Tool for migrating from Lwt_log to Logs

bin/lwt_log_to_logs/dune

@@ -0,0 +1,5 @@
+(executable
+ (public_name lwt-log-to-logs)
+ (package lwt_log_to_logs)
+ (name main)
+ (libraries cmdliner migrate_utils ocamlformat_utils))

bin/lwt_log_to_logs/main.ml

@@ -0,0 +1,381 @@
+open Ocamlformat_utils.Parsing
+open Asttypes
+open Parsetree
+open Ast_helper
+open Ocamlformat_utils.Ast_utils
+module Occ = Migrate_utils.Occ
+
+let add_comment state ?loc text =
+  Migrate_utils.add_comment state ?loc ("TODO: lwt-log-to-logs: " ^ text)
+
+let mk_lwt_return_unit = Exp.ident (mk_longident [ "Lwt"; "return_unit" ])
+
+let mk_log section cmd args =
+  (* Logs.$cmd ~src:$section (fun fmt -> fmt $arg) *)
+  let msgf =
+    let fmt_pat = Pat.var (mk_loc "fmt") and fmt_exp = mk_exp_var "fmt" in
+    let body = Exp.apply fmt_exp args in
+    Exp.function_ [ mk_function_param fmt_pat ] None (Pfunction_body body)
+  in
+  let src_arg =
+    match section with
+    | Some (section, `Lbl) -> [ (mk_lbl "src", section) ]
+    | Some (section, `Opt) -> [ (mk_lblopt "src", section) ]
+    | None -> []
+  in
+  mk_apply_ident [ "Logs"; cmd ] (src_arg @ [ (Nolabel, msgf) ])
+
+let mk_set_level section lvl =
+  mk_apply_simple [ "Logs"; "Src"; "set_level" ] [ section; lvl ]
+
+let mk_format_reporter_of_channel channel =
+  mk_let_var "logs_formatter"
+    (mk_apply_simple [ "Format"; "formatter_of_out_channel" ] [ channel ])
+  @@ fun fmt ->
+  mk_apply_ident
+    [ "Logs"; "format_reporter" ]
+    [ (mk_lbl "app", fmt); (mk_lbl "dst", fmt); (Nolabel, mk_unit_val) ]
+
+let mk_channel ~state ~template ~close_mode channel =
+  if Option.is_some template then
+    add_comment state
+      "Lwt_log.channel: The [~template] argument is unsupported. Use \
+       [~pp_header] instead.";
+  (match close_mode.pexp_desc with
+  | Pexp_variant (cstr, None) when cstr.txt.txt = "Keep" -> ()
+  | _ ->
+      add_comment state
+        "Lwt_log.channel: The [~close_mode] argument has been dropped. The \
+         behavior is always [`Keep].");
+  add_comment state
+    "Format.formatter_of_out_channel: Argument is a [Lwt_io.output_channel] \
+     but a [out_channel] is expected.";
+  mk_format_reporter_of_channel channel
+
+let mk_file ~state ~mode ~perm ~file_name =
+  let mk_mode append_mode =
+    Exp.list
+      [
+        append_mode;
+        mk_constr_exp [ "Open_wronly" ];
+        mk_constr_exp [ "Open_creat" ];
+        mk_constr_exp [ "Open_text" ];
+      ]
+  in
+  let mode =
+    mk_let_var "append_mode"
+      (Exp.match_
+         (value_of_lblopt ~default:(mk_variant_exp "Append") mode)
+         [
+           Exp.case (mk_variant_pat "Append") (mk_constr_exp [ "Open_append" ]);
+           Exp.case (mk_variant_pat "Truncate") (mk_constr_exp [ "Open_trunc" ]);
+         ])
+      mk_mode
+  in
+  let perm = value_of_lblopt ~default:(mk_const_int "0o640") perm in
+  add_comment state "[file]: Channel is never closed.";
+  mk_format_reporter_of_channel
+    (mk_apply_simple [ "open_out_gen" ] [ mode; perm; file_name ])
+
+let mk_reporter report_f =
+  let report =
+    let open Mk_function in
+    mk_function
+      (return report_f $ arg "src" $ arg "level" $ arg ~lbl:`Lbl "over"
+     $ arg "k" $ arg "msgf")
+  in
+  Exp.record [ (mk_longident [ "Logs"; "report" ], None, Some report) ] None
+
+let call_reporter r src level over k msgf =
+  Exp.apply
+    (Exp.field r (mk_longident [ "Logs"; "report" ]))
+    [
+      (Nolabel, src);
+      (Nolabel, level);
+      (mk_lbl "over", over);
+      (Nolabel, k);
+      (Nolabel, msgf);
+    ]
+
+let mk_broadcast ~state:_ loggers =
+  mk_let_var "broadcast_reporters" loggers @@ fun reporters_var ->
+  mk_reporter (fun src level over k msgf ->
+      let f k r _unit = call_reporter r src level over k msgf in
+      let f =
+        let open Mk_function in
+        mk_function (return f $ arg "k" $ arg "r" $ arg "_unit")
+      in
+      mk_apply_simple [ "List"; "fold_left" ]
+        [ f; k; reporters_var; mk_unit_val ])
+
+let mk_dispatch ~state:_ dispatch_f =
+  mk_let_var "dispatch_f" dispatch_f @@ fun dispatch_f ->
+  mk_reporter (fun src level ->
+      call_reporter
+        (Exp.apply dispatch_f [ (Nolabel, src); (Nolabel, level) ])
+        src level)
+
+let mk_syslog ~state ~paths ~facility =
+  let socket_arg =
+    match paths with
+    | Some (paths, lbl) ->
+        let lbl = match lbl with `Lbl -> mk_lbl | `Opt -> mk_lblopt in
+        (match paths.pexp_desc with
+        | Pexp_list [ _ ] -> ()
+        | _ ->
+            add_comment state
+              "[Logs_syslog_unix.unix_reporter] take a single path but a list \
+               is passed.");
+        [ (lbl "socket", paths) ]
+    | None -> []
+  in
+  add_comment state
+    "Add dependency on library [logs-syslog.unix] and package [logs-syslog].";
+  add_comment state "The [~facility] argument is not of the right type.";
+  Exp.apply
+    (mk_exp_ident [ "Logs_syslog_unix"; "unix_reporter" ])
+    (socket_arg @ [ (mk_lbl "facility", facility); (Nolabel, mk_unit_val) ])
+
+(** Whether an expression can be used as a format spec. *)
+let format_safe exp =
+  match exp.pexp_desc with
+  | Pexp_constant { pconst_desc = Pconst_string (s, _, _); _ } ->
+      String.for_all (function '%' | '@' -> false | _ -> true) s
+  | _ -> false
+
+let rewrite_apply_lwt_log ~state (unit, ident) args =
+  let open Unpack_apply in
+  let ignore_lblarg ?(cmt = "") arg k =
+    take_lblopt arg @@ fun value ->
+    (match value with
+    | Some (_, kind) ->
+        let prefix = match kind with `Lbl -> '~' | `Opt -> '?' in
+        Printf.ksprintf (add_comment state)
+          "Labelled argument %c%s was dropped.%s" prefix arg cmt
+    | None -> ());
+    k
+  in
+  let logf ~ident ~mk_log logs_name =
+    take_lblopt "section" @@ fun section ->
+    take_lblopt "exn" @@ fun exn ->
+    ignore_lblarg "location" @@ ignore_lblarg "logger" @@ take
+    @@ fun fmt_arg ->
+    take_all @@ fun args ->
+    let fmt_arg, args =
+      (* Log calls that don't end in [_f] use a ["%s"] format string to avoid
+         any typing and escaping issues. *)
+      if String.ends_with ~suffix:"_f" ident || format_safe fmt_arg then
+        (fmt_arg, args)
+      else (mk_const_string "%s", (Nolabel, fmt_arg) :: args)
+    in
+    let fmt_arg, args =
+      (* Print the [exn] argument. *)
+      match exn with
+      | Some (exn, lbl) ->
+          if lbl = `Opt then
+            add_comment state
+              "Last argument is a [exception option] while [exception] is \
+               expected.";
+          ( Exp.infix (mk_loc "^^") fmt_arg (mk_const_string "@\n%s"),
+            args
+            @ [ (Nolabel, mk_apply_simple [ "Printexc"; "to_string" ] [ exn ]) ]
+          )
+      | None -> (fmt_arg, args)
+    in
+    Some (mk_log section logs_name ((Nolabel, fmt_arg) :: args))
+  in
+  let log_unit ~ident n = logf ~ident ~mk_log n in
+  let log_lwt ~ident n =
+    let mk_log section n args =
+      Exp.sequence (mk_log section n args) mk_lwt_return_unit
+    in
+    logf ~ident ~mk_log n
+  in
+  let mk_level cstr = return (Some (mk_constr_exp [ "Logs"; cstr ])) in
+
+  unapply args
+  @@
+  match unit with
+  | "Lwt_log_core" -> (
+      match ident with
+      | "ign_debug" | "ign_debug_f" -> log_unit ~ident "debug"
+      | "ign_info" | "ign_info_f" -> log_unit ~ident "info"
+      | "ign_notice" | "ign_notice_f" -> log_unit ~ident "app"
+      | "ign_warning" | "ign_warning_f" -> log_unit ~ident "warn"
+      | "ign_error" | "ign_error_f" -> log_unit ~ident "err"
+      | "ign_fatal" | "ign_fatal_f" ->
+          add_comment state "This message was previously on the [fatal] level.";
+          log_unit ~ident "err"
+      | "debug" | "debug_f" -> log_lwt ~ident "debug"
+      | "info" | "info_f" -> log_lwt ~ident "info"
+      | "notice" | "notice_f" -> log_lwt ~ident "app"
+      | "warning" | "warning_f" -> log_lwt ~ident "warn"
+      | "error" | "error_f" -> log_lwt ~ident "err"
+      | "fatal" | "fatal_f" ->
+          add_comment state "This message was previously on the [fatal] level.";
+          log_lwt ~ident "err"
+      | "make" ->
+          (* [Lwt_log.Section.make] is detected as [("Lwt_log_core", "make")]. *)
+          take @@ fun name ->
+          return (Some (mk_apply_simple [ "Logs"; "Src"; "create" ] [ name ]))
+      | "set_level" ->
+          take @@ fun section ->
+          take @@ fun lvl ->
+          return (Some (mk_set_level section (mk_exp_some lvl)))
+      | "reset_level" ->
+          take @@ fun section ->
+          return (Some (mk_set_level section mk_exp_none))
+      | "null" -> return (Some (mk_exp_ident [ "Logs"; "nop_reporter" ]))
+      | "!default" ->
+          return (Some (mk_apply_simple [ "Logs"; "reporter" ] [ mk_unit_val ]))
+      | "default :=" ->
+          take @@ fun r ->
+          return (Some (mk_apply_simple [ "Logs"; "set_reporter" ] [ r ]))
+      | "default" ->
+          add_comment state "Use [Logs.set_reporter : reporter -> unit].";
+          return None
+      | "broadcast" ->
+          take @@ fun loggers -> return (Some (mk_broadcast ~state loggers))
+      | "dispatch" -> take @@ fun f -> return (Some (mk_dispatch ~state f))
+      | "Debug" -> mk_level "Debug"
+      | "Info" -> mk_level "Info"
+      | "Notice" -> mk_level "App"
+      | "Warning" -> mk_level "Warning"
+      | "Error" -> mk_level "Error"
+      | "Fatal" -> mk_level "Error"
+      | "add_rule" | "close" ->
+          add_comment state (ident ^ " is no longer supported.");
+          return None
+      | _ -> return None)
+  | "Lwt_log" -> (
+      match ident with
+      | "channel" ->
+          take_lblopt "template" @@ fun template ->
+          take_lbl "close_mode" @@ fun close_mode ->
+          take_lbl "channel" @@ fun channel ->
+          take @@ fun _unit ->
+          return (Some (mk_channel ~state ~template ~close_mode channel))
+      | "syslog" ->
+          ignore_lblarg "template" @@ take_lblopt "paths"
+          @@ fun paths ->
+          take_lbl "facility" @@ fun facility ->
+          take @@ fun _unit -> return (Some (mk_syslog ~state ~paths ~facility))
+      | "file" ->
+          ignore_lblarg "template" @@ take_lblopt "mode"
+          @@ fun mode ->
+          take_lblopt "perm" @@ fun perm ->
+          take_lbl "file_name" @@ fun file_name ->
+          take @@ fun _unit ->
+          return (Some (mk_file ~state ~mode ~perm ~file_name))
+      | _ -> return None)
+  | _ -> return None
+
+let rewrite_expression ~state exp =
+  match
+    rewrite_apply exp (fun lid args ->
+        Occ.may_rewrite state lid (fun ident ->
+            rewrite_apply_lwt_log ~state ident args))
+  with
+  | Some _ as x -> x
+  | None -> (
+      (* Rewrite uses of [Lwt_log.default]. *)
+      match exp.pexp_desc with
+      | Pexp_prefix ({ txt = "!"; _ }, { pexp_desc = Pexp_ident lid; _ }) ->
+          Occ.may_rewrite state lid (fun (unit, ident) ->
+              rewrite_apply_lwt_log ~state (unit, "!" ^ ident) [])
+      | Pexp_infix ({ txt = ":="; _ }, { pexp_desc = Pexp_ident lid; _ }, rhs)
+        ->
+          Occ.may_rewrite state lid (fun (unit, ident) ->
+              rewrite_apply_lwt_log ~state
+                (unit, ident ^ " :=")
+                [ (Nolabel, rhs) ])
+      | _ -> None)
+
+let rewrite_type ~state typ =
+  match typ.ptyp_desc with
+  | Ptyp_constr (lid, params) ->
+      Occ.may_rewrite state lid (fun ident ->
+          match (ident, params) with
+          | ("Lwt_log_core", "section"), [] ->
+              Some (mk_typ_constr [ "Logs"; "src" ])
+          | ("Lwt_log_core", "level"), [] ->
+              Some (mk_typ_constr [ "Logs"; "level" ])
+          | _ -> None)
+  | _ -> None
+
+let rewrite_pat ~state pat =
+  let mk_level cstr =
+    Some (Pat.construct (mk_longident [ "Logs"; cstr ]) None)
+  in
+  match pat.ppat_desc with
+  | Ppat_construct (lid, arg) ->
+      Occ.may_rewrite state lid (fun (unit, ident) ->
+          match unit with
+          | "Lwt_log_core" -> (
+              match (ident, arg) with
+              | "Debug", None -> mk_level "Debug"
+              | "Info", None -> mk_level "Info"
+              | "Notice", None -> mk_level "App"
+              | "Warning", None -> mk_level "Warning"
+              | "Error", None -> mk_level "Error"
+              | "Fatal", None -> mk_level "Error"
+              | _ -> None)
+          | _ -> None)
+  | _ -> None
+
+let mapper ~state =
+  let default = Ast_mapper.default_mapper in
+  let rec call_rewrite ~default ~loc f m x =
+    Migrate_utils.set_default_comment_loc state loc;
+    (* Apply the rewrite again if it succeed *)
+    match f x with
+    | Some x -> call_rewrite ~default ~loc f m x
+    | None -> default m x
+  in
+  let expr m x =
+    call_rewrite ~default:default.expr ~loc:x.pexp_loc
+      (rewrite_expression ~state)
+      m x
+  in
+  let typ m x =
+    call_rewrite ~default:default.typ ~loc:x.ptyp_loc (rewrite_type ~state) m x
+  in
+  let pat m x =
+    call_rewrite ~default:default.pat ~loc:x.ppat_loc (rewrite_pat ~state) m x
+  in
+  { default with expr; typ; pat }
+
+let modify_ast ~fname:_ =
+  let structure state str =
+    let m = mapper ~state in
+    m.structure m str
+  in
+  let signature state sg =
+    let m = mapper ~state in
+    m.signature m sg
+  in
+  { Migrate_utils.structure; signature }
+
+let main migrate =
+  let units = function
+    | "Lwt_log" | "Lwt_daemon" | "Lwt_log_core" | "Lwt_log_rules" -> true
+    | _ -> false
+  in
+  let packages = [ "lwt_log"; "lwt_log.core" ] in
+  if migrate then Migrate_utils.migrate ~packages ~units ~modify_ast
+  else Migrate_utils.print_occurrences ~packages ~units
+
+open Cmdliner
+
+let opt_migrate =
+  let doc =
+    "Modify the source code instead of printing occurrences of Lwt_log."
+  in
+  Arg.(value & flag & info ~doc [ "migrate" ])
+
+let cmd =
+  let doc = "Migrate your codebase from Lwt_log to Logs." in
+  let info = Cmd.info "lwt-log-to-logs" ~version:"%%VERSION%%" ~doc in
+  Cmd.v info Term.(const main $ opt_migrate)
+
+let () = exit (Cmd.eval cmd)