Conditional operands do not seem to evaluate lazily #85
Description
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:
- 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>
- 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)) })
}- Rendering fails with "Unable to convert count parameter to LeafData collection" as thrown by the
Counttag if the parameter is no collection. In this case, a breakpoint inCountprints the following for the first parameter (given thatctx.childrenisnil):
(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.