private bool TryRewriteTagHelperStart(
MarkupStartTagSyntax startTag,
MarkupEndTagSyntax endTag,
out MarkupTagHelperStartTagSyntax rewritten,
out TagHelperInfo tagHelperInfo)
{
rewritten = null;
tagHelperInfo = null;
// Get tag name of the current block
var tagName = startTag.GetTagNameWithOptionalBang();
// Could not determine tag name, it can't be a TagHelper, continue on and track the element.
if (string.IsNullOrEmpty(tagName) || tagName.StartsWith("!", StringComparison.Ordinal))
{
return(false);
}
TagHelperBinding tagHelperBinding;
if (!IsPotentialTagHelperStart(tagName, startTag))
{
return(false);
}
var tracker = CurrentTagHelperTracker;
var tagNameScope = tracker?.TagName ?? string.Empty;
// We're now in a start tag block, we first need to see if the tag block is a tag helper.
var elementAttributes = GetAttributeNameValuePairs(startTag);
tagHelperBinding = _tagHelperBinder.GetBinding(
tagName,
elementAttributes,
CurrentParentTagName,
CurrentParentIsTagHelper);
// If there aren't any TagHelperDescriptors registered then we aren't a TagHelper
if (tagHelperBinding == null)
{
// If the current tag matches the current TagHelper scope it means the parent TagHelper matched
// all the required attributes but the current one did not; therefore, we need to increment the
// OpenMatchingTags counter for current the TagHelperBlock so we don't end it too early.
// ex: <myth req="..."><myth></myth></myth> We don't want the first myth to close on the inside
// tag.
if (string.Equals(tagNameScope, tagName, StringComparison.OrdinalIgnoreCase))
{
tracker.OpenMatchingTags++;
}
return(false);
}
ValidateParentAllowsTagHelper(tagName, startTag);
ValidateBinding(tagHelperBinding, tagName, startTag);
// We're in a start TagHelper block.
ValidateStartTagSyntax(tagName, startTag);
var rewrittenStartTag = TagHelperBlockRewriter.Rewrite(
tagName,
_featureFlags,
startTag,
tagHelperBinding,
_errorSink,
_source);
var tagMode = TagHelperBlockRewriter.GetTagMode(startTag, endTag, tagHelperBinding);
tagHelperInfo = new TagHelperInfo(tagName, tagMode, tagHelperBinding);
rewritten = rewrittenStartTag;
return(true);
}
public override SyntaxNode VisitMarkupElement(MarkupElementSyntax node)
{
if (IsPartOfStartTag(node))
{
// If this element is inside a start tag, it is some sort of malformed case like
// <p @do { someattribute=\"btn\"></p>, where the end "p" tag is inside the start "p" tag.
// We don't want to do tag helper parsing for this tag.
return(base.VisitMarkupElement(node));
}
MarkupTagHelperStartTagSyntax tagHelperStart = null;
MarkupTagHelperEndTagSyntax tagHelperEnd = null;
TagHelperInfo tagHelperInfo = null;
// Visit the start tag.
var startTag = (MarkupTagBlockSyntax)Visit(node.StartTag);
if (startTag != null)
{
var tagName = startTag.GetTagName();
if (TryRewriteTagHelperStart(startTag, out tagHelperStart, out tagHelperInfo))
{
// This is a tag helper.
if (tagHelperInfo.TagMode == TagMode.SelfClosing || tagHelperInfo.TagMode == TagMode.StartTagOnly)
{
var tagHelperElement = SyntaxFactory.MarkupTagHelperElement(tagHelperStart, body: new SyntaxList <RazorSyntaxNode>(), endTag: null);
var rewrittenTagHelper = tagHelperElement.WithTagHelperInfo(tagHelperInfo);
if (node.Body.Count == 0)
{
return(rewrittenTagHelper);
}
// This tag contains a body which needs to be moved to the parent.
var rewrittenNodes = SyntaxListBuilder <RazorSyntaxNode> .Create();
rewrittenNodes.Add(rewrittenTagHelper);
var rewrittenBody = VisitList(node.Body);
rewrittenNodes.AddRange(rewrittenBody);
return(SyntaxFactory.MarkupElement(startTag: null, body: rewrittenNodes.ToList(), endTag: null));
}
else if (node.EndTag == null)
{
// Start tag helper with no corresponding end tag.
_errorSink.OnError(
RazorDiagnosticFactory.CreateParsing_TagHelperFoundMalformedTagHelper(
new SourceSpan(SourceLocationTracker.Advance(startTag.GetSourceLocation(_source), "<"), tagName.Length),
tagName));
}
else
{
// Tag helper start tag. Keep track.
var tracker = new TagHelperTracker(_tagHelperPrefix, tagHelperInfo);
_trackerStack.Push(tracker);
}
}
else
{
// Non-TagHelper tag.
ValidateParentAllowsPlainTag(startTag);
if (!startTag.IsSelfClosing() && !startTag.IsVoidElement())
{
var tracker = new TagTracker(tagName, isTagHelper: false);
_trackerStack.Push(tracker);
}
}
}
// Visit body between start and end tags.
var body = VisitList(node.Body);
// Visit end tag.
var endTag = (MarkupTagBlockSyntax)Visit(node.EndTag);
if (endTag != null)
{
var tagName = endTag.GetTagName();
if (TryRewriteTagHelperEnd(endTag, out tagHelperEnd))
{
// This is a tag helper
if (startTag == null)
{
// The end tag helper has no corresponding start tag, create an error.
_errorSink.OnError(
RazorDiagnosticFactory.CreateParsing_TagHelperFoundMalformedTagHelper(
new SourceSpan(SourceLocationTracker.Advance(endTag.GetSourceLocation(_source), "</"), tagName.Length), tagName));
}
}
else
{
// Non tag helper end tag.
if (startTag == null)
{
// Standalone end tag. We may need to error if it is not supposed to be here.
// If there was a corresponding start tag, we would have already added this error.
ValidateParentAllowsPlainTag(endTag);
}
else if (!endTag.IsVoidElement())
{
// Since a start tag exists, we must already be tracking it.
// Pop the stack as we're done with the end tag.
_trackerStack.Pop();
}
}
}
if (tagHelperInfo != null)
{
// If we get here it means this element was rewritten as a tag helper.
var tagHelperElement = SyntaxFactory.MarkupTagHelperElement(tagHelperStart, body, tagHelperEnd);
return(tagHelperElement.WithTagHelperInfo(tagHelperInfo));
}
// There was no matching tag helper for this element. Return.
return(node.Update(startTag, body, endTag));
}