`root_module` generates duplicate module definition when `logs.lwt` is a dependency.

[mefyl]

Expected Behavior

When eg. (root_modules root) is used, dune produces a working Root module that reexports all libraries dependencies.

Actual Behavior

The produced module exports Logs and other related modules twice, causing the following error:

dune build --root /tmp/dune/
File "root.ml-gen", line 17, characters 0-18:
17 | module Logs = Logs
     ^^^^^^^^^^^^^^^^^^
Error: Multiple definition of the module name Logs.
       Names must be unique in a given structure or signature.

Reproduction

PR with a reproducing test: #6147

Dockerfile reproducing the error

FROM alpine:3.16.2

RUN apk --no-cache add gcc make musl-dev opam
RUN opam init --compiler="4.14.0" --disable-sandboxing --yes
RUN opam install --yes dune logs lwt
RUN printf > /root/dune-project '(lang dune 3.4)\n'
RUN printf > /root/dune '(library\n\
 (name root_module)\n\
 (root_module root)\n\
 (libraries logs.lwt))\n'
RUN printf > /root/root_module.ml 'module Logs = Root.Logs\n'
RUN eval $(opam env) && cd /root && dune build

Specifications

• Version of dune (output of dune --version):

Shared cache: disabled
Workspace root: /tmp/dune
Auto-detected concurrency: 12
Running[0]: /tmp/dune/_opam/bin/ocamlc.opt -config > /tmp/dune_eef136_output
Dune context:                   
 { name = "default"
 ; kind = "default"
 ; profile = Dev
 ; merlin = true
 ; for_host = None
 ; fdo_target_exe = None
 ; build_dir = "default"
 ; toplevel_path = Some External "/tmp/dune/_opam/lib/toplevel"
 ; ocaml_bin = External "/tmp/dune/_opam/bin"
 ; ocaml = Ok External "/tmp/dune/_opam/bin/ocaml"
 ; ocamlc = External "/tmp/dune/_opam/bin/ocamlc.opt"
 ; ocamlopt = Ok External "/tmp/dune/_opam/bin/ocamlopt.opt"
 ; ocamldep = Ok External "/tmp/dune/_opam/bin/ocamldep.opt"
 ; ocamlmklib = Ok External "/tmp/dune/_opam/bin/ocamlmklib.opt"
 ; env =
     map
       { "DUNE_OCAML_HARDCODED" : "/tmp/dune/_opam/lib"
       ; "DUNE_OCAML_STDLIB" : "/tmp/dune/_opam/lib/ocaml"
       ; "DUNE_SOURCEROOT" : "/tmp/dune"
       ; "INSIDE_DUNE" : "/tmp/dune/_build/default"
       ; "OCAMLFIND_IGNORE_DUPS_IN" : "/tmp/dune/_build/install/default/lib"
       ; "OCAMLPATH" : "/tmp/dune/_build/install/default/lib"
       ; "OCAMLTOP_INCLUDE_PATH" :
           "/tmp/dune/_build/install/default/lib/toplevel"
       ; "OCAML_COLOR" : "always"
       ; "OPAMCOLOR" : "always"
       }
 ; findlib_paths = [ External "/tmp/dune/_opam/lib" ]
 ; arch_sixtyfour = true
 ; natdynlink_supported = true
 ; supports_shared_libraries = true
 ; ocaml_config =
     { version = "4.14.0"
     ; standard_library_default = "/tmp/dune/_opam/lib/ocaml"
     ; standard_library = "/tmp/dune/_opam/lib/ocaml"
     ; standard_runtime = "the_standard_runtime_variable_was_deleted"
     ; ccomp_type = "cc"
     ; c_compiler = "gcc"
     ; ocamlc_cflags =
         [ "-O2"; "-fno-strict-aliasing"; "-fwrapv"; "-pthread"; "-fPIC" ]
     ; ocamlc_cppflags = [ "-D_FILE_OFFSET_BITS=64" ]
     ; ocamlopt_cflags =
         [ "-O2"; "-fno-strict-aliasing"; "-fwrapv"; "-pthread"; "-fPIC" ]
     ; ocamlopt_cppflags = [ "-D_FILE_OFFSET_BITS=64" ]
     ; bytecomp_c_compiler =
         [ "gcc"
         ; "-O2"
         ; "-fno-strict-aliasing"
         ; "-fwrapv"
         ; "-pthread"
         ; "-fPIC"
         ; "-D_FILE_OFFSET_BITS=64"
         ]
     ; bytecomp_c_libraries = [ "-lm"; "-lpthread" ]
     ; native_c_compiler =
         [ "gcc"
         ; "-O2"
         ; "-fno-strict-aliasing"
         ; "-fwrapv"
         ; "-pthread"
         ; "-fPIC"
         ; "-D_FILE_OFFSET_BITS=64"
         ]
     ; native_c_libraries = [ "-lm" ]
     ; native_pack_linker = [ "ld"; "-r"; "-o" ]
     ; cc_profile = []
     ; architecture = "amd64"
     ; model = "default"
     ; int_size = 63
     ; word_size = 64
     ; system = "linux"
     ; asm = [ "as" ]
     ; asm_cfi_supported = true
     ; with_frame_pointers = false
     ; ext_exe = ""
     ; ext_obj = ".o"
     ; ext_asm = ".s"
     ; ext_lib = ".a"
     ; ext_dll = ".so"
     ; os_type = "Unix"
     ; default_executable_name = "a.out"
     ; systhread_supported = true
     ; host = "x86_64-pc-linux-gnu"
     ; target = "x86_64-pc-linux-gnu"
     ; profiling = false
     ; flambda = false
     ; spacetime = false
     ; safe_string = true
     ; exec_magic_number = "Caml1999X031"
     ; cmi_magic_number = "Caml1999I031"
     ; cmo_magic_number = "Caml1999O031"
     ; cma_magic_number = "Caml1999A031"
     ; cmx_magic_number = "Caml1999Y031"
     ; cmxa_magic_number = "Caml1999Z031"
     ; ast_impl_magic_number = "Caml1999M031"
     ; ast_intf_magic_number = "Caml1999N031"
     ; cmxs_magic_number = "Caml1999D031"
     ; cmt_magic_number = "Caml1999T031"
     ; natdynlink_supported = true
     ; supports_shared_libraries = true
     ; windows_unicode = false
     }
 }
Actual targets:                 
- alias @@default
Running[1]: (cd _build/.sandbox/66237914947f915ee42bf707f638bfb4/default && /tmp/dune/_opam/bin/ocamlc.opt -w @1..3@5..28@30..39@43@46..47@49..57@61..62@67@69-40 -strict-sequence -strict-formats -short-paths -keep-locs -w -49 -nopervasives -nostdlib -g -bin-annot -I .root_module.objs/byte -I .root_module.objs/public_cmi -I /tmp/dune/_opam/lib/logs -I /tmp/dune/_opam/lib/lwt -no-alias-deps -opaque -o .root_module.objs/byte/root_module__Root.cmo -c -impl root.ml-gen)
Command [1] exited with code 2:    
$ (cd _build/.sandbox/66237914947f915ee42bf707f638bfb4/default && /tmp/dune/_opam/bin/ocamlc.opt -w @1..3@5..28@30..39@43@46..47@49..57@61..62@67@69-40 -strict-sequence -strict-formats -short-paths -keep-locs -w -49 -nopervasives -nostdlib -g -bin-annot -I .root_module.objs/byte -I .root_module.objs/public_cmi -I /tmp/dune/_opam/lib/logs -I /tmp/dune/_opam/lib/lwt -no-alias-deps -opaque -o .root_module.objs/byte/root_module__Root.cmo -c -impl root.ml-gen)
File "root.ml-gen", line 17, characters 0-18:
17 | module Logs = Logs
     ^^^^^^^^^^^^^^^^^^
Error: Multiple definition of the module name Logs.
       Names must be unique in a given structure or signature.

• Version of ocaml (output of ocamlc --version): 4.14.0

• Operating system (distribution and version): Gentoo

[toots]

Same problem here with threads as a dependency.