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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;
}