I've finished most of the needed YAML work, esp. for YAML::XS.

libyaml upstream has now a patch with the new options NonStrict and IndentlessMap https://github.com/yaml/libyaml/pull/8

YAML::XS in https://github.com/ingydotnet/yaml-libyaml-pm/pull/43

YAML::XS writes now proper YAML which can be read with YAML.pm, and passes the CPAN::Meta validation tests. See https://github.com/Perl-Toolchain-Gang/CPAN-Meta/pull/107

For CPAN::Meta I've added validation tests for all existing YAML loaders, so you can see what's going on, and which version is conforming or fails. YAML::XS, YAML::Tiny, CPAN::Meta::YAML, YAML::Syck do pass now, YAML fails.

I have also patches for Parse::CPAN::META and CPAN-Meta-YAML to use the new versions, but only in cperl, no PR yet.

I've also started merging libsyck from upstream into YAML::Syck, which came up with some horrible private extensions, and made them mergable to upstream. But this work is still ongoing at https://github.com/rurban/syck/commits/0.71 and https://github.com/rurban/YAML-Syck/commits/merge-upstream.

TODO (optional)

• YAML.pm would need a patch to read old YAML::XS with $IndentlessMap=1.
• YAML::Syck
• syck