Demo does not run on OCaml 5.0: `Error: Unbound module Demo` after `Sys_error("Broken pipe")`

[lukstafi]

When I run:

:~/ppx_debug$ dune exec ./demo/debug/debug.exe -- trace debug.trace -f calls | head -n 6
File "demo/lib/other.ml", line 4, characters 8-19:
Error: Unbound module Demo

My complete session for reference:

:~/ppx_debug$ opam install . --deps-only
The following actions will be performed:
  ∗ install ppx_deriving        5.2.1
  ∗ install linenoise           1.4.0
  ∗ install containers          3.11
  ∗ install ppx_deriving_yojson 3.7.0
===== ∗ 4 =====
Do you want to continue? [Y/n] Y

<><> Processing actions <><><><><><><><><><><><><><><><><><><><><><><><><><><><>
⬇ retrieved ppx_deriving.5.2.1  (cached)
⬇ retrieved containers.3.11  (https://opam.ocaml.org/cache)
⬇ retrieved linenoise.1.4.0  (https://opam.ocaml.org/cache)
⬇ retrieved ppx_deriving_yojson.3.7.0  (https://opam.ocaml.org/cache)
∗ installed linenoise.1.4.0
∗ installed ppx_deriving.5.2.1
∗ installed containers.3.11
∗ installed ppx_deriving_yojson.3.7.0
Done.
:~/ppx_debug$ make
dune test
File "ppx_debug_common/interpret_cmt.ml", line 450, characters 9-40:
450 |          Load_path.init cmt.cmt_loadpath;
               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Error: This expression has type
         auto_include:Load_path.auto_include_callback -> unit
       but an expression was expected of type unit
       because it is in the left-hand side of a sequence
make: *** [Makefile:8: all] Error 1             
lukstafi@DESKTOP-6RRUNR4:~/ppx_debug$ make
dune test
rm /tmp/ppx_debug* debugger.json chrome.json *.trace > /dev/null 2>&1 || true
dune exec ./demo/app/app.exe
Done: 99% (121/122, 1 left) (jobs: 1)dune exec ./demo/debug/debug.exe -- trace debug.trace > chrome.json
Done: 99% (135/136, 1 left) (jobs: 1)dune exec ./demo/debug/debug.exe -- trace debug.trace -f debugger > debugger.json
Done: 46% (6/13, 7 left) (jobs: 0)dune exec ./demo/debug/debug.exe -- trace debug.trace -f calls | head -n 6
Done: 27% (23/85, 62 left) (jobs: 0)    1 demo/lib/lib.ml:40 main = ()
    6 demo/lib/lib.ml:25 consume (t: (Misc 1)) = 1
   13 demo/lib/lib.ml:11 depth (t: (Node [(Node [(Leaf 1)]); (Leaf 2)])) = 2
   18 demo/lib/lib.ml:14 _lambda (c: (Leaf 2)), (t: 0) = 0
   21 demo/lib/lib.ml:11 depth (t: (Leaf 2)) = 0
   26 demo/lib/lib.ml:14 _lambda (c: (Node [(Leaf 1)])), (t: 0) = 1
debug: internal error, uncaught exception:
       Sys_error("Broken pipe")
       Raised by primitive operation at Stdlib in file "stdlib.ml" (inlined), line 339, characters 0-54
       Called from Stdlib__Format.formatter_of_out_channel.(fun) in file "format.ml", line 999, characters 50-58
       Called from Ppx_debug_runtime__Main.act_on.(fun) in file "ppx_debug_runtime/main.ml", line 44, characters 8-68
       Called from Stdlib__List.iter in file "list.ml", line 110, characters 12-15
       Called from Stdlib__List.iter in file "list.ml", line 110, characters 12-15
       Called from Cmdliner_term.app.(fun) in file "cmdliner_term.ml", line 24, characters 19-24
       Called from Cmdliner_eval.run_parser in file "cmdliner_eval.ml", line 34, characters 37-44
Fatal error: exception Sys_error("Broken pipe")
Raised by primitive operation at Stdlib in file "stdlib.ml" (inlined), line 339, characters 0-54
Called from Stdlib__Format.formatter_of_out_channel.(fun) in file "format.ml", line 999, characters 50-58
Called from Stdlib__Format.pp_print_flush in file "format.ml" (inlined), line 673, characters 30-51
Called from Stdlib__Format.flush_standard_formatters in file "format.ml" (inlined), line 1474, characters 2-47
Called from Stdlib.at_exit.new_exit in file "stdlib.ml", line 564, characters 59-63
Called from Stdlib.do_at_exit in file "stdlib.ml" (inlined), line 574, characters 2-31
Called from Stdlib.exit in file "stdlib.ml", line 577, characters 2-15
Called from Dune__exe__Debug in file "demo/debug/debug.ml", line 3, characters 9-52
dune exec ./demo/debug/debug.exe -- trace debug.trace -f tree | head -n 6
Done: 20% (6/30, 24 left) (jobs: 0)(1) demo/lib/lib.ml:40 main
  (6) demo/lib/lib.ml:25 consume (t: (Misc 1))
  (6) demo/lib/lib.ml:25 consume = 1
  (13) demo/lib/lib.ml:11 depth (t: (Node [(Node [(Leaf 1)]); (Leaf 2)]))
    (18) demo/lib/lib.ml:14 _lambda (c: (Leaf 2)), (t: 0)
      (21) demo/lib/lib.ml:11 depth (t: (Leaf 2))
debug: internal error, uncaught exception:
       Sys_error("Broken pipe")
       Raised by primitive operation at Stdlib in file "stdlib.ml" (inlined), line 339, characters 0-54
       Called from Stdlib__Format.formatter_of_out_channel.(fun) in file "format.ml", line 999, characters 50-58
       Called from Ppx_debug_runtime__Main.act_on.(fun) in file "ppx_debug_runtime/main.ml", line 52, characters 8-72
       Called from Stdlib__List.iter in file "list.ml", line 110, characters 12-15
       Called from Ppx_debug_runtime__Main.act_on.(fun) in file "ppx_debug_runtime/main.ml", line 53, characters 8-23
       Called from Stdlib__List.iter in file "list.ml", line 110, characters 12-15
       Called from Ppx_debug_runtime__Main.act_on.(fun) in file "ppx_debug_runtime/main.ml", line 53, characters 8-23
       Called from Stdlib__List.iter in file "list.ml", line 110, characters 12-15
       Called from Cmdliner_term.app.(fun) in file "cmdliner_term.ml", line 24, characters 19-24
       Called from Cmdliner_eval.run_parser in file "cmdliner_eval.ml", line 34, characters 37-44
Fatal error: exception Sys_error("Broken pipe")
Raised by primitive operation at Stdlib in file "stdlib.ml" (inlined), line 339, characters 0-54
Called from Stdlib__Format.formatter_of_out_channel.(fun) in file "format.ml", line 999, characters 50-58
Called from Stdlib__Format.pp_print_flush in file "format.ml" (inlined), line 673, characters 30-51
Called from Stdlib__Format.flush_standard_formatters in file "format.ml" (inlined), line 1474, characters 2-47
Called from Stdlib.at_exit.new_exit in file "stdlib.ml", line 564, characters 59-63
Called from Stdlib.do_at_exit in file "stdlib.ml" (inlined), line 574, characters 2-31
Called from Stdlib.exit in file "stdlib.ml", line 577, characters 2-15
Called from Dune__exe__Debug in file "demo/debug/debug.ml", line 3, characters 9-52
ls chrome.json debugger.json *.trace /tmp/ppx_debug* || true
/tmp/ppx_debug.txt  /tmp/ppx_debug_tool.txt  chrome.json  debug.trace  debugger.json
lukstafi@DESKTOP-6RRUNR4:~/ppx_debug$ dune exec ./demo/debug/debug.exe -- trace debug.trace -f calls | head -n 6
File "demo/lib/other.ml", line 4, characters 8-19:
Error: Unbound module Demo

[lukstafi]

I see the same output in OCaml 4.14.1.

[lukstafi]

Maybe there is some problem with my system. I'm using WSL 2 on Windows 11 (the default install running Ubuntu).

[lukstafi]

I only get the Broken pipe error on Windows WSL 2, but on native Ubuntu I still get Unbound module Demo. Full logs:

$ make
dune test
rm /tmp/ppx_debug* debugger.json chrome.json *.trace > /dev/null 2>&1 || true
dune exec ./demo/app/app.exe
Done: 99% (121/122, 1 left) (jobs: 1)dune exec ./demo/debug/debug.exe -- trace debug.trace > chrome.json
Done: 99% (135/136, 1 left) (jobs: 1)dune exec ./demo/debug/debug.exe -- trace debug.trace -f debugger > debugger.json
Done: 28% (32/111, 79 left) (jobs: 0)dune exec ./demo/debug/debug.exe -- trace debug.trace -f calls | head -n 6
Done: 46% (6/13, 7 left) (jobs: 0)    1 demo/lib/lib.ml:40 main = ()
    6 demo/lib/lib.ml:25 consume (t: (Misc 1)) = 1
   13 demo/lib/lib.ml:11 depth (t: (Node [(Node [(Leaf 1)]); (Leaf 2)])) = 2
   18 demo/lib/lib.ml:14 _lambda (c: (Leaf 2)), (t: 0) = 0
   21 demo/lib/lib.ml:11 depth (t: (Leaf 2)) = 0
   26 demo/lib/lib.ml:14 _lambda (c: (Node [(Leaf 1)])), (t: 0) = 1
dune exec ./demo/debug/debug.exe -- trace debug.trace -f tree | head -n 6
Done: 20% (6/30, 24 left) (jobs: 0)(1) demo/lib/lib.ml:40 main
  (6) demo/lib/lib.ml:25 consume (t: (Misc 1))
  (6) demo/lib/lib.ml:25 consume = 1
  (13) demo/lib/lib.ml:11 depth (t: (Node [(Node [(Leaf 1)]); (Leaf 2)]))
    (18) demo/lib/lib.ml:14 _lambda (c: (Leaf 2)), (t: 0)
      (21) demo/lib/lib.ml:11 depth (t: (Leaf 2))
ls chrome.json debugger.json *.trace /tmp/ppx_debug* || true
chrome.json  debugger.json  debug.trace  /tmp/ppx_debug_tool.txt  /tmp/ppx_debug.txt
lukstafi@lukstafi-HP-Elite-Mini:~/ppx_debug$ dune exec ./demo/debug/debug.exe -- trace debug.trace > chrome.json
File "demo/lib/other.ml", line 4, characters 8-19:
Error: Unbound module Demo
:~/ppx_debug$ dune exec ./demo/debug/debug.exe -- trace debug.trace
File "demo/lib/other.ml", line 4, characters 8-19:
Error: Unbound module Demo

[lukstafi]

Demo is not mentioned, i.e. dune describe pp demo/lib/other.ml | grep Demo is empty.

[dariusf]

I'm on macOS and can't reproduce the broken pipe issue unfortunately.

About Unbound module Demo, the fix is to set the environment variable PPX_DEBUG='{"libraries": ["demo/lib"]}'.

The reason this is needed is that given a type name from the cmt, we need to know how to access the printer for it from the project's main module - that's what is provided above.