| 1 | import { isObjectType, isListType, isNonNullType, isAbstractType } from '../type/definition';
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| 2 | /**
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| 3 | * Provided two types, return true if the types are equal (invariant).
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| 4 | */
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| 5 |
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| 6 | export function isEqualType(typeA, typeB) {
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| 7 | // Equivalent types are equal.
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| 8 | if (typeA === typeB) {
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| 9 | return true;
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| 10 | } // If either type is non-null, the other must also be non-null.
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| 11 |
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| 12 |
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| 13 | if (isNonNullType(typeA) && isNonNullType(typeB)) {
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| 14 | return isEqualType(typeA.ofType, typeB.ofType);
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| 15 | } // If either type is a list, the other must also be a list.
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| 16 |
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| 17 |
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| 18 | if (isListType(typeA) && isListType(typeB)) {
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| 19 | return isEqualType(typeA.ofType, typeB.ofType);
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| 20 | } // Otherwise the types are not equal.
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| 21 |
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| 22 |
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| 23 | return false;
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| 24 | }
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| 25 | /**
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| 26 | * Provided a type and a super type, return true if the first type is either
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| 27 | * equal or a subset of the second super type (covariant).
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| 28 | */
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| 29 |
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| 30 | export function isTypeSubTypeOf(schema, maybeSubType, superType) {
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| 31 | // Equivalent type is a valid subtype
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| 32 | if (maybeSubType === superType) {
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| 33 | return true;
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| 34 | } // If superType is non-null, maybeSubType must also be non-null.
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| 35 |
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| 36 |
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| 37 | if (isNonNullType(superType)) {
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| 38 | if (isNonNullType(maybeSubType)) {
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| 39 | return isTypeSubTypeOf(schema, maybeSubType.ofType, superType.ofType);
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| 40 | }
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| 41 |
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| 42 | return false;
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| 43 | }
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| 44 |
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| 45 | if (isNonNullType(maybeSubType)) {
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| 46 | // If superType is nullable, maybeSubType may be non-null or nullable.
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| 47 | return isTypeSubTypeOf(schema, maybeSubType.ofType, superType);
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| 48 | } // If superType type is a list, maybeSubType type must also be a list.
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| 49 |
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| 50 |
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| 51 | if (isListType(superType)) {
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| 52 | if (isListType(maybeSubType)) {
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| 53 | return isTypeSubTypeOf(schema, maybeSubType.ofType, superType.ofType);
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| 54 | }
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| 55 |
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| 56 | return false;
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| 57 | }
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| 58 |
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| 59 | if (isListType(maybeSubType)) {
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| 60 | // If superType is not a list, maybeSubType must also be not a list.
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| 61 | return false;
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| 62 | } // If superType type is an abstract type, maybeSubType type may be a currently
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| 63 | // possible object type.
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| 64 |
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| 65 |
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| 66 | if (isAbstractType(superType) && isObjectType(maybeSubType) && schema.isPossibleType(superType, maybeSubType)) {
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| 67 | return true;
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| 68 | } // Otherwise, the child type is not a valid subtype of the parent type.
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| 69 |
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| 70 |
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| 71 | return false;
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| 72 | }
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| 73 | /**
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| 74 | * Provided two composite types, determine if they "overlap". Two composite
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| 75 | * types overlap when the Sets of possible concrete types for each intersect.
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| 76 | *
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| 77 | * This is often used to determine if a fragment of a given type could possibly
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| 78 | * be visited in a context of another type.
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| 79 | *
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| 80 | * This function is commutative.
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| 81 | */
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| 82 |
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| 83 | export function doTypesOverlap(schema, typeA, typeB) {
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| 84 | // Equivalent types overlap
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| 85 | if (typeA === typeB) {
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| 86 | return true;
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| 87 | }
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| 88 |
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| 89 | if (isAbstractType(typeA)) {
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| 90 | if (isAbstractType(typeB)) {
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| 91 | // If both types are abstract, then determine if there is any intersection
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| 92 | // between possible concrete types of each.
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| 93 | return schema.getPossibleTypes(typeA).some(function (type) {
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| 94 | return schema.isPossibleType(typeB, type);
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| 95 | });
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| 96 | } // Determine if the latter type is a possible concrete type of the former.
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| 97 |
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| 98 |
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| 99 | return schema.isPossibleType(typeA, typeB);
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| 100 | }
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| 101 |
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| 102 | if (isAbstractType(typeB)) {
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| 103 | // Determine if the former type is a possible concrete type of the latter.
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| 104 | return schema.isPossibleType(typeB, typeA);
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| 105 | } // Otherwise the types do not overlap.
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| 106 |
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| 107 |
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| 108 | return false;
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| 109 | }
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