mdx: add --verbosity=info flag if Dune is in verbose mode

This hack usually doesn't add much to the output and can greatly help
debugging mdx scripts with Dune.

Signed-off-by: Antonin Décimo <antonin@tarides.com>

Author: MisterDA

src/dune_rules/mdx.ml

@@ -8,6 +8,9 @@ let color_always =
      [ Command.Args.A "--color=always" ]
     else [])
 
+let verbosity =
+  lazy (if !Log.verbose then [ Command.Args.A "--verbosity=info" ] else [])
+
 module Files = struct
   type t =
     { src : Path.Build.t
@@ -72,7 +75,7 @@ module Deps = struct
   let rule ~dir ~mdx_prog files =
     let open Command.Args in
     Command.run ~dir:(Path.build dir) mdx_prog
-      ([ A "deps" ] @ Lazy.force color_always
+      ([ A "deps" ] @ Lazy.force color_always @ Lazy.force verbosity
       @ [ Dep (Path.build files.Files.src) ])
       ~stdout_to:files.Files.deps
 
@@ -324,6 +327,7 @@ let gen_rules_for_single_file stanza ~sctx ~dir ~expander ~mdx_prog
           in
           ( mdx_prog
           , [ A "test" ] @ prelude_args @ Lazy.force color_always
+            @ Lazy.force verbosity
             @ [ A "-o"; Target files.corrected; Dep (Path.build files.src) ] )
       in
       let deps, sandbox =
@@ -379,7 +383,7 @@ let mdx_prog_gen t ~sctx ~dir ~scope ~expander ~mdx_prog =
   let action =
     Command.run ~dir:(Path.build dir) mdx_prog ~stdout_to:file
       ([ A "dune-gen"; prelude_args; Resolve.Memo.args directory_args ]
-      @ Lazy.force color_always)
+      @ Lazy.force color_always @ Lazy.force verbosity)
   in
   let open Memo.O in
   let* () = Super_context.add_rule sctx ~loc ~dir action in