fix: use Fragment VNodes for if-elseif-else children #3047
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| [api_dynamic_component("x-foo", $cmp.trackedProp.foo, stc0)], | ||
| 0 | ||
| ) | ||
| : null, |
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@jodarove This now returns null if there's nothing in the else branch
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I think this should be ok, it looks like there's a check when mounting the vnodes to see if the value is null.
We also return an array of null values in the if:true/false cases from the tmpl function.
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Yup. I modeled this after codegen's behavior for if:true/false.
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| const childrenExpression = codeGen.genFragment( | ||
| t.literal(ifBlockKey), | ||
| transformChildren(conditionalParentBlock) |
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genFragment has a third parameter that lets us specify whether this fragment is stable or not. A subsequent perf optimization we can do is to detect whether the children here are dynamic or static and set the stable flag appropriately.
Leaving that for a separate PR after #3030 gets merged. Getting that merged sooner will unblock some of the integration work.
| @@ -5,17 +5,25 @@ const $fragment3 = parseFragment`<h1${3}>things</h1>`; | |||
| const $fragment4 = parseFragment`<h1${3}>hello</h1>`; | |||
| const $fragment5 = parseFragment`<h1${3}>world!</h1>`; | |||
| function tmpl($api, $cmp, $slotset, $ctx) { | |||
| const { t: api_text, st: api_static_fragment, f: api_flatten } = $api; | |||
| return api_flatten([ | |||
| const { t: api_text, st: api_static_fragment, fr: api_fragment } = $api; | |||
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The original goal of this test was just to ensure that the returned values were wrapped with api_flatten. Since we're using fragments now I think we can rename it to with-siblings or something else.
* feat: lwc:if, lwc:elseif, and lwc:else directives (#2985) * feat: refactor parser context to support new behavior for slot name tracking (#2990) * feat(template-compiler): add codegen portion for else-if directives (#2995) * fix: use Fragment VNodes for if-elseif-else children (#3047) Co-authored-by: Pierre-Marie Dartus <p.dartus@salesforce.com> Co-authored-by: James Tu <j.tu@salesforce.com>
Details
Builds on top of #3034 to resolve issue with diffing algo. if-elseif-else children are now properly marked as fragments so that the diffing algo can update the nodes properly.
Has dependencies on both #3034 and #3030 and should only be merged into a branch that contains both those changes.
Does this pull request introduce a breaking change?
Does this pull request introduce an observable change?
GUS work item