RFC: Block String

This RFC adds a new form of `StringValue`, the multi-line string, similar to that found in Python and Scala.

A multi-line string starts and ends with a triple-quote:

```
"""This is a triple-quoted string
and it can contain multiple lines"""
```

Multi-line strings are useful for typing literal bodies of text where new lines should be interpretted literally. In fact, the only escape sequence used is `\"""` and `\` is otherwise allowed unescaped. This is beneficial when writing documentation within strings which may reference the back-slash often:

```
"""
In a multi-line string \n and C:\\ are unescaped.
"""
```

The primary value of multi-line strings are to write long-form input directly in query text, in tools like GraphiQL, and as a prerequisite to another pending RFC to allow docstring style documentation in the Schema Definition Language.

Ref: graphql/graphql-js#926

src/Language/AST/StringValueNode.php

@@ -9,4 +9,9 @@ class StringValueNode extends Node implements ValueNode
      * @var string
      */
     public $value;
+
+    /**
+     * @var boolean|null
+     */
+    public $block;
 }

src/Language/Lexer.php

@@ -3,6 +3,7 @@ namespace GraphQL\Language;
 
 use GraphQL\Error\SyntaxError;
 use GraphQL\Utils\Utils;
+use GraphQL\Utils\BlockString;
 
 /**
  * A Lexer is a stateful stream generator in that every time
@@ -201,7 +202,15 @@ class Lexer
                     ->readNumber($line, $col, $prev);
             // "
             case 34:
-                return $this->moveStringCursor(-1, -1 * $bytes)
+                list(,$nextCode) = $this->readChar();
+                list(,$nextNextCode) = $this->moveStringCursor(1, 1)->readChar();
+
+                if ($nextCode === 34 && $nextNextCode === 34) {
+                    return $this->moveStringCursor(-2, (-1 * $bytes) - 1)
+                        ->readBlockString($line, $col, $prev);
+                }
+
+                return $this->moveStringCursor(-2, (-1 * $bytes) - 1)
                     ->readString($line, $col, $prev);
         }
 
@@ -370,12 +379,28 @@ class Lexer
         $value = '';
 
         while (
-            $code &&
+            $code !== null &&
             // not LineTerminator
-            $code !== 10 && $code !== 13 &&
+            $code !== 10 && $code !== 13
-            // not Quote (")
-            $code !== 34
         ) {
+            // Closing Quote (")
+            if ($code === 34) {
+                $value .= $chunk;
+
+                // Skip quote
+                $this->moveStringCursor(1, 1);
+
+                return new Token(
+                    Token::STRING,
+                    $start,
+                    $this->position,
+                    $line,
+                    $col,
+                    $prev,
+                    $value
+                );
+            }
+
             $this->assertValidStringCharacterCode($code, $this->position);
             $this->moveStringCursor(1, $bytes);
 
@@ -421,27 +446,83 @@ class Lexer
             list ($char, $code, $bytes) = $this->readChar();
         }
 
-        if ($code !== 34) {
+        throw new SyntaxError(
-            throw new SyntaxError(
+            $this->source,
-                $this->source,
+            $this->position,
-                $this->position,
+            'Unterminated string.'
-                'Unterminated string.'
+        );
-            );
+    }
+
+    /**
+     * Reads a block string token from the source file.
+     *
+     * """("?"?(\\"""|\\(?!=""")|[^"\\]))*"""
+     */
+    private function readBlockString($line, $col, Token $prev)
+    {
+        $start = $this->position;
+
+        // Skip leading quotes and read first string char:
+        list ($char, $code, $bytes) = $this->moveStringCursor(3, 3)->readChar();
+
+        $chunk = '';
+        $value = '';
+
+        while ($code !== null) {
+            // Closing Triple-Quote (""")
+            if ($code === 34) {
+                // Move 2 quotes
+                list(,$nextCode) = $this->moveStringCursor(1, 1)->readChar();
+                list(,$nextNextCode) = $this->moveStringCursor(1, 1)->readChar();
+
+                if ($nextCode === 34 && $nextNextCode === 34) {
+                    $value .= $chunk;
+
+                    $this->moveStringCursor(1, 1);
+
+                    return new Token(
+                        Token::BLOCK_STRING,
+                        $start,
+                        $this->position,
+                        $line,
+                        $col,
+                        $prev,
+                        BlockString::value($value)
+                    );
+                } else {
+                    // move cursor back to before the first quote
+                    $this->moveStringCursor(-2, -2);
+                }
+            }
+
+            $this->assertValidBlockStringCharacterCode($code, $this->position);
+            $this->moveStringCursor(1, $bytes);
+
+            list(,$nextCode) = $this->readChar();
+            list(,$nextNextCode) = $this->moveStringCursor(1, 1)->readChar();
+            list(,$nextNextNextCode) = $this->moveStringCursor(1, 1)->readChar();
+
+            // Escape Triple-Quote (\""")
+            if ($code === 92 &&
+                $nextCode === 34 &&
+                $nextNextCode === 34 &&
+                $nextNextNextCode === 34
+            ) {
+                $this->moveStringCursor(1, 1);
+                $value .= $chunk . '"""';
+                $chunk = '';
+            } else {
+                $this->moveStringCursor(-2, -2);
+                $chunk .= $char;
+            }
+
+            list ($char, $code, $bytes) = $this->readChar();
         }
 
-        $value .= $chunk;
+        throw new SyntaxError(
-
+            $this->source,
-        // Skip trailing quote:
-        $this->moveStringCursor(1, 1);
-
-        return new Token(
-            Token::STRING,
-            $start,
             $this->position,
-            $line,
+            'Unterminated string.'
-            $col,
-            $prev,
-            $value
         );
     }
 
@@ -457,6 +538,18 @@ class Lexer
         }
     }
 
+    private function assertValidBlockStringCharacterCode($code, $position)
+    {
+        // SourceCharacter
+        if ($code < 0x0020 && $code !== 0x0009 && $code !== 0x000A && $code !== 0x000D) {
+            throw new SyntaxError(
+                $this->source,
+                $position,
+                'Invalid character within String: ' . Utils::printCharCode($code)
+            );
+        }
+    }
+
     /**
      * Reads from body starting at startPosition until it finds a non-whitespace
      * or commented character, then places cursor to the position of that character.
@@ -537,7 +630,7 @@ class Lexer
             $byteStreamPosition = $this->byteStreamPosition;
         }
 
-        $code = 0;
+        $code = null;
         $utf8char = '';
         $bytes = 0;
         $positionOffset = 0;

src/Language/Parser.php

@@ -655,9 +655,11 @@ class Parser
                     'loc' => $this->loc($token)
                 ]);
             case Token::STRING:
+            case Token::BLOCK_STRING:
                 $this->lexer->advance();
                 return new StringValueNode([
                     'value' => $token->value,
+                    'block' => $token->kind === Token::BLOCK_STRING,
                     'loc' => $this->loc($token)
                 ]);
             case Token::NAME:

src/Language/Printer.php

@@ -139,6 +139,9 @@ class Printer
                     return $node->value;
                 },
                 NodeKind::STRING => function(StringValueNode $node) {
+                    if ($node->block) {
+                       return "\"\"\"\n" . str_replace('"""', '\\"""', $node->value) . "\n\"\"\"";
+                    }
                     return json_encode($node->value);
                 },
                 NodeKind::BOOLEAN => function(BooleanValueNode $node) {

src/Language/Token.php

@@ -27,6 +27,7 @@ class Token
     const INT = 'Int';
     const FLOAT = 'Float';
     const STRING = 'String';
+    const BLOCK_STRING = 'BlockString';
     const COMMENT = 'Comment';
 
     /**
@@ -57,6 +58,7 @@ class Token
         $description[self::INT] = 'Int';
         $description[self::FLOAT] = 'Float';
         $description[self::STRING] = 'String';
+        $description[self::BLOCK_STRING] = 'BlockString';
         $description[self::COMMENT] = 'Comment';
 
         return $description[$kind];

src/Utils/BlockString.php

@@ -0,0 +1,61 @@
+<?php
+namespace GraphQL\Utils;
+
+class BlockString {
+    /**
+     * Produces the value of a block string from its parsed raw value, similar to
+     * Coffeescript's block string, Python's docstring trim or Ruby's strip_heredoc.
+     *
+     * This implements the GraphQL spec's BlockStringValue() static algorithm.
+     */
+    public static function value($rawString) {
+        // Expand a block string's raw value into independent lines.
+        $lines = preg_split("/\\r\\n|[\\n\\r]/", $rawString);
+    
+        // Remove common indentation from all lines but first.
+        $commonIndent = null;
+        $linesLength = count($lines);
+
+        for ($i = 1; $i < $linesLength; $i++) {
+            $line = $lines[$i];
+            $indent = self::leadingWhitespace($line);
+    
+            if (
+                $indent < mb_strlen($line) &&
+                ($commonIndent === null || $indent < $commonIndent)
+            ) {
+                $commonIndent = $indent;
+                if ($commonIndent === 0) {
+                    break;
+                }
+            }
+        }
+    
+        if ($commonIndent) {
+            for ($i = 1; $i < $linesLength; $i++) {
+                $line = $lines[$i];
+                $lines[$i] = mb_substr($line, $commonIndent);
+            }
+        }
+    
+        // Remove leading and trailing blank lines.
+        while (count($lines) > 0 && trim($lines[0], " \t") === '') {
+            array_shift($lines);
+        }
+        while (count($lines) > 0 && trim($lines[count($lines) - 1], " \t") === '') {
+            array_pop($lines);
+        }
+
+        // Return a string of the lines joined with U+000A.
+        return implode("\n", $lines);
+    }
+
+    private static function leadingWhitespace($str) {
+        $i = 0;
+        while ($i < mb_strlen($str) && ($str[$i] === ' ' || $str[$i] === '\t')) {
+          $i++;
+        }
+
+        return $i;
+    }
+}

tests/Language/LexerTest.php

@@ -223,7 +223,101 @@ class LexerTest extends \PHPUnit_Framework_TestCase
         ], (array) $this->lexOne('"\u1234\u5678\u90AB\uCDEF"'));
     }
 
-    public function reportsUsefulErrors() {
+    /**
+     * @it lexes block strings
+     */
+    public function testLexesBlockString()
+    {
+        $this->assertArraySubset([
+            'kind' => Token::BLOCK_STRING,
+            'start' => 0,
+            'end' => 12,
+            'value' => 'simple'
+        ], (array) $this->lexOne('"""simple"""'));
+
+        $this->assertArraySubset([
+            'kind' => Token::BLOCK_STRING,
+            'start' => 0,
+            'end' => 19,
+            'value' => ' white space '
+        ], (array) $this->lexOne('""" white space """'));
+
+        $this->assertArraySubset([
+            'kind' => Token::BLOCK_STRING,
+            'start' => 0,
+            'end' => 22,
+            'value' => 'contains " quote'
+        ], (array) $this->lexOne('"""contains " quote"""'));
+
+        $this->assertArraySubset([
+            'kind' => Token::BLOCK_STRING,
+            'start' => 0,
+            'end' => 31,
+            'value' => 'contains """ triplequote'
+        ], (array) $this->lexOne('"""contains \\""" triplequote"""'));
+
+        $this->assertArraySubset([
+            'kind' => Token::BLOCK_STRING,
+            'start' => 0,
+            'end' => 16,
+            'value' => "multi\nline"
+        ], (array) $this->lexOne("\"\"\"multi\nline\"\"\""));
+
+        $this->assertArraySubset([
+            'kind' => Token::BLOCK_STRING,
+            'start' => 0,
+            'end' => 28,
+            'value' => "multi\nline\nnormalized"
+        ], (array) $this->lexOne("\"\"\"multi\rline\r\nnormalized\"\"\""));
+
+        $this->assertArraySubset([
+            'kind' => Token::BLOCK_STRING,
+            'start' => 0,
+            'end' => 32,
+            'value' => 'unescaped \\n\\r\\b\\t\\f\\u1234'
+        ], (array) $this->lexOne('"""unescaped \\n\\r\\b\\t\\f\\u1234"""'));
+
+        $this->assertArraySubset([
+            'kind' => Token::BLOCK_STRING,
+            'start' => 0,
+            'end' => 19,
+            'value' => 'slashes \\\\ \\/'
+        ], (array) $this->lexOne('"""slashes \\\\ \\/"""'));
+
+        $this->assertArraySubset([
+            'kind' => Token::BLOCK_STRING,
+            'start' => 0,
+            'end' => 68,
+            'value' => "spans\n  multiple\n    lines"
+        ], (array) $this->lexOne("\"\"\"
+
+        spans
+          multiple
+            lines
+
+        \"\"\""));
+    }
+
+    public function reportsUsefulBlockStringErrors() {
+        return [
+            ['"""', "Syntax Error GraphQL (1:4) Unterminated string.\n\n1: \"\"\"\n      ^\n"],
+            ['"""no end quote', "Syntax Error GraphQL (1:16) Unterminated string.\n\n1: \"\"\"no end quote\n                  ^\n"],
+            ['"""contains unescaped ' . json_decode('"\u0007"') . ' control char"""', "Syntax Error GraphQL (1:23) Invalid character within String: \"\\u0007\""],
+            ['"""null-byte is not ' . json_decode('"\u0000"') . ' end of file"""', "Syntax Error GraphQL (1:21) Invalid character within String: \"\\u0000\""],
+        ];
+    }
+
+    /**
+     * @dataProvider reportsUsefulBlockStringErrors
+     * @it lex reports useful block string errors
+     */
+    public function testReportsUsefulBlockStringErrors($str, $expectedMessage)
+    {
+        $this->setExpectedException(SyntaxError::class, $expectedMessage);
+        $this->lexOne($str);
+    }
+
+    public function reportsUsefulStringErrors() {
         return [
             ['"', "Syntax Error GraphQL (1:2) Unterminated string.\n\n1: \"\n    ^\n"],
             ['"no end quote', "Syntax Error GraphQL (1:14) Unterminated string.\n\n1: \"no end quote\n                ^\n"],
@@ -243,10 +337,10 @@ class LexerTest extends \PHPUnit_Framework_TestCase
     }
 
     /**
-     * @dataProvider reportsUsefulErrors
+     * @dataProvider reportsUsefulStringErrors
      * @it lex reports useful string errors
      */
-    public function testReportsUsefulErrors($str, $expectedMessage)
+    public function testLexReportsUsefulStringErrors($str, $expectedMessage)
     {
         $this->setExpectedException(SyntaxError::class, $expectedMessage);
         $this->lexOne($str);

tests/Language/ParserTest.php

@@ -497,7 +497,8 @@ fragment $fragmentName on Type {
                 [
                     'kind' => NodeKind::STRING,
                     'loc' => ['start' => 5, 'end' => 10],
-                    'value' => 'abc'
+                    'value' => 'abc',
+                    'block' => false
                 ]
             ]
         ], $this->nodeToArray(Parser::parseValue('[123 "abc"]')));

tests/Language/PrinterTest.php

@@ -146,7 +146,9 @@ subscription StoryLikeSubscription($input: StoryLikeSubscribeInput) {
 }
 
 fragment frag on Friend {
-  foo(size: $size, bar: $b, obj: {key: "value"})
+  foo(size: $size, bar: $b, obj: {key: "value", block: """
+    block string uses \"""
+  """})
 }
 
 {

tests/Language/VisitorTest.php

@@ -615,6 +615,12 @@ class VisitorTest extends \PHPUnit_Framework_TestCase
             [ 'enter', 'StringValue', 'value', 'ObjectField' ],
             [ 'leave', 'StringValue', 'value', 'ObjectField' ],
             [ 'leave', 'ObjectField', 0, null ],
+            [ 'enter', 'ObjectField', 1, null ],
+            [ 'enter', 'Name', 'name', 'ObjectField' ],
+            [ 'leave', 'Name', 'name', 'ObjectField' ],
+            [ 'enter', 'StringValue', 'value', 'ObjectField' ],
+            [ 'leave', 'StringValue', 'value', 'ObjectField' ],
+            [ 'leave', 'ObjectField', 1, null ],
             [ 'leave', 'ObjectValue', 'value', 'Argument' ],
             [ 'leave', 'Argument', 2, null ],
             [ 'leave', 'Field', 0, null ],

tests/Language/kitchen-sink-noloc.ast

@@ -556,7 +556,20 @@
                                             },
                                             "value": {
                                                 "kind": "StringValue",
-                                                "value": "value"
+                                                "value": "value",
+                                                "block": false
+                                            }
+                                        },
+                                        {
+                                            "kind": "ObjectField",
+                                            "name": {
+                                                "kind": "Name",
+                                                "value": "block"
+                                            },
+                                            "value": {
+                                                "kind": "StringValue",
+                                                "value": "block string uses \"\"\"",
+                                                "block": true
                                             }
                                         }
                                     ]

tests/Language/kitchen-sink.ast

@@ -2,7 +2,7 @@
     "kind": "Document",
     "loc": {
         "start": 0,
-        "end": 1087
+        "end": 1136
     },
     "definitions": [
         {
@@ -959,7 +959,7 @@
             "kind": "FragmentDefinition",
             "loc": {
                 "start": 942,
-                "end": 1018
+                "end": 1067
             },
             "name": {
                 "kind": "Name",
@@ -989,14 +989,14 @@
                 "kind": "SelectionSet",
                 "loc": {
                     "start": 966,
-                    "end": 1018
+                    "end": 1067
                 },
                 "selections": [
                     {
                         "kind": "Field",
                         "loc": {
                             "start": 970,
-                            "end": 1016
+                            "end": 1065
                         },
                         "name": {
                             "kind": "Name",
@@ -1071,13 +1071,13 @@
                                 "kind": "Argument",
                                 "loc": {
                                     "start": 996,
-                                    "end": 1015
+                                    "end": 1064
                                 },
                                 "value": {
                                     "kind": "ObjectValue",
                                     "loc": {
                                         "start": 1001,
-                                        "end": 1015
+                                        "end": 1064
                                     },
                                     "fields": [
                                         {
@@ -1100,7 +1100,32 @@
                                                     "start": 1007,
                                                     "end": 1014
                                                 },
-                                                "value": "value"
+                                                "value": "value",
+                                                "block": false
+                                            }
+                                        },
+                                        {
+                                            "kind": "ObjectField",
+                                            "loc": {
+                                                "start": 1016,
+                                                "end": 1063
+                                            },
+                                            "name": {
+                                                "kind": "Name",
+                                                "loc": {
+                                                    "start": 1016,
+                                                    "end": 1021
+                                                },
+                                                "value": "block"
+                                            },
+                                            "value": {
+                                                "kind": "StringValue",
+                                                "loc": {
+                                                    "start": 1023,
+                                                    "end": 1063
+                                                },
+                                                "value": "block string uses \"\"\"",
+                                                "block": true
                                             }
                                         }
                                     ]
@@ -1123,8 +1148,8 @@
         {
             "kind": "OperationDefinition",
             "loc": {
-                "start": 1020,
+                "start": 1069,
-                "end": 1086
+                "end": 1135
             },
             "operation": "query",
             "variableDefinitions": [],
@@ -1132,21 +1157,21 @@
             "selectionSet": {
                 "kind": "SelectionSet",
                 "loc": {
-                    "start": 1020,
+                    "start": 1069,
-                    "end": 1086
+                    "end": 1135
                 },
                 "selections": [
                     {
                         "kind": "Field",
                         "loc": {
-                            "start": 1024,
+                            "start": 1073,
-                            "end": 1075
+                            "end": 1124
                         },
                         "name": {
                             "kind": "Name",
                             "loc": {
-                                "start": 1024,
+                                "start": 1073,
-                                "end": 1031
+                                "end": 1080
                             },
                             "value": "unnamed"
                         },
@@ -1154,22 +1179,22 @@
                             {
                                 "kind": "Argument",
                                 "loc": {
-                                    "start": 1032,
+                                    "start": 1081,
-                                    "end": 1044
+                                    "end": 1093
                                 },
                                 "value": {
                                     "kind": "BooleanValue",
                                     "loc": {
-                                        "start": 1040,
+                                        "start": 1089,
-                                        "end": 1044
+                                        "end": 1093
                                     },
                                     "value": true
                                 },
                                 "name": {
                                     "kind": "Name",
                                     "loc": {
-                                        "start": 1032,
+                                        "start": 1081,
-                                        "end": 1038
+                                        "end": 1087
                                     },
                                     "value": "truthy"
                                 }
@@ -1177,22 +1202,22 @@
                             {
                                 "kind": "Argument",
                                 "loc": {
-                                    "start": 1046,
+                                    "start": 1095,
-                                    "end": 1059
+                                    "end": 1108
                                 },
                                 "value": {
                                     "kind": "BooleanValue",
                                     "loc": {
-                                        "start": 1054,
+                                        "start": 1103,
-                                        "end": 1059
+                                        "end": 1108
                                     },
                                     "value": false
                                 },
                                 "name": {
                                     "kind": "Name",
                                     "loc": {
-                                        "start": 1046,
+                                        "start": 1095,
-                                        "end": 1052
+                                        "end": 1101
                                     },
                                     "value": "falsey"
                                 }
@@ -1200,21 +1225,21 @@
                             {
                                 "kind": "Argument",
                                 "loc": {
-                                    "start": 1061,
+                                    "start": 1110,
-                                    "end": 1074
+                                    "end": 1123
                                 },
                                 "value": {
                                     "kind": "NullValue",
                                     "loc": {
-                                        "start": 1070,
+                                        "start": 1119,
-                                        "end": 1074
+                                        "end": 1123
                                     }
                                 },
                                 "name": {
                                     "kind": "Name",
                                     "loc": {
-                                        "start": 1061,
+                                        "start": 1110,
-                                        "end": 1068
+                                        "end": 1117
                                     },
                                     "value": "nullish"
                                 }
@@ -1225,14 +1250,14 @@
                     {
                         "kind": "Field",
                         "loc": {
-                            "start": 1079,
+                            "start": 1128,
-                            "end": 1084
+                            "end": 1133
                         },
                         "name": {
                             "kind": "Name",
                             "loc": {
-                                "start": 1079,
+                                "start": 1128,
-                                "end": 1084
+                                "end": 1133
                             },
                             "value": "query"
                         },

tests/Language/kitchen-sink.graphql

@@ -48,7 +48,11 @@ subscription StoryLikeSubscription($input: StoryLikeSubscribeInput) {
 }
 
 fragment frag on Friend {
-  foo(size: $size, bar: $b, obj: {key: "value"})
+  foo(size: $size, bar: $b, obj: {key: "value", block: """
+
+      block string uses \"""
+
+  """})
 }
 
 {

tests/Language/schema-kitchen-sink.graphql

@@ -1,9 +1,7 @@
-# Copyright (c) 2015, Facebook, Inc.
+# Copyright (c) 2015-present, Facebook, Inc.
-# All rights reserved.
 #
-# This source code is licensed under the BSD-style license found in the
+# This source code is licensed under the MIT license found in the
-# LICENSE file in the root directory of this source tree. An additional grant
+# LICENSE file in the root directory of this source tree.
-# of patent rights can be found in the PATENTS file in the same directory.
 
 schema {
   query: QueryType