src/Utils/BreakingChangesFinder.php
public static function findTypesAddedToUnions(
        Schema $oldSchema,
        Schema $newSchema
    ) {
        $oldTypeMap = $oldSchema->getTypeMap();
        $newTypeMap = $newSchema->getTypeMap();

        $typesAddedToUnion = [];
        foreach ($newTypeMap as $typeName => $newType) {
            $oldType = $oldTypeMap[$typeName] ?? null;
            if (! ($oldType instanceof UnionType) || ! ($newType instanceof UnionType)) {
                continue;
            }

            $typeNamesInOldUnion = [];
            foreach ($oldType->getTypes() as $type) {
                $typeNamesInOldUnion[$type->name] = true;
            }
            foreach ($newType->getTypes() as $type) {
                if (isset($typeNamesInOldUnion[$type->name])) {
                    continue;
                }

                $typesAddedToUnion[] = [
                    'type'        => self::DANGEROUS_CHANGE_TYPE_ADDED_TO_UNION,
                    'description' => sprintf('%s was added to union type %s.', $type->name, $typeName),
                ];
            }
        }

        return $typesAddedToUnion;
    }
public static function findTypesAddedToUnions(
        Schema $oldSchema,
        Schema $newSchema
    ) {
        $oldTypeMap = $oldSchema->getTypeMap();
        $newTypeMap = $newSchema->getTypeMap();

        $typesAddedToUnion = [];
        foreach ($newTypeMap as $typeName => $newType) {
            $oldType = $oldTypeMap[$typeName] ?? null;
            if (! ($oldType instanceof UnionType) || ! ($newType instanceof UnionType)) {
                continue;
            }

            $typeNamesInOldUnion = [];
            foreach ($oldType->getTypes() as $type) {
                $typeNamesInOldUnion[$type->name] = true;
            }
            foreach ($newType->getTypes() as $type) {
                if (isset($typeNamesInOldUnion[$type->name])) {
                    continue;
                }

                $typesAddedToUnion[] = [
                    'type'        => self::DANGEROUS_CHANGE_TYPE_ADDED_TO_UNION,
                    'description' => sprintf('%s was added to union type %s.', $type->name, $typeName),
                ];
            }
        }

        return $typesAddedToUnion;
    }
Given two schemas, returns an Array containing descriptions of any dangerous
changes in the newSchema related to adding types to a union type.

@return string[][]