/// <summary>
/// Starts the generation of a <see cref="TagHelperChunk"/>.
/// </summary>
/// <param name="target">
/// The <see cref="Block"/> responsible for this <see cref="TagHelperChunkGenerator"/>.
/// </param>
/// <param name="context">A <see cref="ChunkGeneratorContext"/> instance that contains information about
/// the current chunk generation process.</param>
public override void GenerateStartParentChunk(Block target, ChunkGeneratorContext context)
{
var tagHelperBlock = target as TagHelperBlock;
Debug.Assert(
tagHelperBlock != null,
$"A {nameof(TagHelperChunkGenerator)} must only be used with {nameof(TagHelperBlock)}s.");
var attributes = new List <TagHelperAttributeTracker>();
// We need to create a chunk generator to create chunks for each of the attributes.
var chunkGenerator = context.Host.CreateChunkGenerator(
context.ClassName,
context.RootNamespace,
context.SourceFile);
foreach (var attribute in tagHelperBlock.Attributes)
{
ParentChunk attributeChunkValue = null;
if (attribute.Value != null)
{
// Populates the chunk tree with chunks associated with attributes
attribute.Value.Accept(chunkGenerator);
var chunks = chunkGenerator.Context.ChunkTreeBuilder.Root.Children;
var first = chunks.FirstOrDefault();
attributeChunkValue = new ParentChunk
{
Association = first?.Association,
Children = chunks,
Start = first == null ? SourceLocation.Zero : first.Start
};
}
var attributeChunk = new TagHelperAttributeTracker(
attribute.Name,
attributeChunkValue,
attribute.ValueStyle);
attributes.Add(attributeChunk);
// Reset the chunk tree builder so we can build a new one for the next attribute
chunkGenerator.Context.ChunkTreeBuilder = new ChunkTreeBuilder();
}
var unprefixedTagName = tagHelperBlock.TagName.Substring(_tagHelperDescriptors.First().Prefix.Length);
context.ChunkTreeBuilder.StartParentChunk(
new TagHelperChunk(
unprefixedTagName,
tagHelperBlock.TagMode,
attributes,
_tagHelperDescriptors),
target,
topLevel: false);
}
private static bool CanPreallocateBoundAttribute(
IEnumerable <TagHelperAttributeDescriptor> associatedAttributeDescriptors,
TagHelperAttributeTracker attribute)
{
// If the attribute value is a Dynamic value, it cannot be preallocated.
if (CSharpTagHelperCodeRenderer.IsDynamicAttributeValue(attribute.Value))
{
return(false);
}
// Only attributes that are associated with string typed properties can be preallocated.
var attributeName = attribute.Name;
var allStringProperties = associatedAttributeDescriptors
.All(attributeDescriptor => attributeDescriptor.IsStringProperty);
return(allStringProperties);
}
private void RenderUnboundAttribute(TagHelperAttributeTracker attribute)
{
// Render children to provide IntelliSense at design time. No need for the execution context logic, it's
// a runtime feature.
if (_designTimeMode)
{
if (attribute.Value != null)
{
_bodyVisitor.Accept(attribute.Value);
}
return;
}
Debug.Assert(attribute.Value != null);
var attributeValueStyleParameter = $"global::{typeof(HtmlAttributeValueStyle).FullName}.{attribute.ValueStyle}";
// All simple text and minimized attributes will be pre-allocated.
var preallocatedValue = attribute.Value as PreallocatedTagHelperAttributeChunk;
if (preallocatedValue != null)
{
_writer
.WriteStartInstanceMethodInvocation(
ExecutionContextVariableName,
_tagHelperContext.ExecutionContextAddHtmlAttributeMethodName)
.Write(preallocatedValue.AttributeVariableAccessor)
.WriteEndMethodInvocation();
}
else if (IsDynamicAttributeValue(attribute.Value))
{
// Dynamic attribute value should be run through the conditional attribute removal system. It's
// unbound and contains C#.
// TagHelper attribute rendering is buffered by default. We do not want to write to the current
// writer.
var currentTargetWriter = _context.TargetWriterName;
var currentWriteAttributeMethodName = _context.Host.GeneratedClassContext.WriteAttributeValueMethodName;
_context.TargetWriterName = null;
Debug.Assert(attribute.Value is ParentChunk);
var children = ((ParentChunk)attribute.Value).Children;
var attributeCount = children.Count(c => c is DynamicCodeAttributeChunk || c is LiteralCodeAttributeChunk);
_writer
.WriteStartMethodInvocation(_tagHelperContext.BeginAddHtmlAttributeValuesMethodName)
.Write(ExecutionContextVariableName)
.WriteParameterSeparator()
.WriteStringLiteral(attribute.Name)
.WriteParameterSeparator()
.Write(attributeCount.ToString(CultureInfo.InvariantCulture))
.WriteParameterSeparator()
.Write(attributeValueStyleParameter)
.WriteEndMethodInvocation();
_attributeCodeVisitor.Accept(attribute.Value);
_writer.WriteMethodInvocation(
_tagHelperContext.EndAddHtmlAttributeValuesMethodName,
ExecutionContextVariableName);
_context.TargetWriterName = currentTargetWriter;
}
else
{
// This is a data-* attribute which includes C#. Do not perform the conditional attribute removal or
// other special cases used when IsDynamicAttributeValue(). But the attribute must still be buffered to
// determine its final value.
// Attribute value is not plain text, must be buffered to determine its final value.
BuildBufferedWritingScope(attribute.Value, htmlEncodeValues: true);
_writer
.WriteStartInstanceMethodInvocation(
ExecutionContextVariableName,
_tagHelperContext.ExecutionContextAddHtmlAttributeMethodName)
.WriteStringLiteral(attribute.Name)
.WriteParameterSeparator()
.WriteStartMethodInvocation(_tagHelperContext.MarkAsHtmlEncodedMethodName);
RenderBufferedAttributeValueAccessor(_writer);
_writer
.WriteEndMethodInvocation(endLine: false)
.WriteParameterSeparator()
.Write(attributeValueStyleParameter)
.WriteEndMethodInvocation();
}
}
private string RenderBoundAttribute(
TagHelperAttributeTracker attribute,
string tagHelperVariableName,
string previousValueAccessor,
TagHelperAttributeDescriptor attributeDescriptor)
{
var currentValueAccessor = string.Format(
CultureInfo.InvariantCulture,
"{0}.{1}",
tagHelperVariableName,
attributeDescriptor.PropertyName);
if (attributeDescriptor.IsIndexer)
{
var dictionaryKey = attribute.Name.Substring(attributeDescriptor.Name.Length);
currentValueAccessor += $"[\"{dictionaryKey}\"]";
}
// If this attribute value has not been seen before, need to record its value.
if (previousValueAccessor == null)
{
var preallocatedAttributeValueChunk = attribute.Value as PreallocatedTagHelperAttributeChunk;
if (preallocatedAttributeValueChunk != null)
{
RenderBoundPreAllocatedAttribute(preallocatedAttributeValueChunk, currentValueAccessor);
return currentValueAccessor;
}
// Bufferable attributes are attributes that can have Razor code inside of them. Such
// attributes have string values and may be calculated using a temporary TextWriter or other
// buffer.
var bufferableAttribute = attributeDescriptor.IsStringProperty;
RenderNewAttributeValueAssignment(
attributeDescriptor,
bufferableAttribute,
attribute.Value,
currentValueAccessor);
if (_designTimeMode)
{
// Execution contexts are a runtime feature.
return currentValueAccessor;
}
// We need to inform the context of the attribute value.
_writer
.WriteStartInstanceMethodInvocation(
ExecutionContextVariableName,
_tagHelperContext.ExecutionContextAddTagHelperAttributeMethodName)
.WriteStringLiteral(attribute.Name)
.WriteParameterSeparator()
.Write(currentValueAccessor)
.WriteParameterSeparator()
.Write($"global::{typeof(HtmlAttributeValueStyle).FullName}.{attribute.ValueStyle}")
.WriteEndMethodInvocation();
return currentValueAccessor;
}
else
{
// The attribute value has already been determined and accessor was passed to us as
// previousValueAccessor, we don't want to evaluate the value twice so lets just use the
// previousValueLocation.
_writer
.WriteStartAssignment(currentValueAccessor)
.Write(previousValueAccessor)
.WriteLine(";");
return previousValueAccessor;
}
}
private void RenderUnboundAttribute(TagHelperAttributeTracker attribute)
{
// Render children to provide IntelliSense at design time. No need for the execution context logic, it's
// a runtime feature.
if (_designTimeMode)
{
if (attribute.Value != null)
{
_bodyVisitor.Accept(attribute.Value);
}
return;
}
Debug.Assert(attribute.Value != null);
var attributeValueStyleParameter = $"global::{typeof(HtmlAttributeValueStyle).FullName}.{attribute.ValueStyle}";
// All simple text and minimized attributes will be pre-allocated.
var preallocatedValue = attribute.Value as PreallocatedTagHelperAttributeChunk;
if (preallocatedValue != null)
{
_writer
.WriteStartInstanceMethodInvocation(
ExecutionContextVariableName,
_tagHelperContext.ExecutionContextAddHtmlAttributeMethodName)
.Write(preallocatedValue.AttributeVariableAccessor)
.WriteEndMethodInvocation();
}
else if (IsDynamicAttributeValue(attribute.Value))
{
// Dynamic attribute value should be run through the conditional attribute removal system. It's
// unbound and contains C#.
// TagHelper attribute rendering is buffered by default. We do not want to write to the current
// writer.
var currentTargetWriter = _context.TargetWriterName;
var currentWriteAttributeMethodName = _context.Host.GeneratedClassContext.WriteAttributeValueMethodName;
_context.TargetWriterName = null;
Debug.Assert(attribute.Value is ParentChunk);
var children = ((ParentChunk)attribute.Value).Children;
var attributeCount = children.Count(c => c is DynamicCodeAttributeChunk || c is LiteralCodeAttributeChunk);
_writer
.WriteStartMethodInvocation(_tagHelperContext.BeginAddHtmlAttributeValuesMethodName)
.Write(ExecutionContextVariableName)
.WriteParameterSeparator()
.WriteStringLiteral(attribute.Name)
.WriteParameterSeparator()
.Write(attributeCount.ToString(CultureInfo.InvariantCulture))
.WriteParameterSeparator()
.Write(attributeValueStyleParameter)
.WriteEndMethodInvocation();
_attributeCodeVisitor.Accept(attribute.Value);
_writer.WriteMethodInvocation(
_tagHelperContext.EndAddHtmlAttributeValuesMethodName,
ExecutionContextVariableName);
_context.TargetWriterName = currentTargetWriter;
}
else
{
// This is a data-* attribute which includes C#. Do not perform the conditional attribute removal or
// other special cases used when IsDynamicAttributeValue(). But the attribute must still be buffered to
// determine its final value.
// Attribute value is not plain text, must be buffered to determine its final value.
BuildBufferedWritingScope(attribute.Value, htmlEncodeValues: true);
_writer
.WriteStartInstanceMethodInvocation(
ExecutionContextVariableName,
_tagHelperContext.ExecutionContextAddHtmlAttributeMethodName)
.WriteStringLiteral(attribute.Name)
.WriteParameterSeparator()
.WriteStartMethodInvocation(_tagHelperContext.MarkAsHtmlEncodedMethodName);
RenderBufferedAttributeValueAccessor(_writer);
_writer
.WriteEndMethodInvocation(endLine: false)
.WriteParameterSeparator()
.Write(attributeValueStyleParameter)
.WriteEndMethodInvocation();
}
}
private string RenderBoundAttribute(
TagHelperAttributeTracker attribute,
string tagHelperVariableName,
string previousValueAccessor,
TagHelperAttributeDescriptor attributeDescriptor)
{
var currentValueAccessor = string.Format(
CultureInfo.InvariantCulture,
"{0}.{1}",
tagHelperVariableName,
attributeDescriptor.PropertyName);
if (attributeDescriptor.IsIndexer)
{
var dictionaryKey = attribute.Name.Substring(attributeDescriptor.Name.Length);
currentValueAccessor += $"[\"{dictionaryKey}\"]";
}
// If this attribute value has not been seen before, need to record its value.
if (previousValueAccessor == null)
{
var preallocatedAttributeValueChunk = attribute.Value as PreallocatedTagHelperAttributeChunk;
if (preallocatedAttributeValueChunk != null)
{
RenderBoundPreAllocatedAttribute(preallocatedAttributeValueChunk, currentValueAccessor);
return(currentValueAccessor);
}
// Bufferable attributes are attributes that can have Razor code inside of them. Such
// attributes have string values and may be calculated using a temporary TextWriter or other
// buffer.
var bufferableAttribute = attributeDescriptor.IsStringProperty;
RenderNewAttributeValueAssignment(
attributeDescriptor,
bufferableAttribute,
attribute.Value,
currentValueAccessor);
if (_designTimeMode)
{
// Execution contexts are a runtime feature.
return(currentValueAccessor);
}
// We need to inform the context of the attribute value.
_writer
.WriteStartInstanceMethodInvocation(
ExecutionContextVariableName,
_tagHelperContext.ExecutionContextAddTagHelperAttributeMethodName)
.WriteStringLiteral(attribute.Name)
.WriteParameterSeparator()
.Write(currentValueAccessor)
.WriteParameterSeparator()
.Write($"global::{typeof(HtmlAttributeValueStyle).FullName}.{attribute.ValueStyle}")
.WriteEndMethodInvocation();
return(currentValueAccessor);
}
else
{
// The attribute value has already been determined and accessor was passed to us as
// previousValueAccessor, we don't want to evaluate the value twice so lets just use the
// previousValueLocation.
_writer
.WriteStartAssignment(currentValueAccessor)
.Write(previousValueAccessor)
.WriteLine(";");
return(previousValueAccessor);
}
}
