Programmatic retrieval of const documentation

General Usage
1

How do I programmatically get the documentation for a documented constant?


module MyMod

"""
This is MyAlias
""" 
const MyAlias = Val{:Alias}

end

using .MyMod

Docs.doc(MyMod.MyAlias)
....

“…” just gives the documentation for Val.

UPDATE:

I have a workaround for my particular situation but it doesn’t answer the more general question. I’m creating a constant in a macro so it looks a bit like this (note this is just for proof of concept and I didn’t really do any macro hygiene checking).

macro mymacro(const_name)
    const_name_symbol = QuoteNode(const_name)
    MyConst = :(const $const_name = Val{$const_name}())
    quote
        Base.@__doc__($MyConst)

        function my_get_doc(::Type{Val{$sym_name}})
            return Base.Docs.doc(Base.Docs.Binding($(@__MODULE__()), $(const_name_symbol)))
        end
    end
end
1 Like
2

Well, I got as far as using Base.Docs.doc(Base.Docs.Binding(Main, :MyAlias)). However, I can’t figure out how to make a function that figures out the module and name without using a macro.

3 
@doc MyAlias
4

That only works if I use a macro. If I use a function it no longer works.

julia> my_get_doc(x) = @doc x
my_get_doc (generic function with 1 method)

julia> my_get_doc(MyMod.MyAlias)
  No documentation found.

  Binding x does not exist.
5

Oh I see. I don’t think it’s possible, because docstrings are attached to symbols, not to values.

6

It’s just a little odd because Docs.doc works on functions without using a macro to turn it into a symbol.

7

Hmm interesting. After poking around in the internals, it looks like Base.doc is a lot smarter than just a symbol lookup, but clearly its not foolproof.

8

I briefly tried to look into it and I think the problem is that Base.doc looks at the type but @doc receives the exact expression and turns it into a symbol. If there were a way to find the name of the exact instance of the variable being passed then I think it would be possible.