add option to compiler provider to only build dependencies

src/rebar_prv_compile.erl

@@ -30,22 +30,41 @@ init(State) ->
                                                                {example, "rebar3 compile"},
                                                                {short_desc, "Compile apps .app.src and .erl files."},
                                                                {desc, "Compile apps .app.src and .erl files."},
-                                                               {opts, []}])),
+                                                               {opts, [{deps_only, $d, "deps_only", undefined,
+                                                                        "Only compile dependencies, no project apps will be built."}]}])),
     {ok, State1}.
 
 -spec do(rebar_state:t()) -> {ok, rebar_state:t()} | {error, string()}.
 do(State) ->
+    IsDepsOnly = is_deps_only(State),
     DepsPaths = rebar_state:code_paths(State, all_deps),
     PluginDepsPaths = rebar_state:code_paths(State, all_plugin_deps),
     rebar_utils:remove_from_code_path(PluginDepsPaths),
     code:add_pathsa(DepsPaths),
 
-    ProjectApps = rebar_state:project_apps(State),
     Providers = rebar_state:providers(State),
     Deps = rebar_state:deps_to_build(State),
-    Cwd = rebar_state:dir(State),
-
     copy_and_build_apps(State, Providers, Deps),
+
+    State1 = case IsDepsOnly of
+                 true ->
+                     State;
+                 false ->
+                     handle_project_apps(DepsPaths, Providers, State)
+             end,
+
+    rebar_utils:cleanup_code_path(rebar_state:code_paths(State1, default)
+                                  ++ rebar_state:code_paths(State, all_plugin_deps)),
+
+    {ok, State1}.
+
+is_deps_only(State) ->
+    {Args, _} = rebar_state:command_parsed_args(State),
+    proplists:get_value(deps_only, Args, false).
+
+handle_project_apps(DepsPaths, Providers, State) ->
+    Cwd = rebar_state:dir(State),
+    ProjectApps = rebar_state:project_apps(State),
     {ok, ProjectApps1} = rebar_digraph:compile_order(ProjectApps),
 
     %% Run top level hooks *before* project apps compiled but *after* deps are
@@ -66,10 +85,9 @@ do(State) ->
         true ->
             true
     end,
-    rebar_utils:cleanup_code_path(rebar_state:code_paths(State3, default)
-                                 ++ rebar_state:code_paths(State, all_plugin_deps)),
 
-    {ok, State3}.
+    State3.
+
 
 -spec format_error(any()) -> iolist().
 format_error({missing_artifact, File}) ->

test/rebar_compile_SUITE.erl

@@ -23,7 +23,7 @@ all() ->
      deps_in_path, checkout_priority, highest_version_of_pkg_dep,
      parse_transform_test, erl_first_files_test, mib_test,
      umbrella_mib_first_test, only_default_transitive_deps, clean_all,
-     profile_deps, deps_build_in_prod,
+     profile_deps, deps_build_in_prod, only_deps,
      override_deps, override_add_deps, override_del_deps,
      override_opts, override_add_opts, override_del_opts,
      apply_overrides_exactly_once,
@@ -1655,6 +1655,25 @@ profile_deps(Config) ->
         {ok, [{dep, "some_dep"},{dep, "other_dep"}]}
     ).
 
+only_deps(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]),
+
+    Deps = rebar_test_utils:expand_deps(git, [{"some_dep", "0.0.1", [{"other_dep", "0.0.1", []}]}]),
+    TopDeps = rebar_test_utils:top_level_deps(Deps),
+    {SrcDeps, _} = rebar_test_utils:flat_deps(Deps),
+    mock_git_resource:mock([{deps, SrcDeps}]),
+
+    RConfFile = rebar_test_utils:create_config(AppDir, [{deps, TopDeps}]),
+    {ok, RConf} = file:consult(RConfFile),
+    rebar_test_utils:run_and_check(
+        Config, RConf, ["compile", "--deps_only"],
+        {ok, [{app_not_exist, Name}, {dep, "some_dep"},{dep, "other_dep"}]}
+    ).
+
 %% verify a deps prod profile is used
 %% tested by checking prod hooks run and outputs to default profile dir for dep
 %% and prod deps are installed for dep

test/rebar_test_utils.erl

@@ -266,6 +266,14 @@ check_results(AppDir, Expected, ProfileRun) ->
                         ok
                 end
         ; ({dep_not_exist, Name}) ->
+                ct:pal("Dep Not Exist Name: ~p", [Name]),
+                case lists:keyfind(Name, 1, DepsNames) of
+                    false ->
+                        ok;
+                    {Name, _App} ->
+                        error({app_found, Name})
+                end
+        ; ({app_not_exist, Name}) ->
                 ct:pal("App Not Exist Name: ~p", [Name]),
                 case lists:keyfind(Name, 1, DepsNames) of
                     false ->