Mini Shell
# traceback_exception_init() adapted from trio
#
# _ExceptionPrintContext and traceback_exception_format() copied from the standard
# library
from __future__ import annotations
import collections.abc
import sys
import textwrap
import traceback
from functools import singledispatch
from types import TracebackType
from typing import Any, List, Optional
from ._exceptions import BaseExceptionGroup
max_group_width = 15
max_group_depth = 10
_cause_message = (
"\nThe above exception was the direct cause of the following exception:\n\n"
)
_context_message = (
"\nDuring handling of the above exception, another exception occurred:\n\n"
)
def _format_final_exc_line(etype, value):
valuestr = _safe_string(value, "exception")
if value is None or not valuestr:
line = f"{etype}\n"
else:
line = f"{etype}: {valuestr}\n"
return line
def _safe_string(value, what, func=str):
try:
return func(value)
except BaseException:
return f"<{what} {func.__name__}() failed>"
class _ExceptionPrintContext:
def __init__(self):
self.seen = set()
self.exception_group_depth = 0
self.need_close = False
def indent(self):
return " " * (2 * self.exception_group_depth)
def emit(self, text_gen, margin_char=None):
if margin_char is None:
margin_char = "|"
indent_str = self.indent()
if self.exception_group_depth:
indent_str += margin_char + " "
if isinstance(text_gen, str):
yield textwrap.indent(text_gen, indent_str, lambda line: True)
else:
for text in text_gen:
yield textwrap.indent(text, indent_str, lambda line: True)
def exceptiongroup_excepthook(
etype: type[BaseException], value: BaseException, tb: TracebackType | None
) -> None:
sys.stderr.write("".join(traceback.format_exception(etype, value, tb)))
class PatchedTracebackException(traceback.TracebackException):
def __init__(
self,
exc_type: type[BaseException],
exc_value: BaseException,
exc_traceback: TracebackType | None,
*,
limit: int | None = None,
lookup_lines: bool = True,
capture_locals: bool = False,
compact: bool = False,
_seen: set[int] | None = None,
) -> None:
kwargs: dict[str, Any] = {}
if sys.version_info >= (3, 10):
kwargs["compact"] = compact
is_recursive_call = _seen is not None
if _seen is None:
_seen = set()
_seen.add(id(exc_value))
self.stack = traceback.StackSummary.extract(
traceback.walk_tb(exc_traceback),
limit=limit,
lookup_lines=lookup_lines,
capture_locals=capture_locals,
)
self.exc_type = exc_type
# Capture now to permit freeing resources: only complication is in the
# unofficial API _format_final_exc_line
self._str = _safe_string(exc_value, "exception")
try:
self.__notes__ = getattr(exc_value, "__notes__", None)
except KeyError:
# Workaround for https://github.com/python/cpython/issues/98778 on Python
# <= 3.9, and some 3.10 and 3.11 patch versions.
HTTPError = getattr(sys.modules.get("urllib.error", None), "HTTPError", ())
if sys.version_info[:2] <= (3, 11) and isinstance(exc_value, HTTPError):
self.__notes__ = None
else:
raise
if exc_type and issubclass(exc_type, SyntaxError):
# Handle SyntaxError's specially
self.filename = exc_value.filename
lno = exc_value.lineno
self.lineno = str(lno) if lno is not None else None
self.text = exc_value.text
self.offset = exc_value.offset
self.msg = exc_value.msg
if sys.version_info >= (3, 10):
end_lno = exc_value.end_lineno
self.end_lineno = str(end_lno) if end_lno is not None else None
self.end_offset = exc_value.end_offset
elif (
exc_type
and issubclass(exc_type, (NameError, AttributeError))
and getattr(exc_value, "name", None) is not None
):
suggestion = _compute_suggestion_error(exc_value, exc_traceback)
if suggestion:
self._str += f". Did you mean: '{suggestion}'?"
if lookup_lines:
# Force all lines in the stack to be loaded
for frame in self.stack:
frame.line
self.__suppress_context__ = (
exc_value.__suppress_context__ if exc_value is not None else False
)
# Convert __cause__ and __context__ to `TracebackExceptions`s, use a
# queue to avoid recursion (only the top-level call gets _seen == None)
if not is_recursive_call:
queue = [(self, exc_value)]
while queue:
te, e = queue.pop()
if e and e.__cause__ is not None and id(e.__cause__) not in _seen:
cause = PatchedTracebackException(
type(e.__cause__),
e.__cause__,
e.__cause__.__traceback__,
limit=limit,
lookup_lines=lookup_lines,
capture_locals=capture_locals,
_seen=_seen,
)
else:
cause = None
if compact:
need_context = (
cause is None and e is not None and not e.__suppress_context__
)
else:
need_context = True
if (
e
and e.__context__ is not None
and need_context
and id(e.__context__) not in _seen
):
context = PatchedTracebackException(
type(e.__context__),
e.__context__,
e.__context__.__traceback__,
limit=limit,
lookup_lines=lookup_lines,
capture_locals=capture_locals,
_seen=_seen,
)
else:
context = None
# Capture each of the exceptions in the ExceptionGroup along with each
# of their causes and contexts
if e and isinstance(e, BaseExceptionGroup):
exceptions = []
for exc in e.exceptions:
texc = PatchedTracebackException(
type(exc),
exc,
exc.__traceback__,
lookup_lines=lookup_lines,
capture_locals=capture_locals,
_seen=_seen,
)
exceptions.append(texc)
else:
exceptions = None
te.__cause__ = cause
te.__context__ = context
te.exceptions = exceptions
if cause:
queue.append((te.__cause__, e.__cause__))
if context:
queue.append((te.__context__, e.__context__))
if exceptions:
queue.extend(zip(te.exceptions, e.exceptions))
def format(self, *, chain=True, _ctx=None):
if _ctx is None:
_ctx = _ExceptionPrintContext()
output = []
exc = self
if chain:
while exc:
if exc.__cause__ is not None:
chained_msg = _cause_message
chained_exc = exc.__cause__
elif exc.__context__ is not None and not exc.__suppress_context__:
chained_msg = _context_message
chained_exc = exc.__context__
else:
chained_msg = None
chained_exc = None
output.append((chained_msg, exc))
exc = chained_exc
else:
output.append((None, exc))
for msg, exc in reversed(output):
if msg is not None:
yield from _ctx.emit(msg)
if exc.exceptions is None:
if exc.stack:
yield from _ctx.emit("Traceback (most recent call last):\n")
yield from _ctx.emit(exc.stack.format())
yield from _ctx.emit(exc.format_exception_only())
elif _ctx.exception_group_depth > max_group_depth:
# exception group, but depth exceeds limit
yield from _ctx.emit(f"... (max_group_depth is {max_group_depth})\n")
else:
# 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())
yield from _ctx.emit(exc.format_exception_only())
num_excs = len(exc.exceptions)
if num_excs <= max_group_width:
n = num_excs
else:
n = 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 max_group_width is not None:
truncated = i >= 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)
else:
remaining = num_excs - 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
def format_exception_only(self):
"""Format the exception part of the traceback.
The return value is a generator of strings, each ending in a newline.
Normally, the generator emits a single string; however, for
SyntaxError exceptions, it emits several lines that (when
printed) display detailed information about where the syntax
error occurred.
The message indicating which exception occurred is always the last
string in the output.
"""
if self.exc_type is None:
yield traceback._format_final_exc_line(None, self._str)
return
stype = self.exc_type.__qualname__
smod = self.exc_type.__module__
if smod not in ("__main__", "builtins"):
if not isinstance(smod, str):
smod = "<unknown>"
stype = smod + "." + stype
if not issubclass(self.exc_type, SyntaxError):
yield _format_final_exc_line(stype, self._str)
elif traceback_exception_format_syntax_error is not None:
yield from traceback_exception_format_syntax_error(self, stype)
else:
yield from traceback_exception_original_format_exception_only(self)
if isinstance(self.__notes__, collections.abc.Sequence):
for note in self.__notes__:
note = _safe_string(note, "note")
yield from [line + "\n" for line in note.split("\n")]
elif self.__notes__ is not None:
yield _safe_string(self.__notes__, "__notes__", func=repr)
traceback_exception_original_format = traceback.TracebackException.format
traceback_exception_original_format_exception_only = (
traceback.TracebackException.format_exception_only
)
traceback_exception_format_syntax_error = getattr(
traceback.TracebackException, "_format_syntax_error", None
)
if sys.excepthook is sys.__excepthook__:
traceback.TracebackException.__init__ = ( # type: ignore[assignment]
PatchedTracebackException.__init__
)
traceback.TracebackException.format = ( # type: ignore[assignment]
PatchedTracebackException.format
)
traceback.TracebackException.format_exception_only = ( # type: ignore[assignment]
PatchedTracebackException.format_exception_only
)
sys.excepthook = exceptiongroup_excepthook
# Ubuntu's system Python has a sitecustomize.py file that imports
# apport_python_hook and replaces sys.excepthook.
#
# The custom hook captures the error for crash reporting, and then calls
# sys.__excepthook__ to actually print the error.
#
# We don't mind it capturing the error for crash reporting, but we want to
# take over printing the error. So we monkeypatch the apport_python_hook
# module so that instead of calling sys.__excepthook__, it calls our custom
# hook.
#
# More details: https://github.com/python-trio/trio/issues/1065
if getattr(sys.excepthook, "__name__", None) in (
"apport_excepthook",
# on ubuntu 22.10 the hook was renamed to partial_apport_excepthook
"partial_apport_excepthook",
):
# patch traceback like above
traceback.TracebackException.__init__ = ( # type: ignore[assignment]
PatchedTracebackException.__init__
)
traceback.TracebackException.format = ( # type: ignore[assignment]
PatchedTracebackException.format
)
traceback.TracebackException.format_exception_only = ( # type: ignore[assignment]
PatchedTracebackException.format_exception_only
)
from types import ModuleType
import apport_python_hook
# monkeypatch the sys module that apport has imported
fake_sys = ModuleType("exceptiongroup_fake_sys")
fake_sys.__dict__.update(sys.__dict__)
fake_sys.__excepthook__ = exceptiongroup_excepthook
apport_python_hook.sys = fake_sys
@singledispatch
def format_exception_only(__exc: BaseException) -> List[str]:
return list(
PatchedTracebackException(
type(__exc), __exc, None, compact=True
).format_exception_only()
)
@format_exception_only.register
def _(__exc: type, value: BaseException) -> List[str]:
return format_exception_only(value)
@singledispatch
def format_exception(
__exc: BaseException,
limit: Optional[int] = None,
chain: bool = True,
) -> List[str]:
return list(
PatchedTracebackException(
type(__exc), __exc, __exc.__traceback__, limit=limit, compact=True
).format(chain=chain)
)
@format_exception.register
def _(
__exc: type,
value: BaseException,
tb: TracebackType,
limit: Optional[int] = None,
chain: bool = True,
) -> List[str]:
return format_exception(value, limit, chain)
@singledispatch
def print_exception(
__exc: BaseException,
limit: Optional[int] = None,
file: Any = None,
chain: bool = True,
) -> None:
if file is None:
file = sys.stderr
for line in PatchedTracebackException(
type(__exc), __exc, __exc.__traceback__, limit=limit
).format(chain=chain):
print(line, file=file, end="")
@print_exception.register
def _(
__exc: type,
value: BaseException,
tb: TracebackType,
limit: Optional[int] = None,
file: Any = None,
chain: bool = True,
) -> None:
print_exception(value, limit, file, chain)
def print_exc(
limit: Optional[int] = None,
file: Any | None = None,
chain: bool = True,
) -> None:
value = sys.exc_info()[1]
print_exception(value, limit, file, chain)
# Python levenshtein edit distance code for NameError/AttributeError
# suggestions, backported from 3.12
_MAX_CANDIDATE_ITEMS = 750
_MAX_STRING_SIZE = 40
_MOVE_COST = 2
_CASE_COST = 1
_SENTINEL = object()
def _substitution_cost(ch_a, ch_b):
if ch_a == ch_b:
return 0
if ch_a.lower() == ch_b.lower():
return _CASE_COST
return _MOVE_COST
def _compute_suggestion_error(exc_value, tb):
wrong_name = getattr(exc_value, "name", None)
if wrong_name is None or not isinstance(wrong_name, str):
return None
if isinstance(exc_value, AttributeError):
obj = getattr(exc_value, "obj", _SENTINEL)
if obj is _SENTINEL:
return None
obj = exc_value.obj
try:
d = dir(obj)
except Exception:
return None
else:
assert isinstance(exc_value, NameError)
# find most recent frame
if tb is None:
return None
while tb.tb_next is not None:
tb = tb.tb_next
frame = tb.tb_frame
d = list(frame.f_locals) + list(frame.f_globals) + list(frame.f_builtins)
if len(d) > _MAX_CANDIDATE_ITEMS:
return None
wrong_name_len = len(wrong_name)
if wrong_name_len > _MAX_STRING_SIZE:
return None
best_distance = wrong_name_len
suggestion = None
for possible_name in d:
if possible_name == wrong_name:
# A missing attribute is "found". Don't suggest it (see GH-88821).
continue
# No more than 1/3 of the involved characters should need changed.
max_distance = (len(possible_name) + wrong_name_len + 3) * _MOVE_COST // 6
# Don't take matches we've already beaten.
max_distance = min(max_distance, best_distance - 1)
current_distance = _levenshtein_distance(
wrong_name, possible_name, max_distance
)
if current_distance > max_distance:
continue
if not suggestion or current_distance < best_distance:
suggestion = possible_name
best_distance = current_distance
return suggestion
def _levenshtein_distance(a, b, max_cost):
# A Python implementation of Python/suggestions.c:levenshtein_distance.
# Both strings are the same
if a == b:
return 0
# Trim away common affixes
pre = 0
while a[pre:] and b[pre:] and a[pre] == b[pre]:
pre += 1
a = a[pre:]
b = b[pre:]
post = 0
while a[: post or None] and b[: post or None] and a[post - 1] == b[post - 1]:
post -= 1
a = a[: post or None]
b = b[: post or None]
if not a or not b:
return _MOVE_COST * (len(a) + len(b))
if len(a) > _MAX_STRING_SIZE or len(b) > _MAX_STRING_SIZE:
return max_cost + 1
# Prefer shorter buffer
if len(b) < len(a):
a, b = b, a
# Quick fail when a match is impossible
if (len(b) - len(a)) * _MOVE_COST > max_cost:
return max_cost + 1
# Instead of producing the whole traditional len(a)-by-len(b)
# matrix, we can update just one row in place.
# Initialize the buffer row
row = list(range(_MOVE_COST, _MOVE_COST * (len(a) + 1), _MOVE_COST))
result = 0
for bindex in range(len(b)):
bchar = b[bindex]
distance = result = bindex * _MOVE_COST
minimum = sys.maxsize
for index in range(len(a)):
# 1) Previous distance in this row is cost(b[:b_index], a[:index])
substitute = distance + _substitution_cost(bchar, a[index])
# 2) cost(b[:b_index], a[:index+1]) from previous row
distance = row[index]
# 3) existing result is cost(b[:b_index+1], a[index])
insert_delete = min(result, distance) + _MOVE_COST
result = min(insert_delete, substitute)
# cost(b[:b_index+1], a[:index+1])
row[index] = result
if result < minimum:
minimum = result
if minimum > max_cost:
# Everything in this row is too big, so bail early.
return max_cost + 1
return result
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