Dasel fails to parse a "null" yaml file

[varac]

Describe the bug

Dasel fails to parse yaml file with null as the only content.

To Reproduce

1. echo 'null' > /tmp/null.yml
2. echo '---' > /tmp/null2.yml
3. touch /tmp/null3.yml
4. dasel -f /tmp/null.yml .
5. repeat with other files
6. All cmds fail with panic: reflect: call of reflect.Value.Interface on zero Value

Expected behavior

Dasel should not fail on valid (but empty) yaml.

Desktop (please complete the following information):

• OS: Ubuntu 20.10
• Version: v1.13.2

Additional context

yamllint, yq or ytt all don't fail on the same input files.

[TomWright]

Thank you for the clear examples. I'll take a look at this soon 👍

[TomWright]

Hi @varac,

I've made the changes required to get this working as expected. The fixes should also apply to other formats.

The one strange thing I've noticed is that empty YAML documents are marshal'd as JSON - this is down to the YAML package being used and I have raised an issue here: go-yaml/yaml#708

echo 'null' | go dasel -p yaml .
{}
echo '---' | go dasel -p yaml .
{}
echo '' | dasel -p yaml . 
{}

[varac]

Thanks!

[TomWright]

It seems that {} is actually the correct representation: https://stackoverflow.com/questions/33510094/syntax-for-empty-dictionary-in-yaml

I'm happy to merge this in and get it released now.

[TomWright]

This is now released under v1.13.3.