gh-139551: add support for BaseExceptionGroup in IDLE

Lib/idlelib/run.py

@@ -250,30 +250,98 @@ def print_exception():
     sys.last_exc = val
     seen = set()
 
-    def print_exc(typ, exc, tb):
+    def print_exc(typ, exc, tb, prefix=""):
         seen.add(id(exc))
         context = exc.__context__
         cause = exc.__cause__
+        exclude = ("run.py", "rpc.py", "threading.py", "queue.py",
+                   "debugger_r.py", "bdb.py")
         if cause is not None and id(cause) not in seen:
-            print_exc(type(cause), cause, cause.__traceback__)
-            print("\nThe above exception was the direct cause "
-                  "of the following exception:\n", file=efile)
+            print_exc(type(cause), cause, cause.__traceback__, prefix)
+            if prefix:
+                print(f"{prefix}|\n{prefix}| The above exception was the direct cause "
+                      f"of the following exception:\n{prefix}|", file=efile)
+            else:
+                print("\nThe above exception was the direct cause "
+                      "of the following exception:\n", file=efile)
         elif (context is not None and
               not exc.__suppress_context__ and
               id(context) not in seen):
-            print_exc(type(context), context, context.__traceback__)
-            print("\nDuring handling of the above exception, "
-                  "another exception occurred:\n", file=efile)
-        if tb:
-            tbe = traceback.extract_tb(tb)
-            print('Traceback (most recent call last):', file=efile)
-            exclude = ("run.py", "rpc.py", "threading.py", "queue.py",
-                       "debugger_r.py", "bdb.py")
-            cleanup_traceback(tbe, exclude)
-            traceback.print_list(tbe, file=efile)
-        lines = get_message_lines(typ, exc, tb)
-        for line in lines:
-            print(line, end='', file=efile)
+            print_exc(type(context), context, context.__traceback__, prefix)
+            if prefix:
+                print(f"{prefix}|\n{prefix}| During handling of the above exception, "
+                      f"another exception occurred:\n{prefix}|", file=efile)
+            else:
+                print("\nDuring handling of the above exception, "
+                      "another exception occurred:\n", file=efile)
+        if isinstance(exc, BaseExceptionGroup):
+            if tb:
+                if not prefix:
+                    print("  + Exception Group Traceback (most recent call last):", file=efile)
+                else:
+                    print(f"{prefix}| Exception Group Traceback (most recent call last):", file=efile)
+                tbe = traceback.extract_tb(tb)
+                cleanup_traceback(tbe, exclude)
+                for line in traceback.format_list(tbe):
+                    for subline in line.rstrip().splitlines():
+                        if not prefix:
+                            print(f"  | {subline}", file=efile)
+                        else:
+                            print(f"{prefix}| {subline}", file=efile)
+            lines = get_message_lines(typ, exc, tb)
+            for line in lines:
+                if not prefix:
+                    print(f"  | {line}", end="", file=efile)
+                else:
+                    print(f"{prefix}| {line}", end="", file=efile)
+
+            for i, sub in enumerate(exc.exceptions, 1):
+                if i == 1:
+                    first_line_pre = "+-"
+                else:
+                    first_line_pre = "  "
+                if not prefix:
+                    print(f"  {first_line_pre}+---------------- {i} ----------------", file=efile)
+                else:
+                    print(f"{prefix}{first_line_pre}+---------------- {i} ----------------", file=efile)
+                if id(sub) not in seen:
+                    if not prefix:
+                        print_exc(type(sub), sub, sub.__traceback__, "    ")
+                    else:
+                        print_exc(type(sub), sub, sub.__traceback__, prefix + "  ")
+                    need_print_underline = not isinstance(sub, BaseExceptionGroup)
+                else:
+                    if not prefix:
+                        print("f    | <exception {type(sub).__name__} has printed>")
+                    else:
+                        print(f"{prefix}  | <exception {type(sub).__name__} has printed>")
+                    need_print_underline = True
+                if need_print_underline:
+                    if not prefix:
+                        print("    +------------------------------------", file=efile)
+                    else:
+                        print(f"  {prefix}+------------------------------------", file=efile)
+
+        else:
+            if tb:
+                if prefix:
+                    print(f"{prefix}| Traceback (most recent call last):", file=efile)
+                else:
+                    print("Traceback (most recent call last):", file=efile)
+                tbe = traceback.extract_tb(tb)
+                cleanup_traceback(tbe, exclude)
+                if prefix:
+                    for line in traceback.format_list(tbe):
+                        for subline in line.rstrip().splitlines():
+                            print(f"{prefix}| {subline}", file=efile)
+                else:
+                    traceback.print_list(tbe, file=efile)
+            lines = get_message_lines(typ, exc, tb)
+            for line in lines:
+                if prefix:
+                    print(f"{prefix}| {line}", end="", file=efile)
+                else:
+                    print(line, end='', file=efile)
 
     print_exc(typ, val, tb)
 

Misc/NEWS.d/next/IDLE/2025-10-04-22-34-06.gh-issue-139551.hJDxw6.rst

@@ -0,0 +1 @@
+Add the support with BaseExceptionGroup in IDLE