Exempt reexported external modules from the API docstring check

Project.toml

@@ -1,7 +1,7 @@
 name = "SciMLTesting"
 uuid = "09d9d899-5365-40a9-917a-5f67fddea283"
 authors = ["SciML"]
-version = "2.6.2"
+version = "2.6.3"
 
 [deps]
 Aqua = "4c88cf16-eb10-579e-8560-4a9242c79595"

src/SciMLTesting.jl

@@ -1031,6 +1031,23 @@ else
     end
 end
 
+# A module name that is public only because the module itself was reexported. Julia
+# exports a module's own name, so `using Dep` inside a facade puts `:Dep` into the
+# facade's public API; the docstring obligation for it belongs to the package that
+# defines the module, not to every reexporter. Deliberately restricted to `Module`
+# values: a reexported function, type or constant still owes a docstring, since that
+# one resolves through the binding to the defining package's docs.
+function _is_external_module_reexport(pkg::Module, name::Symbol)
+    isdefined(pkg, name) || return false
+    value = try
+        getfield(pkg, name)
+    catch
+        return false
+    end
+    value isa Module || return false
+    return !_is_within_module(value, pkg)
+end
+
 # Only names owned by this package's module hierarchy require a local rendered API
 # entry. External public reexports are audited separately by `public_reexports`.
 function _requires_local_rendering(pkg::Module, name::Symbol)
@@ -1141,7 +1158,10 @@ Two checks, each its own nested `@testset`:
   * **docstrings** (`docstrings = true`, on by default): every public API name has a
     docstring. A re-exported name documented in its defining package counts as
     documented (the check follows the binding, not a local docstring), so a repo is
-    not forced to redocument names it re-exports from a dependency.
+    not forced to redocument names it re-exports from a dependency. A re-exported
+    *module* name — public only because `using Dep` exports `Dep` itself — is exempt
+    entirely, mirroring the rendered check; the obligation to document `Dep` belongs
+    to `Dep`. Re-exported functions, types and constants are not exempt.
   * **rendered** (`rendered = true`, on by default): every public API name appears inside a
     ```` ```@docs ```` block somewhere under `docs_src`, so it is rendered in the
     manual. Re-exported modules inherit the defining package's rendered module
@@ -1199,7 +1219,13 @@ function run_api_docs(
     @testset "$testset" begin
         if docstrings
             skip = Set{Symbol}(Symbol.(ignore))
-            undocumented = sort!(filter(n -> !(n in skip) && !_has_docstring(pkg, n), api))
+            undocumented = sort!(
+                filter(
+                    n -> !(n in skip) && !_is_external_module_reexport(pkg, n) &&
+                        !_has_docstring(pkg, n),
+                    api,
+                )
+            )
             @testset "public API has docstrings" begin
                 docstrings_broken ? (@test_broken isempty(undocumented)) :
                     (@test isempty(undocumented))

test/runtests.jl

@@ -201,6 +201,15 @@ module LocalModuleFixture
     export LocalSubmodule
 end
 
+# Reexports an undocumented external module and an undocumented external function
+# next to an undocumented local name, so the docstrings check can be shown to exempt
+# the module and only the module.
+module UndocumentedModuleReexportFixture
+    import ..ReexportOwnerFixture: OwnedModule, owned_function
+    export OwnedModule, owned_function, local_undocumented
+    local_undocumented() = nothing
+end
+
 # A minimal AbstractTestSet that just collects every recorded result (including
 # nested testsets) and NEVER throws on finish. Wrapping a run_qa call in one lets a
 # test inspect the Broken/Pass/Fail/Error counts a broken-marker produced without
@@ -1145,6 +1154,48 @@ end
         @test c[:fail] == 0 && c[:error] == 0
         @test c[:pass] == 1
 
+        # A reexported external module is public only because Julia exports a module's
+        # own name; documenting it belongs to the package that defines it.
+        c = counts_of() do
+            run_api_docs(
+                UndocumentedModuleReexportFixture;
+                rendered = false,
+                ignore = (:owned_function, :local_undocumented),
+            )
+        end
+        @test c[:fail] == 0 && c[:error] == 0
+
+        # The exemption covers modules only: a reexported function is still reported.
+        c = counts_of() do
+            run_api_docs(
+                UndocumentedModuleReexportFixture;
+                rendered = false,
+                ignore = (:local_undocumented,),
+            )
+        end
+        @test c[:fail] == 1
+
+        @test SciMLTesting._is_external_module_reexport(
+            UndocumentedModuleReexportFixture, :OwnedModule
+        )
+        @test !SciMLTesting._is_external_module_reexport(
+            UndocumentedModuleReexportFixture, :owned_function
+        )
+        @test !SciMLTesting._is_external_module_reexport(
+            LocalModuleFixture, :LocalSubmodule
+        )
+
+        # A package's own undocumented submodule is still the package's to document.
+        # Only on 1.11+: the 1.10 `@doc` fallback renders an undocumented module as
+        # "No docstring or readme file found", which `_has_docstring`'s substring never
+        # matched, so no module is ever reported as undocumented there.
+        @static if VERSION >= v"1.11"
+            c = counts_of() do
+                run_api_docs(LocalModuleFixture; rendered = false)
+            end
+            @test c[:fail] == 1
+        end
+
         # docstrings_broken records Broken while names remain undocumented (migration).
         c = counts_of() do
             run_api_docs(ApiFixture; rendered = false, docstrings_broken = true)