override_file and default_file can be something is not a file

[Sbozzolo]

ClimaParams.jl/src/file_parsing.jl

Lines 400 to 426 in ec828db

	"""
	create_toml_dict(FT;
	override_file,
	default_file,
	)
	Creates a `ParamDict{FT}` struct, by reading and merging upto
	two TOML files or Julia Dicts with override information taking precedence over
	default information.
	"""
	function create_toml_dict(
	::Type{FT};
	override_file::Union{Nothing, String, Dict} = nothing,
	default_file::Union{String, Dict} = joinpath(@__DIR__, "parameters.toml"),
	) where {FT <: AbstractFloat}
	default_dict =
	default_file isa String ? TOML.parsefile(default_file) : default_file
	default_toml_dict = ParamDict{FT}(default_dict, nothing)
	isnothing(override_file) && return default_toml_dict
	override_dict =
	override_file isa String ? TOML.parsefile(override_file) : override_file
	override_toml_dict = ParamDict{FT}(override_dict, override_dict)
	return merge_override_default_values(override_toml_dict, default_toml_dict)
	end

This function has a really counter-intuitive behavior, where you can pass a dictionary to an override_file/default_file. If we want to support this feature, it should be in different method instead of having a function that does all sorts of stuff and that can only be understood by reading the source code.

[nefrathenrici]

Would it be clearer if the kwargs were changed? It is useful to be able to mix files and Dicts, so I would like to keep this functionality

[Sbozzolo]

I think that an argument that takes nothing, string, and dict will always be a little confusing.

Maybe you could do this:

1. you have a method that only takes dictionaries (dictionaries are the "primitive type", file reading can be reduced to this case)
2. you a methods that just call 1. with the input read from file

create_toml_dict(; override_file::String, default_file::String) = create_toml_dict(; override_dict = Toml.parse(override_file), default_dict = Toml.parse(default_file)
create_toml_dict(; override_dict::Dict, default_file::String) = create_toml_dict(; default_dict = Toml.parse(default_file), override_dict)
create_toml_dict(; override_file::String, default_dict::Dict) = create_toml_dict(; default_dict, override_dict = Toml.parse(override_file)

Or something like this.

More generally, to me this looks like a problem with the constructor of ParamDict. At this end, this just is just a constructor, so maybe we should just provide the correct constructors.