/// <summary>
/// Provided two composite types, determine if they "overlap". Two composite
/// types overlap when the Sets of possible concrete types for each intersect.
///
/// This is often used to determine if a fragment of a given type could possibly
/// be visited in a context of another type.
///
/// This function is commutative.
/// </summary>
public static bool DoTypesOverlap(this ISchema schema, IGraphType typeA, IGraphType typeB)
{
if (typeA.Equals(typeB))
{
return(true);
}
var a = typeA as IAbstractGraphType;
var b = typeB as IAbstractGraphType;
if (a != null)
{
if (b != null)
{
return(a.PossibleTypes.Any(type => b.IsPossibleType(type)));
}
return(a.IsPossibleType(typeB));
}
if (b != null)
{
return(b.IsPossibleType(typeA));
}
return(false);
}
private bool DoTypesConflict(IGraphType type1, IGraphType type2)
{
if (type1 is ListGraphType type1List)
{
return(type2 is ListGraphType type2List?DoTypesConflict(type1List.ResolvedType, type2List.ResolvedType) : true);
}
if (type2 is ListGraphType)
{
return(true);
}
if (type1 is NonNullGraphType type1NonNull)
{
return(type2 is NonNullGraphType type2NonNull?DoTypesConflict(type1NonNull.ResolvedType, type2NonNull.ResolvedType) : true);
}
if (type2 is NonNullGraphType)
{
return(true);
}
if (type1.IsLeafType() || type2.IsLeafType())
{
return(!type1.Equals(type2));
}
return(false);
}
/// <summary>
/// Provided a type and a super type, return true if the first type is either
/// equal or a subset of the second super type (covariant).
/// </summary>
public static bool IsSubtypeOf(this IGraphType maybeSubType, IGraphType superType, ISchema schema)
{
if (maybeSubType.Equals(superType))
{
return(true);
}
// If superType is non-null, maybeSubType must also be nullable.
if (superType is NonNullGraphType)
{
if (maybeSubType is NonNullGraphType)
{
var sub = (NonNullGraphType)maybeSubType;
var sup = (NonNullGraphType)superType;
return(IsSubtypeOf(sub.ResolvedType, sup.ResolvedType, schema));
}
return(false);
}
else if (maybeSubType is NonNullGraphType)
{
var sub = (NonNullGraphType)maybeSubType;
return(IsSubtypeOf(sub.ResolvedType, superType, schema));
}
// If superType type is a list, maybeSubType type must also be a list.
if (superType is ListGraphType)
{
if (maybeSubType is ListGraphType)
{
var sub = (ListGraphType)maybeSubType;
var sup = (ListGraphType)superType;
return(IsSubtypeOf(sub.ResolvedType, sup.ResolvedType, schema));
}
return(false);
}
else if (maybeSubType is ListGraphType)
{
// If superType is not a list, maybeSubType must also be not a list.
return(false);
}
// If superType type is an abstract type, maybeSubType type may be a currently
// possible object type.
if (superType is IAbstractGraphType &&
maybeSubType is IObjectGraphType)
{
return(((IAbstractGraphType)superType).IsPossibleType(maybeSubType));
}
return(false);
}