TagHelper with no end tag: parsing issues
NoneGiven opened this issue · comments
Create a TagHelper with WithoutEndTag structure:
[HtmlTargetElement("msg-helper", TagStructure = TagStructure.WithoutEndTag)]
public class MsgHelperTagHelper : TagHelper {
public string Msg { get; set; }
public override void Process(TagHelperContext context, TagHelperOutput output) {
output.TagName = "";
output.Content.SetContent("<div>" + Msg + "</div>");
}
}
Create a Razor view that uses it inside a C# if block:
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>Asdf</title>
</head>
<body>
@if (1 + 2 == 3) {
<msg-helper msg="Hello">
}
else {
<div>Hi</div>
}
</body>
</html>
Razor reports two incorrect errors, the first one on the tag helper element:
The "msg-helper" element was not closed. All elements must either be self-closing or have a matching end tag.
And the second on the closing tag:
Encountered end tag "html" with no matching start tag. Are your start/end tags properly balanced?
Moving the tag helper outside the if/else blocks in the same markup makes the errors disappear.
I believe this is failing at the parser stage, which is well before any tag helpers happen.
I believe this issue happens because Razor doesn't know where the tag starts and ends - it doesn't know about tag helpers.
You need to wrap the <msg-helper .... > tag in the <text> ... </text> pseudo-tag to tell Razor where the HTML begins and ends.
@if (1 + 2 == 3) {
<text>
<msg-helper msg="Hello">
</text>
}
else {
<div>Hi</div>
}The Razor parser knows just a bit about HTML, and just a bit about C#, so you sometimes have to give it hints about where things start and end.
@NTaylorMullen @DamianEdwards can you confirm if my statement is all there is to it?
You can just make the element self-closing (like the error message says):
@if (1 + 2 == 3) {
<msg-helper msg="Hello" />
}
else {
<div>Hi</div>
}