Fix when functional component render method retrun null (fix #5536) #5539
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src/core/vdom/create-element.js
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| @@ -99,7 +99,7 @@ export function _createElement ( | |||
| // direct component options / constructor | |||
| vnode = createComponent(tag, data, context, children) | |||
| } | |||
| if (vnode !== undefined) { | |||
| if (vnode !== undefined && vnode !== null) { | |||
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yes but the lint forced to use !==
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Actually you can just use isUndef(vnode) here
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flow has some problems
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@yyx990803
if use isUndef like this:
if (isUndef(vnode)) {
return createEmptyVNode()
} else {
if (ns) applyNS(vnode, ns)
return vnode
}or use isDef
then run test:
> vue@2.3.0 test /Users/xiongyang/workspace/gebilaoxiong/vue
> npm run lint && flow check && npm run test:types && npm run test:cover && npm run test:e2e -- --env phantomjs && npm run test:ssr && npm run test:weex
> vue@2.3.0 lint /Users/xiongyang/workspace/gebilaoxiong/vue
> eslint src build test
src/core/vdom/create-element.js:106
106: return vnode
^^^^^ undefined. This type is incompatible with the expected return type of
51: ): VNode {
^^^^^ VNode
src/core/vdom/create-element.js:111
111: vnode.ns = ns
^^ property `ns`. Property cannot be assigned on possibly undefined value
111: vnode.ns = ns
^^^^^ undefined
src/core/vdom/create-element.js:112
112: if (vnode.tag === 'foreignObject') {
^^^ property `tag`. Property not found in possibly undefined value
112: if (vnode.tag === 'foreignObject') {
^^^^^ undefined
src/core/vdom/create-element.js:116
116: if (Array.isArray(vnode.children)) {
^^^^^^^^ property `children`. Property not found in possibly undefined value
116: if (Array.isArray(vnode.children)) {
^^^^^ undefined
Found 4 errors
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Sadly, flow does not support custom type predicate function.
One workaround is to annotate function isDef(obj): %checks {}, using internal type check. But strangely flow does not pick up wildcard export.
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According to my years of |
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Dear @gebilaoxiong amigo, your contribution is important for Vue's community. Keep going! Personally I think this is a valid bug and needs to be fixed. So please be patient. I also think the |
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Thanks for your reply, I just got a joke 😄 |
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Oh, this is closed automatically by GitHub. But I think this pull request needs some polish (use |
src/core/vdom/create-element.js
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| @@ -99,7 +99,7 @@ export function _createElement ( | |||
| // direct component options / constructor | |||
| vnode = createComponent(tag, data, context, children) | |||
| } | |||
| if (vnode !== undefined) { | |||
| if (vnode != null) { | |||
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Now you can use isDef. Flow will pick it up.
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wow,lucky day!thanks everyone |
issue: #5536
Originally I wanted to use
isDefbut the flow was a bit of a problemWhat kind of change does this PR introduce? (check at least one)
Does this PR introduce a breaking change? (check one)
If yes, please describe the impact and migration path for existing applications:
The PR fulfills these requirements:
devbranch for v2.x (or to a previous version branch), not themasterbranchfix #xxx[,#xxx], where "xxx" is the issue number)If adding a new feature, the PR's description includes:
Other information: