Add application:set_env/1 and application:set_env/2

It is equivalent to calling application:set_env/4 on
each application individually, except it is more efficient.

When given duplicate apps or duplicate keys, set_env/1
and set_env/2 will warn. The warning will also be emitted
during boot:

    $ erl -config dupkeys.config -s erlang halt
    2019-02-27 11:16:02.653100 application: kernel; duplicate parameter: key1
    =WARNING REPORT==== 27-Feb-2019::11:16:02.653100 ===
    application: kernel; duplicate parameter: key1

    $ erl -config dupapps.config -s erlang halt
    2019-02-27 11:16:02.653100 duplicate application config: kernel
    =WARNING REPORT==== 27-Feb-2019::11:16:02.653100 ===
    duplicate application config: kernel

Prior to this patch, the behaviour was unspecified,
and duplicate keys and duplicate apps would behave
different depending on the amount of config, the name
of the config files, and how those configs would be
listed. The goal is to raise an error in the future.

1 files changed, 97 insertions, 0 deletions

diff --git a/lib/kernel/test/application_SUITE.erl b/lib/kernel/test/application_SUITE.erl
index 5c35b82207..94d7c17712 100644
--- a/lib/kernel/test/application_SUITE.erl
+++ b/lib/kernel/test/application_SUITE.erl
@@ -31,6 +31,7 @@
 	 otp_3002/1, otp_3184/1, otp_4066/1, otp_4227/1, otp_5363/1,
 	 otp_5606/1,
 	 start_phases/1, get_key/1, get_env/1,
+	 set_env/1, set_env_persistent/1, set_env_errors/1,
 	 permit_false_start_local/1, permit_false_start_dist/1, script_start/1, 
 	 nodedown_start/1, init2973/0, loop2973/0, loop5606/1]).
 
@@ -55,6 +56,7 @@ all() ->
      load_use_cache, ensure_started, {group, reported_bugs}, start_phases,
      script_start, nodedown_start, permit_false_start_local,
      permit_false_start_dist, get_key, get_env, ensure_all_started,
+     set_env, set_env_persistent, set_env_errors,
      {group, distr_changed}, config_change, shutdown_func, shutdown_timeout,
      shutdown_deadlock, config_relative_paths,
      persistent_env].
@@ -1944,6 +1946,101 @@ get_appls([_ | T], Res) ->
 get_appls([], Res) ->
     Res.
 
+%% Test set_env/1.
+set_env(Conf) when is_list(Conf) ->
+    ok = application:set_env([{appinc, [{own2, persist}, {not_in_app, persist}]},
+			      {unknown_app, [{key, persist}]}]),
+
+    %% own_env1 and own2 are set in appinc
+    undefined = application:get_env(appinc, own_env1),
+    {ok, persist} = application:get_env(appinc, own2),
+    {ok, persist} = application:get_env(appinc, not_in_app),
+    {ok, persist} = application:get_env(unknown_app, key),
+
+    ok = application:load(appinc()),
+    {ok, value1} = application:get_env(appinc, own_env1),
+    {ok, val2} = application:get_env(appinc, own2),
+    {ok, persist} = application:get_env(appinc, not_in_app),
+    {ok, persist} = application:get_env(unknown_app, key),
+
+    %% On reload, values are lost
+    ok = application:unload(appinc),
+    ok = application:load(appinc()),
+    {ok, value1} = application:get_env(appinc, own_env1),
+    {ok, val2} = application:get_env(appinc, own2),
+    undefined = application:get_env(appinc, not_in_app),
+
+    %% Clean up
+    ok = application:unload(appinc).
+
+%% Test set_env/2 with persistent true.
+set_env_persistent(Conf) when is_list(Conf) ->
+    Opts = [{persistent, true}],
+    ok = application:set_env([{appinc, [{own2, persist}, {not_in_app, persist}]},
+			      {unknown_app, [{key, persist}]}], Opts),
+
+    %% own_env1 and own2 are set in appinc
+    undefined = application:get_env(appinc, own_env1),
+    {ok, persist} = application:get_env(appinc, own2),
+    {ok, persist} = application:get_env(appinc, not_in_app),
+    {ok, persist} = application:get_env(unknown_app, key),
+
+    ok = application:load(appinc()),
+    {ok, value1} = application:get_env(appinc, own_env1),
+    {ok, persist} = application:get_env(appinc, own2),
+    {ok, persist} = application:get_env(appinc, not_in_app),
+    {ok, persist} = application:get_env(unknown_app, key),
+
+    %% On reload, values are not lost
+    ok = application:unload(appinc),
+    ok = application:load(appinc()),
+    {ok, value1} = application:get_env(appinc, own_env1),
+    {ok, persist} = application:get_env(appinc, own2),
+    {ok, persist} = application:get_env(appinc, not_in_app),
+
+    %% Clean up
+    ok = application:unload(appinc).
+
+set_env_errors(Conf) when is_list(Conf) ->
+    "application: 1; application name must be an atom" =
+	badarg_msg(fun() -> application:set_env([{1, []}]) end),
+
+    "application: foo; parameters must be a list" =
+	badarg_msg(fun() -> application:set_env([{foo, bar}]) end),
+
+    "invalid application config: foo_bar" =
+	badarg_msg(fun() -> application:set_env([foo_bar]) end),
+
+    "application: foo; invalid parameter name: 1" =
+	badarg_msg(fun() -> application:set_env([{foo, [{1, 2}]}]) end),
+
+    "application: foo; invalid parameter: config" =
+	badarg_msg(fun() -> application:set_env([{foo, [config]}]) end),
+
+    "application: kernel; erroneous parameter: distributed" =
+	badarg_msg(fun() -> application:set_env([{kernel, [{distributed, config}]}]) end),
+
+    %% This will raise in the future
+    ct:capture_start(),
+    _ = application:set_env([{foo, []}, {foo, []}]),
+    timer:sleep(100),
+    ct:capture_stop(),
+    [_ | _] = string:find(ct:capture_get(), "duplicate application config: foo"),
+
+    ct:capture_start(),
+    _ = application:set_env([{foo, [{bar, baz}, {bar, bat}]}]),
+    timer:sleep(100),
+    ct:capture_stop(),
+    [_ | _] = string:find(ct:capture_get(), "application: foo; duplicate parameter: bar"),
+
+    ok.
+
+badarg_msg(Fun) ->
+    try Fun() of
+	_ -> ct:fail(try_succeeded)
+    catch
+	error:{badarg, Msg} -> Msg
+    end.
 
 %% Test set_env/4 and unset_env/3 with persistent true.
 persistent_env(Conf) when is_list(Conf) ->