private Dictionary <string, TagHelperPair> FindMatchingTagHelpers(RazorCodeActionContext context, MarkupStartTagSyntax startTag)
{
// Get all data necessary for matching
var tagName = startTag.Name.Content;
string parentTagName = null;
if (startTag.Parent?.Parent is MarkupElementSyntax parentElement)
{
parentTagName = parentElement.StartTag.Name.Content;
}
else if (startTag.Parent?.Parent is MarkupTagHelperElementSyntax parentTagHelperElement)
{
parentTagName = parentTagHelperElement.StartTag.Name.Content;
}
var attributes = _tagHelperFactsService.StringifyAttributes(startTag.Attributes);
// Find all matching tag helpers
var matching = new Dictionary <string, TagHelperPair>();
foreach (var tagHelper in context.DocumentSnapshot.Project.TagHelpers)
{
if (tagHelper.TagMatchingRules.All(rule => TagHelperMatchingConventions.SatisfiesRule(tagName, parentTagName, attributes, rule)))
{
matching.Add(tagHelper.Name, new TagHelperPair {
Short = tagHelper
});
}
}
// Iterate and find the fully qualified version
foreach (var tagHelper in context.DocumentSnapshot.Project.TagHelpers)
{
if (matching.TryGetValue(tagHelper.Name, out var tagHelperPair))
{
if (tagHelperPair != null && tagHelper != tagHelperPair.Short)
{
tagHelperPair.FullyQualified = tagHelper;
}
}
}
return(matching);
}
/// <summary>
/// Gets all tag helpers that match the given HTML tag criteria.
/// </summary>
/// <param name="tagName">The name of the HTML tag to match. Providing a '*' tag name
/// retrieves catch-all <see cref="TagHelperDescriptor"/>s (descriptors that target every tag).</param>
/// <param name="attributes">Attributes on the HTML tag.</param>
/// <param name="parentTagName">The parent tag name of the given <paramref name="tagName"/> tag.</param>
/// <param name="parentIsTagHelper">Is the parent tag of the given <paramref name="tagName"/> tag a tag helper.</param>
/// <returns><see cref="TagHelperDescriptor"/>s that apply to the given HTML tag criteria.
/// Will return <c>null</c> if no <see cref="TagHelperDescriptor"/>s are a match.</returns>
public TagHelperBinding GetBinding(
string tagName,
IReadOnlyList <KeyValuePair <string, string> > attributes,
string parentTagName,
bool parentIsTagHelper)
{
if (!string.IsNullOrEmpty(_tagHelperPrefix) &&
(tagName.Length <= _tagHelperPrefix.Length ||
!tagName.StartsWith(_tagHelperPrefix, StringComparison.OrdinalIgnoreCase)))
{
// The tagName doesn't have the tag helper prefix, we can short circuit.
return(null);
}
IEnumerable <TagHelperDescriptor> descriptors;
// Ensure there's a HashSet to use.
if (!_registrations.TryGetValue(TagHelperMatchingConventions.ElementCatchAllName, out HashSet <TagHelperDescriptor> catchAllDescriptors))
{
descriptors = new HashSet <TagHelperDescriptor>(TagHelperDescriptorComparer.Default);
}
else
{
descriptors = catchAllDescriptors;
}
// If we have a tag name associated with the requested name, we need to combine matchingDescriptors
// with all the catch-all descriptors.
if (_registrations.TryGetValue(tagName, out HashSet <TagHelperDescriptor> matchingDescriptors))
{
descriptors = matchingDescriptors.Concat(descriptors);
}
var tagNameWithoutPrefix = _tagHelperPrefix != null ? new StringSegment(tagName, _tagHelperPrefix.Length) : tagName;
StringSegment parentTagNameWithoutPrefix = parentTagName;
if (_tagHelperPrefix != null && parentIsTagHelper)
{
parentTagNameWithoutPrefix = new StringSegment(parentTagName, _tagHelperPrefix.Length);
}
Dictionary <TagHelperDescriptor, IReadOnlyList <TagMatchingRuleDescriptor> > applicableDescriptorMappings = null;
foreach (var descriptor in descriptors)
{
// We're avoiding desccriptor.TagMatchingRules.Where and applicableRules.Any() to avoid
// Enumerator allocations on this hotpath
List <TagMatchingRuleDescriptor> applicableRules = null;
for (var i = 0; i < descriptor.TagMatchingRules.Count; i++)
{
var rule = descriptor.TagMatchingRules[i];
if (TagHelperMatchingConventions.SatisfiesRule(tagNameWithoutPrefix, parentTagNameWithoutPrefix, attributes, rule))
{
if (applicableRules is null)
{
applicableRules = new List <TagMatchingRuleDescriptor>();
}
applicableRules.Add(rule);
}
}
if (applicableRules != null && applicableRules.Count > 0)
{
if (applicableDescriptorMappings == null)
{
applicableDescriptorMappings = new Dictionary <TagHelperDescriptor, IReadOnlyList <TagMatchingRuleDescriptor> >();
}
applicableDescriptorMappings[descriptor] = applicableRules;
}
}
if (applicableDescriptorMappings == null)
{
return(null);
}
var tagHelperBinding = new TagHelperBinding(
tagName,
attributes,
parentTagName,
applicableDescriptorMappings,
_tagHelperPrefix);
return(tagHelperBinding);
}