Avoid unnecessary Docs.META initializations (#48469)

If the target module does not have a Docs.META dict (e.g. if
`--strip-metadata` is used), `Docs.meta()` has the side effect of
creating a new IdDict and initializing the Docs.META field of the target
module.

We need to avoid eval'ing into modules after they've been closed, so for
methods that do not mutate the new IdDict we should avoid the init.

Resolves #48390.

Co-authored-by: Steve Kelly <kd2cca@gmail.com>

Author: topolarity

base/docs/Docs.jl

@@ -73,9 +73,9 @@ const modules = Module[]
 const META    = gensym(:meta)
 const METAType = IdDict{Any,Any}
 
-function meta(m::Module)
+function meta(m::Module; autoinit::Bool=true)
     if !isdefined(m, META) || getfield(m, META) === nothing
-        initmeta(m)
+        autoinit ? initmeta(m) : return nothing
     end
     return getfield(m, META)::METAType
 end
@@ -161,7 +161,8 @@ end
 function docstr(binding::Binding, typesig = Union{})
     @nospecialize typesig
     for m in modules
-        dict = meta(m)
+        dict = meta(m; autoinit=false)
+        isnothing(dict) && continue
         if haskey(dict, binding)
             docs = dict[binding].docs
             if haskey(docs, typesig)

stdlib/REPL/src/docview.jl

@@ -164,7 +164,8 @@ function doc(binding::Binding, sig::Type = Union{})
     results, groups = DocStr[], MultiDoc[]
     # Lookup `binding` and `sig` for matches in all modules of the docsystem.
     for mod in modules
-        dict = meta(mod)
+        dict = meta(mod; autoinit=false)
+        isnothing(dict) && continue
         if haskey(dict, binding)
             multidoc = dict[binding]
             push!(groups, multidoc)
@@ -565,7 +566,8 @@ Return documentation for a particular `field` of a type if it exists.
 """
 function fielddoc(binding::Binding, field::Symbol)
     for mod in modules
-        dict = meta(mod)
+        dict = meta(mod; autoinit=false)
+        isnothing(dict) && continue
         if haskey(dict, binding)
             multidoc = dict[binding]
             if haskey(multidoc.docs, Union{})
@@ -834,7 +836,9 @@ function apropos(io::IO, needle::Regex)
     for mod in modules
         # Module doc might be in README.md instead of the META dict
         docsearch(doc(mod), needle) && println(io, mod)
-        for (k, v) in meta(mod)
+        dict = meta(mod; autoinit=false)
+        isnothing(dict) && continue
+        for (k, v) in dict
             docsearch(v, needle) && println(io, k)
         end
     end