| import { |
| isAbstractType, |
| isInterfaceType, |
| isListType, |
| isNonNullType, |
| isObjectType, |
| } from '../type/definition.mjs'; |
| |
| /** |
| * Provided two types, return true if the types are equal (invariant). |
| */ |
| export function isEqualType(typeA, typeB) { |
| // Equivalent types are equal. |
| if (typeA === typeB) { |
| return true; |
| } // If either type is non-null, the other must also be non-null. |
| |
| if (isNonNullType(typeA) && isNonNullType(typeB)) { |
| return isEqualType(typeA.ofType, typeB.ofType); |
| } // If either type is a list, the other must also be a list. |
| |
| if (isListType(typeA) && isListType(typeB)) { |
| return isEqualType(typeA.ofType, typeB.ofType); |
| } // Otherwise the types are not equal. |
| |
| return false; |
| } |
| /** |
| * 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). |
| */ |
| |
| export function isTypeSubTypeOf(schema, maybeSubType, superType) { |
| // Equivalent type is a valid subtype |
| if (maybeSubType === superType) { |
| return true; |
| } // If superType is non-null, maybeSubType must also be non-null. |
| |
| if (isNonNullType(superType)) { |
| if (isNonNullType(maybeSubType)) { |
| return isTypeSubTypeOf(schema, maybeSubType.ofType, superType.ofType); |
| } |
| |
| return false; |
| } |
| |
| if (isNonNullType(maybeSubType)) { |
| // If superType is nullable, maybeSubType may be non-null or nullable. |
| return isTypeSubTypeOf(schema, maybeSubType.ofType, superType); |
| } // If superType type is a list, maybeSubType type must also be a list. |
| |
| if (isListType(superType)) { |
| if (isListType(maybeSubType)) { |
| return isTypeSubTypeOf(schema, maybeSubType.ofType, superType.ofType); |
| } |
| |
| return false; |
| } |
| |
| if (isListType(maybeSubType)) { |
| // If superType is not a list, maybeSubType must also be not a list. |
| return false; |
| } // If superType type is an abstract type, check if it is super type of maybeSubType. |
| // Otherwise, the child type is not a valid subtype of the parent type. |
| |
| return ( |
| isAbstractType(superType) && |
| (isInterfaceType(maybeSubType) || isObjectType(maybeSubType)) && |
| schema.isSubType(superType, maybeSubType) |
| ); |
| } |
| /** |
| * 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. |
| */ |
| |
| export function doTypesOverlap(schema, typeA, typeB) { |
| // Equivalent types overlap |
| if (typeA === typeB) { |
| return true; |
| } |
| |
| if (isAbstractType(typeA)) { |
| if (isAbstractType(typeB)) { |
| // If both types are abstract, then determine if there is any intersection |
| // between possible concrete types of each. |
| return schema |
| .getPossibleTypes(typeA) |
| .some((type) => schema.isSubType(typeB, type)); |
| } // Determine if the latter type is a possible concrete type of the former. |
| |
| return schema.isSubType(typeA, typeB); |
| } |
| |
| if (isAbstractType(typeB)) { |
| // Determine if the former type is a possible concrete type of the latter. |
| return schema.isSubType(typeB, typeA); |
| } // Otherwise the types do not overlap. |
| |
| return false; |
| } |