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gh-139551: add support for BaseExceptionGroup in IDLE #139563

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a84a178
add the support for BaseExceptionGroup
Locked-chess-official Oct 4, 2025
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require change
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bug fix
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remove extra line
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Fix exceptions printing logic in run.py
Locked-chess-official Oct 16, 2025
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102 changes: 85 additions & 17 deletions Lib/idlelib/run.py
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Original file line number Diff line number Diff line change
Expand Up @@ -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=""):
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Since this is anyway a local function, I'd suggest having other helpers to reduce the complexity of the function.

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):
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For instance, here, I would suggest using a separate function, say print_exc_group() that you would define locally as well.

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@picnixz picnixz Oct 5, 2025 •
edited
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The change that if isinstance(val, BaseExceptionGroup) branch becomes a function alone is difficult because it is a closure function.

Even with that, it's not really important. What is the issue with it being a local function? print_exc is already a local function. Just pass the arguments you need to that local function.

if tb:
if not prefix:
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Let's swap the if to be consistent with the other ifs.

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)
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I would prefer that - is stored as a variable, say sep = '-' * N where N is the number of '-' you want to print. You would also be able to use "prefix2".

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The code in traceback.py use many "-" to print instead of sep = '-' * N: (for example now in 3.13.7)

                # format exception group
                is_toplevel = (_ctx.exception_group_depth == 0)
                if is_toplevel:
                    _ctx.exception_group_depth += 1

                if exc.stack:
                    yield from _ctx.emit(
                        'Exception Group Traceback (most recent call last):\n',
                        margin_char = '+' if is_toplevel else None)
                    yield from _ctx.emit(exc.stack.format(colorize=colorize))

                yield from _ctx.emit(exc.format_exception_only(colorize=colorize))
                num_excs = len(exc.exceptions)
                if num_excs <= self.max_group_width:
                    n = num_excs
                else:
                    n = self.max_group_width + 1
                _ctx.need_close = False
                for i in range(n):
                    last_exc = (i == n-1)
                    if last_exc:
                        # The closing frame may be added by a recursive call
                        _ctx.need_close = True

                    if self.max_group_width is not None:
                        truncated = (i >= self.max_group_width)
                    else:
                        truncated = False
                    title = f'{i+1}' if not truncated else '...'
                    yield (_ctx.indent() +
                           ('+-' if i==0 else '  ') +
                           f'+---------------- {title} ----------------\n')
                    _ctx.exception_group_depth += 1
                    if not truncated:
                        yield from exc.exceptions[i].format(chain=chain, _ctx=_ctx, colorize=colorize)
                    else:
                        remaining = num_excs - self.max_group_width
                        plural = 's' if remaining > 1 else ''
                        yield from _ctx.emit(
                            f"and {remaining} more exception{plural}\n")

                    if last_exc and _ctx.need_close:
                        yield (_ctx.indent() +
                               "+------------------------------------\n")
                        _ctx.need_close = False
                    _ctx.exception_group_depth -= 1

                if is_toplevel:
                    assert _ctx.exception_group_depth == 1
                    _ctx.exception_group_depth = 0

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Then I would like you to actually split the lines as it's done, not have everything on a single line (as you can see each group containing - is on its own line).

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)

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1 change: 1 addition & 0 deletions Misc/NEWS.d/next/IDLE/2025-10-04-22-34-06.gh-issue-139551.hJDxw6.rst
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Original file line number Diff line number Diff line change
@@ -0,0 +1 @@
Add the support with BaseExceptionGroup in IDLE
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