Lists always have non-null elements

Because in the vast majority of cases a list of something do not allow
null. This is especially true for Doctrine collection of entities returned
by getter, but also for most inputs used in setter.

If a list of mixed null and non-null elements is needed then a custom
type should be defined via annotation.

Author: PowerKiKi

src/Factory/AbstractFieldsConfigurationFactory.php

@@ -140,7 +140,7 @@ final protected function getTypeFromPhpDeclaration(ReflectionMethod $method, ?st
         $type = $this->getTypeFromRegistry($name, $isEntityId);
 
         if ($isList) {
-            $type = Type::listOf($type);
+            $type = Type::listOf(Type::nonNull($type));
         }
 
         if (!$isNullable) {
@@ -200,7 +200,7 @@ final protected function getTypeFromReturnTypeHint(ReflectionMethod $method, str
                 throw new Exception('The method ' . $this->getMethodFullName($method) . ' is type hinted with a return type of `' . $returnTypeName . '`, but the entity contained in that collection could not be automatically detected. Either fix the type hint, fix the doctrine mapping, or specify the type with `@API\Field` annotation.');
             }
 
-            $type = Type::listOf($this->getTypeFromRegistry($targetEntity, false));
+            $type = Type::listOf(Type::nonNull($this->getTypeFromRegistry($targetEntity, false)));
             if (!$returnType->allowsNull()) {
                 $type = Type::nonNull($type);
             }

tests/data/ArrayOfEntity.graphqls

@@ -1,5 +1,5 @@
 type ArrayOfEntity {
-  users: [User]!
+  users: [User!]!
   id: ID!
   creationDate: DateTime!
 }

tests/data/IgnoredGetter.graphqls

@@ -1,6 +1,6 @@
 type IgnoredGetter {
   public: String!
-  publicWithArgs(arg1: String!, arg2: Int!, arg3: [String] = ["foo"]): [String]!
+  publicWithArgs(arg1: String!, arg2: Int!, arg3: [String!] = ["foo"]): [String!]!
   isValid: Boolean!
   hasMoney: Boolean!
   id: ID!

tests/data/PostOutput.graphqls

@@ -14,8 +14,8 @@ type Post {
 
   """Date of publication"""
   publicationDate: DateTime!
-  words: [String]!
-  hasWords(words: [String]!): Boolean!
+  words: [String!]!
+  hasWords(words: [String!]!): Boolean!
   isLong(wordLimit: Int = 50): Boolean!
   isAllowedEditing(user: UserID!): Boolean!
   id: ID!

tests/data/UserOutput.graphqls

@@ -15,8 +15,8 @@ type User {
     The status of posts as defined in \GraphQLTests\Doctrine\Blog\Model\Post
     """
     status: PostStatus = public
-  ): [Post]!
-  postsWithIds(ids: [ID]!): [Post]!
+  ): [Post!]!
+  postsWithIds(ids: [ID!]!): [Post!]!
   manager: User
   id: ID!
   creationDate: DateTime!