--variable, --metadata and boolean values

[bpj]

I guess this one is for @tarleb

I tried unsuccessfully to use a variable like -V foo as a boolean in Lua.
Something like -M foo, -M foo=true or -M foo=false does indeed result in a boolean value for that metadata field in Lua. With -V foo pandoc.utils.type returns "Doc" for the value of PANDOC_WRITER_OPTIONS.variables.foo, but apparently that value stringifies to "true"! I find this doubly confusing as I had expected a boolean, and I would have expected a string rather than a Doc for some other value.

Using a variable for a filter switch would be more convenient as it could be accessed "directly" rather than writing a Meta filter which extracts the value from metadata and assigns it to a script-wide variable before running the main filter.

Obviously I could write code which converts a Doc to a string and a string which "looks like a bool" to a bool but should that really be necessary?

Is this expected behavior or should I report it as a bug?

[tarleb]

The conversion to a boolean would need to happen during command args parsing. The correct type is chosen if the variable is defined in a defaults file:

# these will have type boolean in Lua
variables:
  foo: true
  bar: false

I agree that it's confusing that we do the conversion for metadata but not for variables. Please open an issue for that.

---

The Doc was chosen over string because that's the object's type in Haskell. I don't think user-supplied variables can't be anything other than booleans, simple strings, lists, or maps, so I guess it would be safe to convert Doc's back into strings. But, in theory, the Doc value might contain extra info like formatting or ANSI character styles, and that information would be lost if a string value was used instead of Doc. So I'd rather be safe and not do any lossy type conversion.

But I'd reconsider my stance if the Doc type poses a problem.

[massifrg]

A possible way around is decoding the stringified variable's value as JSON.

local variables = PANDOC_WRITER_OPTIONS.variables or {}
local foo = pandoc.json.decode(tostring(variables.foo), false)

I'm actually using this way around to put data structures in variables and metadata for filters and writers.