RFC: Descriptions as strings

As discussed in facebook/graphql#90

This proposes replacing leading comment blocks as descriptions in the schema definition language with leading strings (typically block strings).

While I think there is some reduced ergonomics of using a string literal instead of a comment to write descriptions (unless perhaps you are accustomed to Python or Clojure), there are some compelling advantages:

* Descriptions are first-class in the AST of the schema definition language.
* Comments can remain "ignored" characters.
* No ambiguity between commented out regions and descriptions.

Specific to this reference implementation, since this is a breaking change and comment descriptions in the experimental SDL have fairly wide usage, I've left the comment description implementation intact and allow it to be enabled via an option. This should help with allowing upgrading with minimal impact on existing codebases and aid in automated transforms.

BREAKING CHANGE: This does not parse descriptions from comments by default anymore and the value of description in Nodes changed from string to StringValueNode

src/Language/AST/DirectiveDefinitionNode.php

@@ -22,4 +22,9 @@ class DirectiveDefinitionNode extends Node implements TypeSystemDefinitionNode
      * @var NameNode[]
      */
     public $locations;
+    
+    /**
+     * @var StringValueNode|null
+     */
+    public $description;
 }

src/Language/AST/EnumTypeDefinitionNode.php

@@ -24,7 +24,7 @@ class EnumTypeDefinitionNode extends Node implements TypeDefinitionNode
     public $values;
 
     /**
-     * @var string
+     * @var StringValueNode|null
      */
     public $description;
 }

src/Language/AST/EnumValueDefinitionNode.php

@@ -19,7 +19,7 @@ class EnumValueDefinitionNode extends Node
     public $directives;
 
     /**
-     * @var string
+     * @var StringValueNode|null
      */
     public $description;
 }

src/Language/AST/FieldDefinitionNode.php

@@ -29,7 +29,7 @@ class FieldDefinitionNode extends Node
     public $directives;
 
     /**
-     * @var string
+     * @var StringValueNode|null
      */
     public $description;
 }

src/Language/AST/InputObjectTypeDefinitionNode.php

@@ -24,7 +24,7 @@ class InputObjectTypeDefinitionNode extends Node implements TypeDefinitionNode
     public $fields;
 
     /**
-     * @var string
+     * @var StringValueNode|null
      */
     public $description;
 }

src/Language/AST/InputValueDefinitionNode.php

@@ -29,7 +29,7 @@ class InputValueDefinitionNode extends Node
     public $directives;
 
     /**
-     * @var string
+     * @var StringValueNode|null
      */
     public $description;
 }

src/Language/AST/InterfaceTypeDefinitionNode.php

@@ -24,7 +24,7 @@ class InterfaceTypeDefinitionNode extends Node implements TypeDefinitionNode
     public $fields = [];
 
     /**
-     * @var string
+     * @var StringValueNode|null
      */
     public $description;
 }

src/Language/AST/ObjectTypeDefinitionNode.php

@@ -29,7 +29,7 @@ class ObjectTypeDefinitionNode extends Node implements TypeDefinitionNode
     public $fields;
 
     /**
-     * @var string
+     * @var StringValueNode|null
      */
     public $description;
 }

src/Language/AST/ScalarTypeDefinitionNode.php

@@ -19,7 +19,7 @@ class ScalarTypeDefinitionNode extends Node implements TypeDefinitionNode
     public $directives;
 
     /**
-     * @var string
+     * @var StringValueNode|null
      */
     public $description;
 }

src/Language/AST/UnionTypeDefinitionNode.php

@@ -24,7 +24,7 @@ class UnionTypeDefinitionNode extends Node implements TypeDefinitionNode
     public $types = [];
 
     /**
-     * @var string
+     * @var StringValueNode|null
      */
     public $description;
 }

src/Language/Lexer.php

@@ -92,13 +92,18 @@ class Lexer
      */
     public function advance()
     {
-        $token = $this->lastToken = $this->token;
+        $this->lastToken = $this->token;
+        $token = $this->token = $this->lookahead();
+        return $token;
+    }
 
+    public function lookahead()
+    {
+        $token = $this->token;
         if ($token->kind !== Token::EOF) {
             do {
-                $token = $token->next = $this->readToken($token);
+                $token = $token->next ?: ($token->next = $this->readToken($token));
             } while ($token->kind === Token::COMMENT);
-            $this->token = $token;
         }
         return $token;
     }

src/Language/Parser.php

@@ -340,7 +340,7 @@ class Parser
                 case 'fragment':
                     return $this->parseFragmentDefinition();
 
-                // Note: the Type System IDL is an experimental non-spec addition.
+                // Note: The schema definition language is an experimental addition.
                 case 'schema':
                 case 'scalar':
                 case 'type':
@@ -354,6 +354,11 @@ class Parser
             }
         }
 
+        // Note: The schema definition language is an experimental addition.
+        if ($this->peekDescription()) {
+            return $this->parseTypeSystemDefinition();
+        }
+
         throw $this->unexpected();
     }
 
@@ -656,12 +661,7 @@ class Parser
                 ]);
             case Token::STRING:
             case Token::BLOCK_STRING:
-                $this->lexer->advance();
+                return $this->parseStringLiteral();
-                return new StringValueNode([
-                    'value' => $token->value,
-                    'block' => $token->kind === Token::BLOCK_STRING,
-                    'loc' => $this->loc($token)
-                ]);
             case Token::NAME:
                 if ($token->value === 'true' || $token->value === 'false') {
                     $this->lexer->advance();
@@ -692,6 +692,20 @@ class Parser
         throw $this->unexpected();
     }
 
+    /**
+     * @return StringValueNode
+     */
+    function parseStringLiteral() {
+        $token = $this->lexer->token;
+        $this->lexer->advance();
+
+        return new StringValueNode([
+            'value' => $token->value,
+            'block' => $token->kind === Token::BLOCK_STRING,
+            'loc' => $this->loc($token)
+        ]);
+    }
+
     /**
      * @return BooleanValueNode|EnumValueNode|FloatValueNode|IntValueNode|StringValueNode|VariableNode
      * @throws SyntaxError
@@ -852,8 +866,13 @@ class Parser
      */
     function parseTypeSystemDefinition()
     {
-        if ($this->peek(Token::NAME)) {
+        // Many definitions begin with a description and require a lookahead.
-            switch ($this->lexer->token->value) {
+        $keywordToken = $this->peekDescription()
+            ? $this->lexer->lookahead()
+            : $this->lexer->token;
+
+        if ($keywordToken->kind === Token::NAME) {
+            switch ($keywordToken->value) {
                 case 'schema': return $this->parseSchemaDefinition();
                 case 'scalar': return $this->parseScalarTypeDefinition();
                 case 'type': return $this->parseObjectTypeDefinition();
@@ -869,6 +888,22 @@ class Parser
         throw $this->unexpected();
     }
 
+    /**
+     * @return bool
+     */
+    function peekDescription() {
+        return $this->peek(Token::STRING) || $this->peek(Token::BLOCK_STRING);
+    }
+
+    /**
+     * @return StringValueNode|null
+     */
+    function parseDescription() {
+        if ($this->peekDescription()) {
+            return $this->parseStringLiteral();
+        }
+    }
+
     /**
      * @return SchemaDefinitionNode
      * @throws SyntaxError
@@ -916,12 +951,11 @@ class Parser
     function parseScalarTypeDefinition()
     {
         $start = $this->lexer->token;
+        $description = $this->parseDescription();
         $this->expectKeyword('scalar');
         $name = $this->parseName();
         $directives = $this->parseDirectives();
 
-        $description = $this->getDescriptionFromAdjacentCommentTokens($start);
-
         return new ScalarTypeDefinitionNode([
             'name' => $name,
             'directives' => $directives,
@@ -937,6 +971,7 @@ class Parser
     function parseObjectTypeDefinition()
     {
         $start = $this->lexer->token;
+        $description = $this->parseDescription();
         $this->expectKeyword('type');
         $name = $this->parseName();
         $interfaces = $this->parseImplementsInterfaces();
@@ -948,8 +983,6 @@ class Parser
             Token::BRACE_R
         );
 
-        $description = $this->getDescriptionFromAdjacentCommentTokens($start);
-
         return new ObjectTypeDefinitionNode([
             'name' => $name,
             'interfaces' => $interfaces,
@@ -982,14 +1015,13 @@ class Parser
     function parseFieldDefinition()
     {
         $start = $this->lexer->token;
+        $description = $this->parseDescription();
         $name = $this->parseName();
         $args = $this->parseArgumentDefs();
         $this->expect(Token::COLON);
         $type = $this->parseTypeReference();
         $directives = $this->parseDirectives();
 
-        $description = $this->getDescriptionFromAdjacentCommentTokens($start);
-
         return new FieldDefinitionNode([
             'name' => $name,
             'arguments' => $args,
@@ -1018,6 +1050,7 @@ class Parser
     function parseInputValueDef()
     {
         $start = $this->lexer->token;
+        $description = $this->parseDescription();
         $name = $this->parseName();
         $this->expect(Token::COLON);
         $type = $this->parseTypeReference();
@@ -1026,7 +1059,6 @@ class Parser
             $defaultValue = $this->parseConstValue();
         }
         $directives = $this->parseDirectives();
-        $description = $this->getDescriptionFromAdjacentCommentTokens($start);
         return new InputValueDefinitionNode([
             'name' => $name,
             'type' => $type,
@@ -1044,6 +1076,7 @@ class Parser
     function parseInterfaceTypeDefinition()
     {
         $start = $this->lexer->token;
+        $description = $this->parseDescription();
         $this->expectKeyword('interface');
         $name = $this->parseName();
         $directives = $this->parseDirectives();
@@ -1053,8 +1086,6 @@ class Parser
             Token::BRACE_R
         );
 
-        $description = $this->getDescriptionFromAdjacentCommentTokens($start);
-
         return new InterfaceTypeDefinitionNode([
             'name' => $name,
             'directives' => $directives,
@@ -1071,14 +1102,13 @@ class Parser
     function parseUnionTypeDefinition()
     {
         $start = $this->lexer->token;
+        $description = $this->parseDescription();
         $this->expectKeyword('union');
         $name = $this->parseName();
         $directives = $this->parseDirectives();
         $this->expect(Token::EQUALS);
         $types = $this->parseUnionMembers();
 
-        $description = $this->getDescriptionFromAdjacentCommentTokens($start);
-
         return new UnionTypeDefinitionNode([
             'name' => $name,
             'directives' => $directives,
@@ -1114,6 +1144,7 @@ class Parser
     function parseEnumTypeDefinition()
     {
         $start = $this->lexer->token;
+        $description = $this->parseDescription();
         $this->expectKeyword('enum');
         $name = $this->parseName();
         $directives = $this->parseDirectives();
@@ -1123,8 +1154,6 @@ class Parser
             Token::BRACE_R
         );
 
-        $description = $this->getDescriptionFromAdjacentCommentTokens($start);
-
         return new EnumTypeDefinitionNode([
             'name' => $name,
             'directives' => $directives,
@@ -1140,11 +1169,10 @@ class Parser
     function parseEnumValueDefinition()
     {
         $start = $this->lexer->token;
+        $description = $this->parseDescription();
         $name = $this->parseName();
         $directives = $this->parseDirectives();
 
-        $description = $this->getDescriptionFromAdjacentCommentTokens($start);
-
         return new EnumValueDefinitionNode([
             'name' => $name,
             'directives' => $directives,
@@ -1160,6 +1188,7 @@ class Parser
     function parseInputObjectTypeDefinition()
     {
         $start = $this->lexer->token;
+        $description = $this->parseDescription();
         $this->expectKeyword('input');
         $name = $this->parseName();
         $directives = $this->parseDirectives();
@@ -1169,8 +1198,6 @@ class Parser
             Token::BRACE_R
         );
 
-        $description = $this->getDescriptionFromAdjacentCommentTokens($start);
-
         return new InputObjectTypeDefinitionNode([
             'name' => $name,
             'directives' => $directives,
@@ -1206,6 +1233,7 @@ class Parser
     function parseDirectiveDefinition()
     {
         $start = $this->lexer->token;
+        $description = $this->parseDescription();
         $this->expectKeyword('directive');
         $this->expect(Token::AT);
         $name = $this->parseName();
@@ -1217,7 +1245,8 @@ class Parser
             'name' => $name,
             'arguments' => $args,
             'locations' => $locations,
-            'loc' => $this->loc($start)
+            'loc' => $this->loc($start),
+            'description' => $description
         ]);
     }
 
@@ -1234,28 +1263,4 @@ class Parser
         } while ($this->skip(Token::PIPE));
         return $locations;
     }
-
-    /**
-     * @param Token $nameToken
-     * @return null|string
-     */
-    private function getDescriptionFromAdjacentCommentTokens(Token $nameToken)
-    {
-        $description = null;
-
-        $currentToken = $nameToken;
-        $previousToken = $currentToken->prev;
-
-        while ($previousToken->kind == Token::COMMENT
-            && ($previousToken->line + 1) == $currentToken->line
-        ) {
-            $description = $previousToken->value . $description;
-
-            // walk the tokens backwards until no longer adjacent comments
-            $currentToken = $previousToken;
-            $previousToken = $currentToken->prev;
-        }
-
-        return $description;
-    }
 }

src/Language/Printer.php

@@ -138,9 +138,9 @@ class Printer
                 NodeKind::FLOAT => function(FloatValueNode $node) {
                     return $node->value;
                 },
-                NodeKind::STRING => function(StringValueNode $node) {
+                NodeKind::STRING => function(StringValueNode $node, $key) {
                     if ($node->block) {
-                       return $this->printBlockString($node->value);
+                       return $this->printBlockString($node->value, $key === 'description');
                     }
                     return json_encode($node->value);
                 },
@@ -192,74 +192,101 @@ class Printer
                 },
 
                 NodeKind::SCALAR_TYPE_DEFINITION => function(ScalarTypeDefinitionNode $def) {
-                    return $this->join(['scalar', $def->name, $this->join($def->directives, ' ')], ' ');
+                    return $this->join([
+                        $def->description,
+                        $this->join(['scalar', $def->name, $this->join($def->directives, ' ')], ' ')
+                    ], "\n");
                 },
                 NodeKind::OBJECT_TYPE_DEFINITION => function(ObjectTypeDefinitionNode $def) {
                     return $this->join([
+                        $def->description,
+                        $this->join([
                             'type',
                             $def->name,
                             $this->wrap('implements ', $this->join($def->interfaces, ', ')),
                             $this->join($def->directives, ' '),
                             $this->block($def->fields)
-                    ], ' ');
+                        ], ' ')
+                    ], "\n");
                 },
                 NodeKind::FIELD_DEFINITION => function(FieldDefinitionNode $def) {
-                    return $def->name
+                    return $this->join([
+                        $def->description,
+                        $def->name
                          . $this->wrap('(', $this->join($def->arguments, ', '), ')')
                          . ': ' . $def->type
-                         . $this->wrap(' ', $this->join($def->directives, ' '));
+                         . $this->wrap(' ', $this->join($def->directives, ' '))
+                    ], "\n");
                 },
                 NodeKind::INPUT_VALUE_DEFINITION => function(InputValueDefinitionNode $def) {
                     return $this->join([
+                        $def->description,
+                        $this->join([
                             $def->name . ': ' . $def->type,
                             $this->wrap('= ', $def->defaultValue),
                             $this->join($def->directives, ' ')
-                    ], ' ');
+                        ], ' ')
+                    ], "\n");
                 },
                 NodeKind::INTERFACE_TYPE_DEFINITION => function(InterfaceTypeDefinitionNode $def) {
                     return $this->join([
+                        $def->description,
+                        $this->join([
                             'interface',
                             $def->name,
                             $this->join($def->directives, ' '),
                             $this->block($def->fields)
-                    ], ' ');
+                        ], ' ')
+                    ], "\n");
                 },
                 NodeKind::UNION_TYPE_DEFINITION => function(UnionTypeDefinitionNode $def) {
                     return $this->join([
+                        $def->description,
+                        $this->join([
                             'union',
                             $def->name,
                             $this->join($def->directives, ' '),
                             '= ' . $this->join($def->types, ' | ')
-                    ], ' ');
+                        ], ' ')
+                    ], "\n");
                 },
                 NodeKind::ENUM_TYPE_DEFINITION => function(EnumTypeDefinitionNode $def) {
                     return $this->join([
+                        $def->description,
+                        $this->join([
                             'enum',
                             $def->name,
                             $this->join($def->directives, ' '),
                             $this->block($def->values)
-                    ], ' ');
+                        ], ' ')
+                    ], "\n");
                 },
                 NodeKind::ENUM_VALUE_DEFINITION => function(EnumValueDefinitionNode $def) {
                     return $this->join([
-                        $def->name,
+                        $def->description,
-                        $this->join($def->directives, ' ')
+                        $this->join([$def->name, $this->join($def->directives, ' ')], ' ')
-                    ], ' ');
+                    ], "\n");
                 },
                 NodeKind::INPUT_OBJECT_TYPE_DEFINITION => function(InputObjectTypeDefinitionNode $def) {
                     return $this->join([
+                        $def->description,
+                        $this->join([
                             'input',
                             $def->name,
                             $this->join($def->directives, ' '),
                             $this->block($def->fields)
-                    ], ' ');
+                        ], ' ')
+                    ], "\n");
                 },
                 NodeKind::TYPE_EXTENSION_DEFINITION => function(TypeExtensionDefinitionNode $def) {
                     return "extend {$def->definition}";
                 },
                 NodeKind::DIRECTIVE_DEFINITION => function(DirectiveDefinitionNode $def) {
-                    return 'directive @' . $def->name . $this->wrap('(', $this->join($def->arguments, ', '), ')')
+                    return $this->join([
-                        . ' on ' . $this->join($def->locations, ' | ');
+                        $def->description,
+                        'directive @' . $def->name . $this->wrap('(', $this->join($def->arguments, ', '), ')')
+                        . ' on ' . $this->join($def->locations, ' | ')
+                    ], "\n");
                 }
             ]
         ]);
@@ -316,9 +343,13 @@ class Printer
      * trailing blank line. However, if a block string starts with whitespace and is
      * a single-line, adding a leading blank line would strip that whitespace.
      */
-    private function printBlockString($value) {
+    private function printBlockString($value, $isDescription) {
-        return ($value[0] === ' ' || $value[0] === "\t") && strpos($value, "\n") === false
+        return (($value[0] === ' ' || $value[0] === "\t") && strpos($value, "\n") === false)
-            ? '"""' . str_replace('"""', '\\"""', $value) . '"""'
+            ? ('"""' . str_replace('"""', '\\"""', $value) . '"""')
-            : $this->indent("\"\"\"\n" . str_replace('"""', '\\"""', $value)) . "\n\"\"\"";
+            : (
+                $isDescription
+                    ? ("\"\"\"\n" . str_replace('"""', '\\"""', $value) . "\n\"\"\"")
+                    : ($this->indent("\"\"\"\n" . str_replace('"""', '\\"""', $value)) . "\n\"\"\"")
+                );
     }
 }

src/Language/Visitor.php

@@ -133,17 +133,17 @@ class Visitor
 
         NodeKind::SCHEMA_DEFINITION => ['directives', 'operationTypes'],
         NodeKind::OPERATION_TYPE_DEFINITION => ['type'],
-        NodeKind::SCALAR_TYPE_DEFINITION => ['name', 'directives'],
+        NodeKind::SCALAR_TYPE_DEFINITION => ['description', 'name', 'directives'],
-        NodeKind::OBJECT_TYPE_DEFINITION => ['name', 'interfaces', 'directives', 'fields'],
+        NodeKind::OBJECT_TYPE_DEFINITION => ['description', 'name', 'interfaces', 'directives', 'fields'],
-        NodeKind::FIELD_DEFINITION => ['name', 'arguments', 'type', 'directives'],
+        NodeKind::FIELD_DEFINITION => ['description', 'name', 'arguments', 'type', 'directives'],
-        NodeKind::INPUT_VALUE_DEFINITION => ['name', 'type', 'defaultValue', 'directives'],
+        NodeKind::INPUT_VALUE_DEFINITION => ['description', 'name', 'type', 'defaultValue', 'directives'],
-        NodeKind::INTERFACE_TYPE_DEFINITION => [ 'name', 'directives', 'fields' ],
+        NodeKind::INTERFACE_TYPE_DEFINITION => ['description', 'name', 'directives', 'fields'],
-        NodeKind::UNION_TYPE_DEFINITION => [ 'name', 'directives', 'types' ],
+        NodeKind::UNION_TYPE_DEFINITION => ['description', 'name', 'directives', 'types'],
-        NodeKind::ENUM_TYPE_DEFINITION => [ 'name', 'directives', 'values' ],
+        NodeKind::ENUM_TYPE_DEFINITION => ['description', 'name', 'directives', 'values'],
-        NodeKind::ENUM_VALUE_DEFINITION => [ 'name', 'directives' ],
+        NodeKind::ENUM_VALUE_DEFINITION => ['description', 'name', 'directives'],
-        NodeKind::INPUT_OBJECT_TYPE_DEFINITION => [ 'name', 'directives', 'fields' ],
+        NodeKind::INPUT_OBJECT_TYPE_DEFINITION => ['description', 'name', 'directives', 'fields'],
         NodeKind::TYPE_EXTENSION_DEFINITION => [ 'definition' ],
-        NodeKind::DIRECTIVE_DEFINITION => [ 'name', 'arguments', 'locations' ]
+        NodeKind::DIRECTIVE_DEFINITION => ['description', 'name', 'arguments', 'locations']
     ];
 
     /**

src/Utils/BuildSchema.php

@@ -75,15 +75,21 @@ class BuildSchema
      * Given that AST it constructs a GraphQL\Type\Schema. The resulting schema
      * has no resolve methods, so execution will use default resolvers.
      *
+     * Accepts options as a third argument:
+     *
+     *    - commentDescriptions:
+     *        Provide true to use preceding comments as the description.
+     *
+     *
      * @api
      * @param DocumentNode $ast
      * @param callable $typeConfigDecorator
      * @return Schema
      * @throws Error
      */
-    public static function buildAST(DocumentNode $ast, callable $typeConfigDecorator = null)
+    public static function buildAST(DocumentNode $ast, callable $typeConfigDecorator = null, array $options = [])
     {
-        $builder = new self($ast, $typeConfigDecorator);
+        $builder = new self($ast, $typeConfigDecorator, $options);
         return $builder->buildSchema();
     }
 
@@ -92,12 +98,14 @@ class BuildSchema
     private $nodeMap;
     private $typeConfigDecorator;
     private $loadedTypeDefs;
+    private $options;
 
-    public function __construct(DocumentNode $ast, callable $typeConfigDecorator = null)
+    public function __construct(DocumentNode $ast, callable $typeConfigDecorator = null, array $options = [])
     {
         $this->ast = $ast;
         $this->typeConfigDecorator = $typeConfigDecorator;
         $this->loadedTypeDefs = [];
+        $this->options = $options;
     }
 
     public function buildSchema()
@@ -584,17 +592,28 @@ class BuildSchema
     }
 
     /**
-     * Given an ast node, returns its string description based on a contiguous
+     * Given an ast node, returns its string description.
-     * block full-line of comments preceding it.
      */
     public function getDescription($node)
+    {
+        if ($node->description) {
+            return $node->description->value;
+        }
+        if (isset($this->options['commentDescriptions'])) {
+            $rawValue = $this->getLeadingCommentBlock($node);
+            if ($rawValue !== null) {
+                return BlockString::value("\n" . $rawValue);
+            }
+        }
+    }
+
+    public function getLeadingCommentBlock($node)
     {
         $loc = $node->loc;
         if (!$loc || !$loc->startToken) {
             return ;
         }
         $comments = [];
-        $minSpaces = null;
         $token = $loc->startToken->prev;
         while (
             $token &&
@@ -604,16 +623,11 @@ class BuildSchema
             $token->line !== $token->prev->line
         ) {
             $value = $token->value;
-            $spaces = $this->leadingSpaces($value);
-            if ($minSpaces === null || $spaces < $minSpaces) {
-                $minSpaces = $spaces;
-            }
             $comments[] = $value;
             $token = $token->prev;
         }
-        return implode("\n", array_map(function($comment) use ($minSpaces) {
+
-            return mb_substr(str_replace("\n", '', $comment), $minSpaces);
+        return implode("\n", array_reverse($comments));
-        }, array_reverse($comments)));
     }
 
     /**
@@ -631,12 +645,6 @@ class BuildSchema
         return self::buildAST($doc, $typeConfigDecorator);
     }
 
-    // Count the number of spaces on the starting side of a string.
-    private function leadingSpaces($str)
-    {
-        return strlen($str) - strlen(ltrim($str));
-    }
-
     public function cannotExecuteSchema()
     {
         throw new Error(

src/Utils/SchemaPrinter.php

@@ -19,15 +19,24 @@ use GraphQL\Type\Definition\Directive;
 class SchemaPrinter
 {
     /**
+     * Accepts options as a second argument:
+     *
+     *    - commentDescriptions:
+     *        Provide true to use preceding comments as the description.
      * @api
      * @param Schema $schema
      * @return string
      */
-    public static function doPrint(Schema $schema)
+    public static function doPrint(Schema $schema, array $options = [])
     {
-        return self::printFilteredSchema($schema, function($n) {
+        return self::printFilteredSchema(
+            $schema,
+            function($n) {
                 return !self::isSpecDirective($n);
-        }, 'self::isDefinedType');
+            },
+            'self::isDefinedType',
+            $options
+        );
     }
 
     /**
@@ -35,9 +44,14 @@ class SchemaPrinter
      * @param Schema $schema
      * @return string
      */
-    public static function printIntrosepctionSchema(Schema $schema)
+    public static function printIntrosepctionSchema(Schema $schema, array $options = [])
     {
-        return self::printFilteredSchema($schema, [__CLASS__, 'isSpecDirective'], [__CLASS__, 'isIntrospectionType']);
+        return self::printFilteredSchema(
+            $schema,
+            [__CLASS__, 'isSpecDirective'],
+            [__CLASS__, 'isIntrospectionType'],
+            $options
+        );
     }
 
     private static function isSpecDirective($directiveName)
@@ -70,7 +84,7 @@ class SchemaPrinter
         );
     }
 
-    private static function printFilteredSchema(Schema $schema, $directiveFilter, $typeFilter)
+    private static function printFilteredSchema(Schema $schema, $directiveFilter, $typeFilter, $options)
     {
         $directives = array_filter($schema->getDirectives(), function($directive) use ($directiveFilter) {
             return $directiveFilter($directive->name);
@@ -82,8 +96,8 @@ class SchemaPrinter
 
         return implode("\n\n", array_filter(array_merge(
             [self::printSchemaDefinition($schema)],
-            array_map('self::printDirective', $directives),
+            array_map(function($directive) use ($options) { return self::printDirective($directive, $options); }, $directives),
-            array_map('self::printType', $types)
+            array_map(function($type) use ($options) { return self::printType($type, $options); }, $types)
         ))) . "\n";
     }
 
@@ -145,93 +159,93 @@ class SchemaPrinter
         return true;
     }
 
-    public static function printType(Type $type)
+    public static function printType(Type $type, array $options = [])
     {
         if ($type instanceof ScalarType) {
-            return self::printScalar($type);
+            return self::printScalar($type, $options);
         } else if ($type instanceof ObjectType) {
-            return self::printObject($type);
+            return self::printObject($type, $options);
         } else if ($type instanceof InterfaceType) {
-            return self::printInterface($type);
+            return self::printInterface($type, $options);
         } else if ($type instanceof UnionType) {
-            return self::printUnion($type);
+            return self::printUnion($type, $options);
         } else if ($type instanceof EnumType) {
-            return self::printEnum($type);
+            return self::printEnum($type, $options);
         }
         Utils::invariant($type instanceof InputObjectType);
-        return self::printInputObject($type);
+        return self::printInputObject($type, $options);
     }
 
-    private static function printScalar(ScalarType $type)
+    private static function printScalar(ScalarType $type, array $options)
     {
-        return self::printDescription($type) . "scalar {$type->name}";
+        return self::printDescription($options, $type) . "scalar {$type->name}";
     }
 
-    private static function printObject(ObjectType $type)
+    private static function printObject(ObjectType $type, array $options)
     {
         $interfaces = $type->getInterfaces();
         $implementedInterfaces = !empty($interfaces) ?
             ' implements ' . implode(', ', array_map(function($i) {
                 return $i->name;
             }, $interfaces)) : '';
-        return self::printDescription($type) .
+        return self::printDescription($options, $type) .
             "type {$type->name}$implementedInterfaces {\n" .
-                self::printFields($type) . "\n" .
+                self::printFields($options, $type) . "\n" .
             "}";
     }
 
-    private static function printInterface(InterfaceType $type)
+    private static function printInterface(InterfaceType $type, array $options)
     {
-        return self::printDescription($type) . 
+        return self::printDescription($options, $type) .
             "interface {$type->name} {\n" .
-                self::printFields($type) . "\n" .
+                self::printFields($options, $type) . "\n" .
             "}";
     }
 
-    private static function printUnion(UnionType $type)
+    private static function printUnion(UnionType $type, array $options)
     {
-        return self::printDescription($type) .
+        return self::printDescription($options, $type) .
             "union {$type->name} = " . implode(" | ", $type->getTypes());
     }
 
-    private static function printEnum(EnumType $type)
+    private static function printEnum(EnumType $type, array $options)
     {
-        return self::printDescription($type) .
+        return self::printDescription($options, $type) .
             "enum {$type->name} {\n" .
-                self::printEnumValues($type->getValues()) . "\n" .
+                self::printEnumValues($type->getValues(), $options) . "\n" .
             "}";
     }
 
-    private static function printEnumValues($values)
+    private static function printEnumValues($values, $options)
     {
-        return implode("\n", array_map(function($value, $i) {
+        return implode("\n", array_map(function($value, $i) use ($options) {
-            return self::printDescription($value, '  ', !$i) . '  ' .
+            return self::printDescription($options, $value, '  ', !$i) . '  ' .
                 $value->name . self::printDeprecated($value);
         }, $values, array_keys($values)));
     }
 
-    private static function printInputObject(InputObjectType $type)
+    private static function printInputObject(InputObjectType $type, array $options)
     {
         $fields = array_values($type->getFields());
-        return self::printDescription($type) . 
+        return self::printDescription($options, $type) .
             "input {$type->name} {\n" .
-                implode("\n", array_map(function($f, $i) {
+                implode("\n", array_map(function($f, $i) use ($options) {
-                    return self::printDescription($f, '  ', !$i) . '  ' . self::printInputValue($f);
+                    return self::printDescription($options, $f, '  ', !$i) . '  ' . self::printInputValue($f);
                 }, $fields, array_keys($fields))) . "\n" .
             "}";
     }
 
-    private static function printFields($type)
+    private static function printFields($options, $type)
     {
         $fields = array_values($type->getFields());
-        return implode("\n", array_map(function($f, $i) {
+        return implode("\n", array_map(function($f, $i) use ($options) {
-                return self::printDescription($f, '  ', !$i) . '  ' .
+                return self::printDescription($options, $f, '  ', !$i) . '  ' .
-                    $f->name . self::printArgs($f->args, '  ') . ': ' .
+                    $f->name . self::printArgs($options, $f->args, '  ') . ': ' .
                     (string) $f->getType() . self::printDeprecated($f);
             }, $fields, array_keys($fields)));
     }
 
-    private static function printArgs($args, $indentation = '')
+    private static function printArgs($options, $args, $indentation = '')
     {
         if (count($args) === 0) {
             return '';
@@ -242,8 +256,8 @@ class SchemaPrinter
             return '(' . implode(', ', array_map('self::printInputValue', $args)) . ')';
         }
 
-        return "(\n" . implode("\n", array_map(function($arg, $i) use ($indentation) {
+        return "(\n" . implode("\n", array_map(function($arg, $i) use ($indentation, $options) {
-            return self::printDescription($arg, '  ' . $indentation, !$i) . '  ' . $indentation .
+            return self::printDescription($options, $arg, '  ' . $indentation, !$i) . '  ' . $indentation .
                 self::printInputValue($arg);
         }, $args, array_keys($args))) . "\n" . $indentation . ')';
     }
@@ -257,10 +271,10 @@ class SchemaPrinter
         return $argDecl;
     }
 
-    private static function printDirective($directive)
+    private static function printDirective($directive, $options)
     {
-        return self::printDescription($directive) .
+        return self::printDescription($options, $directive) .
-            'directive @' . $directive->name . self::printArgs($directive->args) .
+            'directive @' . $directive->name . self::printArgs($options, $directive->args) .
             ' on ' . implode(' | ', $directive->locations);
     }
 
@@ -277,34 +291,74 @@ class SchemaPrinter
             Printer::doPrint(AST::astFromValue($reason, Type::string())) . ')';
     }
 
-    private static function printDescription($def, $indentation = '', $firstInBlock = true)
+    private static function printDescription($options, $def, $indentation = '', $firstInBlock = true)
     {
         if (!$def->description) {
             return '';
         }
-        $lines = explode("\n", $def->description);
+        $lines = self::descriptionLines($def->description, 120 - strlen($indentation));
+        if (isset($options['commentDescriptions'])) {
+            return self::printDescriptionWithComments($lines, $indentation, $firstInBlock);
+        }
+
+        $description = ($indentation && !$firstInBlock) ? "\n" : '';
+        if (count($lines) === 1 && mb_strlen($lines[0]) < 70) {
+            $description .= $indentation . '"""' . self::escapeQuote($lines[0]) . "\"\"\"\n";
+            return $description;
+        }
+
+        $description .= $indentation . "\"\"\"\n";
+        foreach ($lines as $line) {
+            $description .= $indentation . self::escapeQuote($line) . "\n";
+        }
+        $description .= $indentation . "\"\"\"\n";
+
+        return $description;
+    }
+
+    private static function escapeQuote($line)
+    {
+        return str_replace('"""', '\\"""', $line);
+    }
+
+    private static function printDescriptionWithComments($lines, $indentation, $firstInBlock)
+    {
         $description = $indentation && !$firstInBlock ? "\n" : '';
         foreach ($lines as $line) {
             if ($line === '') {
                 $description .= $indentation . "#\n";
             } else {
-                // For > 120 character long lines, cut at space boundaries into sublines
+                $description .= $indentation . '# ' . $line . "\n";
-                // of ~80 chars.
-                $sublines = self::breakLine($line, 120 - strlen($indentation));
-                foreach ($sublines as $subline) {
-                    $description .= $indentation . '# ' . $subline . "\n";
-                }
             }
         }
+
         return $description;
     }
 
-    private static function breakLine($line, $len)
+    private static function descriptionLines($description, $maxLen) {
+        $lines = [];
+        $rawLines = explode("\n", $description);
+        foreach($rawLines as $line) {
+            if ($line === '') {
+                $lines[] = $line;
+            } else {
+                // For > 120 character long lines, cut at space boundaries into sublines
+                // of ~80 chars.
+                $sublines = self::breakLine($line, $maxLen);
+                foreach ($sublines as $subline) {
+                    $lines[] = $subline;
+                }
+            }
+        }
+        return $lines;
+    }
+
+    private static function breakLine($line, $maxLen)
     {
-        if (strlen($line) < $len + 5) {
+        if (strlen($line) < $maxLen + 5) {
             return [$line];
         }
-        preg_match_all("/((?: |^).{15," . ($len - 40) . "}(?= |$))/", $line, $parts);
+        preg_match_all("/((?: |^).{15," . ($maxLen - 40) . "}(?= |$))/", $line, $parts);
         $parts = $parts[0];
         return array_map(function($part) {
             return trim($part);

tests/Language/SchemaParserTest.php

@@ -45,6 +45,93 @@ type Hello {
         $this->assertEquals($expected, TestUtils::nodeToArray($doc));
     }
 
+    /**
+     * @it parses type with description string
+     */
+    public function testParsesTypeWithDescriptionString()
+    {
+        $body = '
+"Description"
+type Hello {
+  world: String
+}';
+        $doc = Parser::parse($body);
+        $loc = function($start, $end) {return TestUtils::locArray($start, $end);};
+
+        $expected = [
+            'kind' => NodeKind::DOCUMENT,
+            'definitions' => [
+                [
+                    'kind' => NodeKind::OBJECT_TYPE_DEFINITION,
+                    'name' => $this->nameNode('Hello', $loc(20, 25)),
+                    'interfaces' => [],
+                    'directives' => [],
+                    'fields' => [
+                        $this->fieldNode(
+                            $this->nameNode('world', $loc(30, 35)),
+                            $this->typeNode('String', $loc(37, 43)),
+                            $loc(30, 43)
+                        )
+                    ],
+                    'loc' => $loc(1, 45),
+                    'description' => [
+                        'kind' => NodeKind::STRING,
+                        'value' => 'Description',
+                        'loc' => $loc(1, 14),
+                        'block' => false
+                    ]
+                ]
+            ],
+            'loc' => $loc(0, 45)
+        ];
+        $this->assertEquals($expected, TestUtils::nodeToArray($doc));
+    }
+
+    /**
+     * @it parses type with description multi-linestring
+     */
+    public function testParsesTypeWithDescriptionMultiLineString()
+    {
+        $body = '
+"""
+Description
+"""
+# Even with comments between them
+type Hello {
+  world: String
+}';
+        $doc = Parser::parse($body);
+        $loc = function($start, $end) {return TestUtils::locArray($start, $end);};
+
+        $expected = [
+            'kind' => NodeKind::DOCUMENT,
+            'definitions' => [
+                [
+                    'kind' => NodeKind::OBJECT_TYPE_DEFINITION,
+                    'name' => $this->nameNode('Hello', $loc(60, 65)),
+                    'interfaces' => [],
+                    'directives' => [],
+                    'fields' => [
+                        $this->fieldNode(
+                            $this->nameNode('world', $loc(70, 75)),
+                            $this->typeNode('String', $loc(77, 83)),
+                            $loc(70, 83)
+                        )
+                    ],
+                    'loc' => $loc(1, 85),
+                    'description' => [
+                        'kind' => NodeKind::STRING,
+                        'value' => 'Description',
+                        'loc' => $loc(1, 20),
+                        'block' => true
+                    ]
+                ]
+            ],
+            'loc' => $loc(0, 85)
+        ];
+        $this->assertEquals($expected, TestUtils::nodeToArray($doc));
+    }
+
     /**
      * @it Simple extension
      */
@@ -87,6 +174,20 @@ extend type Hello {
         $this->assertEquals($expected, TestUtils::nodeToArray($doc));
     }
 
+    /**
+     * @it Extension do not include descriptions
+     * @expectedException \GraphQL\Error\SyntaxError
+     * @expectedExceptionMessage Syntax Error GraphQL (2:1)
+     */
+    public function testExtensionDoNotIncludeDescriptions() {
+        $body = '
+"Description"
+extend type Hello {
+    world: String
+}';
+        Parser::parse($body);
+    }
+
     /**
      * @it Simple non-null type
      */
@@ -664,47 +765,6 @@ input Hello {
         Parser::parse($body);
     }
 
-    /**
-     * @it Simple type
-     */
-    public function testSimpleTypeDescriptionInComments()
-    {
-        $body = '
-# This is a simple type description.
-# It is multiline *and includes formatting*.
-type Hello {
-  # And this is a field description
-  world: String
-}';
-        $doc = Parser::parse($body);
-        $loc = function($start, $end) {return TestUtils::locArray($start, $end);};
-
-        $fieldNode = $this->fieldNode(
-            $this->nameNode('world', $loc(134, 139)),
-            $this->typeNode('String', $loc(141, 147)),
-            $loc(134, 147)
-        );
-        $fieldNode['description'] = " And this is a field description\n";
-        $expected = [
-            'kind' => NodeKind::DOCUMENT,
-            'definitions' => [
-                [
-                    'kind' => NodeKind::OBJECT_TYPE_DEFINITION,
-                    'name' => $this->nameNode('Hello', $loc(88, 93)),
-                    'interfaces' => [],
-                    'directives' => [],
-                    'fields' => [
-                        $fieldNode
-                    ],
-                    'loc' => $loc(83, 149),
-                    'description' => " This is a simple type description.\n It is multiline *and includes formatting*.\n"
-                ]
-            ],
-            'loc' => $loc(0, 149)
-        ];
-        $this->assertEquals($expected, TestUtils::nodeToArray($doc));
-    }
-
     private function typeNode($name, $loc)
     {
         return [

tests/Language/SchemaPrinterTest.php

@@ -56,6 +56,10 @@ class SchemaPrinterTest extends \PHPUnit_Framework_TestCase
   mutation: MutationType
 }
 
+"""
+This is a description
+of the `Foo` type.
+"""
 type Foo implements Bar {
   one: Type
   two(argument: InputType!): Type

tests/Language/schema-kitchen-sink.graphql

@@ -8,6 +8,10 @@ schema {
   mutation: MutationType
 }
 
+"""
+This is a description
+of the `Foo` type.
+"""
 type Foo implements Bar {
   one: Type
   two(argument: InputType!): Type

tests/Utils/BuildSchemaTest.php

@@ -17,11 +17,11 @@ class BuildSchemaTest extends \PHPUnit_Framework_TestCase
 {
     // Describe: Schema Builder
 
-    private function cycleOutput($body)
+    private function cycleOutput($body, $options = [])
     {
         $ast = Parser::parse($body);
-        $schema = BuildSchema::buildAST($ast);
+        $schema = BuildSchema::buildAST($ast, null, $options);
-        return "\n" . SchemaPrinter::doPrint($schema);
+        return "\n" . SchemaPrinter::doPrint($schema, $options);
     }
 
     /**
@@ -116,6 +116,42 @@ schema {
   query: Hello
 }
 
+"""This is a directive"""
+directive @foo(
+  """It has an argument"""
+  arg: Int
+) on FIELD
+
+"""With an enum"""
+enum Color {
+  RED
+
+  """Not a creative color"""
+  GREEN
+  BLUE
+}
+
+"""What a great type"""
+type Hello {
+  """And a field to boot"""
+  str: String
+}
+';
+
+        $output = $this->cycleOutput($body);
+        $this->assertEquals($body, $output);
+    }
+
+    /**
+     * @it Supports descriptions
+     */
+    public function testSupportsOptionForCommentDescriptions()
+    {
+        $body = '
+schema {
+  query: Hello
+}
+
 # This is a directive
 directive @foo(
   # It has an argument
@@ -137,7 +173,7 @@ type Hello {
   str: String
 }
 ';
-        $output = $this->cycleOutput($body);
+        $output = $this->cycleOutput($body, [ 'commentDescriptions' => true ]);
         $this->assertEquals($body, $output);
     }
 
@@ -1115,44 +1151,4 @@ type World implements Hello {
         $this->assertArrayHasKey('Hello', $types);
         $this->assertArrayHasKey('World', $types);
     }
-
-    public function testScalarDescription()
-    {
-        $schemaDef = '
-# An ISO-8601 encoded UTC date string.
-scalar Date
-
-type Query {
-    now: Date
-    test: String
-}
-';
-        $q = '
-{
-  __type(name: "Date") {
-    name
-    description
-  }
-  strType: __type(name: "String") {
-    name
-    description
-  }
-}
-';
-        $schema = BuildSchema::build($schemaDef);
-        $result = GraphQL::executeQuery($schema, $q)->toArray();
-        $expected = ['data' => [
-            '__type' => [
-                'name' => 'Date',
-                'description' => 'An ISO-8601 encoded UTC date string.'
-            ],
-            'strType' => [
-                'name' => 'String',
-                'description' => 'The `String` scalar type represents textual data, represented as UTF-8' . "\n" .
-                    'character sequences. The String type is most often used by GraphQL to'. "\n" .
-                    'represent free-form human-readable text.'
-            ]
-        ]];
-        $this->assertEquals($expected, $result);
-    }
 }

tests/Utils/SchemaPrinterTest.php

@@ -650,6 +650,257 @@ schema {
   query: Root
 }
 
+"""
+Directs the executor to include this field or fragment only when the `if` argument is true.
+"""
+directive @include(
+  """Included when true."""
+  if: Boolean!
+) on FIELD | FRAGMENT_SPREAD | INLINE_FRAGMENT
+
+"""
+Directs the executor to skip this field or fragment when the `if` argument is true.
+"""
+directive @skip(
+  """Skipped when true."""
+  if: Boolean!
+) on FIELD | FRAGMENT_SPREAD | INLINE_FRAGMENT
+
+"""Marks an element of a GraphQL schema as no longer supported."""
+directive @deprecated(
+  """
+  Explains why this element was deprecated, usually also including a suggestion
+  for how to access supported similar data. Formatted in
+  [Markdown](https://daringfireball.net/projects/markdown/).
+  """
+  reason: String = "No longer supported"
+) on FIELD_DEFINITION | ENUM_VALUE
+
+"""
+A Directive provides a way to describe alternate runtime execution and type validation behavior in a GraphQL document.
+
+In some cases, you need to provide options to alter GraphQL's execution behavior
+in ways field arguments will not suffice, such as conditionally including or
+skipping a field. Directives provide this by describing additional information
+to the executor.
+"""
+type __Directive {
+  name: String!
+  description: String
+  locations: [__DirectiveLocation!]!
+  args: [__InputValue!]!
+  onOperation: Boolean! @deprecated(reason: "Use `locations`.")
+  onFragment: Boolean! @deprecated(reason: "Use `locations`.")
+  onField: Boolean! @deprecated(reason: "Use `locations`.")
+}
+
+"""
+A Directive can be adjacent to many parts of the GraphQL language, a
+__DirectiveLocation describes one such possible adjacencies.
+"""
+enum __DirectiveLocation {
+  """Location adjacent to a query operation."""
+  QUERY
+
+  """Location adjacent to a mutation operation."""
+  MUTATION
+
+  """Location adjacent to a subscription operation."""
+  SUBSCRIPTION
+
+  """Location adjacent to a field."""
+  FIELD
+
+  """Location adjacent to a fragment definition."""
+  FRAGMENT_DEFINITION
+
+  """Location adjacent to a fragment spread."""
+  FRAGMENT_SPREAD
+
+  """Location adjacent to an inline fragment."""
+  INLINE_FRAGMENT
+
+  """Location adjacent to a schema definition."""
+  SCHEMA
+
+  """Location adjacent to a scalar definition."""
+  SCALAR
+
+  """Location adjacent to an object type definition."""
+  OBJECT
+
+  """Location adjacent to a field definition."""
+  FIELD_DEFINITION
+
+  """Location adjacent to an argument definition."""
+  ARGUMENT_DEFINITION
+
+  """Location adjacent to an interface definition."""
+  INTERFACE
+
+  """Location adjacent to a union definition."""
+  UNION
+
+  """Location adjacent to an enum definition."""
+  ENUM
+
+  """Location adjacent to an enum value definition."""
+  ENUM_VALUE
+
+  """Location adjacent to an input object type definition."""
+  INPUT_OBJECT
+
+  """Location adjacent to an input object field definition."""
+  INPUT_FIELD_DEFINITION
+}
+
+"""
+One possible value for a given Enum. Enum values are unique values, not a
+placeholder for a string or numeric value. However an Enum value is returned in
+a JSON response as a string.
+"""
+type __EnumValue {
+  name: String!
+  description: String
+  isDeprecated: Boolean!
+  deprecationReason: String
+}
+
+"""
+Object and Interface types are described by a list of Fields, each of which has
+a name, potentially a list of arguments, and a return type.
+"""
+type __Field {
+  name: String!
+  description: String
+  args: [__InputValue!]!
+  type: __Type!
+  isDeprecated: Boolean!
+  deprecationReason: String
+}
+
+"""
+Arguments provided to Fields or Directives and the input fields of an
+InputObject are represented as Input Values which describe their type and
+optionally a default value.
+"""
+type __InputValue {
+  name: String!
+  description: String
+  type: __Type!
+
+  """
+  A GraphQL-formatted string representing the default value for this input value.
+  """
+  defaultValue: String
+}
+
+"""
+A GraphQL Schema defines the capabilities of a GraphQL server. It exposes all
+available types and directives on the server, as well as the entry points for
+query, mutation, and subscription operations.
+"""
+type __Schema {
+  """A list of all types supported by this server."""
+  types: [__Type!]!
+
+  """The type that query operations will be rooted at."""
+  queryType: __Type!
+
+  """
+  If this server supports mutation, the type that mutation operations will be rooted at.
+  """
+  mutationType: __Type
+
+  """
+  If this server support subscription, the type that subscription operations will be rooted at.
+  """
+  subscriptionType: __Type
+
+  """A list of all directives supported by this server."""
+  directives: [__Directive!]!
+}
+
+"""
+The fundamental unit of any GraphQL Schema is the type. There are many kinds of
+types in GraphQL as represented by the `__TypeKind` enum.
+
+Depending on the kind of a type, certain fields describe information about that
+type. Scalar types provide no information beyond a name and description, while
+Enum types provide their values. Object and Interface types provide the fields
+they describe. Abstract types, Union and Interface, provide the Object types
+possible at runtime. List and NonNull types compose other types.
+"""
+type __Type {
+  kind: __TypeKind!
+  name: String
+  description: String
+  fields(includeDeprecated: Boolean = false): [__Field!]
+  interfaces: [__Type!]
+  possibleTypes: [__Type!]
+  enumValues(includeDeprecated: Boolean = false): [__EnumValue!]
+  inputFields: [__InputValue!]
+  ofType: __Type
+}
+
+"""An enum describing what kind of type a given `__Type` is."""
+enum __TypeKind {
+  """Indicates this type is a scalar."""
+  SCALAR
+
+  """
+  Indicates this type is an object. `fields` and `interfaces` are valid fields.
+  """
+  OBJECT
+
+  """
+  Indicates this type is an interface. `fields` and `possibleTypes` are valid fields.
+  """
+  INTERFACE
+
+  """Indicates this type is a union. `possibleTypes` is a valid field."""
+  UNION
+
+  """Indicates this type is an enum. `enumValues` is a valid field."""
+  ENUM
+
+  """
+  Indicates this type is an input object. `inputFields` is a valid field.
+  """
+  INPUT_OBJECT
+
+  """Indicates this type is a list. `ofType` is a valid field."""
+  LIST
+
+  """Indicates this type is a non-null. `ofType` is a valid field."""
+  NON_NULL
+}
+
+EOT;
+        $this->assertEquals($introspectionSchema, $output);
+    }
+
+    /**
+     * @it Print Introspection Schema with comment description
+     */
+    public function testPrintIntrospectionSchemaWithCommentDescription()
+    {
+        $root = new ObjectType([
+            'name' => 'Root',
+            'fields' => [
+                'onlyField' => ['type' => Type::string()]
+            ]
+        ]);
+
+        $schema = new Schema(['query' => $root]);
+        $output = SchemaPrinter::printIntrosepctionSchema($schema, [
+            'commentDescriptions' => true
+        ]);
+        $introspectionSchema = <<<'EOT'
+schema {
+  query: Root
+}
+
 # Directs the executor to include this field or fragment only when the `if` argument is true.
 directive @include(
   # Included when true.
@@ -845,6 +1096,6 @@ enum __TypeKind {
 }
 
 EOT;
-        $this->assertEquals($output, $introspectionSchema);
+        $this->assertEquals($introspectionSchema, $output);
     }
 }