Description

Similar issue as discussed in #13017 and implemented in #39732, however for query parameters and not for path parameters.

I'd like to produce URLs with encoded slashes in query parameters, e.g. expecting an URL like this:

/search?searchPath=%2Fdummy%2Fsearch%2Fpath

I'm aware that slashes in query parameters would be allowed according to RFC3986. Motivation for encoding the slashes is compatibility with another system (to ensure that exactly the same URLs are being generated by both systems).

With the current implementation of UrlGenerator, I'm unable to produce the above expected output. Providing the parameter unencoded will pass the parameter unencoded to the the url. Encoding the parameter before providing to UrlGenerator results in double-encoding:

echo $urlGenerator('search_route', ['searchPath' => '/dummy/search/path']);
// output: /search?searchPath=/dummy/search/path

echo $urlGenerator('search_route', ['searchPath' => rawurlencode('/dummy/search/path')]);
// output: /search?searchPath=%252Fdummy%252Fsearch%252Fpath

The cause for the behavior in the first example is coming from this line:
https://github.com/symfony/routing/blob/c9678d03b147dbd206ec796d25f84a68e398bb2a/Generator/UrlGenerator.php#L310
where '%2F' is decoded back to '/' after encoding it with http_build_query.

In #39732, the same problem was solved by adding a decoding rule for '%252F' => '%2F' to $decodedChars. Would it be thinkable to apply the same fix for QUERY_FRAGMENT_DECODED?

private const QUERY_FRAGMENT_DECODED = [
        // RFC 3986 explicitly allows those in the query/fragment to reference other URIs unencoded
        '%2F' => '/',
        '%252F' => '%2F',
        '%3F' => '?',