Add WhereDepth for UserPreference

Author: limakzi

doc/ref/mloop.xml

@@ -743,7 +743,11 @@ is an example in the ⪆ code where the idea is actually used.
 <Index Subkey="GAP3 name for Where">Backtrace</Index>
 <Index>Stack trace</Index>
 shows the last <A>nr</A> commands on the execution stack during whose execution
-the error occurred. If not given, <A>nr</A> defaults to 5. (Assume, for the
+the error occurred. If not given, <A>nr</A> defaults to the value of the
+<C>WhereDepth</C> user preference (initially 5).
+If <A>nr</A> or the <C>WhereDepth</C> preference is not a non-negative integer,
+it is treated as 5.
+(Assume, for the
 following example, that after the last example <Ref Func="OnBreak"/>
 has been set back to its default value.). <Ref Func="WhereWithVars"/> acts the
 same as <Ref Func="Where"/> while also showing the arguments and local

lib/error.g

@@ -169,6 +169,9 @@ end);
 
 BIND_GLOBAL("WHERE_INTERNAL", function(depth, showlocals)
     local activecontext;
+    if not IsInt(depth) or depth < 0 then
+        depth := 5;
+    fi;
     if ErrorLVars = fail or ErrorLVars = GetBottomLVars() then
         PrintTo(ERROR_OUTPUT, "not in any function ");
     else
@@ -181,7 +184,7 @@ end);
 BIND_GLOBAL("WhereWithVars", function(arg)
     local   depth;
     if LEN_LIST(arg) = 0 then
-        depth := 5;
+        depth := UserPreference("WhereDepth");
     else
         depth := arg[1];
     fi;
@@ -192,7 +195,7 @@ end);
 BIND_GLOBAL("Where", function(arg)
     local   depth;
     if LEN_LIST(arg) = 0 then
-        depth := 5;
+        depth := UserPreference("WhereDepth");
     else
         depth := arg[1];
     fi;

lib/init.g

@@ -582,6 +582,17 @@ DeclareUserPreference( rec(
   default:= 3,
   check:= val -> IsInt( val ) and 0 <= val,
   ) );
+DeclareUserPreference( rec(
+  name:= "WhereDepth",
+  description:= [
+    "The number of stack frames shown by <C>Where</C> and <C>WhereWithVars</C> \
+when called without an explicit depth argument, e.g. in the default <C>OnBreak</C> \
+handler. Increase this value if the default of 5 is not enough to locate the \
+source of an error."
+    ],
+  default:= 5,
+  check:= val -> IsInt( val ) and 0 <= val,
+  ) );
 DeclareUserPreference( rec(
   name:= "ReproducibleBehaviour",
   description:= [

tst/testinstall/error.tst

@@ -34,3 +34,18 @@ gap> if false then Stabilizer; fi;
 Syntax error: found an expression when a statement was expected in stream:1
 if false then Stabilizer; fi;
                         ^
+
+#
+# WhereDepth user preference
+#
+gap> UserPreference("WhereDepth");
+5
+gap> SetUserPreference("WhereDepth", 10);
+gap> UserPreference("WhereDepth");
+10
+gap> SetUserPreference("WhereDepth", 0);
+gap> UserPreference("WhereDepth");
+0
+gap> SetUserPreference("WhereDepth", 5);
+gap> UserPreference("WhereDepth");
+5