bug #29639 [Yaml] detect circular references (xabbuh)

This PR was merged into the 3.4 branch.

Discussion
----------

[Yaml] detect circular references

| Q             | A
| ------------- | ---
| Branch?       | 3.4
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | #29462
| License       | MIT
| Doc PR        |

Commits
-------

b7487f476b [Yaml] detect circular references

src/Symfony/Component/Yaml/Parser.php

@@ -35,6 +35,7 @@ class Parser
     private $refs = array();
     private $skippedLineNumbers = array();
     private $locallySkippedLineNumbers = array();
+    private $refsBeingParsed = array();
 
     public function __construct()
     {
@@ -212,6 +213,7 @@ class Parser
 
                 if (isset($values['value']) && self::preg_match('#^&(?P<ref>[^ ]+) *(?P<value>.*)#u', $values['value'], $matches)) {
                     $isRef = $matches['ref'];
+                    $this->refsBeingParsed[] = $isRef;
                     $values['value'] = $matches['value'];
                 }
 
@@ -244,6 +246,7 @@ class Parser
                 }
                 if ($isRef) {
                     $this->refs[$isRef] = end($data);
+                    array_pop($this->refsBeingParsed);
                 }
             } elseif (
                 self::preg_match('#^(?P<key>(?:![^\s]++\s++)?(?:'.Inline::REGEX_QUOTED_STRING.'|(?:!?!php/const:)?[^ \'"\[\{!].*?)) *\:(\s++(?P<value>.+))?$#u', rtrim($this->currentLine), $values)
@@ -287,6 +290,10 @@ class Parser
                     if (isset($values['value'][0]) && '*' === $values['value'][0]) {
                         $refName = substr(rtrim($values['value']), 1);
                         if (!array_key_exists($refName, $this->refs)) {
+                            if (false !== $pos = array_search($refName, $this->refsBeingParsed, true)) {
+                                throw new ParseException(sprintf('Circular reference [%s, %s] detected for reference "%s".', implode(', ', \array_slice($this->refsBeingParsed, $pos)), $refName, $refName), $this->currentLineNb + 1, $this->currentLine, $this->filename);
+                            }
+
                             throw new ParseException(sprintf('Reference "%s" does not exist.', $refName), $this->getRealCurrentLineNb() + 1, $this->currentLine, $this->filename);
                         }
 
@@ -340,6 +347,7 @@ class Parser
                     }
                 } elseif ('<<' !== $key && isset($values['value']) && self::preg_match('#^&(?P<ref>[^ ]++) *+(?P<value>.*)#u', $values['value'], $matches)) {
                     $isRef = $matches['ref'];
+                    $this->refsBeingParsed[] = $isRef;
                     $values['value'] = $matches['value'];
                 }
 
@@ -395,6 +403,7 @@ class Parser
                 }
                 if ($isRef) {
                     $this->refs[$isRef] = $data[$key];
+                    array_pop($this->refsBeingParsed);
                 }
             } else {
                 // multiple documents are not supported
@@ -500,6 +509,7 @@ class Parser
         $parser->totalNumberOfLines = $this->totalNumberOfLines;
         $parser->skippedLineNumbers = $skippedLineNumbers;
         $parser->refs = &$this->refs;
+        $parser->refsBeingParsed = $this->refsBeingParsed;
 
         return $parser->doParse($yaml, $flags);
     }
@@ -689,6 +699,10 @@ class Parser
             }
 
             if (!array_key_exists($value, $this->refs)) {
+                if (false !== $pos = array_search($value, $this->refsBeingParsed, true)) {
+                    throw new ParseException(sprintf('Circular reference [%s, %s] detected for reference "%s".', implode(', ', \array_slice($this->refsBeingParsed, $pos)), $value, $value), $this->currentLineNb + 1, $this->currentLine, $this->filename);
+                }
+
                 throw new ParseException(sprintf('Reference "%s" does not exist.', $value), $this->currentLineNb + 1, $this->currentLine, $this->filename);
             }
 

src/Symfony/Component/Yaml/Tests/ParserTest.php

@@ -2177,6 +2177,48 @@ EOE;
         $this->parser->parse($yaml);
     }
 
+    /**
+     * @dataProvider circularReferenceProvider
+     * @expectedException \Symfony\Component\Yaml\Exception\ParseException
+     * @expectedExceptionMessage Circular reference [foo, bar, foo] detected
+     */
+    public function testDetectCircularReferences($yaml)
+    {
+        $this->parser->parse($yaml, Yaml::PARSE_CUSTOM_TAGS);
+    }
+
+    public function circularReferenceProvider()
+    {
+        $tests = array();
+
+        $yaml = <<<YAML
+foo:
+    - &foo
+      - &bar
+        bar: foobar
+        baz: *foo
+YAML;
+        $tests['sequence'] = array($yaml);
+
+        $yaml = <<<YAML
+foo: &foo
+    bar: &bar
+        foobar: baz
+        baz: *foo
+YAML;
+        $tests['mapping'] = array($yaml);
+
+        $yaml = <<<YAML
+foo: &foo
+    bar: &bar
+        foobar: baz
+        <<: *foo
+YAML;
+        $tests['mapping with merge key'] = array($yaml);
+
+        return $tests;
+    }
+
     /**
      * @dataProvider indentedMappingData
      */