Parser: allowLegacySDLEmptyFields option + minor naming tweaks

src/Language/Parser.php

@@ -66,6 +66,15 @@ class Parser
      *   in the source that they correspond to. This configuration flag
      *   disables that behavior for performance or testing.)
      *
+     *
+     * allowLegacySDLEmptyFields: boolean
+     *   If enabled, the parser will parse empty fields sets in the Schema
+     *   Definition Language. Otherwise, the parser will follow the current
+     *   specification.
+     *
+     *   This option is provided to ease adoption of the final SDL specification
+     *   and will be removed in a future major release.
+     *
      * experimentalFragmentVariables: boolean,
      *   (If enabled, the parser will understand and parse variable definitions
      *   contained in a fragment definition. They'll be represented in the
@@ -1083,6 +1092,16 @@ class Parser
      */
     function parseFieldsDefinition()
     {
+        // Legacy support for the SDL?
+        if (
+            !empty($this->lexer->options['allowLegacySDLEmptyFields']) &&
+            $this->peek(Token::BRACE_L) &&
+            $this->lexer->lookahead()->kind === Token::BRACE_R
+        ) {
+            $this->lexer->advance();
+            $this->lexer->advance();
+            return [];
+        }
         return $this->peek(Token::BRACE_L)
             ? $this->many(
                 Token::BRACE_L,
@@ -1177,6 +1196,9 @@ class Parser
     }
 
     /**
+     * UnionTypeDefinition :
+     *   - Description? union Name Directives[Const]? UnionMemberTypes?
+     *
      * @return UnionTypeDefinitionNode
      * @throws SyntaxError
      */
@@ -1187,7 +1209,7 @@ class Parser
         $this->expectKeyword('union');
         $name = $this->parseName();
         $directives = $this->parseDirectives(true);
-        $types = $this->parseMemberTypesDefinition();
+        $types = $this->parseUnionMemberTypes();
 
         return new UnionTypeDefinitionNode([
             'name' => $name,
@@ -1199,13 +1221,13 @@ class Parser
     }
 
     /**
-     * MemberTypes :
+     * UnionMemberTypes :
-     *   - `|`? NamedType
+     *   - = `|`? NamedType
-     *   - MemberTypes | NamedType
+     *   - UnionMemberTypes | NamedType
      *
      * @return NamedTypeNode[]
      */
-    function parseMemberTypesDefinition()
+    function parseUnionMemberTypes()
     {
         $types = [];
         if ($this->skip(Token::EQUALS)) {
@@ -1424,6 +1446,10 @@ class Parser
     }
 
     /**
+     * UnionTypeExtension :
+     *   - extend union Name Directives[Const]? UnionMemberTypes
+     *   - extend union Name Directives[Const]
+     *
      * @return UnionTypeExtensionNode
      * @throws SyntaxError
      */
@@ -1433,7 +1459,7 @@ class Parser
         $this->expectKeyword('union');
         $name = $this->parseName();
         $directives = $this->parseDirectives(true);
-        $types = $this->parseMemberTypesDefinition();
+        $types = $this->parseUnionMemberTypes();
         if (
             count($directives) === 0 &&
             !$types

tests/Language/SchemaParserTest.php

@@ -861,6 +861,29 @@ input Hello {
         );
     }
 
+    public function testDoesNotAllowEmptyFields()
+    {
+        $body = 'type Hello { }';
+        $this->expectSyntaxError($body, 'Syntax Error: Expected Name, found }', new SourceLocation(1, 14));
+    }
+
+    /**
+     * @it Option: allowLegacySDLEmptyFields supports type with empty fields
+     */
+    public function testAllowLegacySDLEmptyFieldsOption()
+    {
+        $body = 'type Hello { }';
+        $doc = Parser::parse($body, ['allowLegacySDLEmptyFields' => true]);
+        $expected = [
+            'definitions' => [
+                [
+                    'fields' => [],
+                ],
+            ],
+        ];
+        $this->assertArraySubset($expected, $doc->toArray(true));
+    }
+
     private function typeNode($name, $loc)
     {
         return [