improve user-defined config file detection

doc/ocp-indent.md

@@ -98,9 +98,15 @@ requiring them to change their settings in any way (except that, obviously, they
 need to use ocp-indent !).
 
 If a `.ocp-indent` file is found in the current directory or its ancestors, it
-overrides definitions from `$XDG_CONFIG_HOME/ocp/ocp-indent.conf`,
-`~/.ocp/ocp-indent.conf` and the built-in default. The command-line can of
-course still be used to override parameters defined in the files.
+overrides definitions from the user-defined configuration file (see below)
+and the built-in default. The command-line can of course still be used to 
+override parameters defined in the files.
+
+The user-defined configuration file depends on the platform you're using.
+On linux it is `$XDG_CONFIG_HOME/ocp-indent/config` with `$XDG_CONFIG_HOME`
+defaulting to `$HOME/.config/`. On macOS it is
+`$HOME/Library/Application Support/com.OCamlPro.ocp-indent/config`. On
+Windows it is `{FOLDERID_ApplicationData}/OCamlPro/ocp-indent/config`.
 
 Have a look at ocp-indent's own [`.ocp-indent`](.ocp-indent) file for an
 example.

ocp-indent.opam

@@ -35,6 +35,7 @@ depends: [
   "cmdliner" {>= "1.0.0"}
   "ocamlfind"
   "base-bytes"
+  "directories" {>= "0.2"}
 ]
 post-messages: [
   "This package requires additional configuration for use in editors. Install package 'user-setup', or manually:

src/dune

@@ -15,7 +15,7 @@
  (name ocp_indent_lib)
  (wrapped false)
  (public_name ocp-indent.lib)
- (libraries ocp-indent.utils)
+ (libraries ocp-indent.utils directories)
  (modules indentConfig indentBlock indentPrinter)
  (flags :standard -w -9 -warn-error -57)
 )

src/indentArgs.ml

@@ -212,9 +212,13 @@ let info =
         option, or as a configuration definition in one of the following, \
         searched in order: a file named `.ocp-indent' in the current directory \
         or its parents (which allows for per-project indentation settings), \
-        the file `\\$XDG_CONFIG_HOME/ocp/ocp-indent.conf', the file \
-        `\\$HOME/.ocp/ocp-indent.conf', or the environment variable \
-        \\$OCP_INDENT_CONFIG."
+        the user-defined configuration file (see below), or the environment \
+        variable \\$OCP_INDENT_CONFIG.";
+    `P "The user-defined configuration file depends on the platform you're \
+        using. On Linux it is `\\$XDG_CONFIG_HOME/ocp-indent/config' with \
+        `\\$XDG_CONFIG_HOME' defaulting to `\\$HOME/.config/'. On macOS it is \
+        `\\$HOME/Library/Application Support/com.OCamlPro.ocp-indent/config'. \
+        On Windows it is `{FOLDERID_ApplicationData}/OCamlPro/ocp-indent/config'"
   ] @
   IndentConfig.man
   @ [

src/indentConfig.ml

@@ -400,22 +400,24 @@ let rec find_conf_file path =
     if parent <> path then find_conf_file parent
     else None
 
+module App_id = struct
+  let qualifier = "com"
+  let organization = "OCamlPro"
+  let application = "ocp-indent"
+end
+
+module Project_dirs = Directories.Project_dirs (App_id)
+
 let local_default ?(path=Sys.getcwd()) () =
   let conf = default in
   let conf, syn, dlink =
-    try
-      let (/) = Filename.concat in
-      let xdg_path = ( match Sys.getenv "XDG_CONFIG_HOME" with
-          | "" -> (Sys.getenv "HOME") / ".config"
-          | exception Not_found -> (Sys.getenv "HOME") / ".config"
-          | x -> x ) / "ocp" / "ocp-indent.conf" in
-      if Sys.file_exists xdg_path
-      then load ~indent:conf xdg_path
-      else let legacy_path = (Sys.getenv "HOME") / ".ocp" / "ocp-indent.conf" in
-        if  Sys.file_exists legacy_path
-        then load ~indent:conf legacy_path
-        else conf, [], []
-    with Not_found -> conf, [], []
+    let default = conf, [], [] in
+    match Project_dirs.config_dir with
+    | None -> default
+    | Some config_dir ->
+      let config_path = Filename.concat config_dir "config" in
+      if Sys.file_exists config_path then load ~indent:conf config_path
+      else default
   in
   let conf, syn, dlink = match find_conf_file path with
     | Some c ->