1 files changed, 73 insertions, 3 deletions
diff --git a/src/rebar_prv_shell.erl b/src/rebar_prv_shell.erl
index c0cfd6d..dd3e6f6 100644
--- a/src/rebar_prv_shell.erl
+++ b/src/rebar_prv_shell.erl
@@ -36,6 +36,7 @@
          format_error/1]).
 
 -include("rebar.hrl").
+-include_lib("providers/include/providers.hrl").
 
 -define(PROVIDER, shell).
 -define(DEPS, [compile]).
@@ -503,7 +504,12 @@ find_config(State) ->
         no_value ->
             no_config;
         Filename when is_list(Filename) ->
-            rebar_file_utils:consult_config(State, Filename)
+            case is_src_config(Filename) of
+                false ->
+                    rebar_file_utils:consult_config(State, Filename);
+                true ->
+                    consult_env_config(State, Filename)
+            end
     end.
 
 -spec first_value([Fun], State) -> no_value | Value when
@@ -540,5 +546,69 @@ find_config_rebar(State) ->
 
 -spec find_config_relx(rebar_state:t()) -> [tuple()] | no_value.
 find_config_relx(State) ->
-    debug_get_value(sys_config, rebar_state:get(State, relx, []), no_value,
-                    "Found config from relx.").
+    %% The order in relx is to load the src version first;
+    %% we do the same.
+    RelxCfg = rebar_state:get(State, relx, []),
+    Src = debug_get_value(sys_config_src, RelxCfg, no_value,
+                          "Found config.src from relx."),
+    case Src of
+        no_value ->
+            debug_get_value(sys_config, RelxCfg, no_value,
+                            "Found config from relx.");
+        _ ->
+            Src
+    end.
+
+-spec is_src_config(file:filename()) -> boolean().
+is_src_config(Filename) ->
+    filename:extension(Filename) =:= ".src".
+
+-spec consult_env_config(rebar_state:t(), file:filename()) -> [[tuple()]].
+consult_env_config(State, Filename) ->
+    RawString = case file:read_file(Filename) of
+        {error, _} -> "[].";
+        {ok, Bin} -> unicode:characters_to_list(Bin)
+    end,
+    ReplacedStr = replace_env_vars(RawString),
+    case rebar_string:consult(unicode:characters_to_list(ReplacedStr)) of
+        {error, Reason} ->
+            throw(?PRV_ERROR({bad_term_file, Filename, Reason}));
+        [Terms] ->
+            rebar_file_utils:consult_config_terms(State, Terms)
+    end.
+
+%% @doc quick and simple variable substitution writeup.
+%% Supports `${varname}' but not `$varname' nor nested
+%% values such as `${my_${varname}}'.
+%% The variable are also defined as only supporting
+%% the form `[a-zA-Z_]+[a-zA-Z0-9_]*' as per the POSIX
+%% standard.
+-spec replace_env_vars(string()) -> unicode:charlist().
+replace_env_vars("") -> "";
+replace_env_vars("${" ++ Str) ->
+    case until_var_end(Str) of
+        {ok, VarName, Rest} ->
+            replace_varname(VarName) ++ replace_env_vars(Rest);
+        error ->
+            "${" ++ replace_env_vars(Str)
+    end;
+replace_env_vars([Char|Str]) ->
+    [Char | replace_env_vars(Str)].
+
+until_var_end(Str) ->
+    case re:run(Str, "([a-zA-Z_]+[a-zA-Z0-9_]*)}", [{capture, [1], list}]) of
+        nomatch ->
+            error;
+        {match, [Name]} ->
+            {ok, Name, drop_varname(Name, Str)}
+    end.
+
+replace_varname(Var) ->
+    %% os:getenv(Var, "") is only available in OTP-18.0
+    case os:getenv(Var) of
+        false -> "";
+        Val -> Val
+    end.
+
+drop_varname("", "}" ++ Str) -> Str;
+drop_varname([_|Var], [_|Str]) -> drop_varname(Var, Str).