Improve the output of the debugger

M2/Macaulay2/d/interp.dd

@@ -494,7 +494,7 @@ debugger(f:Frame,c:Code):Expr := (
      setDebuggingMode(false);
        oldDebuggerCode := getGlobalVariable(currentS);
        setGlobalVariable(currentS,Expr(PseudocodeClosure(f,c)));
-	 printMessage(codePosition(c), "entering debugger (enter 'help' to see commands)");
+	 printMessage(codePosition(c), "\n"+ "ENTERING DEBUGGER (enter 'help' to see commands, enter 'break' to quit the debugger)");
 	 incrementInterpreterDepth();
 	   if debuggerHook != nullE then (
 		r := applyEE(debuggerHook,True);

M2/Macaulay2/m2/code.m2

@@ -7,6 +7,13 @@ needs "lists.m2"
 needs "methods.m2"
 needs "nets.m2"
 
+-----------------------------------------------------------------------------
+-- Global variables
+-----------------------------------------------------------------------------
+
+debugPrintCarets = true
+debugPrintLineNumbers = true
+
 -----------------------------------------------------------------------------
 -- code
 -----------------------------------------------------------------------------
@@ -37,7 +44,81 @@ codeFunction := (key, func, level) -> if level <= limit then (
 previousMethodsFound = null
 
 codeAddress = pos -> ( pos, ": --source code:" ) -- [addr]:[line]:[char]-[line]:[char]:
-codeContent = (s, e, filelines) -> PRE M2CODE stack filelines_{s-1 .. e-1}
+
+
+protect PrintCaret
+protect PrintLineNum
+codeContent = method(
+    Options => {
+	PrintCaret => true,
+	PrintLineNum => true
+    }
+)
+-----------------------------------------------------------------------------
+-- Updates to codeContent developed by Bryson Kagy, Adam LaClair, Olalekan Ogunmefun, Jay Yang
+-- as part of the 2026 workshop "Building the Future of Macaulay2" at Georgia Tech.
+-- Changed the code to print carets and line numbers in the debugger, and added options to toggle these features on and off with the global variables debugPrintLineNumbers and debugPrintCarets.
+-- Also made it clearer when the user is in the debugger by adding a sentence to the documentation and by printing "ENTERING DEBUGGER" when the user enters the debugger and adding "<M2 debugger>" to the input line while in the debugger.
+-- In codeContent, pos is the FilePosition of the error, s and e are the starting and ending line numbers of the error, and filelines is the list of lines in the file of the error. 
+-----------------------------------------------------------------------------
+
+codeContent (FilePosition,ZZ,ZZ,List) := opt ->  (pos, s, e, filelines) -> (
+    posL := {}; --List, containing the information associated to the error message.
+    strList := {};  --List, used for storing the line numbers as strings.
+    str := ""; -- String, temporary variable used for creating output.
+    leftPadding := 0; --Integer, which we initialize below to 3, spaces printed to the left of line number.
+    rightPadding := 0; --Integer, which we initialize below to 3, spaces printed to the right of line number.
+    outputList := {}; --List, which contains each line error as a string.
+    maxLen := 0; --Integer, maximum length that an integer takes up as a string.
+
+
+    --Initializing variables.
+    posL = toList(pos);
+    leftPadding = 3;
+    rightPadding = 3;
+
+
+    --Get max length of the integer that will be printed as a string.
+    if (opt.PrintLineNum === true) then (
+	strList = for i from s-1 to e-1 list toString((posL#1+(i-s+1)));
+	maxLen = max(length\strList)
+    );
+
+    --Create the first line of output.
+    if (s != e and opt.PrintCaret === true) then (
+	outputList = outputList | { concatenate( ((leftPadding + maxLen + rightPadding + posL#2:" ")), "v") };
+    );    
+
+    --Create the middle lines of output, where print out the code.
+    if (opt.PrintLineNum === true) then (
+	outputList = outputList | for i from s-1 to e-1 list (
+	    concatenate( ((leftPadding + (maxLen - length strList#(i-s+1))):" "), strList#(i-s+1), ((rightPadding):" "), filelines_i )
+	);
+    ) else (
+	    outputList = outputList | filelines_{s-1..e-1};
+    );
+
+
+    --Check whether there are carets to print.
+    if (opt.PrintCaret === true) then (
+	str = "";
+	--Append the padding associated to the line numbers.
+	if (opt.PrintLineNum === true) then ( 
+	    str = concatenate(str, ((leftPadding + (maxLen) + rightPadding):" "));
+	);
+
+        if (s != e) then ( --For multiple lines add a single caret.
+	    str = concatenate(str, (posL#4-1):" ", "^");
+        ) else if (#posL == 3) then ( --Add a single caret.
+	    str = concatenate(str,"^");
+	) else if (#posL == 5 or #posL == 7) then ( --Add a line of carets.
+	    str = concatenate(str, (posL#2):" ", (posL#4 - posL#2):"^");
+	);
+        outputList = outputList | { str };
+    );
+
+    PRE M2CODE stack( outputList )
+);
 
 -- e.g. see code methods(map, Module, List)
 dedupMethods = L -> (
@@ -50,11 +131,17 @@ dedupMethods = L -> (
 	    L#i = join(tag, L#i)));
     toList L)
 
-code = method(Dispatch => Thing)
-code Nothing    := identity
-code FilePosition := x -> (
+code = method(
+    Dispatch => Thing,
+    Options => {
+	PrintCaret => true,
+	PrintLineNum => true
+    }
+)
+code Nothing := opt -> identity
+code FilePosition := opt -> x -> (
     filename := x#0; start := x#1; stop := x#3 ?? x#1;
-     (
+     (	 
 	  wp := set characters " \t\r);";
 	  file := (
 	       if match("startup\\.m2\\.in$", filename) then startupString
@@ -74,11 +161,11 @@ code FilePosition := x -> (
 	       );
 	  file = lines file;
 	  if #file < stop then error("line number ",toString stop, " not found in file ", filename);
-	  DIV splice { codeAddress(x), codeContent(start, stop, file) }
+	  DIV splice { codeAddress(x), codeContent(PrintCaret => debugPrintCarets, PrintLineNum => debugPrintLineNumbers, x, start, stop, file) }
 	  ))
-code Symbol     :=
-code Pseudocode := s -> code locate s
-code Sequence   := s -> (
+code Symbol     := 
+code Pseudocode := opt -> s -> code locate s
+code Sequence   := opt -> s -> (
     key := select(s, x -> not instance(x, Option));
     -- handle strategies
     mesg := "-- code for method: ";
@@ -95,10 +182,10 @@ code Sequence   := s -> (
     if func =!= null or (func = lookup key) =!= null
     then DIV { DIV { mesg, formatDocumentTag s }, codeFunction(s, func, 0) }
     else "-- no method function found: " | formatDocumentTag key)
-code Function   := f -> codeFunction(null, f, 0)
-code Command    := C -> code C#0
-code List       := L -> DIV between_(HR{}) dedupMethods apply(L, code)
-code ZZ         := i -> code previousMethodsFound#i
+code Function   := opt -> f -> codeFunction(null, f, 0)
+code Command    := opt -> C -> code C#0
+code List       := opt -> L -> DIV between_(HR{}) dedupMethods apply(L, code)
+code ZZ         := opt -> i -> code previousMethodsFound#i
 
 -----------------------------------------------------------------------------
 -- edit

M2/Macaulay2/m2/exports.m2

@@ -1351,6 +1351,8 @@ exportMutable {
 	"debugError",
 	"debugLevel",
 	"debuggingMode",
+	"debugPrintCarets",
+	"debugPrintLineNumbers",
 	"defaultPrecision",
 	"dictionaryPath",
 	"engineDebugLevel",

M2/Macaulay2/m2/startup.m2.in

@@ -84,7 +84,12 @@ if firstTime then (
 
      normalPrompts = () -> (
 	  lastprompt := "";
-	  ZZ#{Standard,InputPrompt} = lineno -> concatenate(newline, lastprompt = concatenate(interpreterDepth:"i", toString lineno, " : "));
+--	  ZZ#{Standard,InputPrompt} = lineno -> concatenate(newline, lastprompt = concatenate(interpreterDepth:"i", toString lineno, " : "));
+
+	  ZZ#{Standard,InputPrompt} = lineno -> concatenate(newline, lastprompt = if (interpreterDepth == 1) then concatenate(interpreterDepth:"i", toString lineno, " : ") else concatenate("<M2 Debugger> ", interpreterDepth:"i", toString lineno, " : "));
+--	  if interpreterDepth > 0 then (
+--	      ZZ#{Standard,InputPrompt} = lineno -> concatenate("<M2 Debugger> ",lastprompt);
+--	  );
 	  ZZ#{Standard,InputContinuationPrompt} = lineno -> #lastprompt; -- will print that many blanks, see interp.d
 	  symbol currentPrompts <- normalPrompts;	    -- this avoids the warning about redefining a function
 	  );

M2/Macaulay2/m2/test.m2

@@ -0,0 +1,29 @@
+
+--Global variables affecting printing
+--debugPrintCarets = false
+--debugPrintLineNumbers = true
+
+
+needs "some
+fi
+le"
+
+if (a == 3) then (
+    << a << endl;
+);
+
+value("error 1")
+
+1_1
+
+
+
+(error (1)) +15
+end--
+
+1_1
+
+
+
+load "~/Code/M2/Workshop-2026-Atlanta/test.m2"
+breakpoint()

M2/Macaulay2/packages/Macaulay2Doc/ov_debugging.m2

@@ -88,7 +88,10 @@ document {
     EXAMPLE {"g 4", "g 3"},
     "However, the following attempt results in an error, and the debugger starts up automatically.",
     EXAMPLE "g 2",
-    "You may use ", TO "help", ", as instructed, to view the commands available in the debugger.
+    "Here it says ENTERING DEBUGGER when you enter the deugger. You may use ", TO "help", ", as instructed, to view the commands available in the debugger.
+    While in the debugger, the input line says  \"<M2 debugger>\"  and the line numbers of the error are displayed to the right of the code. 
+    In addition there are carets below the specific characters causing the error or below the starting ending characters if the error is multiple lines.
+    The line numbers and carets can be toggled off by including at the start of your document debugPrintLineNumbers = false; and debugPrintCarets = false; respectively.
     As suggested by the help display, we can use ", TO "listLocalSymbols", " to list the local symbols and their values.",
     EXAMPLE "listLocalSymbols",
     "We see that the value of ", TT "x", " is 0, and that explains the error message about division by zero.