Item14025: JsonRpcContrib requires allow_nonref (when using JSON-XS v3.02).

(NB the below is the result/a side effect of updating a number of Perl modules two days ago; I didn't have time to look more closely at the underlying problem, but starting by adding allow_nonref does not seem to be a bad idea at first glance; see also Item14024)
The following warning seemingly breaks configure in my installation ("Loading ..." forever):

| 2016-03-15T21:02:15+01:00 warning | hash- or arrayref expected (not a simple scalar, use allow_nonref to allow this) at /var/www/apps/foswiki/lib/Foswiki/Contrib/JsonRpcContrib/Response.pm line 135.
 at /var/www/apps/foswiki/lib/Foswiki/Contrib/JsonRpcContrib/Response.pm line 135.
        Foswiki::Contrib::JsonRpcContrib::Response::encode(Foswiki::Contrib::JsonRpcContrib::Response=HASH(0x7f0d8d849480)) called at /var/www/apps/foswiki/lib/Foswiki/Contrib/JsonRpcContrib/Response.pm line 48
        Foswiki::Contrib::JsonRpcContrib::Response::print("Foswiki::Contrib::JsonRpcContrib::Response", Foswiki=HASH(0x7f0d8ce8c278), "code", -32700, "message", "Parse error - invalid json-rpc request: JSON text must be an "...) called at /var/www/apps/foswiki/lib/Foswiki/Contrib/JsonRpcContrib/Server.pm line 89
        Foswiki::Contrib::JsonRpcContrib::Server::__ANON__(Foswiki::Contrib::JsonRpcContrib::Error=HASH(0x7f0d8c004b28), SCALAR(0x55afee321f00)) called at /var/www/.plenv/versions/5.22.1-ithreads-shrplib/lib/perl5/site_perl/5.22.1/Error.pm line 345
        eval {...} called at /var/www/.plenv/versions/5.22.1-ithreads-shrplib/lib/perl5/site_perl/5.22.1/Error.pm line 335
        Error::subs::run_clauses(HASH(0x7f0d8d849d20), Foswiki::Contrib::JsonRpcContrib::Error=HASH(0x7f0d8c004b28), undef, ARRAY(0x7f0d8c60d110)) called at /var/www/.plenv/versions/5.22.1-ithreads-shrplib/lib/perl5/site_perl/5.22.1/Error.pm line 432
        Error::subs::try(CODE(0x7f0d8d5dd990), HASH(0x7f0d8d849d20)) called at /var/www/apps/foswiki/lib/Foswiki/Contrib/JsonRpcContrib/Server.pm line 90
        Foswiki::Contrib::JsonRpcContrib::Server::dispatch(Foswiki::Contrib::JsonRpcContrib::Server=HASH(0x7f0d8d4cd378), Foswiki=HASH(0x7f0d8ce8c278)) called at /var/www/apps/foswiki/lib/Foswiki/Contrib/JsonRpcContrib.pm line 35
        Foswiki::Contrib::JsonRpcContrib::dispatch(Foswiki=HASH(0x7f0d8ce8c278)) called at /var/www/apps/foswiki/lib/Foswiki/UI.pm line 374
        Foswiki::UI::__ANON__() called at /var/www/.plenv/versions/5.22.1-ithreads-shrplib/lib/perl5/site_perl/5.22.1/Error.pm line 421
        eval {...} called at /var/www/.plenv/versions/5.22.1-ithreads-shrplib/lib/perl5/site_perl/5.22.1/Error.pm line 413
        Error::subs::try(CODE(0x7f0d8d3f31b8), HASH(0x7f0d8ce8c080)) called at /var/www/apps/foswiki/lib/Foswiki/UI.pm line 500
        Foswiki::UI::_execute(Foswiki::Request=HASH(0x7f0d8d509268), CODE(0x7f0d8c09e7e8), "jsonrpc", 1) called at /var/www/apps/foswiki/lib/Foswiki/UI.pm line 326
        Foswiki::UI::handleRequest(Foswiki::Request=HASH(0x7f0d8d509268)) called at /var/www/apps/foswiki/lib/Foswiki/Engine/Apache.pm line 91
        Foswiki::Engine::Apache::run(Apache2::RequestRec=SCALAR(0x7f0d8d5fa048)) called at -e line 0
        eval {...} called at -e line 0.
 |

Toggling TRACE in JsonRpcContrib/Request.pm shows the following when directly invoking configure after restarting the web server:

| 2016-03-15T23:10:54+01:00 debug | - JsonRpcContrib::Request - data={"jsonrpc":"2.0","method":"getspec","params":{"get":{"parent":{"depth":0}},"depth":0},"id":"iLoad-schema_0"} |

Can't repro. Can you find out what the value of $message actually is?

-- MichaelDaum - 17 Mar 2016

The complete message reads

Parse error - invalid json-rpc request: JSON text must be an object or array (but found number, string, true, false or null, use allow_nonref to allow this)

Update: I was able to identify JSON-XS (v3.02) as the culprit in my case (an earlier version used to work). See Item14024 (also refers to a related CPAN bug report which has some details).

-- MarkusUeberall - 17 Mar 2016

As noted in Item14024, this seems to only manifest when ModPerl is active. It does not fail with FastCGI.

-- GeorgeClark - 22 Mar 2016

I've found some other references about issues under mod_perl and JSON::XS. It appears that comments in the XS module claim that it's not thread safe, so use in a mod_perl environment can be unpredictable. See CPAN:Cpanel::JSON::XS for one attempt to build a better version. CPAN:JSON::XS states explicitly "This module is not guaranteed to be thread safe and there are no plans to change this ..."

-- GeorgeClark - 26 Mar 2016

We've decided in the release meeting to include a workaround, which has just been merged and will be released in 2.1.1 and 2.2.0.

-- JanKrueger - 04 Apr 2016

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