[Yaml] Allow parsing of unindented closing quotation mark

[johnillo]

Q	A
Branch?	4.3
Bug fix?	yes
New feature?	no
BC breaks?	no
Deprecations?	no
Tests pass?	yes
Fixed tickets	#33082
License	MIT
Doc PR	symfony/symfony-docs#...

Unindented quotation marks are not parsed correctly by the parser. Online parsers accepts values/strings with unindented quotation marks as valid yaml.

$yaml = <<<YAML
---
foo:
  bar: 'baz

'
YAML;
dump($this->parser->parse($yaml));

Before fix

Symfony\Component\Yaml\Exception\ParseException: Malformed inline YAML string: 'baz at line 4.

After fix

array:1 [
  "foo" => array:1 [
    "bar" => "baz\n"
  ]
]

[javiereguiluz]

@johnillo thanks for contributing this fix!

I have a question about the number of \n in the parsed result. Shouldn't we get two \n instead of one?

[nicolas-grekas]

@javiereguiluz:

[xabbuh]

If I do not miss anything, the following YAML string would still not be parsed:

foo:
  bar: 'baz

foobar'

This is due to the fact that the parser does not properly handle the inline notation when split across multiple lines.

From my point of view I would rather invest some time to try to add support for the multi-line notation spanning multiple lines entirely instead of solving it only partially.

[javiereguiluz]

About the missing \n, I guess it's related to the "line folding" feature of the YAML spec: "When encountering a sequence of (possibly indented) line breaks without any additional intermediate characters, the parser ignores the first one and preserves the rest."

[GuilhemN]

I don't think this is valid Yaml, the spec explicitly refers to the indentation of each line when defining quoted scalars ( https://yaml.org/spec/1.1/current.html#l-single-inner(n) ):

s-ignored-prefix(n,single)
( ns-single-char nb-single-char* )?

And s-ignored-prefix imposes parsing n white spaces before any content.

[fabpot]

For the record, we don't thrive to support all the YAML spec. And I agree with @xabbuh that if we were going to add support for this new feature, it should be complete. I don't think this is worth it. @johnillo Do you want to give it a try?

[johnillo]

@fabpot I think I have to agree with you that it's not worth it. I've tried different parsers online and they behave differently on this kind of input.

I'll close this PR. Thanks everyone.