121 lines
3.5 KiB
Plaintext
121 lines
3.5 KiB
Plaintext
// @flow strict
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import type { GraphQLSchema } from '../type/schema';
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import type { GraphQLType, GraphQLCompositeType } from '../type/definition';
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import {
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isInterfaceType,
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isObjectType,
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isListType,
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isNonNullType,
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isAbstractType,
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} from '../type/definition';
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/**
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* Provided two types, return true if the types are equal (invariant).
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*/
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export function isEqualType(typeA: GraphQLType, typeB: GraphQLType): boolean {
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// Equivalent types are equal.
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if (typeA === typeB) {
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return true;
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}
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// If either type is non-null, the other must also be non-null.
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if (isNonNullType(typeA) && isNonNullType(typeB)) {
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return isEqualType(typeA.ofType, typeB.ofType);
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}
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// If either type is a list, the other must also be a list.
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if (isListType(typeA) && isListType(typeB)) {
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return isEqualType(typeA.ofType, typeB.ofType);
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}
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// Otherwise the types are not equal.
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return false;
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}
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/**
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* Provided a type and a super type, return true if the first type is either
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* equal or a subset of the second super type (covariant).
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*/
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export function isTypeSubTypeOf(
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schema: GraphQLSchema,
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maybeSubType: GraphQLType,
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superType: GraphQLType,
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): boolean {
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// Equivalent type is a valid subtype
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if (maybeSubType === superType) {
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return true;
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}
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// If superType is non-null, maybeSubType must also be non-null.
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if (isNonNullType(superType)) {
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if (isNonNullType(maybeSubType)) {
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return isTypeSubTypeOf(schema, maybeSubType.ofType, superType.ofType);
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}
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return false;
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}
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if (isNonNullType(maybeSubType)) {
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// If superType is nullable, maybeSubType may be non-null or nullable.
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return isTypeSubTypeOf(schema, maybeSubType.ofType, superType);
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}
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// If superType type is a list, maybeSubType type must also be a list.
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if (isListType(superType)) {
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if (isListType(maybeSubType)) {
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return isTypeSubTypeOf(schema, maybeSubType.ofType, superType.ofType);
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}
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return false;
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}
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if (isListType(maybeSubType)) {
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// If superType is not a list, maybeSubType must also be not a list.
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return false;
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}
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// If superType type is an abstract type, check if it is super type of maybeSubType.
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// Otherwise, the child type is not a valid subtype of the parent type.
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return (
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isAbstractType(superType) &&
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(isInterfaceType(maybeSubType) || isObjectType(maybeSubType)) &&
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schema.isSubType(superType, maybeSubType)
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);
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}
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/**
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* Provided two composite types, determine if they "overlap". Two composite
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* types overlap when the Sets of possible concrete types for each intersect.
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*
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* This is often used to determine if a fragment of a given type could possibly
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* be visited in a context of another type.
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*
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* This function is commutative.
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*/
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export function doTypesOverlap(
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schema: GraphQLSchema,
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typeA: GraphQLCompositeType,
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typeB: GraphQLCompositeType,
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): boolean {
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// Equivalent types overlap
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if (typeA === typeB) {
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return true;
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}
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if (isAbstractType(typeA)) {
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if (isAbstractType(typeB)) {
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// If both types are abstract, then determine if there is any intersection
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// between possible concrete types of each.
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return schema
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.getPossibleTypes(typeA)
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.some((type) => schema.isSubType(typeB, type));
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}
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// Determine if the latter type is a possible concrete type of the former.
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return schema.isSubType(typeA, typeB);
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}
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if (isAbstractType(typeB)) {
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// Determine if the former type is a possible concrete type of the latter.
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return schema.isSubType(typeB, typeA);
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}
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// Otherwise the types do not overlap.
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return false;
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}
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