Extract code path formatting out of compiler

This allows to reuse the code for any provider that formats source files
out to the user.

The option to configure it does remain compiler-centric for backwards
compatibility

src/rebar.hrl

@@ -27,6 +27,7 @@
 -define(REMOTE_PACKAGE_DIR, "tarballs").
 -define(REMOTE_REGISTRY_FILE, "registry.ets.gz").
 -define(LOCK_FILE, "rebar.lock").
+-define(DEFAULT_COMPILER_SOURCE_FORMAT, relative).
 
 -define(PACKAGE_INDEX_VERSION, 3).
 -define(PACKAGE_TABLE, package_index).

src/rebar_base_compiler.erl

@@ -35,7 +35,6 @@
          error_tuple/4,
          format_error_source/2]).
 
--define(DEFAULT_COMPILER_SOURCE_FORMAT, relative).
 -type desc() :: term().
 -type loc() :: {line(), col()} | line().
 -type line() :: integer().
@@ -138,28 +137,7 @@ error_tuple(Source, Es, Ws, Opts) ->
 -spec format_error_source(file:filename(), rebar_dict() | [{_,_}]) ->
     file:filename().
 format_error_source(Path, Opts) ->
-    Type = case rebar_opts:get(Opts, compiler_source_format,
-                               ?DEFAULT_COMPILER_SOURCE_FORMAT) of
-        V when V == absolute; V == relative; V == build ->
-            V;
-        Other ->
-            ?WARN("Invalid argument ~p for compiler_source_format - "
-                  "assuming ~s~n", [Other, ?DEFAULT_COMPILER_SOURCE_FORMAT]),
-            ?DEFAULT_COMPILER_SOURCE_FORMAT
-    end,
-    case Type of
-        absolute -> resolve_linked_source(Path);
-        build -> Path;
-        relative ->
-            Cwd = rebar_dir:get_cwd(),
-            rebar_dir:make_relative_path(resolve_linked_source(Path), Cwd)
-    end.
-
-%% @private takes a filename and canonicalizes its path if it is a link.
--spec resolve_linked_source(file:filename()) -> file:filename().
-resolve_linked_source(Src) ->
-    {Dir, Base} = rebar_file_utils:split_dirname(Src),
-    filename:join(rebar_file_utils:resolve_link(Dir), Base).
+    rebar_dir:format_source_file_name(Path, Opts).
 
 %% ===================================================================
 %% Internal functions

src/rebar_dir.erl

@@ -26,7 +26,8 @@
          src_dir_opts/2, recursive/2,
          extra_src_dirs/1, extra_src_dirs/2,
          all_src_dirs/1, all_src_dirs/3,
-         retarget_path/2]).
+         retarget_path/2,
+         format_source_file_name/2]).
 
 -include("rebar.hrl").
 
@@ -334,3 +335,39 @@ retarget_path(State, Path, [App|Rest]) ->
         {ok, NewPath}      -> filename:join([rebar_app_info:out_dir(App), NewPath]);
         {error, badparent} -> retarget_path(State, Path, Rest)
     end.
+
+format_source_file_name(Path, Opts) ->
+    Type = case rebar_opts:get(Opts, compiler_source_format,
+                               ?DEFAULT_COMPILER_SOURCE_FORMAT) of
+        V when V == absolute; V == relative; V == build ->
+            V;
+        Other ->
+            warn_source_format_once(Other)
+    end,
+    case Type of
+        absolute -> resolve_linked_source(Path);
+        build -> Path;
+        relative ->
+            Cwd = rebar_dir:get_cwd(),
+            rebar_dir:make_relative_path(resolve_linked_source(Path), Cwd)
+    end.
+
+%% @private displays a warning for the compiler source format option
+%% only once
+-spec warn_source_format_once(term()) -> ok.
+warn_source_format_once(Format) ->
+    Warn = application:get_env(rebar, warn_source_format) =/= {ok, false},
+    application:set_env(rebar, warn_source_format, false),
+    case Warn of
+        false ->
+            ok;
+        true ->
+            ?WARN("Invalid argument ~p for compiler_source_format - "
+                  "assuming ~s~n", [Format, ?DEFAULT_COMPILER_SOURCE_FORMAT])
+    end.
+
+%% @private takes a filename and canonicalizes its path if it is a link.
+-spec resolve_linked_source(file:filename()) -> file:filename().
+resolve_linked_source(Src) ->
+    {Dir, Base} = rebar_file_utils:split_dirname(Src),
+    filename:join(rebar_file_utils:resolve_link(Dir), Base).