// { $getField : { field : "y", input : "$x" } } => "$x.y"
static bool TrySimplifyAsFieldPath(AstGetFieldExpression node, out AstExpression simplified)
{
if (node.CanBeConvertedToFieldPath())
{
var path = node.ConvertToFieldPath();
simplified = AstExpression.FieldPath(path);
return(true);
}
simplified = null;
return(false);
}
public override AstNode VisitGetFieldExpression(AstGetFieldExpression node)
{
if (TrySimplifyAsFieldPath(node, out var simplified))
{
return(simplified);
}
if (TrySimplifyAsLet(node, out simplified))
{
return(simplified);
}
return(base.VisitGetFieldExpression(node));
public override AstNode VisitGetFieldExpression(AstGetFieldExpression node)
{
if (node.FieldName is AstConstantExpression constantFieldName &&
constantFieldName.Value.IsString &&
constantFieldName.Value.AsString == "_elements" &&
node.Input is AstVarExpression varExpression &&
varExpression.Name == "ROOT")
{
throw new UnableToRemoveReferenceToElementsException();
}
return(base.VisitGetFieldExpression(node));
}
// { $getField : { field : "x", input : <input> } } => { $let : { vars : { this : <input> }, in : "$$this.x" } }
bool TrySimplifyAsLet(AstGetFieldExpression node, out AstExpression simplified)
{
if (node.HasSafeFieldName(out var fieldName))
{
var simplifiedInput = VisitAndConvert(node.Input);
var var = AstExpression.Var("this");
var binding = AstExpression.VarBinding(var, simplifiedInput);
simplified = AstExpression.Let(binding, AstExpression.FieldPath($"$$this.{fieldName}"));
return(true);
}
simplified = null;
return(false);
}
