Add a new function code:get_mode() can be used to detect how the code servers behaves

Rationale:
    Some applications (like erlide) have code to be loaded dynamically on a
    node. It may be slow to load everything upfront every time, so if the
    node is in interactive mode, we would like to just append to the load
    path. Currently, there is no direct way to detect if the node is running
    in embedded mode or not so that we can do the right thing.

4 files changed, 28 insertions, 3 deletions

diff --git a/lib/kernel/doc/src/code.xml b/lib/kernel/doc/src/code.xml
index 279c7558bc..a1c3eee6ec 100644
--- a/lib/kernel/doc/src/code.xml
+++ b/lib/kernel/doc/src/code.xml
@@ -738,6 +738,19 @@ rpc:call(Node, code, load_binary, [Module, Filename, Binary]),
 	<c>undefined</c>.</p>
       </desc>
     </func>
+
+    <func>
+      <name="get_mode" arity="0"/>
+      <fsummary>The code_server's mode.</fsummary>
+      <desc>
+        <p>This function returns an atom describing the code_server's mode:
+        <c>interactive</c> or <c>embedded</c>. </p>
+        <p>This information is useful when an external entity (for example,
+        an IDE) provides additional code for a running node. If in interactive
+        mode, it only needs to add to the code path. If in embedded mode,
+        the code has to be loaded with <c>load_binary/3</c></p>
+      </desc>
+    </func>
   </funcs>
 </erlref>
 
diff --git a/lib/kernel/src/code.erl b/lib/kernel/src/code.erl
index 8a543abd6f..03fba96d4b 100644
--- a/lib/kernel/src/code.erl
+++ b/lib/kernel/src/code.erl
@@ -64,7 +64,8 @@
 	 where_is_file/1,
 	 where_is_file/2,
 	 set_primary_archive/4,
-	 clash/0]).
+	 clash/0,
+     get_mode/0]).
 
 -export_type([load_error_rsn/0, load_ret/0]).
 
@@ -293,6 +294,9 @@ replace_path(Name, Dir) when (is_atom(Name) orelse is_list(Name)),
 -spec rehash() -> 'ok'.
 rehash() -> call(rehash).
 
+-spec get_mode() -> 'embedded' | 'interactive'.
+get_mode() -> call(get_mode).
+
 %%-----------------------------------------------------------------
 
 call(Req) ->
diff --git a/lib/kernel/src/code_server.erl b/lib/kernel/src/code_server.erl
index b770fce887..5d74e8620b 100644
--- a/lib/kernel/src/code_server.erl
+++ b/lib/kernel/src/code_server.erl
@@ -422,6 +422,9 @@ handle_call({is_cached,File}, {_From,_Tag}, S=#state{cache=Cache}) ->
 	    end
     end;
 
+handle_call(get_mode, {_From,_Tag}, S=#state{mode=Mode}) ->
+    {reply, Mode, S};
+
 handle_call(Other,{_From,_Tag}, S) ->			
     error_msg(" ** Codeserver*** ignoring ~w~n ",[Other]),
     {noreply,S}.
diff --git a/lib/kernel/test/code_SUITE.erl b/lib/kernel/test/code_SUITE.erl
index d7424c0c9a..4c040f0a0e 100644
--- a/lib/kernel/test/code_SUITE.erl
+++ b/lib/kernel/test/code_SUITE.erl
@@ -33,7 +33,7 @@
 	 purge_stacktrace/1, mult_lib_roots/1, bad_erl_libs/1,
 	 code_archive/1, code_archive2/1, on_load/1, on_load_binary/1,
 	 on_load_embedded/1, on_load_errors/1, big_boot_embedded/1,
-	 native_early_modules/1]).
+	 native_early_modules/1, get_mode/1]).
 
 -export([init_per_testcase/2, end_per_testcase/2, 
 	 init_per_suite/1, end_per_suite/1,
@@ -60,7 +60,7 @@ all() ->
      where_is_file_cached, purge_stacktrace, mult_lib_roots,
      bad_erl_libs, code_archive, code_archive2, on_load,
      on_load_binary, on_load_embedded, on_load_errors,
-     big_boot_embedded, native_early_modules].
+     big_boot_embedded, native_early_modules, get_mode].
 
 groups() -> 
     [].
@@ -1594,6 +1594,11 @@ native_early_modules_1(Architecture) ->
             ok
     end.
 
+get_mode(suite) -> [];
+get_mode(doc) -> ["Test that the mode of the code server is properly retrieved"];
+get_mode(Config) when is_list(Config) ->
+    interactive = code:get_mode().
+
 %%-----------------------------------------------------------------
 %% error_logger handler.
 %% (Copied from stdlib/test/proc_lib_SUITE.erl.)