
</div>
);
let e = await render(<App />);
expect(e.querySelector('#theme1').textContent).toBe('dark');
expect(e.querySelector('#theme2').textContent).toBe('light');
},
);
});
});
21 changes: 14 additions & 7 deletions packages/react-dom/src/server/ReactPartialRenderer.js
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Expand Up @@ -689,14 +689,21 @@ class ReactDOMServerRenderer {
this.providerStack[this.providerIndex] = null;
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What does .length assignment do in V8? I'd like to make sure it doesn't think the array length change is likely to "stay" because it changes all the time. I think just using null is more straightforward and less surprising to the engine (even though the typing isn't as nice for us).

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OK. But, going back to using null seems to require testing for null when accessing array items by index, since Flow has been told that null and undefined are expected array item values. Or, is there an alternate Flow syntax that allows us to remove the explicit checks?

this.providerIndex -= 1;
const context: ReactContext<any> = provider.type._context;
if (this.providerIndex < 0) {
context._currentValue = context._defaultValue;
} else {
// We assume this type is correct because of the index check above.
const previousProvider: ReactProvider<any> = (this.providerStack[
this.providerIndex
]: any);
// find the correct previous provider based on type
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This comment is redundant, IMO the code speaks for itself

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OK

let previousProvider;
if (this.providerIndex > -1) {
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Seems like we can remove this condition? For loop already covers it.

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OK.

for (let i = this.providerIndex; i >= 0; i -= 1) {
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If you don't mind, i-- would feel a bit more intuitive to me

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Done. I'm used to not allowing infix from our projects lint rules, old habits.

if (this.providerStack[i] !== null && this.providerStack[i] !== undefined &&
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So, do we actually need those checks? I wouldn't expect a provider "below" to ever be null. We only clear them out as we pop. As long as we check i doesn't get below zero we should be fine.

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Agreed. But, Flow doesn't seem to be aware of that. Perhaps we need some special Flow syntax I'm not aware of, which is highly likely?

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I addressed this by changing the array definition to be stricter and pop via setting the length. It didn't seem right to allow null as an array item but then not test for null when iterating over the array, even though the logic of how the array was being manipulated was OK.

(this.providerStack[i]: ReactProvider<any>).type === provider.type) {
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This comment was about why we felt comfortable using Flow any:

// We assume this type is correct because of the index check above.

Please keep it above the any case. Maybe change to "Flow type" to disambiguate.

// We assume this Flow type is correct because of the index check above.

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OK.

previousProvider = this.providerStack[i];
break;
}
}
}
if (previousProvider) {
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Let's initialize it to null and then compare to null instead of a truthy check.

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Good idea.

context._currentValue = previousProvider.props.value;
} else {
context._currentValue = context._defaultValue;
}
}

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