Allow return_to option in recon_trace calls

README.md

@@ -5,7 +5,7 @@ Recon wants to be a set of tools usable in production to diagnose Erlang problem
 
 To build the library:
 
-    ./rebar compile
+    rebar3 compile
 
 Documentation for the library can be obtained at http://ferd.github.io/recon/
 
@@ -27,6 +27,8 @@ all stable changes of the first version of Recon.
 
 *2.x*
 
+- 2.3.2 (current Master)
+  - Allow the `return_to` option in `recon_trace`
 - 2.3.1
   - Updated `app_deps` script to run with rebar3 dependencies
   - Minor docs update

src/recon.app.src

@@ -1,6 +1,6 @@
 {application, recon,
  [{description, "Diagnostic tools for production use"},
-  {vsn, "2.3.1"},
+  {vsn, "2.3.2"},
   {modules, [recon, recon_alloc, recon_lib, recon_trace]},
   {registered, []},
   {applications, [kernel, stdlib]},

src/recon_trace.erl

@@ -194,6 +194,7 @@
                         | {args, args | arity}               % default: args
                         | {io_server, pid()}                 % default: group_leader()
                         | {formatter, formatterfun()}        % default: internal formatter
+                        | return_to | {return_to, boolean()} % default: false
                    %% match pattern options
                         | {scope, global | local}            % default: global
                         ].
@@ -308,6 +309,11 @@ calls(TSpecs = [_|_], Max) ->
 %%  <li>`{io_server, pid() | atom()}': by default, recon logs to the current
 %%      group leader, usually the shell. This option allows to redirect
 %%      trace output to a different IO server (such as a file handle).</li>
+%%  <li>`return_to': If this option is set (in conjunction with the match
+%%      option `{scope, local}'), the function to which the value is returned
+%%      is output in a trace. Note that this is distinct from giving the
+%%      *caller* since exception handling or calls in tail position may
+%%      hide the original caller.</li>
 %% </ul>
 %%
 %% Also note that putting extremely large `Max' values (i.e. `99999999' or
@@ -420,15 +426,26 @@ trace_calls(TSpecs, Pid, Opts) ->
 
 validate_opts(Opts) ->
     PidSpecs = validate_pid_specs(proplists:get_value(pid, Opts, all)),
+    Scope = proplists:get_value(scope, Opts, global),
     TraceOpts = case proplists:get_value(timestamp, Opts, formatter) of
                     formatter -> [];
                     trace -> [timestamp]
                  end ++
                  case proplists:get_value(args, Opts, args) of
                     args -> [];
                     arity -> [arity]
+                 end ++
+                 case proplists:get_value(return_to, Opts, undefined) of
+                     true when Scope =:= local ->
+                         [return_to];
+                     true when Scope =:= global ->
+                         io:format("Option return_to only works with option {scope, local}~n"),
+                         %% Set it anyway
+                         [return_to];
+                     _ ->
+                         []
                  end,
-    MatchOpts = [proplists:get_value(scope, Opts, global)],
+    MatchOpts = [Scope],
     {PidSpecs, TraceOpts, MatchOpts}.
 
 %% Support the regular specs, but also allow `recon:pid_term()' and lists
@@ -498,7 +515,7 @@ format(TraceMsg) ->
             {"~p:~p~s", [M,F,format_args(Args)]};
         %% {trace, Pid, return_to, {M, F, Arity}}
         {return_to, [{M,F,Arity}]} ->
-            {"~p:~p/~p", [M,F,Arity]};
+            {" '--> ~p:~p/~p", [M,F,Arity]};
         %% {trace, Pid, return_from, {M, F, Arity}, ReturnValue}
         {return_from, [{M,F,Arity}, Return]} ->
             {"~p:~p/~p --> ~p", [M,F,Arity, Return]};