private bool TryRewriteTagHelper(Block tagBlock, RewritingContext context)
{
// TODO: Fully handle malformed tags: https://github.com/aspnet/Razor/issues/104
// Get tag name of the current block (doesn't matter if it's an end or start tag)
var tagName = GetTagName(tagBlock);
// Could not determine tag name, it can't be a TagHelper, continue on and track the element.
if (tagName == null)
{
return(false);
}
var descriptors = Enumerable.Empty <TagHelperDescriptor>();
if (IsPotentialTagHelper(tagName, tagBlock))
{
descriptors = _provider.GetTagHelpers(tagName);
}
// If there aren't any TagHelperDescriptors registered then we aren't a TagHelper
if (!descriptors.Any())
{
return(false);
}
if (!IsEndTag(tagBlock))
{
// We're in a begin tag helper block
var validTagStructure = ValidTagStructure(tagName, tagBlock, context);
var builder = TagHelperBlockRewriter.Rewrite(tagName,
validTagStructure,
tagBlock,
descriptors,
context.ErrorSink);
// Found a new tag helper block
TrackTagHelperBlock(builder);
// If it's a self closing block then we don't have to worry about nested children
// within the tag... complete it.
if (IsSelfClosing(tagBlock))
{
BuildCurrentlyTrackedTagHelperBlock();
}
}
else
{
// We're in an end tag helper block.
var tagNameScope = _tagStack.Count > 0 ? _tagStack.Peek().TagName : string.Empty;
// Validate that our end tag helper matches the currently scoped tag helper, if not we
// need to error.
if (tagNameScope.Equals(tagName, StringComparison.OrdinalIgnoreCase))
{
ValidTagStructure(tagName, tagBlock, context);
BuildCurrentlyTrackedTagHelperBlock();
}
else
{
// Current tag helper scope does not match the end tag. Attempt to recover the tag
// helper by looking up the previous tag helper scopes for a matching tag. If we
// can't recover it means there was no corresponding tag helper begin tag.
if (TryRecoverTagHelper(tagName, context))
{
ValidTagStructure(tagName, tagBlock, context);
// Successfully recovered, move onto the next element.
}
else
{
// Could not recover, the end tag helper has no corresponding begin tag, create
// an error based on the current childBlock.
context.ErrorSink.OnError(
tagBlock.Start,
RazorResources.FormatTagHelpersParseTreeRewriter_FoundMalformedTagHelper(tagName));
return(false);
}
}
}
return(true);
}
private bool TryRewriteTagHelper(Block tagBlock, RewritingContext context)
{
// Get tag name of the current block (doesn't matter if it's an end or start tag)
var tagName = GetTagName(tagBlock);
// Could not determine tag name, it can't be a TagHelper, continue on and track the element.
if (tagName == null)
{
return(false);
}
var descriptors = Enumerable.Empty <TagHelperDescriptor>();
if (!IsPotentialTagHelper(tagName, tagBlock))
{
return(false);
}
var tracker = _currentTagHelperTracker;
var tagNameScope = tracker?.Builder.TagName ?? string.Empty;
if (!IsEndTag(tagBlock))
{
// We're now in a start tag block, we first need to see if the tag block is a tag helper.
var providedAttributes = GetAttributeNames(tagBlock);
descriptors = _provider.GetDescriptors(tagName, providedAttributes);
// If there aren't any TagHelperDescriptors registered then we aren't a TagHelper
if (!descriptors.Any())
{
// 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);
}
ValidateParentTagHelperAllowsTagHelper(tagName, tagBlock, context.ErrorSink);
ValidateDescriptors(descriptors, tagName, tagBlock, context.ErrorSink);
// We're in a start TagHelper block.
var validTagStructure = ValidateTagSyntax(tagName, tagBlock, context);
var builder = TagHelperBlockRewriter.Rewrite(
tagName,
validTagStructure,
tagBlock,
descriptors,
context.ErrorSink);
// Track the original start tag so the editor knows where each piece of the TagHelperBlock lies
// for formatting.
builder.SourceStartTag = tagBlock;
// Found a new tag helper block
TrackTagHelperBlock(builder);
// If it's a non-content expecting block then we don't have to worry about nested children within the
// tag. Complete it.
if (builder.TagMode == TagMode.SelfClosing || builder.TagMode == TagMode.StartTagOnly)
{
BuildCurrentlyTrackedTagHelperBlock(endTag: null);
}
}
else
{
// Validate that our end tag matches the currently scoped tag, if not we may need to error.
if (tagNameScope.Equals(tagName, StringComparison.OrdinalIgnoreCase))
{
// If there are additional end tags required before we can build our block it means we're in a
// situation like this: <myth req="..."><myth></myth></myth> where we're at the inside </myth>.
if (tracker.OpenMatchingTags > 0)
{
tracker.OpenMatchingTags--;
return(false);
}
ValidateTagSyntax(tagName, tagBlock, context);
BuildCurrentlyTrackedTagHelperBlock(tagBlock);
}
else
{
descriptors = _provider.GetDescriptors(tagName, attributeNames: Enumerable.Empty <string>());
// If there are not TagHelperDescriptors associated with the end tag block that also have no
// required attributes then it means we can't be a TagHelper, bail out.
if (!descriptors.Any())
{
return(false);
}
var invalidDescriptor = descriptors.FirstOrDefault(
descriptor => descriptor.TagStructure == TagStructure.WithoutEndTag);
if (invalidDescriptor != null)
{
// End tag TagHelper that states it shouldn't have an end tag.
context.ErrorSink.OnError(
tagBlock.Start,
RazorResources.FormatTagHelperParseTreeRewriter_EndTagTagHelperMustNotHaveAnEndTag(
tagName,
invalidDescriptor.TypeName,
invalidDescriptor.TagStructure),
tagBlock.Length);
return(false);
}
// Current tag helper scope does not match the end tag. Attempt to recover the tag
// helper by looking up the previous tag helper scopes for a matching tag. If we
// can't recover it means there was no corresponding tag helper start tag.
if (TryRecoverTagHelper(tagName, tagBlock, context))
{
ValidateParentTagHelperAllowsTagHelper(tagName, tagBlock, context.ErrorSink);
ValidateTagSyntax(tagName, tagBlock, context);
// Successfully recovered, move onto the next element.
}
else
{
// Could not recover, the end tag helper has no corresponding start tag, create
// an error based on the current childBlock.
context.ErrorSink.OnError(
tagBlock.Start,
RazorResources.FormatTagHelpersParseTreeRewriter_FoundMalformedTagHelper(tagName));
return(false);
}
}
}
return(true);
}