Merge branch 'sv/format_status_error_info' into dev

* sv/format_status_error_info:
  Add support for the format_status callback to gen_event
  Extend format_status for gen_server/gen_fsm termination error logging

OTP-8630 sv/format_status_error_info

When a gen_server, gen_fsm process, or gen_event terminates abnormally,
sometimes the text representation of the process state can occupy many
lines of the error log, depending on the definition of the state term. A
mechanism to trim out parts of the state from the log has been added (using
a format_status/2 callback). See the documentation.

3 files changed, 61 insertions, 14 deletions

diff --git a/lib/stdlib/src/gen_event.erl b/lib/stdlib/src/gen_event.erl
index 27ff9441e6..b1e9e3a02f 100644
--- a/lib/stdlib/src/gen_event.erl
+++ b/lib/stdlib/src/gen_event.erl
@@ -677,12 +677,23 @@ report_error(Handler, Reason, State, LastIn, SName) ->
 	    _ ->
 		Reason
 	end,
+    Mod = Handler#handler.module,
+    FmtState = case erlang:function_exported(Mod, format_status, 2) of
+		   true ->
+		       Args = [get(), State],
+		       case catch Mod:format_status(terminate, Args) of
+			   {'EXIT', _} -> State;
+			   Else -> Else
+		       end;
+		   _ ->
+		       State
+	       end,
     error_msg("** gen_event handler ~p crashed.~n"
 	      "** Was installed in ~p~n"
 	      "** Last event was: ~p~n"
 	      "** When handler state == ~p~n"
 	      "** Reason == ~p~n",
-	      [handler(Handler),SName,LastIn,State,Reason1]).
+	      [handler(Handler),SName,LastIn,FmtState,Reason1]).
 
 handler(Handler) when not Handler#handler.id ->
     Handler#handler.module;
@@ -711,10 +722,20 @@ get_modules(MSL) ->
 %%-----------------------------------------------------------------
 %% Status information
 %%-----------------------------------------------------------------
-format_status(_Opt, StatusData) ->
-    [_PDict, SysState, Parent, _Debug, [ServerName, MSL, _Hib]] = StatusData,
+format_status(Opt, StatusData) ->
+    [PDict, SysState, Parent, _Debug, [ServerName, MSL, _Hib]] = StatusData,
     Header = lists:concat(["Status for event handler ", ServerName]),
+    FmtMSL = [case erlang:function_exported(Mod, format_status, 2) of
+		  true ->
+		      Args = [PDict, State],
+		      case catch Mod:format_status(Opt, Args) of
+			  {'EXIT', _} -> MSL;
+			  Else -> MS#handler{state = Else}
+		      end;
+		  _ ->
+		      MS
+	      end || #handler{module = Mod, state = State} = MS <- MSL],
     [{header, Header},
      {data, [{"Status", SysState},
 	     {"Parent", Parent}]},
-     {items, {"Installed handlers", MSL}}].
+     {items, {"Installed handlers", FmtMSL}}].
diff --git a/lib/stdlib/src/gen_fsm.erl b/lib/stdlib/src/gen_fsm.erl
index 9961646418..8d1b46d6ab 100644
--- a/lib/stdlib/src/gen_fsm.erl
+++ b/lib/stdlib/src/gen_fsm.erl
@@ -542,7 +542,18 @@ terminate(Reason, Name, Msg, Mod, StateName, StateData, Debug) ->
  		{shutdown,_}=Shutdown ->
  		    exit(Shutdown);
 		_ ->
-		    error_info(Reason, Name, Msg, StateName, StateData, Debug),
+                    FmtStateData =
+                        case erlang:function_exported(Mod, format_status, 2) of
+                            true ->
+                                Args = [get(), StateData],
+                                case catch Mod:format_status(terminate, Args) of
+                                    {'EXIT', _} -> StateData;
+                                    Else -> Else
+                                end;
+                            _ ->
+                                StateData
+                        end,
+		    error_info(Reason,Name,Msg,StateName,FmtStateData,Debug),
 		    exit(Reason)
 	    end
     end.
@@ -610,15 +621,17 @@ format_status(Opt, StatusData) ->
 	      end,
     Header = lists:concat(["Status for state machine ", NameTag]),
     Log = sys:get_debug(log, Debug, []),
-    Specfic = 
+    DefaultStatus = [{data, [{"StateData", StateData}]}],
+    Specfic =
 	case erlang:function_exported(Mod, format_status, 2) of
 	    true ->
 		case catch Mod:format_status(Opt,[PDict,StateData]) of
-		    {'EXIT', _} -> [{data, [{"StateData", StateData}]}];
-		    Else -> Else
+		    {'EXIT', _} -> DefaultStatus;
+                    StatusList when is_list(StatusList) -> StatusList;
+		    Else -> [Else]
 		end;
 	    _ ->
-		[{data, [{"StateData", StateData}]}]
+		DefaultStatus
 	end,
     [{header, Header},
      {data, [{"Status", SysState},
diff --git a/lib/stdlib/src/gen_server.erl b/lib/stdlib/src/gen_server.erl
index 1c9e5270b6..dc8e7ecd16 100644
--- a/lib/stdlib/src/gen_server.erl
+++ b/lib/stdlib/src/gen_server.erl
@@ -705,7 +705,18 @@ terminate(Reason, Name, Msg, Mod, State, Debug) ->
 		{shutdown,_}=Shutdown ->
 		    exit(Shutdown);
 		_ ->
-		    error_info(Reason, Name, Msg, State, Debug),
+		    FmtState =
+			case erlang:function_exported(Mod, format_status, 2) of
+			    true ->
+				Args = [get(), State],
+				case catch Mod:format_status(terminate, Args) of
+				    {'EXIT', _} -> State;
+				    Else -> Else
+				end;
+			    _ ->
+				State
+			end,
+		    error_info(Reason, Name, Msg, FmtState, Debug),
 		    exit(Reason)
 	    end
     end.
@@ -836,15 +847,17 @@ format_status(Opt, StatusData) ->
 	      end,
     Header = lists:concat(["Status for generic server ", NameTag]),
     Log = sys:get_debug(log, Debug, []),
-    Specfic = 
+    DefaultStatus = [{data, [{"State", State}]}],
+    Specfic =
 	case erlang:function_exported(Mod, format_status, 2) of
 	    true ->
 		case catch Mod:format_status(Opt, [PDict, State]) of
-		    {'EXIT', _} -> [{data, [{"State", State}]}];
-		    Else -> Else
+		    {'EXIT', _} -> DefaultStatus;
+                    StatusList when is_list(StatusList) -> StatusList;
+		    Else -> [Else]
 		end;
 	    _ ->
-		[{data, [{"State", State}]}]
+		DefaultStatus
 	end,
     [{header, Header},
      {data, [{"Status", SysState},