Context System: Don't explicitly set undefined value to children
#42686
+109
−3
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mirka
added
[Type] Bug
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Size Change: +110 B (0%) Total Size: 1.26 MB
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mirka
commented
Jul 25, 2022
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| render( | ||
| <ContextSystemProvider> | ||
| <ConnectedComponent /> |
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This test (passing on trunk) establishes how implicitly undefined children were not a problem as long as the underlying component did not do a cloneElement().
| expect( screen.getByText( 'Pass through' ) ).toBeInTheDocument(); | ||
| } ); | ||
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| test( 'should not accept children via `context`', () => { |
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I actually don't know if this is intentional/desirable, but it is the existing behavior in trunk.
Comment on lines
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| // Setting an `undefined` explicitly can cause unintended overwrites | ||
| // when a `cloneElement()` is involved. | ||
| if ( rendered !== undefined ) { | ||
| // @ts-ignore | ||
| finalComponentProps.children = rendered; | ||
| } |
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In the very unlikely case that someone wants to explicitly wipe out the inherent children of a component using cloneElement(), they can still pass children=null.
For normal components that don't involve cloneElement(), children overrides will be (and have been) ignored anyway.
ciampo
approved these changes
Jul 26, 2022
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Fixes #42380
What?
Prevents the Context System from explicitly setting an
undefinedvalue tochildren.Why?
There was a problem where an
Iconcomponent could not be rendered via theasprop.At first glance, this seemed like a general issue with context-connected components and the
asprop. However, after going through a bunch of test cases, the problem was narrowed down to a relatively specific condition — when the underlying component uses acloneElement()to create the output.There are some subtle differences in how
undefinedchildren are treated depending on how they are undefined. This is usually not a problem, except for when acloneElement()call overrides the original element'schildrenwithprops.children=undefined:gutenberg/packages/icons/src/icon/index.js
Lines 17 to 23 in a256669
How?
Several test cases related to the
childrenprop were added to the unit tests for the Context System. This helps us understand what the existing behavior is, and should give us sufficient confidence that the fix in this PR does not have unexpected side effects.Testing Instructions
In Storybook, try making a
<View as={ Icon }>story like in the code snippet above. The icon SVG should render correctly after the fix in this PR.