@graphql-tools/graphql/esm/validation/rules/PossibleFragmentSpreadsRule.js

Fork of GraphQL.js

import { inspect } from '../../jsutils/inspect.js';
import { GraphQLError } from '../../error/GraphQLError.js';
import { isCompositeType } from '../../type/definition.js';
import { doTypesOverlap } from '../../utilities/typeComparators.js';
import { typeFromAST } from '../../utilities/typeFromAST.js';
/**
 * Possible fragment spread
 *
 * A fragment spread is only valid if the type condition could ever possibly
 * be true: if there is a non-empty intersection of the possible parent types,
 * and possible types which pass the type condition.
 */
export function PossibleFragmentSpreadsRule(context) {
    return {
        InlineFragment(node) {
            const fragType = context.getType();
            const parentType = context.getParentType();
            if (isCompositeType(fragType) &&
                isCompositeType(parentType) &&
                !doTypesOverlap(context.getSchema(), fragType, parentType)) {
                const parentTypeStr = inspect(parentType);
                const fragTypeStr = inspect(fragType);
                context.reportError(new GraphQLError(`Fragment cannot be spread here as objects of type "${parentTypeStr}" can never be of type "${fragTypeStr}".`, { nodes: node }));
            }
        },
        FragmentSpread(node) {
            const fragName = node.name.value;
            const fragType = getFragmentType(context, fragName);
            const parentType = context.getParentType();
            if (fragType && parentType && !doTypesOverlap(context.getSchema(), fragType, parentType)) {
                const parentTypeStr = inspect(parentType);
                const fragTypeStr = inspect(fragType);
                context.reportError(new GraphQLError(`Fragment "${fragName}" cannot be spread here as objects of type "${parentTypeStr}" can never be of type "${fragTypeStr}".`, { nodes: node }));
            }
        },
    };
}
function getFragmentType(context, name) {
    const frag = context.getFragment(name);
    if (frag) {
        const type = typeFromAST(context.getSchema(), frag.typeCondition);
        if (isCompositeType(type)) {
            return type;
        }
    }
    return undefined;
}