Comments confuse the YAML parser

[tamasd]

Symfony version(s) affected: 3.x, 4.x

Description
The Symfony YAML parser component fails to parse a valid YAML file, that can be parsed by other parsers (e.g. spyc).

How to reproduce
This example file is the simplified version (smallest one that can reproduce this issue) of the file I am trying to parse.

foo:
  bar:
    baz:
      {
      }

  # asdf

  ### qwer

The result is:

Unable to parse at line 4 (near "{").
#0 /app/vendor/symfony/yaml/Parser.php(520): Symfony\Component\Yaml\Parser->doParse(' { }\n# asdf\n###...', 0)
#1 /app/vendor/symfony/yaml/Parser.php(373): Symfony\Component\Yaml\Parser->parseBlock(3, '{\n}\n\n# asdf\n\n##...', 0)
#2 /app/vendor/symfony/yaml/Parser.php(520): Symfony\Component\Yaml\Parser->doParse('baz:\n  {\n  }\n\n#...', 0)
#3 /app/vendor/symfony/yaml/Parser.php(373): Symfony\Component\Yaml\Parser->parseBlock(2, 'baz:\n  {\n  }\n\n#...', 0)
#4 /app/vendor/symfony/yaml/Parser.php(520): Symfony\Component\Yaml\Parser->doParse('bar:\n  baz:\n   ...', 0)
#5 /app/vendor/symfony/yaml/Parser.php(373): Symfony\Component\Yaml\Parser->parseBlock(1, 'bar:\n  baz:\n   ...', 0)
#6 /app/vendor/symfony/yaml/Parser.php(142): Symfony\Component\Yaml\Parser->doParse('foo:\n  bar:\n   ...', 0)
#7 /app/vendor/symfony/yaml/Yaml.php(110): Symfony\Component\Yaml\Parser->parse('foo:\n  bar:\n   ...', 0)
#8 /app/src/Test.php(9): Symfony\Component\Yaml\Yaml::parse('foo:\n  bar:\n   ...')
#9 /app/src/Test.php(25): {closure}('foo:\n  bar:\n   ...')

[xabbuh]

Does this not happen if your YAML looks like this?

foo:
  bar:
    baz:
      {
      }

[pierredup]

#32767 fixes this issue (I tested with multiple scenarios, and applying the patch from #32767 fixes all the cases)

[tamasd]

No, it does not. The two comment blocks need to be there.

[xabbuh]

Then I am pretty sure that this behaviour is related to the fact that the component doesn't parse the inline notation when it spans multiple lines (see also #25239). So let's close here as a duplicate of the mentioned issue.

[pierredup]

@tamasd Please try the fix in #32767, that definitely fixes the issue here

[tamasd]

@pierredup applying the patch from that pull request on top of 3.4.30 fixed the issue. Thanks for the link.