Fix issue with unmarshaling yaml maps

[bwhaley]

This works around an issue in the yaml package that causes YAML maps to be unable to be marshalled to JSON.

What was happening was that unmarshaling a map variable like this:

SomeMap:
  SomeKey: SomeVal

would result in a variable of type map[interface{}]interface{} rather than map[string]interface{}. The former cannot be marshaled to JSON correctly since the JSON package (and the JSON spec) require that keys are strings. Hence you could not marshal the map to JSON in a boilerplate template like this:

{{ .SomeMap | toPrettyJson }}

where toPrettyJson is a function in sprig. It would instead just render an empty string.

• Needs a unit test

[bwhaley]

We could alternatively maintain a fork of go-yaml with a single line change, similar to what this person has done.

[yorinasub17]

LGTM! What a nasty yak shave!

[bwhaley]

Thanks for the review. A nasty shave indeed, but it seemed necessary for the problem I'm working on.

Unfortunately, the last version I pushed when I opened the PR didn't quite work. The behavior was not the same as the native Unmarshal for unexpected conditions like an empty string or invalid YAML. I've worked around this in the most recent commit and tests seem to pass now. Mind taking another look?

[bwhaley]

Actually, hold off on the review, it's still not right. 👎

[bwhaley]

Okay, now it should be ready for another round of review!

[bwhaley]

Nope, still finding other errors with the variants of unmarshaling. I'll need to write a more abstract unmarshaler that handles different types. This only works for map[string]interface{}.

[bwhaley]

Finally got to the bottom of it with the latest update. Convert() still needs unit tests.

[bwhaley]

Added unit test for Convert() func.

[yorinasub17]

LGTM! I had a few nits about code style and defensive coding, but feel free to ignore/punt as these are minor issues IMO.

[bwhaley]

All good suggestions. Updated and incorporated in 6e977ec.

[yorinasub17]

LGTM!

[bwhaley]

Thanks for the helpful review!