[BUG] Dasel crash when reading an empty file

[Larandar]

Describe the bug

Dasel will crash if called on an empty file, even if it's by specification in most implementations interpreted as a valid file for that format (yaml and toml).

(Yes, I just read both TOML and YAML specs, and it's ambiguous as in both case an unquoted empty string is corresponding to nil but the lexer seems to assume at least one identifier)

To Reproduce

touch /tmp/bug.toml
dasel -f /tmp/bug.toml

Will fail:

panic: reflect: call of reflect.Value.Interface on zero Value

goroutine 1 [running]:
reflect.valueInterface({0x0?, 0x0?, 0x0?}, 0x0?)
	reflect/value.go:1495 +0xfc
reflect.Value.Interface(...)
	reflect/value.go:1490
github.com/tomwright/dasel/v2.Value.Interface({{0x0, 0x0, 0x0}, 0x0, 0x0, 0x0})
	github.com/tomwright/dasel/v2/value.go:55 +0x6c
...

Expected behavior

Such files should be handled like most parsers interpreted it, so nil. This way creating a new toml file can be as simple as:

touch /tmp/state.toml
dasel put -f /tmp/toml .state.last-execution -t string -v $(date -Iseconds)

Desktop (please complete the following information):

• OS: macOS 14.1
• Version: dasel version 2.4.1

[TomWright]

Thanks for highlighting this @Larandar .

Dasel has an issue with nulls at the moment, stemming from the fact that it uses reflection internally. That said, it shouldn't be too hard to get this working. I'll work on this soon.

[TomWright]

I think I accidentally broke this by commenting this out:

dasel/internal/command/select.go

Line 107 in 3bfb5dd

// todo : check if this is still needed.

I'll try and verify this tonight

[TomWright]

This has been fixed in the development release and will be released soon.

[Larandar]

Ha, the good old "I'm sure this code is not applicable anymore" 👍

[TomWright]

Hey @Larandar,

This was included in the last release.

$ dasel -v
dasel version 2.5.0
$ touch empty.toml
$ dasel -f empty.toml