bug #16259 [Validator] Allow an empty path in a URL with only a fragment or a query (jakzal)

This PR was merged into the 2.3 branch.

Discussion
----------

[Validator] Allow an empty path in a URL with only a fragment or a query

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | #15891
| License       | MIT
| Doc PR        | -

URLs like `http://symfony.com?query=1` or `http://symfony.com#` should be valid.

According to the [RFC3986](https://tools.ietf.org/html/rfc3986#page-16):

> When authority is present, the path must either be empty or begin with a slash ("/") character.
> When authority is not present, the path cannot begin with two slash characters ("//").

Since the RFC describes URIs, the second sentence doesn't apply here as the authority is required in URLs .

Commits
-------

b3a5411 [Validator] Allow an empty path in a URL with only a fragment or a query

src/Symfony/Component/Validator/Constraints/UrlValidator.php

@@ -33,7 +33,7 @@ class UrlValidator extends ConstraintValidator
                 \]  # a IPv6 address
             )
             (:[0-9]+)?                              # a port (optional)
-            (/?|/\S+)                               # a /, nothing or a / with something
+            (/?|/\S+|\?|\#)                         # a /, nothing, a / with something, a query or a fragment
         $~ixu';
 
     /**

src/Symfony/Component/Validator/Tests/Constraints/UrlValidatorTest.php

@@ -111,6 +111,8 @@ class UrlValidatorTest extends AbstractConstraintValidatorTest
             array('http://☎.com/'),
             array('http://username:password@symfony.com'),
             array('http://user-name@symfony.com'),
+            array('http://symfony.com?'),
+            array('http://symfony.com#'),
         );
     }
 
@@ -140,8 +142,6 @@ class UrlValidatorTest extends AbstractConstraintValidatorTest
             array('http://goog_le.com'),
             array('http://google.com::aa'),
             array('http://google.com:aa'),
-            array('http://symfony.com?'),
-            array('http://symfony.com#'),
             array('ftp://google.fr'),
             array('faked://google.fr'),
             array('http://127.0.0.1:aa/'),