Human-readable stack trace in case of cycle

Signed-off-by: Nicolás Ojeda Bär <[email protected]>

Author: nojb

src/dune_rules/ml_sources.ml

@@ -469,6 +469,9 @@ let make
   ~include_subdirs:(loc_include_subdirs, (include_subdirs : Dune_file.Include_subdirs.t))
   ~dirs
   =
+  Memo.push_stack_frame ~human_readable_description:(fun () ->
+    Pp.textf "Finding source files in directory %s" (Path.Build.to_string dir))
+  @@ fun () ->
   let+ modules_of_stanzas =
     let modules =
       let dialects = Dune_project.dialects project in

src/dune_rules/modules_field_evaluator.ml

@@ -404,6 +404,9 @@ let eval
   (settings : Stanza_common.Modules_settings.t)
   =
   let open Memo.O in
+  Memo.push_stack_frame ~human_readable_description:(fun () ->
+    Pp.textf "Evaluating modules field in directory %s" (Path.Build.to_string src_dir))
+  @@ fun () ->
   let* modules0 =
     eval0 ~expander ~loc:stanza_loc ~all_modules ~standard:all_modules settings.modules
   in

test/blackbox-tests/test-cases/modules-expansion.t

@@ -134,44 +134,8 @@ appears. We need to handle this cycle gracefully and report it to the user.
   > EOF
 
   $ dune exec ./mod.exe
-  Internal error, please report upstream including the contents of _build/log.
-  Description:
-    ("internal dependency cycle",
-    { frames =
-        [ ("build-file", In_build_dir "default/lst")
-        ; ("<unnamed>", ())
-        ; ("<unnamed>", ())
-        ; ("load-dir", In_build_dir "default")
-        ]
-    })
-  Raised at Memo.Exec.exec_dep_node.(fun) in file "src/memo/memo.ml", line
-    1289, characters 29-62
-  Called from Fiber__Scheduler.exec in file "vendor/fiber/src/scheduler.ml",
-    line 76, characters 8-11
-  Re-raised at Stdune__Exn.raise_with_backtrace in file
-    "otherlibs/stdune/src/exn.ml", line 38, characters 27-56
-  Called from Fiber__Scheduler.exec in file "vendor/fiber/src/scheduler.ml",
-    line 76, characters 8-11
-  Re-raised at Stdune__Exn.raise_with_backtrace in file
-    "otherlibs/stdune/src/exn.ml", line 38, characters 27-56
-  Called from Fiber__Scheduler.exec in file "vendor/fiber/src/scheduler.ml",
-    line 76, characters 8-11
-  Re-raised at Stdune__Exn.raise_with_backtrace in file
-    "otherlibs/stdune/src/exn.ml", line 38, characters 27-56
-  Called from Fiber__Scheduler.exec in file "vendor/fiber/src/scheduler.ml",
-    line 76, characters 8-11
-  Re-raised at Stdune__Exn.raise_with_backtrace in file
-    "otherlibs/stdune/src/exn.ml", line 38, characters 27-56
-  Called from Fiber__Scheduler.exec in file "vendor/fiber/src/scheduler.ml",
-    line 76, characters 8-11
-  Re-raised at Stdune__Exn.raise_with_backtrace in file
-    "otherlibs/stdune/src/exn.ml", line 38, characters 27-56
-  Called from Fiber__Scheduler.exec in file "vendor/fiber/src/scheduler.ml",
-    line 76, characters 8-11
-  
-  I must not crash.  Uncertainty is the mind-killer. Exceptions are the
-  little-death that brings total obliteration.  I will fully express my cases. 
-  Execution will pass over me and through me.  And when it has gone past, I
-  will unwind the stack along its path.  Where the cases are handled there will
-  be nothing.  Only I will remain.
+  Error: Dependency cycle between:
+     Finding source files in directory _build/default
+  -> Evaluating modules field in directory _build/default
+  -> Finding source files in directory _build/default
   [1]