Refine StyleSheet Flow types #16741
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Refine StyleSheet Flow types #16741
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frantic
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Nov 8, 2017
Libraries/StyleSheet/StyleSheet.js
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| @@ -20,8 +20,8 @@ const flatten = require('flattenStyle'); | |||
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| export type Styles = {[key: string]: Object}; | |||
| export type StyleSheet<S: Styles> = {[key: $Keys<S>]: number}; | |||
| export type StyleValue = {[key: string]: Object} | number | false | null; | |||
| export type StyleProp = StyleValue | Array<StyleValue>; | |||
| export type StyleValue = Object | number | false | null | void; | |||
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According to flattenStyle any "falsy" value works so the users could do thing && styles.blah. I'm not sure if Flow has a special type representing falsy values, but might be a good idea to also include '' (empty string) here
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Good spot, thanks. I don't know of any special falsey type in Flow, so have just gone with empty string.
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Nov 19, 2017
Summary: Nice addition of the recent Flow types for style props in 9c29ee1, however I think there are some slight issues in the definition. `type Styles = {[key: string]: Object}` makes sense, as it's referring to the set of named style groups a user creates a `StyleSheet` from, e.g. ```javascript const styles: StyleSheet = StyleSheet.create({ container: { height: 20 }, text: { color: 'facebook#999', fontSize: 12, }, }: Styles) ``` However `type StyleValue = {[key: string]: Object}` doesn't make sense. You actually want only the `Object` portion of that definition, presuming it's meant to be used like below: ```javascript type MyTextProps = { style: StyleProp, } <MyText style={{ color: 'facebook#999', fontSize: 12 }}>Hello</Text> ``` --- I've also added `void` to the `StyleValue`, as undefined seems to be handled fine, and can be a useful shorthand in JSX. --- And finally, I've allowed nesting of style prop arrays, by making StyleProp self-referencing, as RN seems to flatten those without issue. This can be important if you're passing in a style prop quite high up the component tree, and sticking it in an array with other styles at several points while it's passed down. N/A (These types aren't referenced anywhere else) [INTERNAL] [MINOR] [StyleSheet] - Refine Flow types Closes facebook#16741 Reviewed By: frantic Differential Revision: D6278010 Pulled By: TheSavior fbshipit-source-id: 0170a233ab71d29f445786f5e695463f9730db3a
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Nice addition of the recent Flow types for style props in 9c29ee1, however I think there are some slight issues in the definition.
type Styles = {[key: string]: Object}makes sense, as it's referring to the set of named style groups a user creates aStyleSheetfrom, e.g.However
type StyleValue = {[key: string]: Object}doesn't make sense. You actually want only theObjectportion of that definition, presuming it's meant to be used like below:I've also added
voidto theStyleValue, as undefined seems to be handled fine, and can be a useful shorthand in JSX.And finally, I've allowed nesting of style prop arrays, by making StyleProp self-referencing, as RN seems to flatten those without issue. This can be important if you're passing in a style prop quite high up the component tree, and sticking it in an array with other styles at several points while it's passed down.
Test Plan
N/A (These types aren't referenced anywhere else)
Release Notes
[INTERNAL] [MINOR] [StyleSheet] - Refine Flow types