Extend obsolete to support multiple levels

Obsolete warnings of level 1 will be displayed by default,
level 2 warnings are enabled with the -O command line option.

doc/ref/obsolete.xml

@@ -199,13 +199,16 @@ Note that <C>MultRowVector</C> was also renamed to <C>MultVectorLeft</C>.
 <InfoClass Name="InfoObsolete"/>
 <Description>
 is an info class to display warnings when an obsolete variable is used.
-By default, these warnings are switched off since the info level for 
-this class is 0. Setting it to 1 will trigger warnings if &GAP; will 
-detect that an obsolete variable is used at runtime.
+By default, the info level for this class is set to 1, which will only
+show variables which will be removed in the next major version of GAP.
+Setting it to 2 will trigger further warnings, for variables which have
+alternative names, or may be removed in future.
+
+This class can be set to 0 to disable all obsolete warnings.
 <P/>
-To check that the &GAP; code does not use obsolete variables at the 
+To check that the &GAP; code does not use any obsolete variables at the
 parsing time, and not at a runtime, use <C>-O</C> command line option,
-see <Ref Sect="Command Line Options"/>. 
+see <Ref Sect="Command Line Options"/>.
 </Description>
 </ManSection>
 

lib/info.gi

@@ -429,8 +429,9 @@ end);
 ##
 #V  InfoObsolete
 ##
-##  This info class has a default level of 0.
-##  Warnings can be switched on by setting its level to one.
+##  This info class has a default level of 1.
+##  Warnings can be disabled entirely by setting its level to 0, and further
+##  warnings can be switched on by setting its level to 2.
 ##
 DeclareInfoClass( "InfoObsolete" );
-SetInfoLevel(InfoObsolete,0);
+SetInfoLevel(InfoObsolete,1);

lib/obsolete.gd

@@ -76,19 +76,29 @@
 ##  <#/GAPDoc>
 ##
 
-BIND_GLOBAL( "DeclareObsoleteSynonym", function( name_obsolete, name_current )
-    local value, orig_value;
+BIND_GLOBAL( "DeclareObsoleteSynonym", function( name_obsolete, name_current, level_arg... )
+    local value, orig_value, printed_warning, level;
     if not ForAll( [ name_obsolete, name_current ], IsString ) then
         Error("Each argument of DeclareObsoleteSynonym must be a string\n");
     fi;
+    if Length(level_arg) = 0 then
+        level := 2;
+    else
+        level := level_arg[1];
+    fi;
+
     value := EvalString( name_current );
     if IsFunction( value ) then
         orig_value := value;
+        printed_warning := false;
         value := function (arg)
             local res;
-            Info( InfoObsolete, 1, "'", name_obsolete, "' is obsolete.",
-                "\n#I  It may be removed in a future release of GAP.",
-                "\n#I  Use ", name_current, " instead.");
+            if not printed_warning then
+                Info( InfoObsolete, level, "'", name_obsolete, "' is obsolete.",
+                    "\n#I  It may be removed in a future release of GAP.",
+                    "\n#I  Use ", name_current, " instead.");
+                printed_warning := true;
+            fi;
             # TODO: This will error out if orig_value is a function which returns nothing.
             #return CallFuncList(orig_value, arg);
             res := CallFuncListWrap(orig_value, arg);

tst/testbugfix/2013-06-14-t00300.tst

@@ -3,7 +3,7 @@ gap> foo:=function() return 42; end;
 function(  ) ... end
 gap> DeclareObsoleteSynonym("bar","foo");
 gap> oldLevel := InfoLevel(InfoObsolete);;
-gap> SetInfoLevel(InfoObsolete,1);
+gap> SetInfoLevel(InfoObsolete,2);
 gap> bar();
 #I  'bar' is obsolete.
 #I  It may be removed in a future release of GAP.