private void Process(ComponentExtensionNode node)
{
// First collect all of the information we have about each type parameter
//
// Listing all type parameters that exist
var bindings = new Dictionary <string, GenericTypeNameRewriter.Binding>();
foreach (var attribute in node.Component.GetTypeParameters())
{
bindings.Add(attribute.Name, new GenericTypeNameRewriter.Binding()
{
Attribute = attribute,
});
}
// Listing all type arguments that have been specified.
var hasTypeArgumentSpecified = false;
foreach (var typeArgumentNode in node.TypeArguments)
{
hasTypeArgumentSpecified = true;
var binding = bindings[typeArgumentNode.TypeParameterName];
binding.Node = typeArgumentNode;
binding.Content = GetContent(typeArgumentNode);
}
if (hasTypeArgumentSpecified)
{
// OK this means that the developer has specified at least one type parameter.
// Either they specified everything and its OK to rewrite, or its an error.
if (ValidateTypeArguments(node, bindings))
{
RewriteTypeNames(new GenericTypeNameRewriter(bindings), node);
}
return;
}
// OK if we get here that means that no type arguments were specified, so we will try to infer
// the type.
//
// The actual inference is done by the C# compiler, we just emit an a method that represents the
// use of this component.
// Since we're generating code in a different namespace, we need to 'global qualify' all of the types
// to avoid clashes with our generated code.
RewriteTypeNames(new GlobalQualifiedTypeNameRewriter(bindings.Keys), node);
//
// We need to verify that an argument was provided that 'covers' each type parameter.
//
// For example, consider a repeater where the generic type is the 'item' type, but the developer has
// not set the items. We won't be able to do type inference on this and so it will just be nonsense.
var attributes = node.Attributes.Select(a => a.BoundAttribute).Concat(node.ChildContents.Select(c => c.BoundAttribute));
foreach (var attribute in attributes)
{
if (attribute == null)
{
// Will be null for attributes set on the component that don't match a declared component parameter
continue;
}
// Now we need to parse the type name and extract the generic parameters.
//
// Two cases;
// 1. name is a simple identifier like TItem
// 2. name contains type parameters like Dictionary<string, TItem>
if (!attribute.IsGenericTypedProperty())
{
continue;
}
var parsed = SyntaxFactory.ParseTypeName(attribute.TypeName);
if (parsed is IdentifierNameSyntax identifier)
{
bindings.Remove(identifier.ToString());
}
else
{
var typeParameters = parsed.DescendantNodesAndSelf().OfType <TypeArgumentListSyntax>().SelectMany(arg => arg.Arguments);
foreach (var typeParameter in typeParameters)
{
bindings.Remove(typeParameter.ToString());
}
}
}
// If any bindings remain then this means we would never be able to infer the arguments of this
// component usage because the user hasn't set properties that include all of the types.
if (bindings.Count > 0)
{
// However we still want to generate 'type inference' code because we want the errors to be as
// helpful as possible. So let's substitute 'object' for all of those type parameters, and add
// an error.
RewriteTypeNames(new GenericTypeNameRewriter(bindings), node);
node.Diagnostics.Add(BlazorDiagnosticFactory.Create_GenericComponentTypeInferenceUnderspecified(node.Source, node, node.Component.GetTypeParameters()));
}
// Next we need to generate a type inference 'method' node. This represents a method that we will codegen that
// contains all of the operations on the render tree building. Calling a method to operate on the builder
// will allow the C# compiler to perform type inference.
var documentNode = (DocumentIntermediateNode)Ancestors[Ancestors.Count - 1];
CreateTypeInferenceMethod(documentNode, node, bindings);
}
