output a file even rendering a hidden module

Hidden modules were not rendered, since calling html-generate on them was used
to generate the associated source code.

However, this breaks dune rules in some cases (see issue ocaml#1013), as dune always
expect an output to the command.

This fix is related to the separation of implementation and interface
pipelines (see ocaml#1067).

Signed-off-by: Paul-Elliot <peada@free.fr>

Author: panglesd

src/odoc/rendering.ml

@@ -7,8 +7,7 @@ let documents_of_unit ~warnings_options ~syntax ~renderer ~extra unit =
   |> Odoc_model.Error.handle_warnings ~warnings_options
   >>= fun extra_docs ->
   Ok
-    (if unit.hidden then extra_docs
-     else Renderer.document_of_compilation_unit ~syntax unit :: extra_docs)
+    (Renderer.document_of_compilation_unit ~syntax unit :: extra_docs)
 
 let documents_of_page ~warnings_options ~syntax ~renderer ~extra page =
   Odoc_model.Error.catch_warnings (fun () ->