node_modules/graphql/utilities/typeComparators.js

"use strict";

Object.defineProperty(exports, "__esModule", {
  value: true
});
exports.isEqualType = isEqualType;
exports.isTypeSubTypeOf = isTypeSubTypeOf;
exports.doTypesOverlap = doTypesOverlap;

var _definition = require("../type/definition");

/**
 * Provided two types, return true if the types are equal (invariant).
 */
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 ((0, _definition.isNonNullType)(typeA) && (0, _definition.isNonNullType)(typeB)) {
    return isEqualType(typeA.ofType, typeB.ofType);
  } // If either type is a list, the other must also be a list.


  if ((0, _definition.isListType)(typeA) && (0, _definition.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).
 */


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 ((0, _definition.isNonNullType)(superType)) {
    if ((0, _definition.isNonNullType)(maybeSubType)) {
      return isTypeSubTypeOf(schema, maybeSubType.ofType, superType.ofType);
    }

    return false;
  }

  if ((0, _definition.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 ((0, _definition.isListType)(superType)) {
    if ((0, _definition.isListType)(maybeSubType)) {
      return isTypeSubTypeOf(schema, maybeSubType.ofType, superType.ofType);
    }

    return false;
  }

  if ((0, _definition.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 (0, _definition.isAbstractType)(superType) && ((0, _definition.isInterfaceType)(maybeSubType) || (0, _definition.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.
 */


function doTypesOverlap(schema, typeA, typeB) {
  // Equivalent types overlap
  if (typeA === typeB) {
    return true;
  }

  if ((0, _definition.isAbstractType)(typeA)) {
    if ((0, _definition.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(function (type) {
        return schema.isSubType(typeB, type);
      });
    } // Determine if the latter type is a possible concrete type of the former.


    return schema.isSubType(typeA, typeB);
  }

  if ((0, _definition.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;
}