Start script extensions (#613)

* Extended start script command extensions

Provide a mechanism that allows for the application
to extend the list of commands available to be invoked
from the start script. An application may be able to
define a 'foo' extension that is associated with a 'foo_script'
written and maintained by the applicationr, (this association is
kept in rebar.config), upon invocation of bin/<release_name> foo
the 'foo_script' will then be invoked.

* Add test coverage for extension script

* Ensure extended script usage argument

3 files changed, 120 insertions, 7 deletions

diff --git a/priv/templates/extended_bin b/priv/templates/extended_bin
index 0abf38b..6742cf7 100755
--- a/priv/templates/extended_bin
+++ b/priv/templates/extended_bin
@@ -47,6 +47,7 @@ POST_STOP_HOOKS="{{{ post_stop_hooks }}}"
 PRE_INSTALL_UPGRADE_HOOKS="{{{ pre_install_upgrade_hooks }}}"
 POST_INSTALL_UPGRADE_HOOKS="{{{ post_install_upgrade_hooks }}}"
 STATUS_HOOK="{{{ status_hook }}}"
+EXTENSIONS="{{{ extensions }}}"
 
 relx_usage() {
     command="$1"
@@ -107,7 +108,15 @@ relx_usage() {
             echo "Obtains node status information."
             ;;
         *)
-            echo "Usage: $REL_NAME {start|start_boot <file>|foreground|stop|restart|reboot|pid|ping|console|console_clean|console_boot <file>|attach|remote_console|upgrade|downgrade|install|uninstall|versions|escript|rpc|rpcterms|eval|status}"
+            # check for extension
+            IS_EXTENSION=$(relx_is_extension $command)
+            if [ "$IS_EXTENSION" = "1" ]; then
+                EXTENSION_SCRIPT=$(relx_get_extension_script $command)
+                relx_run_extension $EXTENSION_SCRIPT help
+            else
+                EXTENSIONS=`echo $EXTENSIONS | sed -e 's/|undefined//g'`
+                echo "Usage: $REL_NAME {start|start_boot <file>|foreground|stop|restart|reboot|pid|ping|console|console_clean|console_boot <file>|attach|remote_console|upgrade|downgrade|install|uninstall|versions|escript|rpc|rpcterms|eval|status|$EXTENSIONS}"
+            fi
             ;;
     esac
 }
@@ -285,6 +294,40 @@ relx_run_hooks() {
     done
 }
 
+relx_is_extension() {
+    EXTENSION=$1
+    case "$EXTENSION" in
+        {{{ extensions }}})
+            echo "1" 
+        ;;
+        *)
+            echo "0" 
+        ;;
+    esac
+}
+
+relx_get_extension_script() {
+    EXTENSION=$1
+    # below are the extensions declarations
+    # of the form:
+    # foo_extension="path/to/foo_script";bar_extension="path/to/bar_script"
+    {{{extension_declarations}}}
+    # get the command extension (eg. foo) and 
+    # obtain the actual script filename that it
+    # refers to (eg. "path/to/foo_script"
+    eval echo "$"${EXTENSION}_extension""
+}
+
+relx_run_extension() {
+    # drop the first argument which is the name of the
+    # extension script
+    EXTENSION_SCRIPT=$1
+    shift
+    # all extension script locations are expected to be
+    # relative to the start script location
+    [ "$SCRIPT_DIR/$EXTENSION_SCRIPT" ] && . "$SCRIPT_DIR/$EXTENSION_SCRIPT" $@
+}
+
 find_erts_dir
 export ROOTDIR="$RELEASE_ROOT_DIR"
 export BINDIR="$ERTS_DIR/bin"
@@ -671,7 +714,15 @@ case "$1" in
         relx_usage $TOPIC
         ;;
     *)
-        relx_usage
+        # check for extension
+        IS_EXTENSION=$(relx_is_extension $1)
+        if [ "$IS_EXTENSION" = "1" ]; then
+            EXTENSION_SCRIPT=$(relx_get_extension_script $1)
+            shift
+            relx_run_extension $EXTENSION_SCRIPT $@
+        else
+            relx_usage $1
+        fi
         exit 1
         ;;
 esac
diff --git a/src/rlx_prv_assembler.erl b/src/rlx_prv_assembler.erl
index 2088de6..a6bf5f8 100644
--- a/src/rlx_prv_assembler.erl
+++ b/src/rlx_prv_assembler.erl
@@ -401,9 +401,12 @@ write_bin_file(State, Release, OutputDir, RelDir) ->
                                                            extended_start_script_hooks,
                                                            []),
                                              State),
+                        Extensions = rlx_state:get(State,
+                                                   extended_start_script_extensions,
+                                                   []),
                         extended_bin_file_contents(OsFamily, RelName, RelVsn,
                                                    rlx_release:erts(Release), ErlOpts,
-                                                   Hooks)
+                                                   Hooks, Extensions)
                 end,
     %% We generate the start script by default, unless the user
     %% tells us not too
@@ -787,7 +790,7 @@ bin_file_contents(OsFamily, RelName, RelVsn, ErtsVsn, ErlOpts) ->
     render(Template, [{rel_name, RelName}, {rel_vsn, RelVsn},
                       {erts_vsn, ErtsVsn}, {erl_opts, ErlOpts}]).
 
-extended_bin_file_contents(OsFamily, RelName, RelVsn, ErtsVsn, ErlOpts, Hooks) ->
+extended_bin_file_contents(OsFamily, RelName, RelVsn, ErtsVsn, ErlOpts, Hooks, Extensions) ->
     Template = case OsFamily of
         unix -> extended_bin;
         win32 -> extended_bin_windows
@@ -802,6 +805,21 @@ extended_bin_file_contents(OsFamily, RelName, RelVsn, ErtsVsn, ErlOpts, Hooks) -
     PostInstallUpgradeHooks = string:join(proplists:get_value(post_install_upgrade,
                                                  Hooks, []), " "),
     StatusHook = string:join(proplists:get_value(status, Hooks, []), " "),
+    {ExtensionsList1, ExtensionDeclarations1} =
+        lists:foldl(fun({Name, Script},
+                        {ExtensionsList0, ExtensionDeclarations0}) ->
+                            ExtensionDeclaration = atom_to_list(Name) ++
+                                                   "_extension=\"" ++
+                                                   Script ++ "\"",
+                            {ExtensionsList0 ++ [atom_to_list(Name)],
+                             ExtensionDeclarations0 ++ [ExtensionDeclaration]}
+                    end, {[], []}, Extensions),
+    % pipe separated string of extensions, to show on the start script usage
+    % (eg. foo|bar)
+    ExtensionsList = string:join(ExtensionsList1 ++ ["undefined"], "|"),
+    % command separated string of extension script declarations
+    % (eg. foo_extension="path/to/foo_script")
+    ExtensionDeclarations = string:join(ExtensionDeclarations1, ";"),
     render(Template, [{rel_name, RelName}, {rel_vsn, RelVsn},
                       {erts_vsn, ErtsVsn}, {erl_opts, ErlOpts},
                       {pre_start_hooks, PreStartHooks},
@@ -810,7 +828,9 @@ extended_bin_file_contents(OsFamily, RelName, RelVsn, ErtsVsn, ErlOpts, Hooks) -
                       {post_stop_hooks, PostStopHooks},
                       {pre_install_upgrade_hooks, PreInstallUpgradeHooks},
                       {post_install_upgrade_hooks, PostInstallUpgradeHooks},
-                      {status_hook, StatusHook}]).
+                      {status_hook, StatusHook},
+                      {extensions, ExtensionsList},
+                      {extension_declarations, ExtensionDeclarations}]).
 
 erl_ini(OutputDir, ErtsVsn) ->
     ErtsDirName = string:concat("erts-", ErtsVsn),
diff --git a/test/rlx_extended_bin_SUITE.erl b/test/rlx_extended_bin_SUITE.erl
index c2e6bc2..4407cfc 100644
--- a/test/rlx_extended_bin_SUITE.erl
+++ b/test/rlx_extended_bin_SUITE.erl
@@ -49,7 +49,8 @@
          builtin_pid_start_script_hook/1,
          builtin_wait_for_process_start_script_hook/1,
          mixed_custom_and_builtin_start_script_hooks/1,
-         builtin_status_script/1, custom_status_script/1]).
+         builtin_status_script/1, custom_status_script/1,
+         extension_script/1]).
 
 -include_lib("common_test/include/ct.hrl").
 -include_lib("eunit/include/eunit.hrl").
@@ -82,7 +83,7 @@ all() ->
      replace_os_vars_custom_location, replace_os_vars_dev_mode, replace_os_vars_twice, custom_start_script_hooks,
      builtin_wait_for_vm_start_script_hook, builtin_pid_start_script_hook,
      builtin_wait_for_process_start_script_hook, mixed_custom_and_builtin_start_script_hooks,
-     builtin_status_script, custom_status_script].
+     builtin_status_script, custom_status_script, extension_script].
 
 ping(Config) ->
     LibDir1 = proplists:get_value(lib1, Config),
@@ -1492,6 +1493,47 @@ start_fail_when_circular_argsfiles(Config) ->
     ec_file:write(VmArgs3, "-args_file " ++ VmArgs2 ++ "\n"),
     start_fail_with_vmargs(Config, VmArgs, 5).
 
+extension_script(Config) ->
+    LibDir1 = proplists:get_value(lib1, Config),
+
+    rlx_test_utils:create_full_app(LibDir1, "goal_app", "0.0.1",
+                                   [stdlib,kernel], []),
+
+    OutputDir = filename:join([proplists:get_value(priv_dir, Config),
+                               rlx_test_utils:create_random_name("relx-output")]),
+
+    ConfigFile = filename:join([LibDir1, "relx.config"]),
+    rlx_test_utils:write_config(ConfigFile,
+                 [{release, {foo, "0.0.1"},
+                   [goal_app]},
+                  {lib_dirs, [filename:join(LibDir1, "*")]},
+                  {generate_start_script, true},
+                  {extended_start_script, true},
+                  {extended_start_script_extensions, [
+                        {bar, "extensions/bar"} 
+                  ]},
+                  {overlay, [
+                    {copy, "./bar", "bin/extensions/bar"}]}
+                 ]),
+
+    %% write the extension script
+    ok = file:write_file(filename:join([LibDir1, "./bar"]),
+                         "#!/bin/bash\n"
+                         "echo \\{bar, $REL_NAME, \\'$NAME\\', $COOKIE\\}.\n"
+                         "exit 0"),
+
+    {ok, _State} = relx:do(foo, undefined, [], [LibDir1], 3,
+                           OutputDir, ConfigFile),
+    os:cmd(filename:join([OutputDir, "foo", "bin", "foo start"])),
+    timer:sleep(2000),
+    {ok, "pong"} = sh(filename:join([OutputDir, "foo", "bin", "foo ping"])),
+    %% write the extension script output to a file
+    {ok, Str} = sh(filename:join([OutputDir, "foo", "bin", "foo bar"])),
+    ec_file:write(filename:join([OutputDir, "bar.txt"]), Str),
+    os:cmd(filename:join([OutputDir, "foo", "bin", "foo stop"])),
+    {ok, [Term]} = file:consult(filename:join([OutputDir, "bar.txt"])),
+    {ok, {bar, foo, _, foo} = Term}.
+
 %%-------------------------------------------------------------------
 %% Helper Function for start_fail_when_* tests
 %%-------------------------------------------------------------------