if a provider of the same namespace and name already exists, skip adding new provider

rebar.config

@@ -1,13 +1,13 @@
 %% -*- mode: erlang;erlang-indent-level: 4;indent-tabs-mode: nil -*-
 %% ex: ts=4 sw=4 ft=erlang et
 
-{deps, [{erlware_commons,     "0.16.0"},
+{deps, [{erlware_commons,     "0.18.0"},
         {ssl_verify_hostname, "1.0.5"},
         {certifi,             "0.1.1"},
-        {providers,           "1.5.0"},
+        {providers,           "1.6.0"},
         {getopt,              "0.8.2"},
         {bbmustache,          "1.0.4"},
-        {relx,                "3.8.0"},
+        {relx,                "3.9.0"},
         {cf,                  "0.2.1"},
         {cth_readable,        "1.1.0"},
         {eunit_formatters,    "0.3.1"}]}.

rebar.lock

@@ -2,9 +2,9 @@
  {<<"certifi">>,{pkg,<<"certifi">>,<<"0.1.1">>},0},
  {<<"cf">>,{pkg,<<"cf">>,<<"0.2.1">>},0},
  {<<"cth_readable">>,{pkg,<<"cth_readable">>,<<"1.1.0">>},0},
- {<<"erlware_commons">>,{pkg,<<"erlware_commons">>,<<"0.16.0">>},0},
+ {<<"erlware_commons">>,{pkg,<<"erlware_commons">>,<<"0.18.0">>},0},
  {<<"eunit_formatters">>,{pkg,<<"eunit_formatters">>,<<"0.3.1">>},0},
  {<<"getopt">>,{pkg,<<"getopt">>,<<"0.8.2">>},0},
- {<<"providers">>,{pkg,<<"providers">>,<<"1.5.0">>},0},
- {<<"relx">>,{pkg,<<"relx">>,<<"3.8.0">>},0},
+ {<<"providers">>,{pkg,<<"providers">>,<<"1.6.0">>},0},
+ {<<"relx">>,{pkg,<<"relx">>,<<"3.9.0">>},0},
  {<<"ssl_verify_hostname">>,{pkg,<<"ssl_verify_hostname">>,<<"1.0.5">>},0}].

src/rebar.app.src

@@ -27,6 +27,7 @@
                   certifi,
                   cth_readable,
                   relx,
+                  cf,
                   inets,
                   eunit_formatters]},
   {env, [

src/rebar_state.erl

@@ -370,7 +370,24 @@ providers(State, NewProviders) ->
 
 -spec add_provider(t(), providers:t()) -> t().
 add_provider(State=#state_t{providers=Providers}, Provider) ->
-    State#state_t{providers=[Provider | Providers]}.
+    Name = providers:impl(Provider),
+    Namespace = providers:namespace(Provider),
+    Module = providers:module(Provider),
+    case lists:any(fun(P) ->
+                           case {providers:impl(P), providers:namespace(P)} of
+                               {Name, Namespace} ->
+                                   ?DEBUG("Not adding provider ~p ~p from module ~p because it already exists from module ~p",
+                                          [Namespace, Name, providers:module(P), Module]),
+                                   true;
+                               _ ->
+                                   false
+                           end
+                   end, Providers) of
+        true ->
+            State;
+        false ->
+            State#state_t{providers=[Provider | Providers]}
+    end.
 
 create_logic_providers(ProviderModules, State0) ->
     try