Copying docstrings with `@doc` macro in packages doesn't work on master

[jmert]

Accessing the documentation attached to a binding with @doc name seems to return nothing inside a package, so doing something like copying a docstring from one binding to another no longer works.

For example, with a new package:

$ julia -e 'using Pkg; Pkg.generate("CopyDocs")'
  Generating  project CopyDocs:
    CopyDocs/Project.toml
    CopyDocs/src/CopyDocs.jl
$ cd CopyDocs

and writing the module

$ cat - > src/CopyDocs.jl <<EOF
module CopyDocs
export A, B
"My docstring" function A end
@doc (@doc A) function B end
end
EOF

The docstring for B exists on Julia 1.10 and prior ...

$ julia +1.10 --quiet --project
julia> VERSION
v"1.10.0-rc1"

julia> using CopyDocs

help?> A
search: A as Any any all abs ARGS ans axes atan asin asec any! all! acsc acot acos abs2 Array atanh atand asinh asind asech asecd

  My docstring

help?> B
search: B Bool big Base bind break begin bswap BitSet BigInt BitArray BigFloat binomial basename Broadcast BitVector BitMatrix

  My docstring

but appears to be nothing on master:

$ julia-dev --quiet --project
julia> VERSION
v"1.11.0-DEV.890"

julia> using CopyDocs

help?> A
search: A

  My docstring

help?> B
search: B

After some digging through the Docs code, I've found the pair of PRs #48594 and #51399 that effect Base.Docs.docm(). The former was merged before 1.10 was branched, so that doesn't appear to be the cause — therefore I'm guessing the movement of REPL out of the system image impacted this, though I haven't bisected to be sure.

Using the guess that @doc needs REPL to function, I tried adding it to the package dependencies and loading inside the package, and it does appear to fix the problem with the docstring not copying:

$ sed -i '1 a using REPL' src/CopyDocs.jl
$ julia-dev --project -e 'using Pkg; Pkg.add("REPL")'
...

and then

$ julia-dev --quiet --project
julia> VERSION
v"1.11.0-DEV.890"

julia> using CopyDocs

help?> B
search: B

  My docstring

Of course, I'd rather not have to add a dependency on the REPL.