Merge pull request #23 from ericbmerritt/next

support release discovery in relcool along with app discovery

6 files changed, 470 insertions, 218 deletions

diff --git a/src/rcl_app_discovery.erl b/src/rcl_app_discovery.erl
new file mode 100644
index 0000000..20df1cf
--- /dev/null
+++ b/src/rcl_app_discovery.erl
@@ -0,0 +1,223 @@
+%% -*- erlang-indent-level: 4; indent-tabs-mode: nil; fill-column: 80 -*-
+%%% Copyright 2012 Erlware, LLC. All Rights Reserved.
+%%%
+%%% This file is provided to you under the Apache License,
+%%% Version 2.0 (the "License"); you may not use this file
+%%% except in compliance with the License.  You may obtain
+%%% a copy of the License at
+%%%
+%%%   http://www.apache.org/licenses/LICENSE-2.0
+%%%
+%%% Unless required by applicable law or agreed to in writing,
+%%% software distributed under the License is distributed on an
+%%% "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+%%% KIND, either express or implied.  See the License for the
+%%% specific language governing permissions and limitations
+%%% under the License.
+%%%---------------------------------------------------------------------------
+%%% @author Eric Merritt <[email protected]>
+%%% @copyright (C) 2012 Erlware, LLC.
+%%%
+%%% @doc This provider uses the lib_dir setting of the state. It searches the
+%%% Lib Dirs looking for all OTP Applications that are available. When it finds
+%%% those OTP Applications it loads the information about them and adds them to
+%%% the state of available apps. This implements the rcl_provider behaviour.
+-module(rcl_app_discovery).
+
+-export([do/2,
+         format_error/1]).
+
+-include_lib("relcool/include/relcool.hrl").
+
+%%============================================================================
+%% API
+%%============================================================================
+
+%% @doc recursively dig down into the library directories specified in the state
+%% looking for OTP Applications
+-spec do(rcl_state:t(), [filename:name()]) -> {ok, [rcl_app_info:t()]} | relcool:error().
+do(State, LibDirs) ->
+    rcl_log:info(rcl_state:log(State),
+                 fun() ->
+                          ["Resolving OTP Applications from directories:\n",
+                           [[rcl_util:indent(1), LibDir, "\n"] || LibDir <- LibDirs]]
+                 end),
+    resolve_app_metadata(State, LibDirs).
+
+-spec format_error([ErrorDetail::term()]) -> iolist().
+format_error(ErrorDetails)
+  when erlang:is_list(ErrorDetails) ->
+    [[format_detail(ErrorDetail), "\n"] || ErrorDetail <- ErrorDetails].
+
+%%%===================================================================
+%%% Internal Functions
+%%%===================================================================
+resolve_app_metadata(State, LibDirs) ->
+    AppMeta0 = lists:flatten(ec_plists:map(fun(LibDir) ->
+                                               discover_dir([], LibDir)
+                                           end, LibDirs)),
+    AppMeta1 = setup_overrides(State, AppMeta0),
+
+    Errors = [case El of
+                  {error, Ret} -> Ret;
+                  _ -> El
+              end
+              || El <- AppMeta1,
+                 case El of
+                     {error, _} ->
+                         true;
+                     _ ->
+                         false
+                 end],
+
+    case Errors of
+        [] ->
+            AppMeta2 = lists:flatten(AppMeta1),
+            rcl_log:debug(rcl_state:log(State),
+                          fun() ->
+                                  ["Resolved the following OTP Applications from the system: \n",
+                                   [[rcl_app_info:format(1, App), "\n"] || App <- AppMeta2]]
+                          end),
+            {ok, AppMeta2};
+        _ ->
+            ?RCL_ERROR(Errors)
+    end.
+
+app_name({error, _}) ->
+    undefined;
+app_name(AppMeta) ->
+    rcl_app_info:name(AppMeta).
+
+setup_overrides(State, AppMetas0) ->
+    Overrides = rcl_state:overrides(State),
+    AppMetas1 = [AppMeta || AppMeta <- AppMetas0,
+                            not lists:keymember(app_name(AppMeta), 1, Overrides)],
+    [case is_valid_otp_app(filename:join([FileName, "ebin",
+                                         erlang:atom_to_list(AppName) ++ ".app"])) of
+         [] ->
+             {error, {invalid_override, AppName, FileName}};
+         Error = {error, _} ->
+             Error;
+         App ->
+             rcl_app_info:link(App, true)
+     end || {AppName, FileName} <- Overrides] ++ AppMetas1.
+
+
+
+-spec format_detail(ErrorDetail::term()) -> iolist().
+format_detail({error, {invalid_override, AppName, FileName}}) ->
+    io_lib:format("Override {~p, ~p} is not a valid OTP App. Perhaps you forgot to build it?",
+                  [AppName, FileName]);
+format_detail({accessing, File, eaccess}) ->
+    io_lib:format("permission denied accessing file ~s", [File]);
+format_detail({accessing, File, Type}) ->
+    io_lib:format("error (~p) accessing file ~s", [Type, File]);
+format_detail({no_beam_files, EbinDir}) ->
+    io_lib:format("no beam files found in directory ~s", [EbinDir]);
+format_detail({not_a_directory, EbinDir}) ->
+    io_lib:format("~s is not a directory when it should be a directory", [EbinDir]);
+format_detail({unable_to_load_app, AppDir, _}) ->
+    io_lib:format("Unable to load the application metadata from ~s", [AppDir]);
+format_detail({invalid_app_file, File}) ->
+    io_lib:format("Application metadata file exists but is malformed: ~s",
+                  [File]);
+format_detail({unversioned_app, AppDir, _AppName}) ->
+    io_lib:format("Application metadata exists but version is not available: ~s",
+                  [AppDir]);
+format_detail({app_info_error, {Module, Detail}}) ->
+    Module:format_error(Detail).
+
+-spec discover_dir([file:name()],
+                   file:name()) ->
+                          [rcl_app_info:t() | {error, Reason::term()}] |
+                          rcl_app_info:t() | {error, Reason::term()}.
+discover_dir(IgnoreDirs, File) ->
+    case (not lists:member(File, IgnoreDirs))
+        andalso filelib:is_dir(File) of
+        true ->
+            case file:list_dir(File) of
+                {error, Reason} ->
+                    {error, {accessing, File, Reason}};
+                {ok, List} ->
+                    ec_plists:map(fun(LibDir) ->
+                                     discover_dir(IgnoreDirs, LibDir)
+                                  end, [filename:join([File, Dir]) || Dir <- List])
+            end;
+        false ->
+            is_valid_otp_app(File)
+    end.
+
+-spec is_valid_otp_app(file:name()) -> rcl_app_info:t() | {error, Reason::term()} | [].
+is_valid_otp_app(File) ->
+    %% Is this an ebin dir?
+    EbinDir = filename:dirname(File),
+    case filename:basename(EbinDir) of
+        "ebin" ->
+            case lists:suffix(".app", File) of
+                true ->
+                    has_at_least_one_beam(EbinDir, File);
+                false ->
+                    []
+            end;
+        _ ->
+            []
+    end.
+
+-spec has_at_least_one_beam(file:name(), file:filename()) ->
+                                   rcl_app_info:t() | {error, Reason::term()}.
+has_at_least_one_beam(EbinDir, File) ->
+    case file:list_dir(EbinDir) of
+        {ok, List} ->
+            case lists:any(fun(NFile) -> lists:suffix(".beam", NFile) end, List) of
+                true ->
+                    gather_application_info(EbinDir, File);
+                false ->
+                    {error, {no_beam_files, EbinDir}}
+            end;
+        _ ->
+            {error, {not_a_directory, EbinDir}}
+    end.
+
+-spec gather_application_info(file:name(), file:filename()) ->
+                                     rcl_app_info:t() | {error, Reason::term()}.
+gather_application_info(EbinDir, File) ->
+    AppDir = filename:dirname(EbinDir),
+    case file:consult(File) of
+        {ok, [{application, AppName, AppDetail}]} ->
+            get_vsn(AppDir, AppName, AppDetail);
+        {error, Reason} ->
+            {error, {unable_to_load_app, AppDir, Reason}};
+        _ ->
+            {error, {invalid_app_file, File}}
+    end.
+
+-spec get_vsn(file:name(), atom(), proplists:proplist()) ->
+                     rcl_app_info:t() | {error, Reason::term()}.
+get_vsn(AppDir, AppName, AppDetail) ->
+    case proplists:get_value(vsn, AppDetail) of
+        undefined ->
+            {error, {unversioned_app, AppDir, AppName}};
+        AppVsn ->
+            case get_deps(AppDir, AppName, AppVsn, AppDetail) of
+                {ok, App} ->
+                    App;
+                {error, Detail} ->
+                    {error, {app_info_error, Detail}}
+            end
+    end.
+
+-spec get_deps(file:name(), atom(), string(), proplists:proplist()) ->
+                      {ok, rcl_app_info:t()} | {error, Reason::term()}.
+get_deps(AppDir, AppName, AppVsn, AppDetail) ->
+    ActiveApps = proplists:get_value(applications, AppDetail, []),
+    LibraryApps = proplists:get_value(included_applications, AppDetail, []),
+    rcl_app_info:new(AppName, AppVsn, AppDir, ActiveApps, LibraryApps).
+
+%%%===================================================================
+%%% Test Functions
+%%%===================================================================
+
+-ifndef(NOTEST).
+-include_lib("eunit/include/eunit.hrl").
+
+-endif.
diff --git a/src/rcl_depsolver.erl b/src/rcl_depsolver.erl
index e74cf3b..0cf8c88 100644
--- a/src/rcl_depsolver.erl
+++ b/src/rcl_depsolver.erl
@@ -471,12 +471,13 @@ add_constraint(SrcPkg, SrcVsn, PkgsConstraints, PkgConstraint) ->
             {value, {PkgName, Constraints0}} ->
                 Constraints0
         end,
-    [{PkgName, [{PkgConstraint, {SrcPkg, SrcVsn}} | Constraints1]} |
-     lists:keydelete(PkgName, 1, PkgsConstraints)].
+    [{PkgName, [{PkgConstraint, {SrcPkg, SrcVsn}} | Constraints1]}
+    | lists:keydelete(PkgName, 1, PkgsConstraints)].
 
 %% @doc
 %% Extend the currently active constraints correctly for the given constraints.
--spec extend_constraints(pkg_name(), vsn(), constraints(),constraints()) -> [{pkg_name(), constraints()}].
+-spec extend_constraints(pkg_name(), vsn(), constraints(),constraints()) ->
+                                [{pkg_name(), constraints()}].
 extend_constraints(SrcPkg, SrcVsn, ExistingConstraints0, NewConstraints) ->
     lists:foldl(fun (Constraint, ExistingConstraints1) ->
                         add_constraint(SrcPkg, SrcVsn, ExistingConstraints1, Constraint)
diff --git a/src/rcl_prv_discover.erl b/src/rcl_prv_discover.erl
index 862bd6e..c5a625d 100644
--- a/src/rcl_prv_discover.erl
+++ b/src/rcl_prv_discover.erl
@@ -41,73 +41,33 @@ init(State) ->
 %% @doc recursively dig down into the library directories specified in the state
 %% looking for OTP Applications
 -spec do(rcl_state:t()) -> {ok, rcl_state:t()} | relcool:error().
-do(State) ->
-    LibDirs = get_lib_dirs(State),
-    rcl_log:info(rcl_state:log(State),
-                  fun() ->
-                          ["Resolving OTP Applications from directories:\n",
-                           [[rcl_util:indent(1), LibDir, "\n"] || LibDir <- LibDirs]]
-                  end),
-    resolve_app_metadata(State, LibDirs).
+do(State0) ->
+    LibDirs = get_lib_dirs(State0),
+    case rcl_app_discovery:do(State0, LibDirs) of
+        {ok, AppMeta} ->
+            case rcl_rel_discovery:do(State0, LibDirs, AppMeta) of
+                {ok, Releases} ->
+                    State1 = rcl_state:available_apps(State0, AppMeta),
+                    State3 = lists:foldl(fun(Rel, State2) ->
+                                                 rcl_state:add_release(State2, Rel)
+                                         end, State1, Releases),
+                    {ok, State3};
+                Error ->
+                    Error
+            end;
+        Error ->
+            Error
+    end.
 
--spec format_error([ErrorDetail::term()]) -> iolist().
-format_error(ErrorDetails)
-  when erlang:is_list(ErrorDetails) ->
-    [[format_detail(ErrorDetail), "\n"] || ErrorDetail <- ErrorDetails].
+%% @doc this is here to comply with the signature. However, we do not actually
+%% produce any errors and so simply return an empty string.
+-spec format_error(any()) -> iolist().
+format_error(_) ->
+    "".
 
 %%%===================================================================
 %%% Internal Functions
 %%%===================================================================
-resolve_app_metadata(State, LibDirs) ->
-    AppMeta0 = lists:flatten(ec_plists:map(fun(LibDir) ->
-                                               discover_dir([], LibDir)
-                                           end, LibDirs)),
-    AppMeta1 = setup_overrides(State, AppMeta0),
-
-    Errors = [case El of
-                  {error, Ret} -> Ret;
-                  _ -> El
-              end
-              || El <- AppMeta1,
-                 case El of
-                     {error, _} ->
-                         true;
-                     _ ->
-                         false
-                 end],
-
-    case Errors of
-        [] ->
-            AppMeta2 = lists:flatten(AppMeta1),
-            rcl_log:debug(rcl_state:log(State),
-                          fun() ->
-                                  ["Resolved the following OTP Applications from the system: \n",
-                                   [[rcl_app_info:format(1, App), "\n"] || App <- AppMeta2]]
-                          end),
-            {ok, rcl_state:available_apps(State, AppMeta2)};
-        _ ->
-            ?RCL_ERROR(Errors)
-    end.
-
-app_name({error, _}) ->
-    undefined;
-app_name(AppMeta) ->
-    rcl_app_info:name(AppMeta).
-
-setup_overrides(State, AppMetas0) ->
-    Overrides = rcl_state:overrides(State),
-    AppMetas1 = [AppMeta || AppMeta <- AppMetas0,
-                            not lists:keymember(app_name(AppMeta), 1, Overrides)],
-    [case is_valid_otp_app(filename:join([FileName, "ebin",
-                                         erlang:atom_to_list(AppName) ++ ".app"])) of
-         [] ->
-             {error, {invalid_override, AppName, FileName}};
-         Error = {error, _} ->
-             Error;
-         App ->
-             rcl_app_info:link(App, true)
-     end || {AppName, FileName} <- Overrides] ++ AppMetas1.
-
 get_lib_dirs(State) ->
     LibDirs0 = rcl_state:lib_dirs(State),
     case rcl_state:get(State, disable_default_libs, false) of
@@ -140,121 +100,3 @@ add_system_lib_dir(State, LibDirs) ->
                     LibDirs
             end
     end.
-
--spec format_detail(ErrorDetail::term()) -> iolist().
-format_detail({error, {invalid_override, AppName, FileName}}) ->
-    io_lib:format("Override {~p, ~p} is not a valid OTP App. Perhaps you forgot to build it?",
-                  [AppName, FileName]);
-format_detail({accessing, File, eaccess}) ->
-    io_lib:format("permission denied accessing file ~s", [File]);
-format_detail({accessing, File, Type}) ->
-    io_lib:format("error (~p) accessing file ~s", [Type, File]);
-format_detail({no_beam_files, EbinDir}) ->
-    io_lib:format("no beam files found in directory ~s", [EbinDir]);
-format_detail({not_a_directory, EbinDir}) ->
-    io_lib:format("~s is not a directory when it should be a directory", [EbinDir]);
-format_detail({unable_to_load_app, AppDir, _}) ->
-    io_lib:format("Unable to load the application metadata from ~s", [AppDir]);
-format_detail({invalid_app_file, File}) ->
-    io_lib:format("Application metadata file exists but is malformed: ~s",
-                  [File]);
-format_detail({unversioned_app, AppDir, _AppName}) ->
-    io_lib:format("Application metadata exists but version is not available: ~s",
-                  [AppDir]);
-format_detail({app_info_error, {Module, Detail}}) ->
-    Module:format_error(Detail).
-
--spec discover_dir([file:name()],
-                   file:name()) ->
-                          [rcl_app_info:t() | {error, Reason::term()}] |
-                          rcl_app_info:t() | {error, Reason::term()}.
-discover_dir(IgnoreDirs, File) ->
-    case (not lists:member(File, IgnoreDirs))
-        andalso filelib:is_dir(File) of
-        true ->
-            case file:list_dir(File) of
-                {error, Reason} ->
-                    {error, {accessing, File, Reason}};
-                {ok, List} ->
-                    ec_plists:map(fun(LibDir) ->
-                                     discover_dir(IgnoreDirs, LibDir)
-                                  end, [filename:join([File, Dir]) || Dir <- List])
-            end;
-        false ->
-            is_valid_otp_app(File)
-    end.
-
--spec is_valid_otp_app(file:name()) -> rcl_app_info:t() | {error, Reason::term()} | [].
-is_valid_otp_app(File) ->
-    %% Is this an ebin dir?
-    EbinDir = filename:dirname(File),
-    case filename:basename(EbinDir) of
-        "ebin" ->
-            case lists:suffix(".app", File) of
-                true ->
-                    has_at_least_one_beam(EbinDir, File);
-                false ->
-                    []
-            end;
-        _ ->
-            []
-    end.
-
--spec has_at_least_one_beam(file:name(), file:filename()) ->
-                                   rcl_app_info:t() | {error, Reason::term()}.
-has_at_least_one_beam(EbinDir, File) ->
-    case file:list_dir(EbinDir) of
-        {ok, List} ->
-            case lists:any(fun(NFile) -> lists:suffix(".beam", NFile) end, List) of
-                true ->
-                    gather_application_info(EbinDir, File);
-                false ->
-                    {error, {no_beam_files, EbinDir}}
-            end;
-        _ ->
-            {error, {not_a_directory, EbinDir}}
-    end.
-
--spec gather_application_info(file:name(), file:filename()) ->
-                                     rcl_app_info:t() | {error, Reason::term()}.
-gather_application_info(EbinDir, File) ->
-    AppDir = filename:dirname(EbinDir),
-    case file:consult(File) of
-        {ok, [{application, AppName, AppDetail}]} ->
-            get_vsn(AppDir, AppName, AppDetail);
-        {error, Reason} ->
-            {error, {unable_to_load_app, AppDir, Reason}};
-        _ ->
-            {error, {invalid_app_file, File}}
-    end.
-
--spec get_vsn(file:name(), atom(), proplists:proplist()) ->
-                     rcl_app_info:t() | {error, Reason::term()}.
-get_vsn(AppDir, AppName, AppDetail) ->
-    case proplists:get_value(vsn, AppDetail) of
-        undefined ->
-            {error, {unversioned_app, AppDir, AppName}};
-        AppVsn ->
-            case get_deps(AppDir, AppName, AppVsn, AppDetail) of
-                {ok, App} ->
-                    App;
-                {error, Detail} ->
-                    {error, {app_info_error, Detail}}
-            end
-    end.
-
--spec get_deps(file:name(), atom(), string(), proplists:proplist()) ->
-                      {ok, rcl_app_info:t()} | {error, Reason::term()}.
-get_deps(AppDir, AppName, AppVsn, AppDetail) ->
-    ActiveApps = proplists:get_value(applications, AppDetail, []),
-    LibraryApps = proplists:get_value(included_applications, AppDetail, []),
-    rcl_app_info:new(AppName, AppVsn, AppDir, ActiveApps, LibraryApps).
-
-%%%===================================================================
-%%% Test Functions
-%%%===================================================================
-
--ifndef(NOTEST).
--include_lib("eunit/include/eunit.hrl").
-
--endif.
diff --git a/src/rcl_prv_release.erl b/src/rcl_prv_release.erl
index a98048f..4574a0e 100644
--- a/src/rcl_prv_release.erl
+++ b/src/rcl_prv_release.erl
@@ -101,36 +101,25 @@ find_default_release(State, DepGraph) ->
     end.
 
 resolve_default_release(State0, DepGraph) ->
-    %% Here we will just get the lastest version and run that.
+    %% Here we will just get the highest versioned release and run that.
     case lists:sort(fun release_sort/2,
                     ec_dictionary:to_list(rcl_state:releases(State0))) of
-        All = [{{RelName, RelVsn}, _} | _] ->
+        [{{RelName, RelVsn}, _} | _] ->
             State1 = rcl_state:default_release(State0, RelName, RelVsn),
-            lists:foldl(fun({{RN, RV}, _}, {ok, State2}) ->
-                                solve_release(State2,
-                                              DepGraph, RN, RV);
-                           (_, E) ->
-                                E
-                        end, {ok, State1}, All);
+            solve_release(State1, DepGraph, RelName, RelVsn);
         [] ->
             ?RCL_ERROR(no_releases_in_system)
     end.
 
-
 resolve_default_version(State0, DepGraph, RelName) ->
     %% Here we will just get the lastest version and run that.
     AllReleases = ec_dictionary:to_list(rcl_state:releases(State0)),
     SpecificReleases = [Rel || Rel={{PossibleRelName, _}, _} <- AllReleases,
                                PossibleRelName =:= RelName],
     case lists:sort(fun release_sort/2, SpecificReleases) of
-        All = [{{RelName, RelVsn}, _} | _] ->
+        [{{RelName, RelVsn}, _} | _] ->
             State1 = rcl_state:default_release(State0, RelName, RelVsn),
-            lists:foldl(fun({RN, RV}, {ok, State2}) ->
-                                solve_release(State2,
-                                              DepGraph, RN, RV);
-                           (_, E) ->
-                                E
-                        end, {ok, State1}, All);
+            solve_release(State1, DepGraph, RelName, RelVsn);
         [] ->
             ?RCL_ERROR({no_releases_for, RelName})
     end.
@@ -150,7 +139,11 @@ release_sort({{RelNameA, RelVsnA}, _}, {{RelNameB, RelVsnB}, _}) ->
         ec_semver:lte(RelVsnA, RelVsnB).
 
 solve_release(State0, DepGraph, RelName, RelVsn) ->
+    rcl_log:debug(rcl_state:log(State0),
+                  "Solving Release ~p-~s~n",
+                  [RelName, RelVsn]),
     try
+        io:format("Solving ~p ~p", [RelName, RelVsn]),
         Release = rcl_state:get_release(State0, RelName, RelVsn),
         Goals = rcl_release:goals(Release),
         case Goals of
@@ -176,7 +169,7 @@ set_resolved(State, Release0, Pkgs) ->
                         "Resolved ~p-~s~n",
                         [rcl_release:name(Release1),
                          rcl_release:vsn(Release1)]),
-           rcl_log:info(rcl_state:log(State),
+           rcl_log:debug(rcl_state:log(State),
                          fun() ->
                                  rcl_release:format(1, Release1)
                          end),
diff --git a/src/rcl_rel_discovery.erl b/src/rcl_rel_discovery.erl
new file mode 100644
index 0000000..0fbcf23
--- /dev/null
+++ b/src/rcl_rel_discovery.erl
@@ -0,0 +1,166 @@
+%% -*- erlang-indent-level: 4; indent-tabs-mode: nil; fill-column: 80 -*-
+%%% Copyright 2012 Erlware, LLC. All Rights Reserved.
+%%%
+%%% This file is provided to you under the Apache License,
+%%% Version 2.0 (the "License"); you may not use this file
+%%% except in compliance with the License.  You may obtain
+%%% a copy of the License at
+%%%
+%%%   http://www.apache.org/licenses/LICENSE-2.0
+%%%
+%%% Unless required by applicable law or agreed to in writing,
+%%% software distributed under the License is distributed on an
+%%% "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+%%% KIND, either express or implied.  See the License for the
+%%% specific language governing permissions and limitations
+%%% under the License.
+%%%---------------------------------------------------------------------------
+%%% @author Eric Merritt <[email protected]>
+%%% @copyright (C) 2012 Erlware, LLC.
+%%%
+%%% @doc This provider uses the lib_dir setting of the state. It searches the
+%%% Lib Dirs looking for all OTP Applications that are available. When it finds
+%%% those OTP Applications it loads the information about them and adds them to
+%%% the state of available apps. This implements the rcl_provider behaviour.
+-module(rcl_rel_discovery).
+
+-export([do/3,
+         format_error/1]).
+
+-include_lib("relcool/include/relcool.hrl").
+
+%%============================================================================
+%% API
+%%============================================================================
+
+%% @doc recursively dig down into the library directories specified in the state
+%% looking for OTP Applications
+-spec do(rcl_state:t(), [filename:name()], [rcl_app_info:t()]) ->
+                {ok, [rcl_release:t()]} | relcool:error().
+do(State, LibDirs, AppMeta) ->
+    rcl_log:info(rcl_state:log(State),
+                 fun() ->
+                         ["Resolving available releases from directories:\n",
+                          [[rcl_util:indent(1), LibDir, "\n"] || LibDir <- LibDirs]]
+                 end),
+    resolve_rel_metadata(State, LibDirs, AppMeta).
+
+-spec format_error([ErrorDetail::term()]) -> iolist().
+format_error(ErrorDetails)
+  when erlang:is_list(ErrorDetails) ->
+    [[format_detail(ErrorDetail), "\n"] || ErrorDetail <- ErrorDetails].
+
+%%%===================================================================
+%%% Internal Functions
+%%%===================================================================
+resolve_rel_metadata(State, LibDirs, AppMeta) ->
+    ReleaseMeta0 =
+        lists:flatten(ec_plists:map(fun(LibDir) ->
+                                            discover_dir([], LibDir, AppMeta)
+                                    end, LibDirs)),
+    Errors = [case El of
+                  {error, Ret} -> Ret;
+                  _ -> El
+              end
+              || El <- ReleaseMeta0,
+                 case El of
+                     {error, _} ->
+                         true;
+                     _ ->
+                         false
+                 end],
+
+    case Errors of
+        [] ->
+            ReleaseMeta1 = lists:flatten(ReleaseMeta0),
+            rcl_log:debug(rcl_state:log(State),
+                          fun() ->
+                                  ["Resolved the following OTP Releases from the system: \n",
+                                   [[rcl_release:format(1, Rel), "\n"] || Rel <- ReleaseMeta1]]
+                          end),
+            {ok, ReleaseMeta1};
+        _ ->
+            ?RCL_ERROR(Errors)
+    end.
+
+-spec format_detail(ErrorDetail::term()) -> iolist().
+format_detail({accessing, File, eaccess}) ->
+    io_lib:format("permission denied accessing file ~s", [File]);
+format_detail({accessing, File, Type}) ->
+    io_lib:format("error (~p) accessing file ~s", [Type, File]).
+
+-spec discover_dir([file:name()], file:name(), [rcl_app_info:t()]) ->
+        [rcl_release:t() | {error, Reason::term()}]
+      | rcl_release:t()
+      | {error, Reason::term()}.
+discover_dir(IgnoreDirs, File, AppMeta) ->
+    case (not lists:member(File, IgnoreDirs))
+        andalso filelib:is_dir(File) of
+        true ->
+            case file:list_dir(File) of
+                {error, Reason} ->
+                    {error, {accessing, File, Reason}};
+                {ok, List} ->
+                    ec_plists:map(fun(LibDir) ->
+                                          discover_dir(IgnoreDirs, LibDir, AppMeta)
+                                  end,
+                                 [filename:join([File, Dir]) || Dir <- List])
+            end;
+        false ->
+            is_valid_release(File, AppMeta)
+    end.
+
+-spec is_valid_release(file:name(),
+                       [rcl_app_info:t()]) ->
+        rcl_release:t()
+      | {error, Reason::term()}
+      | [].
+is_valid_release(File, AppMeta) ->
+    case lists:suffix(".rel", File) of
+        true ->
+            resolve_release(File, AppMeta);
+        false ->
+            []
+    end.
+
+resolve_release(RelFile, AppMeta) ->
+    case file:consult(RelFile) of
+        {ok, [{release, {RelName, RelVsn},
+               {erts, ErtsVsn},
+               Apps}]} ->
+            build_release(RelName, RelVsn, ErtsVsn, Apps, AppMeta);
+        {ok, InvalidRelease} ->
+            ?RCL_ERROR({invalid_release_information, InvalidRelease});
+        {error, Reason} ->
+            ?RCL_ERROR({unable_to_read, RelFile, Reason})
+    end.
+
+build_release(RelName, RelVsn, ErtsVsn, Apps, AppMeta) ->
+    Release = rcl_release:erts(rcl_release:new(RelName, RelVsn),
+                               ErtsVsn),
+    resolve_apps(Apps, AppMeta, Release, []).
+
+resolve_apps([], _AppMeta, Release, Acc) ->
+    rcl_release:application_details(Release, Acc);
+resolve_apps([AppInfo | Apps], AppMeta, Release, Acc) ->
+    AppName = erlang:element(1, AppInfo),
+    AppVsn = erlang:element(2, AppInfo),
+    case find_app(AppName, AppVsn, AppMeta) of
+        Error = {error, _} ->
+            Error;
+        ResolvedApp ->
+            resolve_apps(Apps, AppMeta, Release, [ResolvedApp | Acc])
+    end.
+
+find_app(AppName, AppVsn, AppMeta) ->
+    case ec_lists:find(fun(App) ->
+                               NAppName = rcl_app:name(App),
+                               NAppVsn = rcl_app:version(App),
+                               AppName == NAppName andalso
+                                   AppVsn == NAppVsn
+                       end, AppMeta) of
+        {ok, Head} ->
+            Head;
+        error ->
+            ?RCL_ERROR({could_not_find, {AppName, AppVsn}})
+    end.
diff --git a/src/rcl_release.erl b/src/rcl_release.erl
index 560a555..ea20f1f 100644
--- a/src/rcl_release.erl
+++ b/src/rcl_release.erl
@@ -32,6 +32,7 @@
          realize/3,
          applications/1,
          application_details/1,
+         application_details/2,
          realized/1,
          metadata/1,
          format/1,
@@ -72,7 +73,7 @@
                             {app_name(), app_vsn(), app_type() | incl_apps()} |
                             {app_name(), app_vsn(), app_type(), incl_apps()}.
 
--type application_constraint() :: rcl_depsolver:constraint() | string() | binary().
+-type application_constraint() :: rcl_depsolver:raw_constraint() | string() | binary().
 -type application_goal() :: application_constraint()
                           | {application_constraint(), app_type() | incl_apps()}
                           | {application_constraint(), app_type(), incl_apps() | none}.
@@ -134,12 +135,18 @@ applications(#release_t{applications=Apps}) ->
     Apps.
 
 %% @doc this gives the rcl_app_info objects representing the applications in
-%% this release. These can only be populated by the 'realize' call in this
-%% module.
+%% this release. These should only be populated by the 'realize' call in this
+%% module or by reading an existing rel file.
 -spec application_details(t()) -> [rcl_app_info:t()].
 application_details(#release_t{app_detail=App}) ->
     App.
 
+%% @doc this is only expected to be called by a process building a new release
+%% from an existing rel file.
+-spec application_details(t(), [rcl_app_info:t()]) -> t().
+application_details(Release, AppDetail) ->
+    Release#release_t{app_detail=AppDetail}.
+
 -spec realized(t()) -> boolean().
 realized(#release_t{realized=Realized}) ->
     Realized.
@@ -189,7 +196,7 @@ format_error({topo_error, E}) ->
     rcl_topo:format_error(E);
 format_error({failed_to_parse, Con}) ->
     io_lib:format("Failed to parse constraint ~p", [Con]);
-format_error({invalid_constraint, Con}) ->
+format_error({invalid_constraint, _, Con}) ->
     io_lib:format("Invalid constraint specified ~p", [Con]);
 format_error({not_realized, Name, Vsn}) ->
     io_lib:format("Unable to produce metadata release: ~p-~s has not been realized",
@@ -209,10 +216,10 @@ realize_erts(Rel) ->
 process_specs(Rel=#release_t{annotations=Annots,
                              goals=Goals}, World) ->
     ActiveApps = lists:flatten([rcl_app_info:active_deps(El) || El <- World] ++
-                                   [case get_app_name(Goal) of
-                                        {error, _} -> [];
-                                        G -> G
-                                    end || Goal <- Goals]),
+                                  [case get_app_name(Goal) of
+                                       {error, _} -> [];
+                                       G -> G
+                                   end || Goal <- Goals]),
     LibraryApps = lists:flatten([rcl_app_info:library_deps(El) || El <- World]),
     Specs = [create_app_spec(Annots, App, ActiveApps, LibraryApps) || App <- World],
     {ok, Rel#release_t{annotations=Annots,
@@ -308,7 +315,7 @@ parse_goal0(Constraint0, {ok, Release}) ->
 parse_goal0(_, E = {error, _}) ->
     E;
 parse_goal0(Constraint, _) ->
-    ?RCL_ERROR({invalid_constraint, Constraint}).
+    ?RCL_ERROR({invalid_constraint, 1, Constraint}).
 
 parse_goal1(Release = #release_t{annotations=Annots,  goals=Goals},
             Constraint, NewAnnots) ->
@@ -331,25 +338,45 @@ parse_constraint(Constraint0)
         {ok, Constraint1} ->
             {ok, Constraint1}
     end;
-parse_constraint(Constraint)
-  when erlang:is_tuple(Constraint);
-       erlang:is_atom(Constraint) ->
-    case rcl_depsolver:is_valid_constraint(Constraint) of
+parse_constraint(Constraint0)
+  when erlang:is_tuple(Constraint0);
+       erlang:is_atom(Constraint0) ->
+    Constraint1 = parse_version(Constraint0),
+    case rcl_depsolver:is_valid_constraint(Constraint1) of
         false ->
-            ?RCL_ERROR({invalid_constraint, Constraint});
+            ?RCL_ERROR({invalid_constraint, 2, Constraint0});
         true ->
-            {ok, Constraint}
+            {ok, Constraint1}
     end;
 parse_constraint(Constraint) ->
-    ?RCL_ERROR({invalid_constraint, Constraint}).
+    ?RCL_ERROR({invalid_constraint, 3, Constraint}).
 
--spec get_app_name(rcl_depsolver:constraint()) ->
+-spec get_app_name(rcl_depsolver:raw_constraint()) ->
                           AppName::atom() | relcool:error().
 get_app_name(AppName) when erlang:is_atom(AppName) ->
     AppName;
+get_app_name({AppName, _}) when erlang:is_atom(AppName) ->
+    AppName;
 get_app_name({AppName, _, _}) when erlang:is_atom(AppName) ->
     AppName;
 get_app_name({AppName, _, _, _}) when erlang:is_atom(AppName) ->
     AppName;
 get_app_name(V) ->
-    ?RCL_ERROR({invalid_constraint, V}).
+    ?RCL_ERROR({invalid_constraint, 4, V}).
+
+-spec parse_version(rcl_depsolver:raw_constraint()) ->
+                           rcl_depsolver:constraint().
+parse_version({AppName, Version})
+  when erlang:is_binary(Version);
+       erlang:is_list(Version) ->
+    {AppName, rcl_depsolver:parse_version(Version)};
+parse_version({AppName, Version, Constraint})
+  when erlang:is_binary(Version);
+       erlang:is_list(Version) ->
+    {AppName, rcl_depsolver:parse_version(Version), Constraint};
+parse_version({AppName, Version, Constraint0, Constraint1})
+  when erlang:is_binary(Version);
+       erlang:is_list(Version) ->
+    {AppName, rcl_depsolver:parse_version(Version), Constraint1, Constraint0};
+parse_version(Constraint) ->
+    Constraint.