Introduce pluggable protocol buffer compilers

Make it possible for plug in alternative protocol buffer compilers.
The compilers are picked up based on if they export all of the
functions key/0, proto_compile/3, proto_clean/3 and proto_info/2.
The set of compiler modules to choose from, is fetched from the rebar
application environment, from the app_dir modules.

A new config option, {proto_compiler,Compiler}, specifies which of
the available protocol buffer compilers to use. The 'protobuffs'
compiler is now one such compiler (the only one), and it is also the
default, for backwards compatibility.

ebin/rebar.app

@@ -28,6 +28,7 @@
               rebar_neotoma_compiler,
               rebar_otp_app,
               rebar_port_compiler,
+              rebar_proto_compiler,
               rebar_protobuffs_compiler,
               rebar_qc,
               rebar_rel_utils,
@@ -67,6 +68,7 @@
          {modules, [
                     {app_dir, [
                                rebar_abnfc_compiler,
+                               rebar_proto_compiler,
                                rebar_protobuffs_compiler,
                                rebar_neotoma_compiler,
                                rebar_asn1_compiler,

rebar.config.sample

@@ -89,6 +89,12 @@
 %% Options for the ErlyDTL compiler
 {erlydtl_opts, []}.
 
+%% == Proto compiler ==
+{proto_compiler, protobuffs}.
+%% Available compilers for protocol buffer files (*.proto):
+%%   protobuffs  (default)
+
+
 %% == EUnit ==
 
 %% Options for eunit:test()

src/rebar_proto_compiler.erl

@@ -0,0 +1,144 @@
+%% -*- erlang-indent-level: 4;indent-tabs-mode: nil -*-
+%% ex: ts=4 sw=4 et
+%% -------------------------------------------------------------------
+%%
+%% rebar: Erlang Build Tools
+%%
+%% Copyright (c) 2014 Tomas Abrahamsson (tomas.abrahamsson@gmail.com)
+%%
+%% 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_proto_compiler).
+
+-export([compile/2,
+         clean/2]).
+
+%% for internal use only
+-export([info/2]).
+
+-include("rebar.hrl").
+
+-record(proto_compiler,
+        {key        :: atom(), % Corresponds to the {proto_compiler,Key}
+         module     :: atom()
+        }).
+
+%% ===================================================================
+%% Public API
+%% ===================================================================
+
+compile(Config, AppFile) ->
+    case rebar_utils:find_files("src", "^[^._].*\\.proto$") of
+        [] ->
+            ok;
+        Protos ->
+            %% Find a compiler for protocol buffers,
+            %% use that for compiling protocol buffers
+            CompilerModule = select_proto_compiler(Config),
+            CompilerModule:proto_compile(Config, AppFile, Protos)
+    end.
+
+clean(Config, AppFile) ->
+    %% Get a list of generated .beam and .hrl files and then delete them
+    Protos = rebar_utils:find_files("src", "^[^._].*\\.proto$"),
+    case Protos of
+        [] ->
+            ok;
+        _ ->
+            %% Ask the proto compiler to compile the .proto files.
+            CompilerModule = select_proto_compiler(Config),
+            CompilerModule:proto_clean(Config, AppFile, Protos)
+    end.
+
+%% ===================================================================
+%% Internal functions
+%% ===================================================================
+
+info(help, compile) ->
+    info_help("Build protocol buffer (*.proto) sources", compile);
+info(help, clean) ->
+    info_help("Delete protocol buffer (*.proto) build results", clean).
+
+info_help(GeneralDescr, Cmd) ->
+    ?CONSOLE(
+       "~s.~n"
+       ++ "~n"
+       ++ "Valid rebar.config options:~n"
+       ++ "  {proto_compiler, Compiler}~n"
+       ++ "The following protocol buffer compilers are available:~n"
+       ++ "~s~n",
+       [GeneralDescr, format_proto_compiler_list()]),
+    %% Print info for each proto compiler
+    [begin
+         ?CONSOLE("--- ~p ---~n", [Key]),
+         CompilerModule:proto_info(help, Cmd)
+     end
+     || #proto_compiler{key=Key,
+                        module=CompilerModule} <- find_proto_compilers()],
+    ok.
+
+get_default_compiler() ->
+    protobuffs.
+
+find_proto_compilers() ->
+    {ok, RebarModuleGroups} = application:get_env(rebar, modules),
+    {app_dir, Modules} = lists:keyfind(app_dir, 1, RebarModuleGroups),
+    [#proto_compiler{key = M:key(),
+                     module = M}
+     || M <- Modules,
+        is_proto_compiler_module(M)].
+
+is_proto_compiler_module(Module) ->
+    case code:ensure_loaded(Module) of
+        {module, Module} ->
+            lists:all(fun({Function, Arity}) ->
+                              erlang:function_exported(Module, Function, Arity)
+                      end,
+                      [{key, 0},
+                       {proto_compile, 3},
+                       {proto_clean, 3},
+                       {proto_info, 2}]);
+        _ ->
+            false
+    end.
+
+select_proto_compiler(Config) ->
+    Default = get_default_compiler(),
+    Key = rebar_config:get_local(Config, proto_compiler, Default),
+    AvailCompilers = find_proto_compilers(),
+    case lists:keyfind(Key, #proto_compiler.key, AvailCompilers) of
+        #proto_compiler{module=CompilerModule} ->
+            CompilerModule;
+        false ->
+            ?ABORT("No such protocol buffer compiler known, '~s'~n"
+                   ++ "The following are known:~n"
+                   ++ "~s~n",
+                   [Key, format_proto_compiler_list()])
+    end.
+
+format_proto_compiler_list() ->
+    Default = get_default_compiler(),
+    Keys = [Key || #proto_compiler{key=Key} <- find_proto_compilers()],
+    Annotations = [if Key == Default -> " (default)";
+                      true -> ""
+                   end
+                   || Key <- Keys],
+    lists:flatten(
+      [?FMT("  ~p~s~n", [Key, Annotation])
+       || {Key, Annotation} <- lists:zip(Keys, Annotations)]).

src/rebar_protobuffs_compiler.erl

@@ -26,11 +26,12 @@
 %% -------------------------------------------------------------------
 -module(rebar_protobuffs_compiler).
 
--export([compile/2,
-         clean/2]).
+-export([key/0,
+         proto_compile/3,
+         proto_clean/3]).
 
 %% for internal use only
--export([info/2]).
+-export([proto_info/2]).
 
 -include("rebar.hrl").
 
@@ -38,58 +39,48 @@
 %% Public API
 %% ===================================================================
 
-compile(Config, _AppFile) ->
-    case rebar_utils:find_files("src", "^[^._].*\\.proto$") of
-        [] ->
-            ok;
-        FoundFiles ->
-            %% Check for protobuffs library -- if it's not present, fail
-            %% since we have.proto files that need building
-            case protobuffs_is_present() of
-                true ->
-                    %% Build a list of output files - { Proto, Beam, Hrl }
-                    Targets = [{Proto, beam_file(Proto), hrl_file(Proto)} ||
-                                  Proto <- FoundFiles],
+key() ->
+    protobuffs.
 
-                    %% Compile each proto file
-                    compile_each(Config, Targets);
-                false ->
-                    ?ERROR("Protobuffs library not present in code path!\n",
-                           []),
-                    ?FAIL
-            end
+proto_compile(Config, _AppFile, ProtoFiles) ->
+    %% Check for protobuffs library -- if it's not present, fail
+    %% since we have.proto files that need building
+    case protobuffs_is_present() of
+        true ->
+            %% Build a list of output files - { Proto, Beam, Hrl }
+            Targets = [{Proto, beam_file(Proto), hrl_file(Proto)} ||
+                          Proto <- ProtoFiles],
+
+            %% Compile each proto file
+            compile_each(Config, Targets);
+        false ->
+            ?ERROR("Protobuffs library not present in code path!\n",
+                   []),
+            ?FAIL
     end.
 
-clean(_Config, _AppFile) ->
+proto_clean(_Config, _AppFile, ProtoFiles) ->
     %% Get a list of generated .beam and .hrl files and then delete them
-    Protos = rebar_utils:find_files("src", ".*\\.proto$"),
-    BeamFiles = [fq_beam_file(F) || F <- Protos],
-    HrlFiles = [fq_hrl_file(F) || F <- Protos],
+    BeamFiles = [fq_beam_file(F) || F <- ProtoFiles],
+    HrlFiles = [fq_hrl_file(F) || F <- ProtoFiles],
     Targets = BeamFiles ++ HrlFiles,
-    case Targets of
-        [] ->
-            ok;
-        _ ->
-            delete_each(Targets)
-    end.
+    delete_each(Targets).
 
 %% ===================================================================
 %% Internal functions
 %% ===================================================================
 
-info(help, compile) ->
-    info_help("Build Protobuffs (*.proto) sources");
-info(help, clean) ->
-    info_help("Delete Protobuffs (*.proto) build results").
+proto_info(help, compile) ->
+    info_help();
+proto_info(help, clean) ->
+    info_help().
 
-info_help(Description) ->
+info_help() ->
     ?CONSOLE(
-       "~s.~n"
-       "~n"
        "Valid rebar.config options:~n"
        "  erl_opts is passed as compile_flags to "
        "protobuffs_compile:scan_file/2~n",
-       [Description]).
+       []).
 
 protobuffs_is_present() ->
     code:which(protobuffs_compile) =/= non_existing.