Support Psych version 4

[t27duck]

Fixes #1335

Psych's .load method uses .safe_load by default which is not compatible with papertail needs to load.

This implements the suggested fix in the issue which is a similar fix Rails uses throughout its codebase when it needs to load YAML content.

The test case outlined in the issue passes with this change (after I pointed the paperclip gem to the forked branch).

Check the following boxes:

• Wrote good commit messages.
• Feature branch is up-to-date with master (if not - rebase it).
• Squashed related commits together.
• Added tests.
• Added an entry to the Changelog if the new
  code introduces user-observable changes.
• The PR relates to only one subject with a clear title
  and description in grammatically correct, complete sentences.

[gurgelrenan]

Hi @t27duck , thanks for your P.R. Looks good to me.

@jaredbeck do you think that they should add some additional tests? I can't figure out a good way to test this cenario. Perhaps some mock in spec/paper_trail/serializers/yaml_spec.rb?

[jaredbeck]

@jaredbeck do you think that they should add some additional tests? I can't figure out a good way to test this cenario. Perhaps some mock in spec/paper_trail/serializers/yaml_spec.rb?

Yes, a mock should work, e.g.

allow(YAML).to receive(:unsafe_load)
serializer.load
expect(YAML).to have_received(:unsafe_load)

[gurgelrenan]

@t27duck Could you add the required tests?

[t27duck]

@gurgelrenan - Spec added.

Rspec doesn't allow stubbing methods that don't exist on the object that's being stubbed, so based on whichever version of Psych is running with the tests, I had to have the spec check what YAML does implement and set stubs and expectations based on that.

[jaredbeck]

Thanks Tony. This is good enough.

Rspec doesn't allow stubbing methods that don't exist on the object that's being stubbed, ..

For future reference, I wonder if without_partial_double_verification would help ..? I haven't tried.

[gurgelrenan]

Thanks @t27duck 😄