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Conditional operands do not seem to evaluate lazily #85

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ffried opened this issue Dec 8, 2020 · 0 comments
Open

Conditional operands do not seem to evaluate lazily #85

ffried opened this issue Dec 8, 2020 · 0 comments
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bug Something isn't working

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@ffried
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ffried commented Dec 8, 2020 •
edited

Describe the bug

A set of conditional operands as for example if (a || b) seems to evaluate all its operands (a and b) upfront.
This means that b will be evaluated even if a was already true.

To Reproduce

Steps to reproduce the behavior:

  1. Create a leaf file (e.g. page.leaf) with the following contents:
<!DOCTYPE html>
<html>
<body>
#if(!ctx.children || count(ctx.children) <= 0):
<ul>#for(child in ctx.children):<li>#(child)</li>#endfor</ul>
#else:
<p>No children.</p>
#endif
</body>
</html>
  1. Render the page with the following context:
struct Context: Encodable { let ctx: [String]? }
func configure(app: Application) {
    app.get(use: { $0.view.render("page", Context(ctx: nil)) })
}
  1. Rendering fails with "Unable to convert count parameter to LeafData collection" as thrown by the Count tag if the parameter is no collection. In this case, a breakpoint in Count prints the following for the first parameter (given that ctx.children is nil):
(lldb) po ctx.parameters
▿ 1 element
  ▿ 0 : void()?
    ▿ storage : void()?
      ▿ optional : 2 elements
        - .0 : nil
        - .1 : LeafKit.LeafData.NaturalType.void

Expected behavior

The page renders fine, showing "No children." with the following rendered HTML:

<!DOCTYPE html>
<html>
<body>
<p>No children.</p>
</body>
</html>

Environment

  • Vapor Framework version: 4.36.0
  • Leaf Framework version: 4.0.1
  • LeafKit Framework version: 1.0.0
  • Vapor Toolbox version: n/a
  • OS version: macOS 11.0.1 as well as Ubuntu 18.04
  • Swift version: 5.3.1

Additional context

I tried to dig a bit into LeafKit's source, and am pretty sure that the evaluation of all conditional operands is the problem. However, I could also be missing something, in which case my "attempted diagnosis" might be incorrect and the issue is actually something different.
@ffried ffried added the bug Something isn't working label Dec 8, 2020
ffried added a commit to sersoft-gmbh/route-docs that referenced this issue Dec 8, 2020
@ffried
Remove count usage for now due to vapor/leaf-kit#85
046ea54
@tonyarnold tonyarnold mentioned this issue Aug 16, 2022
Merged
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@ffried