diff vendor/symfony/yaml/Parser.php @ 14:1fec387a4317

Update Drupal core to 8.5.2 via Composer

--- a/vendor/symfony/yaml/Parser.php	Mon Apr 23 09:33:26 2018 +0100
+++ b/vendor/symfony/yaml/Parser.php	Mon Apr 23 09:46:53 2018 +0100
@@ -12,17 +12,21 @@
 namespace Symfony\Component\Yaml;
 
 use Symfony\Component\Yaml\Exception\ParseException;
+use Symfony\Component\Yaml\Tag\TaggedValue;
 
 /**
  * Parser parses YAML strings to convert them to PHP arrays.
  *
  * @author Fabien Potencier <[e-mail]>
+ *
+ * @final since version 3.4
  */
 class Parser
 {
-    const TAG_PATTERN = '((?P<tag>![\w!.\/:-]+) +)?';
+    const TAG_PATTERN = '(?P<tag>![\w!.\/:-]+)';
     const BLOCK_SCALAR_HEADER_PATTERN = '(?P<separator>\||>)(?P<modifiers>\+|\-|\d+|\+\d+|\-\d+|\d+\+|\d+\-)?(?P<comments> +#.*)?';
 
+    private $filename;
     private $offset = 0;
     private $totalNumberOfLines;
     private $lines = array();
@@ -32,18 +36,48 @@
     private $skippedLineNumbers = array();
     private $locallySkippedLineNumbers = array();
 
+    public function __construct()
+    {
+        if (func_num_args() > 0) {
+            @trigger_error(sprintf('The constructor arguments $offset, $totalNumberOfLines, $skippedLineNumbers of %s are deprecated and will be removed in 4.0', self::class), E_USER_DEPRECATED);
+
+            $this->offset = func_get_arg(0);
+            if (func_num_args() > 1) {
+                $this->totalNumberOfLines = func_get_arg(1);
+            }
+            if (func_num_args() > 2) {
+                $this->skippedLineNumbers = func_get_arg(2);
+            }
+        }
+    }
+
     /**
-     * Constructor.
+     * Parses a YAML file into a PHP value.
      *
-     * @param int      $offset             The offset of YAML document (used for line numbers in error messages)
-     * @param int|null $totalNumberOfLines The overall number of lines being parsed
-     * @param int[]    $skippedLineNumbers Number of comment lines that have been skipped by the parser
+     * @param string $filename The path to the YAML file to be parsed
+     * @param int    $flags    A bit field of PARSE_* constants to customize the YAML parser behavior
+     *
+     * @return mixed The YAML converted to a PHP value
+     *
+     * @throws ParseException If the file could not be read or the YAML is not valid
      */
-    public function __construct($offset = 0, $totalNumberOfLines = null, array $skippedLineNumbers = array())
+    public function parseFile($filename, $flags = 0)
     {
-        $this->offset = $offset;
-        $this->totalNumberOfLines = $totalNumberOfLines;
-        $this->skippedLineNumbers = $skippedLineNumbers;
+        if (!is_file($filename)) {
+            throw new ParseException(sprintf('File "%s" does not exist.', $filename));
+        }
+
+        if (!is_readable($filename)) {
+            throw new ParseException(sprintf('File "%s" cannot be read.', $filename));
+        }
+
+        $this->filename = $filename;
+
+        try {
+            return $this->parse(file_get_contents($filename), $flags);
+        } finally {
+            $this->filename = null;
+        }
     }
 
     /**
@@ -59,7 +93,7 @@
     public function parse($value, $flags = 0)
     {
         if (is_bool($flags)) {
-            @trigger_error('Passing a boolean flag to toggle exception handling is deprecated since version 3.1 and will be removed in 4.0. Use the Yaml::PARSE_EXCEPTION_ON_INVALID_TYPE flag instead.', E_USER_DEPRECATED);
+            @trigger_error('Passing a boolean flag to toggle exception handling is deprecated since Symfony 3.1 and will be removed in 4.0. Use the Yaml::PARSE_EXCEPTION_ON_INVALID_TYPE flag instead.', E_USER_DEPRECATED);
 
             if ($flags) {
                 $flags = Yaml::PARSE_EXCEPTION_ON_INVALID_TYPE;
@@ -69,7 +103,7 @@
         }
 
         if (func_num_args() >= 3) {
-            @trigger_error('Passing a boolean flag to toggle object support is deprecated since version 3.1 and will be removed in 4.0. Use the Yaml::PARSE_OBJECT flag instead.', E_USER_DEPRECATED);
+            @trigger_error('Passing a boolean flag to toggle object support is deprecated since Symfony 3.1 and will be removed in 4.0. Use the Yaml::PARSE_OBJECT flag instead.', E_USER_DEPRECATED);
 
             if (func_get_arg(2)) {
                 $flags |= Yaml::PARSE_OBJECT;
@@ -77,15 +111,19 @@
         }
 
         if (func_num_args() >= 4) {
-            @trigger_error('Passing a boolean flag to toggle object for map support is deprecated since version 3.1 and will be removed in 4.0. Use the Yaml::PARSE_OBJECT_FOR_MAP flag instead.', E_USER_DEPRECATED);
+            @trigger_error('Passing a boolean flag to toggle object for map support is deprecated since Symfony 3.1 and will be removed in 4.0. Use the Yaml::PARSE_OBJECT_FOR_MAP flag instead.', E_USER_DEPRECATED);
 
             if (func_get_arg(3)) {
                 $flags |= Yaml::PARSE_OBJECT_FOR_MAP;
             }
         }
 
+        if (Yaml::PARSE_KEYS_AS_STRINGS & $flags) {
+            @trigger_error('Using the Yaml::PARSE_KEYS_AS_STRINGS flag is deprecated since Symfony 3.4 as it will be removed in 4.0. Quote your keys when they are evaluable instead.', E_USER_DEPRECATED);
+        }
+
         if (false === preg_match('//u', $value)) {
-            throw new ParseException('The YAML value does not appear to be valid UTF-8.');
+            throw new ParseException('The YAML value does not appear to be valid UTF-8.', -1, null, $this->filename);
         }
 
         $this->refs = array();
@@ -134,24 +172,41 @@
             $this->totalNumberOfLines = count($this->lines);
         }
 
+        if (!$this->moveToNextLine()) {
+            return null;
+        }
+
         $data = array();
         $context = null;
         $allowOverwrite = false;
 
-        while ($this->moveToNextLine()) {
+        while ($this->isCurrentLineEmpty()) {
+            if (!$this->moveToNextLine()) {
+                return null;
+            }
+        }
+
+        // Resolves the tag and returns if end of the document
+        if (null !== ($tag = $this->getLineTag($this->currentLine, $flags, false)) && !$this->moveToNextLine()) {
+            return new TaggedValue($tag, '');
+        }
+
+        do {
             if ($this->isCurrentLineEmpty()) {
                 continue;
             }
 
             // tab?
             if ("\t" === $this->currentLine[0]) {
-                throw new ParseException('A YAML file cannot contain tabs as indentation.', $this->getRealCurrentLineNb() + 1, $this->currentLine);
+                throw new ParseException('A YAML file cannot contain tabs as indentation.', $this->getRealCurrentLineNb() + 1, $this->currentLine, $this->filename);
             }
 
+            Inline::initialize($flags, $this->getRealCurrentLineNb(), $this->filename);
+
             $isRef = $mergeNode = false;
             if (self::preg_match('#^\-((?P<leadspaces>\s+)(?P<value>.+))?$#u', rtrim($this->currentLine), $values)) {
                 if ($context && 'mapping' == $context) {
-                    throw new ParseException('You cannot define a sequence item when in a mapping', $this->getRealCurrentLineNb() + 1, $this->currentLine);
+                    throw new ParseException('You cannot define a sequence item when in a mapping', $this->getRealCurrentLineNb() + 1, $this->currentLine, $this->filename);
                 }
                 $context = 'sequence';
 
@@ -160,12 +215,21 @@
                     $values['value'] = $matches['value'];
                 }
 
+                if (isset($values['value'][1]) && '?' === $values['value'][0] && ' ' === $values['value'][1]) {
+                    @trigger_error($this->getDeprecationMessage('Starting an unquoted string with a question mark followed by a space is deprecated since Symfony 3.3 and will throw \Symfony\Component\Yaml\Exception\ParseException in 4.0.'), E_USER_DEPRECATED);
+                }
+
                 // array
                 if (!isset($values['value']) || '' == trim($values['value'], ' ') || 0 === strpos(ltrim($values['value'], ' '), '#')) {
                     $data[] = $this->parseBlock($this->getRealCurrentLineNb() + 1, $this->getNextEmbedBlock(null, true), $flags);
+                } elseif (null !== $subTag = $this->getLineTag(ltrim($values['value'], ' '), $flags)) {
+                    $data[] = new TaggedValue(
+                        $subTag,
+                        $this->parseBlock($this->getRealCurrentLineNb() + 1, $this->getNextEmbedBlock(null, true), $flags)
+                    );
                 } else {
                     if (isset($values['leadspaces'])
-                        && self::preg_match('#^(?P<key>'.Inline::REGEX_QUOTED_STRING.'|[^ \'"\{\[].*?) *\:(\s+(?P<value>.+))?$#u', rtrim($values['value']), $matches)
+                        && self::preg_match('#^(?P<key>'.Inline::REGEX_QUOTED_STRING.'|[^ \'"\{\[].*?) *\:(\s+(?P<value>.+?))?\s*$#u', $this->trimTag($values['value']), $matches)
                     ) {
                         // this is a compact notation element, add to next block and parse
                         $block = $values['value'];
@@ -182,19 +246,24 @@
                     $this->refs[$isRef] = end($data);
                 }
             } elseif (
-                self::preg_match('#^(?P<key>'.Inline::REGEX_QUOTED_STRING.'|[^ \'"\[\{].*?) *\:(\s+(?P<value>.+))?$#u', rtrim($this->currentLine), $values)
+                self::preg_match('#^(?P<key>(?:![^\s]++\s++)?(?:'.Inline::REGEX_QUOTED_STRING.'|(?:!?!php/const:)?[^ \'"\[\{!].*?)) *\:(\s++(?P<value>.+))?$#u', rtrim($this->currentLine), $values)
                 && (false === strpos($values['key'], ' #') || in_array($values['key'][0], array('"', "'")))
             ) {
                 if ($context && 'sequence' == $context) {
-                    throw new ParseException('You cannot define a mapping item when in a sequence', $this->currentLineNb + 1, $this->currentLine);
+                    throw new ParseException('You cannot define a mapping item when in a sequence', $this->currentLineNb + 1, $this->currentLine, $this->filename);
                 }
                 $context = 'mapping';
 
-                // force correct settings
-                Inline::parse(null, $flags, $this->refs);
                 try {
-                    Inline::$parsedLineNumber = $this->getRealCurrentLineNb();
-                    $key = Inline::parseScalar($values['key']);
+                    $i = 0;
+                    $evaluateKey = !(Yaml::PARSE_KEYS_AS_STRINGS & $flags);
+
+                    // constants in key will be evaluated anyway
+                    if (isset($values['key'][0]) && '!' === $values['key'][0] && Yaml::PARSE_CONSTANT & $flags) {
+                        $evaluateKey = true;
+                    }
+
+                    $key = Inline::parseScalar($values['key'], 0, null, $i, $evaluateKey);
                 } catch (ParseException $e) {
                     $e->setParsedLine($this->getRealCurrentLineNb() + 1);
                     $e->setSnippet($this->currentLine);
@@ -202,37 +271,50 @@
                     throw $e;
                 }
 
+                if (!is_string($key) && !is_int($key)) {
+                    $keyType = is_numeric($key) ? 'numeric key' : 'non-string key';
+                    @trigger_error($this->getDeprecationMessage(sprintf('Implicit casting of %s to string is deprecated since Symfony 3.3 and will throw \Symfony\Component\Yaml\Exception\ParseException in 4.0. Quote your evaluable mapping keys instead.', $keyType)), E_USER_DEPRECATED);
+                }
+
                 // Convert float keys to strings, to avoid being converted to integers by PHP
                 if (is_float($key)) {
                     $key = (string) $key;
                 }
 
-                if ('<<' === $key) {
+                if ('<<' === $key && (!isset($values['value']) || !self::preg_match('#^&(?P<ref>[^ ]+)#u', $values['value'], $refMatches))) {
                     $mergeNode = true;
                     $allowOverwrite = true;
-                    if (isset($values['value']) && 0 === strpos($values['value'], '*')) {
-                        $refName = substr($values['value'], 1);
+                    if (isset($values['value'][0]) && '*' === $values['value'][0]) {
+                        $refName = substr(rtrim($values['value']), 1);
                         if (!array_key_exists($refName, $this->refs)) {
-                            throw new ParseException(sprintf('Reference "%s" does not exist.', $refName), $this->getRealCurrentLineNb() + 1, $this->currentLine);
+                            throw new ParseException(sprintf('Reference "%s" does not exist.', $refName), $this->getRealCurrentLineNb() + 1, $this->currentLine, $this->filename);
                         }
 
                         $refValue = $this->refs[$refName];
 
+                        if (Yaml::PARSE_OBJECT_FOR_MAP & $flags && $refValue instanceof \stdClass) {
+                            $refValue = (array) $refValue;
+                        }
+
                         if (!is_array($refValue)) {
-                            throw new ParseException('YAML merge keys used with a scalar value instead of an array.', $this->getRealCurrentLineNb() + 1, $this->currentLine);
+                            throw new ParseException('YAML merge keys used with a scalar value instead of an array.', $this->getRealCurrentLineNb() + 1, $this->currentLine, $this->filename);
                         }
 
                         $data += $refValue; // array union
                     } else {
-                        if (isset($values['value']) && $values['value'] !== '') {
+                        if (isset($values['value']) && '' !== $values['value']) {
                             $value = $values['value'];
                         } else {
                             $value = $this->getNextEmbedBlock();
                         }
                         $parsed = $this->parseBlock($this->getRealCurrentLineNb() + 1, $value, $flags);
 
+                        if (Yaml::PARSE_OBJECT_FOR_MAP & $flags && $parsed instanceof \stdClass) {
+                            $parsed = (array) $parsed;
+                        }
+
                         if (!is_array($parsed)) {
-                            throw new ParseException('YAML merge keys used with a scalar value instead of an array.', $this->getRealCurrentLineNb() + 1, $this->currentLine);
+                            throw new ParseException('YAML merge keys used with a scalar value instead of an array.', $this->getRealCurrentLineNb() + 1, $this->currentLine, $this->filename);
                         }
 
                         if (isset($parsed[0])) {
@@ -240,8 +322,12 @@
                             // and each of these nodes is merged in turn according to its order in the sequence. Keys in mapping nodes earlier
                             // in the sequence override keys specified in later mapping nodes.
                             foreach ($parsed as $parsedItem) {
+                                if (Yaml::PARSE_OBJECT_FOR_MAP & $flags && $parsedItem instanceof \stdClass) {
+                                    $parsedItem = (array) $parsedItem;
+                                }
+
                                 if (!is_array($parsedItem)) {
-                                    throw new ParseException('Merge items must be arrays.', $this->getRealCurrentLineNb() + 1, $parsedItem);
+                                    throw new ParseException('Merge items must be arrays.', $this->getRealCurrentLineNb() + 1, $parsedItem, $this->filename);
                                 }
 
                                 $data += $parsedItem; // array union
@@ -252,44 +338,59 @@
                             $data += $parsed; // array union
                         }
                     }
-                } elseif (isset($values['value']) && self::preg_match('#^&(?P<ref>[^ ]+) *(?P<value>.*)#u', $values['value'], $matches)) {
+                } elseif ('<<' !== $key && isset($values['value']) && self::preg_match('#^&(?P<ref>[^ ]++) *+(?P<value>.*)#u', $values['value'], $matches)) {
                     $isRef = $matches['ref'];
                     $values['value'] = $matches['value'];
                 }
 
+                $subTag = null;
                 if ($mergeNode) {
                     // Merge keys
-                } elseif (!isset($values['value']) || '' == trim($values['value'], ' ') || 0 === strpos(ltrim($values['value'], ' '), '#')) {
+                } elseif (!isset($values['value']) || '' === $values['value'] || 0 === strpos($values['value'], '#') || (null !== $subTag = $this->getLineTag($values['value'], $flags)) || '<<' === $key) {
                     // hash
                     // if next line is less indented or equal, then it means that the current value is null
                     if (!$this->isNextLineIndented() && !$this->isNextLineUnIndentedCollection()) {
                         // Spec: Keys MUST be unique; first one wins.
                         // But overwriting is allowed when a merge node is used in current block.
                         if ($allowOverwrite || !isset($data[$key])) {
-                            $data[$key] = null;
+                            if (null !== $subTag) {
+                                $data[$key] = new TaggedValue($subTag, '');
+                            } else {
+                                $data[$key] = null;
+                            }
                         } else {
-                            @trigger_error(sprintf('Duplicate key "%s" detected on line %d whilst parsing YAML. Silent handling of duplicate mapping keys in YAML is deprecated since version 3.2 and will throw \Symfony\Component\Yaml\Exception\ParseException in 4.0.', $key, $this->getRealCurrentLineNb() + 1), E_USER_DEPRECATED);
+                            @trigger_error($this->getDeprecationMessage(sprintf('Duplicate key "%s" detected whilst parsing YAML. Silent handling of duplicate mapping keys in YAML is deprecated since Symfony 3.2 and will throw \Symfony\Component\Yaml\Exception\ParseException in 4.0.', $key)), E_USER_DEPRECATED);
                         }
                     } else {
-                        // remember the parsed line number here in case we need it to provide some contexts in error messages below
-                        $realCurrentLineNbKey = $this->getRealCurrentLineNb();
                         $value = $this->parseBlock($this->getRealCurrentLineNb() + 1, $this->getNextEmbedBlock(), $flags);
-                        // Spec: Keys MUST be unique; first one wins.
-                        // But overwriting is allowed when a merge node is used in current block.
-                        if ($allowOverwrite || !isset($data[$key])) {
-                            $data[$key] = $value;
+                        if ('<<' === $key) {
+                            $this->refs[$refMatches['ref']] = $value;
+
+                            if (Yaml::PARSE_OBJECT_FOR_MAP & $flags && $value instanceof \stdClass) {
+                                $value = (array) $value;
+                            }
+
+                            $data += $value;
+                        } elseif ($allowOverwrite || !isset($data[$key])) {
+                            // Spec: Keys MUST be unique; first one wins.
+                            // But overwriting is allowed when a merge node is used in current block.
+                            if (null !== $subTag) {
+                                $data[$key] = new TaggedValue($subTag, $value);
+                            } else {
+                                $data[$key] = $value;
+                            }
                         } else {
-                            @trigger_error(sprintf('Duplicate key "%s" detected on line %d whilst parsing YAML. Silent handling of duplicate mapping keys in YAML is deprecated since version 3.2 and will throw \Symfony\Component\Yaml\Exception\ParseException in 4.0.', $key, $realCurrentLineNbKey + 1), E_USER_DEPRECATED);
+                            @trigger_error($this->getDeprecationMessage(sprintf('Duplicate key "%s" detected whilst parsing YAML. Silent handling of duplicate mapping keys in YAML is deprecated since Symfony 3.2 and will throw \Symfony\Component\Yaml\Exception\ParseException in 4.0.', $key)), E_USER_DEPRECATED);
                         }
                     }
                 } else {
-                    $value = $this->parseValue($values['value'], $flags, $context);
+                    $value = $this->parseValue(rtrim($values['value']), $flags, $context);
                     // Spec: Keys MUST be unique; first one wins.
                     // But overwriting is allowed when a merge node is used in current block.
                     if ($allowOverwrite || !isset($data[$key])) {
                         $data[$key] = $value;
                     } else {
-                        @trigger_error(sprintf('Duplicate key "%s" detected on line %d whilst parsing YAML. Silent handling of duplicate mapping keys in YAML is deprecated since version 3.2 and will throw \Symfony\Component\Yaml\Exception\ParseException in 4.0.', $key, $this->getRealCurrentLineNb() + 1), E_USER_DEPRECATED);
+                        @trigger_error($this->getDeprecationMessage(sprintf('Duplicate key "%s" detected whilst parsing YAML. Silent handling of duplicate mapping keys in YAML is deprecated since Symfony 3.2 and will throw \Symfony\Component\Yaml\Exception\ParseException in 4.0.', $key)), E_USER_DEPRECATED);
                     }
                 }
                 if ($isRef) {
@@ -298,13 +399,16 @@
             } else {
                 // multiple documents are not supported
                 if ('---' === $this->currentLine) {
-                    throw new ParseException('Multiple documents are not supported.', $this->currentLineNb + 1, $this->currentLine);
+                    throw new ParseException('Multiple documents are not supported.', $this->currentLineNb + 1, $this->currentLine, $this->filename);
+                }
+
+                if ($deprecatedUsage = (isset($this->currentLine[1]) && '?' === $this->currentLine[0] && ' ' === $this->currentLine[1])) {
+                    @trigger_error($this->getDeprecationMessage('Starting an unquoted string with a question mark followed by a space is deprecated since Symfony 3.3 and will throw \Symfony\Component\Yaml\Exception\ParseException in 4.0.'), E_USER_DEPRECATED);
                 }
 
                 // 1-liner optionally followed by newline(s)
                 if (is_string($value) && $this->lines[0] === trim($value)) {
                     try {
-                        Inline::$parsedLineNumber = $this->getRealCurrentLineNb();
                         $value = Inline::parse($this->lines[0], $flags, $this->refs);
                     } catch (ParseException $e) {
                         $e->setParsedLine($this->getRealCurrentLineNb() + 1);
@@ -316,8 +420,54 @@
                     return $value;
                 }
 
-                throw new ParseException('Unable to parse.', $this->getRealCurrentLineNb() + 1, $this->currentLine);
+                // try to parse the value as a multi-line string as a last resort
+                if (0 === $this->currentLineNb) {
+                    $previousLineWasNewline = false;
+                    $previousLineWasTerminatedWithBackslash = false;
+                    $value = '';
+
+                    foreach ($this->lines as $line) {
+                        // If the indentation is not consistent at offset 0, it is to be considered as a ParseError
+                        if (0 === $this->offset && !$deprecatedUsage && isset($line[0]) && ' ' === $line[0]) {
+                            throw new ParseException('Unable to parse.', $this->getRealCurrentLineNb() + 1, $this->currentLine, $this->filename);
+                        }
+                        if ('' === trim($line)) {
+                            $value .= "\n";
+                        } elseif (!$previousLineWasNewline && !$previousLineWasTerminatedWithBackslash) {
+                            $value .= ' ';
+                        }
+
+                        if ('' !== trim($line) && '\\' === substr($line, -1)) {
+                            $value .= ltrim(substr($line, 0, -1));
+                        } elseif ('' !== trim($line)) {
+                            $value .= trim($line);
+                        }
+
+                        if ('' === trim($line)) {
+                            $previousLineWasNewline = true;
+                            $previousLineWasTerminatedWithBackslash = false;
+                        } elseif ('\\' === substr($line, -1)) {
+                            $previousLineWasNewline = false;
+                            $previousLineWasTerminatedWithBackslash = true;
+                        } else {
+                            $previousLineWasNewline = false;
+                            $previousLineWasTerminatedWithBackslash = false;
+                        }
+                    }
+
+                    try {
+                        return Inline::parse(trim($value));
+                    } catch (ParseException $e) {
+                        // fall-through to the ParseException thrown below
+                    }
+                }
+
+                throw new ParseException('Unable to parse.', $this->getRealCurrentLineNb() + 1, $this->currentLine, $this->filename);
             }
+        } while ($this->moveToNextLine());
+
+        if (null !== $tag) {
+            $data = new TaggedValue($tag, $data);
         }
 
         if (Yaml::PARSE_OBJECT_FOR_MAP & $flags && !is_object($data) && 'mapping' === $context) {
@@ -345,7 +495,10 @@
             $skippedLineNumbers[] = $lineNumber;
         }
 
-        $parser = new self($offset, $this->totalNumberOfLines, $skippedLineNumbers);
+        $parser = new self();
+        $parser->offset = $offset;
+        $parser->totalNumberOfLines = $this->totalNumberOfLines;
+        $parser->skippedLineNumbers = $skippedLineNumbers;
         $parser->refs = &$this->refs;
 
         return $parser->doParse($yaml, $flags);
@@ -354,9 +507,11 @@
     /**
      * Returns the current line number (takes the offset into account).
      *
+     * @internal
+     *
      * @return int The current line number
      */
-    private function getRealCurrentLineNb()
+    public function getRealCurrentLineNb()
     {
         $realCurrentLineNumber = $this->currentLineNb + $this->offset;
 
@@ -397,7 +552,7 @@
         $blockScalarIndentations = array();
 
         if ($this->isBlockScalarHeader()) {
-            $blockScalarIndentations[] = $this->getCurrentLineIndentation();
+            $blockScalarIndentations[] = $oldLineIndentation;
         }
 
         if (!$this->moveToNextLine()) {
@@ -405,12 +560,32 @@
         }
 
         if (null === $indentation) {
-            $newIndent = $this->getCurrentLineIndentation();
+            $newIndent = null;
+            $movements = 0;
+
+            do {
+                $EOF = false;
+
+                // empty and comment-like lines do not influence the indentation depth
+                if ($this->isCurrentLineEmpty() || $this->isCurrentLineComment()) {
+                    $EOF = !$this->moveToNextLine();
+
+                    if (!$EOF) {
+                        ++$movements;
+                    }
+                } else {
+                    $newIndent = $this->getCurrentLineIndentation();
+                }
+            } while (!$EOF && null === $newIndent);
+
+            for ($i = 0; $i < $movements; ++$i) {
+                $this->moveToPreviousLine();
+            }
 
             $unindentedEmbedBlock = $this->isStringUnIndentedCollectionItem();
 
             if (!$this->isCurrentLineEmpty() && 0 === $newIndent && !$unindentedEmbedBlock) {
-                throw new ParseException('Indentation problem.', $this->getRealCurrentLineNb() + 1, $this->currentLine);
+                throw new ParseException('Indentation problem.', $this->getRealCurrentLineNb() + 1, $this->currentLine, $this->filename);
             }
         } else {
             $newIndent = $indentation;
@@ -419,6 +594,8 @@
         $data = array();
         if ($this->getCurrentLineIndentation() >= $newIndent) {
             $data[] = substr($this->currentLine, $newIndent);
+        } elseif ($this->isCurrentLineEmpty() || $this->isCurrentLineComment()) {
+            $data[] = $this->currentLine;
         } else {
             $this->moveToPreviousLine();
 
@@ -445,16 +622,16 @@
             $indent = $this->getCurrentLineIndentation();
 
             // terminate all block scalars that are more indented than the current line
-            if (!empty($blockScalarIndentations) && $indent < $previousLineIndentation && trim($this->currentLine) !== '') {
+            if (!empty($blockScalarIndentations) && $indent < $previousLineIndentation && '' !== trim($this->currentLine)) {
                 foreach ($blockScalarIndentations as $key => $blockScalarIndentation) {
-                    if ($blockScalarIndentation >= $this->getCurrentLineIndentation()) {
+                    if ($blockScalarIndentation >= $indent) {
                         unset($blockScalarIndentations[$key]);
                     }
                 }
             }
 
             if (empty($blockScalarIndentations) && !$this->isCurrentLineComment() && $this->isBlockScalarHeader()) {
-                $blockScalarIndentations[] = $this->getCurrentLineIndentation();
+                $blockScalarIndentations[] = $indent;
             }
 
             $previousLineIndentation = $indent;
@@ -469,27 +646,16 @@
                 continue;
             }
 
-            // we ignore "comment" lines only when we are not inside a scalar block
-            if (empty($blockScalarIndentations) && $this->isCurrentLineComment()) {
-                // remember ignored comment lines (they are used later in nested
-                // parser calls to determine real line numbers)
-                //
-                // CAUTION: beware to not populate the global property here as it
-                // will otherwise influence the getRealCurrentLineNb() call here
-                // for consecutive comment lines and subsequent embedded blocks
-                $this->locallySkippedLineNumbers[] = $this->getRealCurrentLineNb();
-
-                continue;
-            }
-
             if ($indent >= $newIndent) {
                 $data[] = substr($this->currentLine, $newIndent);
+            } elseif ($this->isCurrentLineComment()) {
+                $data[] = $this->currentLine;
             } elseif (0 == $indent) {
                 $this->moveToPreviousLine();
 
                 break;
             } else {
-                throw new ParseException('Indentation problem.', $this->getRealCurrentLineNb() + 1, $this->currentLine);
+                throw new ParseException('Indentation problem.', $this->getRealCurrentLineNb() + 1, $this->currentLine, $this->filename);
             }
         }
 
@@ -549,19 +715,25 @@
             }
 
             if (!array_key_exists($value, $this->refs)) {
-                throw new ParseException(sprintf('Reference "%s" does not exist.', $value), $this->currentLineNb + 1, $this->currentLine);
+                throw new ParseException(sprintf('Reference "%s" does not exist.', $value), $this->currentLineNb + 1, $this->currentLine, $this->filename);
             }
 
             return $this->refs[$value];
         }
 
-        if (self::preg_match('/^'.self::TAG_PATTERN.self::BLOCK_SCALAR_HEADER_PATTERN.'$/', $value, $matches)) {
+        if (self::preg_match('/^(?:'.self::TAG_PATTERN.' +)?'.self::BLOCK_SCALAR_HEADER_PATTERN.'$/', $value, $matches)) {
             $modifiers = isset($matches['modifiers']) ? $matches['modifiers'] : '';
 
             $data = $this->parseBlockScalar($matches['separator'], preg_replace('#\d+#', '', $modifiers), (int) abs($modifiers));
 
-            if (isset($matches['tag']) && '!!binary' === $matches['tag']) {
-                return Inline::evaluateBinaryScalar($data);
+            if ('' !== $matches['tag']) {
+                if ('!!binary' === $matches['tag']) {
+                    return Inline::evaluateBinaryScalar($data);
+                } elseif ('tagged' === $matches['tag']) {
+                    return new TaggedValue(substr($matches['tag'], 1), $data);
+                } elseif ('!' !== $matches['tag']) {
+                    @trigger_error($this->getDeprecationMessage(sprintf('Using the custom tag "%s" for the value "%s" is deprecated since Symfony 3.3. It will be replaced by an instance of %s in 4.0.', $matches['tag'], $data, TaggedValue::class)), E_USER_DEPRECATED);
+                }
             }
 
             return $data;
@@ -571,19 +743,21 @@
             $quotation = '' !== $value && ('"' === $value[0] || "'" === $value[0]) ? $value[0] : null;
 
             // do not take following lines into account when the current line is a quoted single line value
-            if (null !== $quotation && preg_match('/^'.$quotation.'.*'.$quotation.'(\s*#.*)?$/', $value)) {
+            if (null !== $quotation && self::preg_match('/^'.$quotation.'.*'.$quotation.'(\s*#.*)?$/', $value)) {
                 return Inline::parse($value, $flags, $this->refs);
             }
 
+            $lines = array();
+
             while ($this->moveToNextLine()) {
                 // unquoted strings end before the first unindented line
-                if (null === $quotation && $this->getCurrentLineIndentation() === 0) {
+                if (null === $quotation && 0 === $this->getCurrentLineIndentation()) {
                     $this->moveToPreviousLine();
 
                     break;
                 }
 
-                $value .= ' '.trim($this->currentLine);
+                $lines[] = trim($this->currentLine);
 
                 // quoted string values end with a line that is terminated with the quotation character
                 if ('' !== $this->currentLine && substr($this->currentLine, -1) === $quotation) {
@@ -591,11 +765,25 @@
                 }
             }
 
+            for ($i = 0, $linesCount = count($lines), $previousLineBlank = false; $i < $linesCount; ++$i) {
+                if ('' === $lines[$i]) {
+                    $value .= "\n";
+                    $previousLineBlank = true;
+                } elseif ($previousLineBlank) {
+                    $value .= $lines[$i];
+                    $previousLineBlank = false;
+                } else {
+                    $value .= ' '.$lines[$i];
+                    $previousLineBlank = false;
+                }
+            }
+
             Inline::$parsedLineNumber = $this->getRealCurrentLineNb();
+
             $parsedValue = Inline::parse($value, $flags, $this->refs);
 
             if ('mapping' === $context && is_string($parsedValue) && '"' !== $value[0] && "'" !== $value[0] && '[' !== $value[0] && '{' !== $value[0] && '!' !== $value[0] && false !== strpos($parsedValue, ': ')) {
-                throw new ParseException('A colon cannot be used in an unquoted mapping value.');
+                throw new ParseException('A colon cannot be used in an unquoted mapping value.', $this->getRealCurrentLineNb() + 1, $value, $this->filename);
             }
 
             return $parsedValue;
@@ -726,11 +914,15 @@
     private function isNextLineIndented()
     {
         $currentIndentation = $this->getCurrentLineIndentation();
-        $EOF = !$this->moveToNextLine();
+        $movements = 0;
 
-        while (!$EOF && $this->isCurrentLineEmpty()) {
+        do {
             $EOF = !$this->moveToNextLine();
-        }
+
+            if (!$EOF) {
+                ++$movements;
+            }
+        } while (!$EOF && ($this->isCurrentLineEmpty() || $this->isCurrentLineComment()));
 
         if ($EOF) {
             return false;
@@ -738,7 +930,9 @@
 
         $ret = $this->getCurrentLineIndentation() > $currentIndentation;
 
-        $this->moveToPreviousLine();
+        for ($i = 0; $i < $movements; ++$i) {
+            $this->moveToPreviousLine();
+        }
 
         return $ret;
     }
@@ -773,7 +967,7 @@
         //checking explicitly the first char of the trim is faster than loops or strpos
         $ltrimmedLine = ltrim($this->currentLine, ' ');
 
-        return '' !== $ltrimmedLine && $ltrimmedLine[0] === '#';
+        return '' !== $ltrimmedLine && '#' === $ltrimmedLine[0];
     }
 
     private function isCurrentLineLastLineInDocument()
@@ -799,7 +993,7 @@
 
         // remove leading comments
         $trimmedValue = preg_replace('#^(\#.*?\n)+#s', '', $value, -1, $count);
-        if ($count == 1) {
+        if (1 === $count) {
             // items have been removed, update the offset
             $this->offset += substr_count($value, "\n") - substr_count($trimmedValue, "\n");
             $value = $trimmedValue;
@@ -807,7 +1001,7 @@
 
         // remove start of the document marker (---)
         $trimmedValue = preg_replace('#^\-\-\-.*?\n#s', '', $value, -1, $count);
-        if ($count == 1) {
+        if (1 === $count) {
             // items have been removed, update the offset
             $this->offset += substr_count($value, "\n") - substr_count($trimmedValue, "\n");
             $value = $trimmedValue;
@@ -827,19 +1021,25 @@
     private function isNextLineUnIndentedCollection()
     {
         $currentIndentation = $this->getCurrentLineIndentation();
-        $notEOF = $this->moveToNextLine();
+        $movements = 0;
 
-        while ($notEOF && $this->isCurrentLineEmpty()) {
-            $notEOF = $this->moveToNextLine();
-        }
+        do {
+            $EOF = !$this->moveToNextLine();
 
-        if (false === $notEOF) {
+            if (!$EOF) {
+                ++$movements;
+            }
+        } while (!$EOF && ($this->isCurrentLineEmpty() || $this->isCurrentLineComment()));
+
+        if ($EOF) {
             return false;
         }
 
         $ret = $this->getCurrentLineIndentation() === $currentIndentation && $this->isStringUnIndentedCollectionItem();
 
-        $this->moveToPreviousLine();
+        for ($i = 0; $i < $movements; ++$i) {
+            $this->moveToPreviousLine();
+        }
 
         return $ret;
     }
@@ -905,4 +1105,56 @@
 
         return $ret;
     }
+
+    /**
+     * Trim the tag on top of the value.
+     *
+     * Prevent values such as `!foo {quz: bar}` to be considered as
+     * a mapping block.
+     */
+    private function trimTag($value)
+    {
+        if ('!' === $value[0]) {
+            return ltrim(substr($value, 1, strcspn($value, " \r\n", 1)), ' ');
+        }
+
+        return $value;
+    }
+
+    private function getLineTag($value, $flags, $nextLineCheck = true)
+    {
+        if ('' === $value || '!' !== $value[0] || 1 !== self::preg_match('/^'.self::TAG_PATTERN.' *( +#.*)?$/', $value, $matches)) {
+            return;
+        }
+
+        if ($nextLineCheck && !$this->isNextLineIndented()) {
+            return;
+        }
+
+        $tag = substr($matches['tag'], 1);
+
+        // Built-in tags
+        if ($tag && '!' === $tag[0]) {
+            throw new ParseException(sprintf('The built-in tag "!%s" is not implemented.', $tag), $this->getRealCurrentLineNb() + 1, $value, $this->filename);
+        }
+
+        if (Yaml::PARSE_CUSTOM_TAGS & $flags) {
+            return $tag;
+        }
+
+        throw new ParseException(sprintf('Tags support is not enabled. You must use the flag `Yaml::PARSE_CUSTOM_TAGS` to use "%s".', $matches['tag']), $this->getRealCurrentLineNb() + 1, $value, $this->filename);
+    }
+
+    private function getDeprecationMessage($message)
+    {
+        $message = rtrim($message, '.');
+
+        if (null !== $this->filename) {
+            $message .= ' in '.$this->filename;
+        }
+
+        $message .= ' on line '.($this->getRealCurrentLineNb() + 1);
+
+        return $message.'.';
+    }
 }