New command line option --alwaystrace

The option --alwaystrace sets a new global variable
AlwaysPrintTracebackOnError. If set to true `OnBreak()` is always
called before exiting `ErrorInner`.

Author: ssiccha

lib/error.g

@@ -185,7 +185,7 @@ BIND_GLOBAL("ErrorInner",
         LEAVE_ALL_NAMESPACES();
         JUMP_TO_CATCH(1);
     fi;
-        
+
     # Local functions that print the user feedback.
     printEarlyMessage := function(stream, earlyMessage)
         PrintTo(stream, "Error, ");
@@ -222,12 +222,21 @@ BIND_GLOBAL("ErrorInner",
     if QUITTING or not BreakOnError then
         # If we skip the break loop, the standard behaviour is to print only
         # the earlyMessage. If SilentNonInteractiveErrors is true we do not
-        # print any messages.
-        # This is used by HPC-GAP to e.g. suppress error messages in worker
+        # print any messages. If AlwaysPrintTracebackOnError is true we also
+        # call OnBreak(), which by default prints the traceback.
+        # SilentNonInteractiveErrors superseeds AlwaysPrintTracebackOnError.
+        # It is used by HPC-GAP to e.g. suppress error messages in worker
         # threads.
         if not SilentNonInteractiveErrors then
             printEarlyMessage("*errout*", earlyMessage);
-            PrintTo("*errout*", "\n");
+            if AlwaysPrintTracebackOnError then
+                printEarlyTraceback("*errout*", context, printThisStatement);
+                if IsBound(OnBreak) and IsFunction(OnBreak) then
+                    OnBreak();
+                fi;
+            else
+                PrintTo("*errout*", "\n");
+            fi;
         fi;
         if IsHPCGAP then
             # In HPC-GAP we want to access error messages encountered in
@@ -236,6 +245,17 @@ BIND_GLOBAL("ErrorInner",
             LastErrorMessage := "";
             lastErrorStream := OutputTextString(LastErrorMessage, true);
             printEarlyMessage(lastErrorStream, earlyMessage);
+            if AlwaysPrintTracebackOnError then
+                printEarlyTraceback(lastErrorStream, context, printThisStatement);
+                # FIXME: Also make HPCGAP work with OnBreak().
+                # If AlwaysPrintTracebackOnError is true, the output of
+                # OnBreak() should also be put into LastErrorMessage.
+                # To do this there needs to be a way to put its output
+                # into lastErrorStream.
+                # OnBreak() is documented to not take any arguments.
+                # One could work around that if there were e.g. a GAP error
+                # stream which all error functions print to.
+            fi;
             CloseStream(lastErrorStream);
             MakeImmutable(LastErrorMessage);
         fi;
@@ -249,6 +269,14 @@ BIND_GLOBAL("ErrorInner",
     printEarlyTraceback("*errout*", context, printThisStatement);
 
     if SHOULD_QUIT_ON_BREAK() then
+        # Again, the default is to not print the rest of the traceback.
+        # If AlwaysPrintTracebackOnError is true we do so anyways.
+        if
+            AlwaysPrintTracebackOnError
+            and IsBound(OnBreak) and IsFunction(OnBreak)
+        then
+            OnBreak();
+        fi;
         FORCE_QUIT_GAP(1);
     fi;
 

lib/init.g

@@ -236,6 +236,8 @@ fi;
 ##
 ##  - Unbind `DEBUG_LOADING', since later the `-D' option can be checked.
 ##  - Set or disable break loop according to the `-T' option.
+##  - Set whether traceback may be suppressed (e.g. by `-T') according to the
+##    `--alwaystrace' option.
 ##
 CallAndInstallPostRestore( function()
     if DEBUG_LOADING then
@@ -248,10 +250,15 @@ CallAndInstallPostRestore( function()
 
     if IsHPCGAP then
       BindThreadLocal( "BreakOnError", not GAPInfo.CommandLineOptions.T );
+      BindThreadLocal(
+        "AlwaysPrintTracebackOnError",
+        GAPInfo.CommandLineOptions.alwaystrace
+      );
       BindThreadLocal( "SilentNonInteractiveErrors", false );
       BindThreadLocal( "LastErrorMessage", "" );
     else
       ASS_GVAR( "BreakOnError", not GAPInfo.CommandLineOptions.T );
+      ASS_GVAR( "AlwaysPrintTracebackOnError", GAPInfo.CommandLineOptions.alwaystrace );
       ASS_GVAR( "SilentNonInteractiveErrors", false );
     fi;
 end);

lib/system.g

@@ -95,6 +95,7 @@ BIND_GLOBAL( "GAPInfo", rec(
       rec( short:= "N", default := false, help := ["do not use hidden implications"] ),
       rec( short:= "O", default := false, help := ["disable/enable loading of obsolete files"] ),
       rec( short:= "T", long := "nobreakloop", default := false, help := ["disable/enable break loop and error traceback"] ),
+      rec( long := "alwaystrace", default := false, help := ["always print error traceback (overrides behaviour of -T)"] ),
       rec( long := "quitonbreak", default := false, help := ["quit GAP with non-zero return value instead of entering break loop"]),
       ,
       rec( short:= "L", default := "", arg := "<file>", help := [ "restore a saved workspace"] ),