switch from loading modules to read compile info to using `beam_lib`

fixes #216 and #220

src/rebar_erlc_compiler.erl

@@ -256,24 +256,21 @@ needs_compile(Source, Target, Opts, Parents) ->
 
 source_changed(TargetLastMod, I) -> TargetLastMod < filelib:last_modified(I).
 
-opts_changed(Opts, Target) ->
-    Basename = filename:basename(Target, ".beam"),
-    Dirname = filename:dirname(Target),
-    ObjectFile = filename:join([Dirname, Basename]),
-    _ = purge(list_to_atom(Basename)),
-    case code:load_abs(ObjectFile) of
-        {module, Mod} ->
-            Compile = Mod:module_info(compile),
-            lists:sort(Opts) =/= lists:sort(proplists:get_value(options,
-                                                                Compile));
-        {error, nofile} -> false
+opts_changed(NewOpts, Target) ->
+    case compile_info(Target) of
+        {ok, Opts} -> lists:sort(Opts) =/= lists:sort(NewOpts);
+        _          -> true
     end.
 
-purge(Mod) ->
-    %% remove old code if necessary
-    _ = code:purge(Mod),
-    %% move current code to old
-    _ = code:delete(Mod).
+compile_info(Target) ->
+    case beam_lib:chunks(Target, [compile_info]) of
+        {ok, {_mod, Chunks}} ->
+            CompileInfo = proplists:get_value(compile_info, Chunks, []),
+            {ok, proplists:get_value(options, CompileInfo, [])};
+        {error, beam_lib, Reason} ->
+            ?WARN("Couldn't read debug info from ~p for reason: ~p", [Target, Reason]),
+            {error, Reason}
+    end.
 
 check_erlcinfo(_Config, #erlcinfo{vsn=?ERLCINFO_VSN}) ->
     ok;

src/rebar_otp_app.erl

@@ -166,23 +166,15 @@ ebin_modules(App, Dir) ->
     [rebar_utils:beam_to_mod(N) || N <- Filtered].
 
 beam_src(Beam) ->
-    try
-        Mod = list_to_atom(filename:basename(Beam, ".beam")),
-        _ = purge(Mod),
-        {module, Mod} = code:load_abs(filename:rootname(Beam, ".beam")),
-        Compile = Mod:module_info(compile),
-        proplists:get_value(source, Compile, [])
-    catch
-        error:undef -> [];
-        error:nofile -> []
+    case beam_lib:chunks(Beam, [compile_info]) of
+        {ok, {_mod, Chunks}} ->
+            CompileInfo = proplists:get_value(compile_info, Chunks, []),
+            proplists:get_value(source, CompileInfo, []);
+        {error, beam_lib, Reason} ->
+            ?WARN("Couldn't read debug info from ~p for reason: ~p", [Beam, Reason]),
+            []
     end.
 
-purge(Mod) ->
-    %% remove old code if necessary
-    _ = code:purge(Mod),
-    %% move current code to old
-    _ = code:delete(Mod).
-
 ensure_registered(AppData) ->
     case lists:keyfind(registered, 1, AppData) of
         false ->

test/rebar_compile_SUITE.erl

@@ -11,8 +11,7 @@
          build_checkout_deps/1,
          recompile_when_opts_change/1,
          dont_recompile_when_opts_dont_change/1,
-         dont_recompile_yrl_or_xrl/1,
-         purge_before_load/1]).
+         dont_recompile_yrl_or_xrl/1]).
 
 -include_lib("common_test/include/ct.hrl").
 -include_lib("eunit/include/eunit.hrl").
@@ -34,7 +33,7 @@ all() ->
     [build_basic_app, build_release_apps,
      build_checkout_apps, build_checkout_deps,
      recompile_when_opts_change, dont_recompile_when_opts_dont_change,
-     dont_recompile_yrl_or_xrl, purge_before_load].
+     dont_recompile_yrl_or_xrl].
 
 build_basic_app(Config) ->
     AppDir = ?config(apps, Config),
@@ -185,12 +184,3 @@ dont_recompile_yrl_or_xrl(Config) ->
 
     ?assert(ModTime == NewModTime).
 
-purge_before_load(Config) ->
-    AppDir = ?config(apps, Config),
-
-    Name = rebar_test_utils:create_random_name("app1_"),
-    Vsn = rebar_test_utils:create_random_vsn(),
-    rebar_test_utils:create_app(AppDir, Name, Vsn, [kernel, stdlib]),
-
-    Tasks = ["do", "compile,compile,compile"],
-    rebar_test_utils:run_and_check(Config, [], Tasks, {ok, [{app, Name}]}).

test/rebar_eunit_SUITE.erl

@@ -21,7 +21,7 @@ end_per_suite(_Config) ->
     ok.
 
 init_per_testcase(_, Config) ->
-    rebar_test_utils:init_rebar_state(Config).
+    rebar_test_utils:init_rebar_state(Config, "eunit_").
 
 all() ->
     [test_basic_app].
@@ -29,9 +29,9 @@ all() ->
 test_basic_app(Config) ->
     AppDir = ?config(apps, Config),
 
-    Name = rebar_test_utils:create_random_name("eunit_"),
+    Name = rebar_test_utils:create_random_name("basic_"),
     Vsn = rebar_test_utils:create_random_vsn(),
     rebar_test_utils:create_app(AppDir, Name, Vsn, [kernel, stdlib]),
-    
+
     RebarConfig = [{erl_opts, [{d, some_define}]}],
     rebar_test_utils:run_and_check(Config, RebarConfig, ["eunit"], {ok, [{app, Name}]}).