Apply suggestions from PR review

Suggested by @panglesd.

src/odoc/bin/main.ml

@@ -41,17 +41,17 @@ let convert_fpath =
 let convert_src_fpath =
   let parse inp =
     match Arg.(conv_parser file) inp with
-    | Ok s -> Result.Ok (Html_page.File (Fs.File.of_string s))
+    | Ok s -> Result.Ok (Html_page.Source.File (Fs.File.of_string s))
     | Error _ as e -> e
-  and print = Html_page.pp in
+  and print = Html_page.Source.pp in
   Arg.conv (parse, print)
 
 let convert_src_dir =
   let parse inp =
     match Arg.(conv_parser dir) inp with
-    | Ok s -> Result.Ok (Html_page.Root (Fs.File.of_string s))
+    | Ok s -> Result.Ok (Html_page.Source.Root (Fs.File.of_string s))
     | Error _ as e -> e
-  and print = Html_page.pp in
+  and print = Html_page.Source.pp in
   Arg.conv (parse, print)
 
 (** On top of the conversion 'string', split into segs. *)
@@ -743,8 +743,9 @@ module Odoc_html_args = struct
 
   let source_root =
     let doc =
-      "Source code root for the compilation unit. It must have been compiled \
-       with --source-parent passed."
+      "Source code root for the compilation unit. Used to find the source file \
+       from the value of --source-name it was compiled with. Incompatible with \
+       --source-file."
     in
     Arg.(
       value

src/odoc/html_page.ml

@@ -16,13 +16,17 @@
 
 open Odoc_model
 
-type source = File of Fpath.t | Root of Fpath.t
+module Source = struct
+  type t = File of Fpath.t | Root of Fpath.t
 
-let pp fmt = function
-  | File f -> Format.fprintf fmt "File: %a" Fpath.pp f
-  | Root f -> Format.fprintf fmt "File: %a" Fpath.pp f
+  let pp fmt = function
+    | File f -> Format.fprintf fmt "File: %a" Fpath.pp f
+    | Root f -> Format.fprintf fmt "File: %a" Fpath.pp f
 
-let to_string f = Format.asprintf "%a" pp f
+  let to_string f = Format.asprintf "%a" pp f
+end
+
+type source = Source.t
 
 type args = {
   html_config : Odoc_html.Config.t;
@@ -38,7 +42,7 @@ let source_documents source_info source ~syntax =
   | Some { Lang.Source_info.id; infos }, Some src -> (
       let file =
         match src with
-        | File f -> f
+        | Source.File f -> f
         | Root f ->
             let open Odoc_model.Paths.Identifier in
             let rec get_path_dir : SourceDir.t -> Fpath.t = function
@@ -78,7 +82,7 @@ let source_documents source_info source ~syntax =
         (Error.filename_only
            "--source argument is invalid on compilation unit that were not \
             compiled with --source-parent and --source-name"
-           (to_string src));
+           (Source.to_string src));
       []
   | None, None -> []
 

src/odoc/html_page.mli

@@ -16,9 +16,13 @@
 
 open Odoc_document
 
-type source = File of Fpath.t | Root of Fpath.t
+module Source : sig
+  type t = File of Fpath.t | Root of Fpath.t
 
-val pp : Format.formatter -> source -> unit
+  val pp : Format.formatter -> t -> unit
+end
+
+type source = Source.t
 
 type args = {
   html_config : Odoc_html.Config.t;