public override void VisitTagHelperBody(TagHelperBodyIntermediateNode node)
{
// Wrap the component's children in a ChildContent node if we have some significant
// content.
if (node.Children.Count == 0)
{
return;
}
// If we get a single HTML content node containing only whitespace,
// then this is probably a tag that looks like '<MyComponent> </MyComponent>
//
// We don't want to create a child content for this case, because it can conflict
// with a child content that's set via an attribute. We don't want the formatting
// of insignificant whitespace to be annoying when setting attributes directly.
if (node.Children.Count == 1 && IsIgnorableWhitespace(node.Children[0]))
{
return;
}
// From here we fork and behave differently based on whether the component's child content is
// implicit or explicit.
//
// Explicit child content will look like: <MyComponent><ChildContent><div>...</div></ChildContent></MyComponent>
// compared with implicit: <MyComponent><div></div></MyComponent>
//
// Using implicit child content:
// 1. All content is grouped into a single child content lambda, and assigned to the property 'ChildContent'
//
// Using explicit child content:
// 1. All content must be contained within 'child content' elements that are direct children
// 2. Whitespace outside of 'child content' elements will be ignored (not an error)
// 3. Non-whitespace outside of 'child content' elements will cause an error
// 4. All 'child content' elements must match parameters on the component (exception for ChildContent,
// which is always allowed.
// 5. Each 'child content' element will generate its own lambda, and be assigned to the property
// that matches the element name.
if (!node.Children.OfType <TagHelperIntermediateNode>().Any(t => t.TagHelpers.Any(th => th.IsChildContentTagHelper())))
{
// This node has implicit child content. It may or may not have an attribute that matches.
var attribute = _component.Component.BoundAttributes
.Where(a => string.Equals(a.Name, ComponentsApi.RenderTreeBuilder.ChildContent, StringComparison.Ordinal))
.FirstOrDefault();
_children.Add(RewriteChildContent(attribute, node.Source, node.Children));
return;
}
// OK this node has explicit child content, we can rewrite it by visiting each node
// in sequence, since we:
// a) need to rewrite each child content element
// b) any significant content outside of a child content is an error
for (var i = 0; i < node.Children.Count; i++)
{
var child = node.Children[i];
if (IsIgnorableWhitespace(child))
{
continue;
}
if (child is TagHelperIntermediateNode tagHelperNode &&
tagHelperNode.TagHelpers.Any(th => th.IsChildContentTagHelper()))
{
// This is a child content element
var attribute = _component.Component.BoundAttributes
.Where(a => string.Equals(a.Name, tagHelperNode.TagName, StringComparison.Ordinal))
.FirstOrDefault();
_children.Add(RewriteChildContent(attribute, child.Source, child.Children));
continue;
}
// If we get here then this is significant content inside a component with explicit child content.
child.Diagnostics.Add(ComponentDiagnosticFactory.Create_ChildContentMixedWithExplicitChildContent(child.Source, _component));
_children.Add(child);
}
bool IsIgnorableWhitespace(IntermediateNode n)
{
if (n is HtmlContentIntermediateNode html &&
html.Children.Count == 1 &&
html.Children[0] is IntermediateToken token &&
string.IsNullOrWhiteSpace(token.Content))
{
return(true);
}
return(false);
}
}