Add Dialyzer plugin

Build project-specific PLT
$ rebar build-plt

Check the PLT for consistency and rebuild it if it is not up-to-date
$ rebar check-plt

Analyze the code for discrepancies
$ rebar dialyze

Delete project-specific PLT
$ rebar delete-plt

Valid rebar.config options:
  %% Store PLT in ~/.rebar/plt (Default)
  {dialyzer_plt_location,shared}
  %% Store PLT locally inside the project in .rebar
  {dialyzer_plt_location,local}
  %% Store PLT in custom directory
  {dialyzer_plt_location,"custom_path"}
  {dialyzer_plt_extra_apps,[app1,app2]}
  {dialyzer_warnings,[unmatched_returns,error_handling]}

2 files changed, 244 insertions, 0 deletions

diff --git a/src/rebar.erl b/src/rebar.erl
index 2d356dd..9a5fc28 100644
--- a/src/rebar.erl
+++ b/src/rebar.erl
@@ -456,6 +456,12 @@ qc                                       Test QuickCheck properties
 
 xref                                     Run cross reference analysis
 
+dialyze                                  Analyze the code for discrepancies
+build-plt                                Build project-specific PLT
+check-plt                                Check the PLT for consistency and
+                                         rebuild it if it is not up-to-date
+delete-plt                               Delete project-specific PLT
+
 shell                                    Start a shell similar to
                                          'erl -pa ebin -pa deps/*/ebin'
 
@@ -527,7 +533,9 @@ filter_flags(Config, [Item | Rest], Commands) ->
 
 command_names() ->
     [
+     "build-plt",
      "check-deps",
+     "check-plt",
      "clean",
      "compile",
      "create",
@@ -535,7 +543,9 @@ command_names() ->
      "create-lib",
      "create-node",
      "ct",
+     "delete-plt",
      "delete-deps",
+     "dialyze",
      "doc",
      "eunit",
      "escriptize",
diff --git a/src/rebar_dialyzer.erl b/src/rebar_dialyzer.erl
new file mode 100644
index 0000000..5f0cb1e
--- /dev/null
+++ b/src/rebar_dialyzer.erl
@@ -0,0 +1,234 @@
+%% -*- erlang-indent-level: 4;indent-tabs-mode: nil -*-
+%% ex: ts=4 sw=4 et
+%% -------------------------------------------------------------------
+%%
+%% rebar: Erlang Build Tools
+%%
+%% Copyright (c) 2014-2015 Tuncer Ayaz
+%%
+%% Permission is hereby granted, free of charge, to any person obtaining a copy
+%% of this software and associated documentation files (the "Software"), to deal
+%% in the Software without restriction, including without limitation the rights
+%% to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+%% copies of the Software, and to permit persons to whom the Software is
+%% furnished to do so, subject to the following conditions:
+%%
+%% The above copyright notice and this permission notice shall be included in
+%% all copies or substantial portions of the Software.
+%%
+%% THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+%% IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+%% FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+%% AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+%% LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+%% OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+%% THE SOFTWARE.
+%% -------------------------------------------------------------------
+-module(rebar_dialyzer).
+
+-export([
+         dialyze/2,
+         'build-plt'/2,
+         'check-plt'/2,
+         'delete-plt'/2
+        ]).
+
+%% for internal use only
+-export([info/2]).
+
+-include("rebar.hrl").
+
+%% ===================================================================
+%% Public API
+%% ===================================================================
+
+dialyze(Config, AppFile) ->
+    {NewConfig, Plt} = plt(Config, AppFile),
+    ok = check_plt_existence(Plt),
+
+    Opts = [
+            {analysis_type, succ_typings},
+            %% http://erlang.org/pipermail/erlang-bugs/2015-February/004781.html
+            %% TODO: remove once the minimum required Erlang/OTP release
+            %% includes a Dialyzer version without the bug, or alternatively
+            %% add a config option to always check the PLT, as this may be
+            %% needed by some users.
+            {check_plt, false},
+            {init_plt, Plt},
+            {files_rec, ["ebin"]},
+            {warnings, warnings(Config)}
+           ],
+    ?DEBUG("dialyze opts:~n~p~n", [Opts]),
+    case run(Opts) of
+        [] ->
+            {ok, NewConfig};
+        Ws ->
+            print_warnings(Ws),
+            ?FAIL
+    end.
+
+'build-plt'(Config, AppFile) ->
+    {Config1, AppDirs} = app_dirs(Config, AppFile),
+    {NewConfig, Plt} = plt(Config1, AppFile),
+    Opts = [
+            {analysis_type, plt_build},
+            {output_plt, Plt},
+            {files_rec, AppDirs}
+           ],
+    ?DEBUG("build-plt opts:~n~p~n", [Opts]),
+    case run(Opts) of
+        [] ->
+            {ok, NewConfig};
+        Ws ->
+            %% As plt_build may raise warnings but still successfully
+            %% create the PLT, we cannot interpret this as failure,
+            %% and therefore all we can do is report warnings.
+            print_warnings(Ws)
+    end.
+
+'check-plt'(Config, AppFile) ->
+    {NewConfig, Plt} = plt(Config, AppFile),
+    ok = check_plt_existence(Plt),
+
+    Opts = [
+            {analysis_type, plt_check},
+            %% http://erlang.org/pipermail/erlang-bugs/2015-February/004781.html
+            %% Without this, the PLT will be checked twice.
+            %% TODO: remove once the minimum required Erlang/OTP release
+            %% includes a Dialyzer version without the bug.
+            {check_plt, false},
+            {init_plt, Plt}
+           ],
+    ?DEBUG("build-plt opts:~n~p~n", [Opts]),
+    case run(Opts) of
+        [] ->
+            {ok, NewConfig};
+        Ws ->
+            print_warnings(Ws),
+            ?FAIL
+    end.
+
+'delete-plt'(Config, AppFile) ->
+    {NewConfig, Plt} = plt(Config, AppFile),
+    ?DEBUG("Delete PLT '~s'~n", [Plt]),
+    ok = rebar_file_utils:delete_each([Plt]),
+    {ok, NewConfig}.
+
+%% ===================================================================
+%% Internal functions
+%% ===================================================================
+
+info(help, dialyze) ->
+    info_help("Analyze the code for discrepancies");
+info(help, 'build-plt') ->
+    info_help("Build project-specific PLT");
+info(help, 'check-plt') ->
+    info_help("Check the PLT for consistency and rebuild it if it"
+              " is not up-to-date");
+info(help, 'delete-plt') ->
+    info_help("Delete project-specific PLT").
+
+info_help(Description) ->
+    ?CONSOLE(
+       "~s.~n"
+       "~n"
+       "Valid rebar.config options:~n"
+       "  ~p~n"
+       "  ~p~n"
+       "  ~p~n"
+       "  ~p~n"
+       "  ~p~n",
+       [
+        Description,
+        {dialyzer_plt_location, shared},
+        {dialyzer_plt_location, local},
+        {dialyzer_plt_location, "custom_path"},
+        {dialyzer_plt_extra_apps, [app1, app2]},
+        {dialyzer_warnings, [unmatched_returns, error_handling]}
+       ]).
+
+plt(Config, AppFile) ->
+    PltDir = plt_dir(Config),
+    {NewConfig, RawAppName} = rebar_app_utils:app_name(Config, AppFile),
+    AppName = atom_to_list(RawAppName),
+    OtpRel = rebar_utils:otp_release(),
+    Plt = filename:join([PltDir, AppName ++ "_" ++ OtpRel ++ "_plt"]),
+    ok = filelib:ensure_dir(Plt),
+    {NewConfig, Plt}.
+
+plt_dir(Config) ->
+    Location = rebar_config:get_local(Config, dialyzer_plt_location, shared),
+    plt_dir1(Config, Location).
+
+plt_dir1(_Config, Location) when is_list(Location) ->
+    case filelib:is_dir(Location) of
+        false ->
+            ?ABORT("PLT directory does not exist: ~s~n", [Location]);
+        true ->
+            Location
+    end;
+plt_dir1(_Config, shared) ->
+    {ok, Home} = init:get_argument(home),
+    filename:join([Home, ".rebar", "plt"]);
+plt_dir1(Config, local) ->
+    BaseDir = rebar_utils:base_dir(Config),
+    filename:join([BaseDir, ".rebar"]).
+
+check_plt_existence(Plt) ->
+    case filelib:is_regular(Plt) of
+        true ->
+            ok;
+        false ->
+            ?ABORT("PLT '~s' does not exist.~n"
+                   "Please run 'rebar build-plt' first.~n", [Plt])
+    end.
+
+%% dialyzer:run/1 wrapper to gracefully fail in case of Dialyzer errors
+run(Opts) ->
+    try dialyzer:run(Opts) of
+        Ws -> Ws
+    catch
+        throw:{dialyzer_error, Reason} ->
+            ?ABORT("Dialyzer error:~n~s~n", [Reason])
+    end.
+
+warnings(Config) ->
+    rebar_config:get_local(Config, dialyzer_warnings, []).
+
+print_warnings(Ws) ->
+    lists:foreach(
+      fun(W) ->
+              ?CONSOLE("~s~n", [format_warning(W)])
+      end,
+      Ws).
+
+format_warning(W) ->
+    dialyzer:format_warning(W, fullpath).
+
+app_dirs(Config, AppFile) ->
+    {NewConfig, AppFileApps} = app_file_apps(Config, AppFile),
+    ?DEBUG("app file apps:~n~p~n", [AppFileApps]),
+    Deps = deps_apps(Config),
+    ?DEBUG("deps apps:~n~p~n", [Deps]),
+    ExtraApps = rebar_config:get_local(Config, dialyzer_plt_extra_apps, []),
+    ?DEBUG("extra apps:~n~p~n", [ExtraApps]),
+    %% erts is assumed, and has to be present unconditionally.
+    Erts = [erts],
+    Apps = ordsets:from_list(Erts ++ AppFileApps ++ Deps ++ ExtraApps),
+    AppDirs = [app_lib_dir(App) || App <- ordsets:to_list(Apps)],
+    ?DEBUG("app dirs:~n~p~n", [AppDirs]),
+    {NewConfig, AppDirs}.
+
+app_file_apps(Config, AppFile) ->
+    rebar_app_utils:app_applications(Config, AppFile).
+
+deps_apps(Config) ->
+    [element(1, Dep) || Dep <- rebar_config:get_local(Config, deps, [])].
+
+app_lib_dir(App) ->
+    case code:lib_dir(App, ebin) of
+        {error, _}=Err ->
+            ?ABORT("Failed to get ebin dir for app: ~p~n~p~n", [App, Err]);
+        Dir ->
+            Dir
+    end.