.ocamlinit: XDG base directory lookup. (#8834)

Changes

@@ -131,6 +131,13 @@ Working version
    (Whitequark and Jacques-Henri Jourdan, review by Gabriel Scherer
     and Xavier Clerc)
 
+* #8834, `ocaml`: adhere to the XDG base directory specification to
+  locate an `.ocamlinit` file. Reads an `$XDG_CONFIG_HOME/ocaml/init.ml`
+  file before trying to lookup `~/.ocamlinit`. On Windows the behaviour
+  is unchanged.
+  (Daniel C. Bünzli, review by David Allsopp, Armaël Guéneau and
+   Nicolás Ojeda Bär)
+
 ### Standard library:
 
 - #8832: List.find_map : ('a -> 'b option) -> 'a list -> 'b option

man/ocaml.m

@@ -302,8 +302,14 @@ is invoked, it will read phrases from an initialization file before
 giving control to the user. The default file is
 .B .ocamlinit
 in the current directory if it exists, otherwise
+.B XDG_CONFIG_HOME/ocaml/init.ml
+according to the XDG base directory specification lookup if it exists (on
+Windows this is skipped), otherwise
 .B .ocamlinit
-in the user's home directory. You can specify a different initialization file
+in the user's home directory (
+.B HOME
+variable).
+You can specify a different initialization file
 by using the
 .BI \-init \ file
 option, and disable initialization files by using the
@@ -327,7 +333,10 @@ When printing error messages, the toplevel system
 attempts to underline visually the location of the error. It
 consults the TERM variable to determines the type of output terminal
 and look up its capabilities in the terminal database.
-
+.TP
+.B XDG_CONFIG_HOME HOME
+.B .ocamlinit
+lookup procedure (see above).
 .SH SEE ALSO
 .BR ocamlc (1), \ ocamlopt (1), \ ocamlrun (1).
 .br

manual/manual/cmds/top.etex

@@ -66,9 +66,12 @@ its contents are read as a sequence of OCaml phrases
 and executed as per the "#use" directive
 described in section~\ref{s:toplevel-directives}.
 The evaluation outcode for each phrase are not displayed.
-If the current directory does not contain an ".ocamlinit" file, but
-the user's home directory (environment variable "HOME") does, the
-latter is read and executed as described below.
+If the current directory does not contain an ".ocamlinit" file,
+the file "XDG_CONFIG_HOME/ocaml/init.ml" is looked up according
+to the XDG base directory specification and used instead (on Windows
+this is skipped). If that file doesn't exist then an [.ocamlinit] file
+in the users' home directory (determined via environment variable "HOME") is
+used if existing.
 
 The toplevel system does not perform line editing, but it can
 easily be used in conjunction with an external line editor such as
@@ -132,7 +135,8 @@ attempts to underline visually the location of the error. It
 consults the "TERM" variable to determines the type of output terminal
 and look up its capabilities in the terminal database.
 
-\item["HOME"] Directory where the ".ocamlinit" file is searched.
+\item["XDG_CONFIG_HOME", "HOME"]
+".ocamlinit" lookup procedure (see above).
 \end{options}
 \end{unix}
 

manual/manual/cmds/unified-options.etex

@@ -287,7 +287,8 @@ the toplevel is running with the "#directory" directive
 \item["-init" \var{file}]
 Load the given file instead of the default initialization file.
 The default file is ".ocamlinit" in the current directory if it
-exists, otherwise ".ocamlinit" in the user's home directory.
+exists, otherwise "XDG_CONFIG_HOME/ocaml/init.ml" or
+".ocamlinit" in the user's home directory.
 }%top
 
 \notop{%

toplevel/opttoploop.ml

@@ -544,17 +544,42 @@ let _ =
   Clflags.dlcode := true;
   ()
 
+let find_ocamlinit () =
+  let ocamlinit = ".ocamlinit" in
+  if Sys.file_exists ocamlinit then Some ocamlinit else
+  let getenv var = match Sys.getenv var with
+    | exception Not_found -> None | "" -> None | v -> Some v
+  in
+  let exists_in_dir dir file = match dir with
+    | None -> None
+    | Some dir ->
+        let file = Filename.concat dir file in
+        if Sys.file_exists file then Some file else None
+  in
+  let home_dir () = getenv "HOME" in
+  let config_dir () =
+    if Sys.win32 then None else
+    match getenv "XDG_CONFIG_HOME" with
+    | Some _ as v -> v
+    | None ->
+        match home_dir () with
+        | None -> None
+        | Some dir -> Some (Filename.concat dir ".config")
+  in
+  let init_ml = Filename.concat "ocaml" "init.ml" in
+  match exists_in_dir (config_dir ()) init_ml with
+  | Some _ as v -> v
+  | None -> exists_in_dir (home_dir ()) ocamlinit
+
 let load_ocamlinit ppf =
   if !Clflags.noinit then ()
   else match !Clflags.init_file with
   | Some f -> if Sys.file_exists f then ignore (use_silently ppf f)
               else fprintf ppf "Init file not found: \"%s\".@." f
   | None ->
-     if Sys.file_exists ".ocamlinit" then ignore (use_silently ppf ".ocamlinit")
-     else try
-       let home_init = Filename.concat (Sys.getenv "HOME") ".ocamlinit" in
-       if Sys.file_exists home_init then ignore (use_silently ppf home_init)
-     with Not_found -> ()
+      match find_ocamlinit () with
+      | None -> ()
+      | Some file -> ignore (use_silently ppf file)
 ;;
 
 let set_paths () =

toplevel/toploop.ml

@@ -498,17 +498,42 @@ let _ =
   Env.import_crcs ~source:Sys.executable_name crc_intfs;
   ()
 
+let find_ocamlinit () =
+  let ocamlinit = ".ocamlinit" in
+  if Sys.file_exists ocamlinit then Some ocamlinit else
+  let getenv var = match Sys.getenv var with
+    | exception Not_found -> None | "" -> None | v -> Some v
+  in
+  let exists_in_dir dir file = match dir with
+    | None -> None
+    | Some dir ->
+        let file = Filename.concat dir file in
+        if Sys.file_exists file then Some file else None
+  in
+  let home_dir () = getenv "HOME" in
+  let config_dir () =
+    if Sys.win32 then None else
+    match getenv "XDG_CONFIG_HOME" with
+    | Some _ as v -> v
+    | None ->
+        match home_dir () with
+        | None -> None
+        | Some dir -> Some (Filename.concat dir ".config")
+  in
+  let init_ml = Filename.concat "ocaml" "init.ml" in
+  match exists_in_dir (config_dir ()) init_ml with
+  | Some _ as v -> v
+  | None -> exists_in_dir (home_dir ()) ocamlinit
+
 let load_ocamlinit ppf =
   if !Clflags.noinit then ()
   else match !Clflags.init_file with
   | Some f -> if Sys.file_exists f then ignore (use_silently ppf f)
               else fprintf ppf "Init file not found: \"%s\".@." f
   | None ->
-     if Sys.file_exists ".ocamlinit" then ignore (use_silently ppf ".ocamlinit")
-     else try
-       let home_init = Filename.concat (Sys.getenv "HOME") ".ocamlinit" in
-       if Sys.file_exists home_init then ignore (use_silently ppf home_init)
-     with Not_found -> ()
+      match find_ocamlinit () with
+      | None -> ()
+      | Some file -> ignore (use_silently ppf file)
 ;;
 
 let set_paths () =