debugging.py

"""Interactive debugging with PDB, the Python Debugger."""
import argparse
import functools
import sys
import types
from typing import Any
from typing import Callable
from typing import Generator
from typing import List
from typing import Optional
from typing import Tuple
from typing import Type
from typing import TYPE_CHECKING
from typing import Union

from _pytest import outcomes
from _pytest._code import ExceptionInfo
from _pytest.config import Config
from _pytest.config import ConftestImportFailure
from _pytest.config import hookimpl
from _pytest.config import PytestPluginManager
from _pytest.config.argparsing import Parser
from _pytest.config.exceptions import UsageError
from _pytest.nodes import Node
from _pytest.reports import BaseReport

if TYPE_CHECKING:
    from _pytest.capture import CaptureManager
    from _pytest.runner import CallInfo


def _validate_usepdb_cls(value: str) -> Tuple[str, str]:
    """Validate syntax of --pdbcls option."""
    try:
        modname, classname = value.split(":")
    except ValueError as e:
        raise argparse.ArgumentTypeError(
            f"{value!r} is not in the format 'modname:classname'"
        ) from e
    return (modname, classname)


def pytest_addoption(parser: Parser) -> None:
    group = parser.getgroup("general")
    group._addoption(
        "--pdb",
        dest="usepdb",
        action="store_true",
        help="Start the interactive Python debugger on errors or KeyboardInterrupt",
    )
    group._addoption(
        "--pdbcls",
        dest="usepdb_cls",
        metavar="modulename:classname",
        type=_validate_usepdb_cls,
        help="Specify a custom interactive Python debugger for use with --pdb."
        "For example: --pdbcls=IPython.terminal.debugger:TerminalPdb",
    )
    group._addoption(
        "--trace",
        dest="trace",
        action="store_true",
        help="Immediately break when running each test",
    )


def pytest_configure(config: Config) -> None:
    import pdb

    if config.getvalue("trace"):
        config.pluginmanager.register(PdbTrace(), "pdbtrace")
    if config.getvalue("usepdb"):
        config.pluginmanager.register(PdbInvoke(), "pdbinvoke")

    pytestPDB._saved.append(
        (pdb.set_trace, pytestPDB._pluginmanager, pytestPDB._config)
    )
    pdb.set_trace = pytestPDB.set_trace
    pytestPDB._pluginmanager = config.pluginmanager
    pytestPDB._config = config

    # NOTE: not using pytest_unconfigure, since it might get called although
    #       pytest_configure was not (if another plugin raises UsageError).
    def fin() -> None:
        (
            pdb.set_trace,
            pytestPDB._pluginmanager,
            pytestPDB._config,
        ) = pytestPDB._saved.pop()

    config.add_cleanup(fin)


class pytestPDB:
    """Pseudo PDB that defers to the real pdb."""

    _pluginmanager: Optional[PytestPluginManager] = None
    _config: Optional[Config] = None
    _saved: List[
        Tuple[Callable[..., None], Optional[PytestPluginManager], Optional[Config]]
    ] = []
    _recursive_debug = 0
    _wrapped_pdb_cls: Optional[Tuple[Type[Any], Type[Any]]] = None

    @classmethod
    def _is_capturing(cls, capman: Optional["CaptureManager"]) -> Union[str, bool]:
        if capman:
            return capman.is_capturing()
        return False

    @classmethod
    def _import_pdb_cls(cls, capman: Optional["CaptureManager"]):
        if not cls._config:
            import pdb

            # Happens when using pytest.set_trace outside of a test.
            return pdb.Pdb

        usepdb_cls = cls._config.getvalue("usepdb_cls")

        if cls._wrapped_pdb_cls and cls._wrapped_pdb_cls[0] == usepdb_cls:
            return cls._wrapped_pdb_cls[1]

        if usepdb_cls:
            modname, classname = usepdb_cls

            try:
                __import__(modname)
                mod = sys.modules[modname]

                # Handle --pdbcls=pdb:pdb.Pdb (useful e.g. with pdbpp).
                parts = classname.split(".")
                pdb_cls = getattr(mod, parts[0])
                for part in parts[1:]:
                    pdb_cls = getattr(pdb_cls, part)
            except Exception as exc:
                value = ":".join((modname, classname))
                raise UsageError(
                    f"--pdbcls: could not import {value!r}: {exc}"
                ) from exc
        else:
            import pdb

            pdb_cls = pdb.Pdb

        wrapped_cls = cls._get_pdb_wrapper_class(pdb_cls, capman)
        cls._wrapped_pdb_cls = (usepdb_cls, wrapped_cls)
        return wrapped_cls

    @classmethod
    def _get_pdb_wrapper_class(cls, pdb_cls, capman: Optional["CaptureManager"]):
        import _pytest.config

        # Type ignored because mypy doesn't support "dynamic"
        # inheritance like this.
        class PytestPdbWrapper(pdb_cls):  # type: ignore[valid-type,misc]
            _pytest_capman = capman
            _continued = False

            def do_debug(self, arg):
                cls._recursive_debug += 1
                ret = super().do_debug(arg)
                cls._recursive_debug -= 1
                return ret

            def do_continue(self, arg):
                ret = super().do_continue(arg)
                if cls._recursive_debug == 0:
                    assert cls._config is not None
                    tw = _pytest.config.create_terminal_writer(cls._config)
                    tw.line()

                    capman = self._pytest_capman
                    capturing = pytestPDB._is_capturing(capman)
                    if capturing:
                        if capturing == "global":
                            tw.sep(">", "PDB continue (IO-capturing resumed)")
                        else:
                            tw.sep(
                                ">",
                                "PDB continue (IO-capturing resumed for %s)"
                                % capturing,
                            )
                        assert capman is not None
                        capman.resume()
                    else:
                        tw.sep(">", "PDB continue")
                assert cls._pluginmanager is not None
                cls._pluginmanager.hook.pytest_leave_pdb(config=cls._config, pdb=self)
                self._continued = True
                return ret

            do_c = do_cont = do_continue

            def do_quit(self, arg):
                """Raise Exit outcome when quit command is used in pdb.

                This is a bit of a hack - it would be better if BdbQuit
                could be handled, but this would require to wrap the
                whole pytest run, and adjust the report etc.
                """
                ret = super().do_quit(arg)

                if cls._recursive_debug == 0:
                    outcomes.exit("Quitting debugger")

                return ret

            do_q = do_quit
            do_exit = do_quit

            def setup(self, f, tb):
                """Suspend on setup().

                Needed after do_continue resumed, and entering another
                breakpoint again.
                """
                ret = super().setup(f, tb)
                if not ret and self._continued:
                    # pdb.setup() returns True if the command wants to exit
                    # from the interaction: do not suspend capturing then.
                    if self._pytest_capman:
                        self._pytest_capman.suspend_global_capture(in_=True)
                return ret

            def get_stack(self, f, t):
                stack, i = super().get_stack(f, t)
                if f is None:
                    # Find last non-hidden frame.
                    i = max(0, len(stack) - 1)
                    while i and stack[i][0].f_locals.get("__tracebackhide__", False):
                        i -= 1
                return stack, i

        return PytestPdbWrapper

    @classmethod
    def _init_pdb(cls, method, *args, **kwargs):
        """Initialize PDB debugging, dropping any IO capturing."""
        import _pytest.config

        if cls._pluginmanager is None:
            capman: Optional[CaptureManager] = None
        else:
            capman = cls._pluginmanager.getplugin("capturemanager")
        if capman:
            capman.suspend(in_=True)

        if cls._config:
            tw = _pytest.config.create_terminal_writer(cls._config)
            tw.line()

            if cls._recursive_debug == 0:
                # Handle header similar to pdb.set_trace in py37+.
                header = kwargs.pop("header", None)
                if header is not None:
                    tw.sep(">", header)
                else:
                    capturing = cls._is_capturing(capman)
                    if capturing == "global":
                        tw.sep(">", f"PDB {method} (IO-capturing turned off)")
                    elif capturing:
                        tw.sep(
                            ">",
                            "PDB %s (IO-capturing turned off for %s)"
                            % (method, capturing),
                        )
                    else:
                        tw.sep(">", f"PDB {method}")

        _pdb = cls._import_pdb_cls(capman)(**kwargs)

        if cls._pluginmanager:
            cls._pluginmanager.hook.pytest_enter_pdb(config=cls._config, pdb=_pdb)
        return _pdb

    @classmethod
    def set_trace(cls, *args, **kwargs) -> None:
        """Invoke debugging via ``Pdb.set_trace``, dropping any IO capturing."""
        frame = sys._getframe().f_back
        _pdb = cls._init_pdb("set_trace", *args, **kwargs)
        _pdb.set_trace(frame)


class PdbInvoke:
    def pytest_exception_interact(
        self, node: Node, call: "CallInfo[Any]", report: BaseReport
    ) -> None:
        capman = node.config.pluginmanager.getplugin("capturemanager")
        if capman:
            capman.suspend_global_capture(in_=True)
            out, err = capman.read_global_capture()
            sys.stdout.write(out)
            sys.stdout.write(err)
        assert call.excinfo is not None
        _enter_pdb(node, call.excinfo, report)

    def pytest_internalerror(self, excinfo: ExceptionInfo[BaseException]) -> None:
        tb = _postmortem_traceback(excinfo)
        post_mortem(tb)


class PdbTrace:
    @hookimpl(hookwrapper=True)
    def pytest_pyfunc_call(self, pyfuncitem) -> Generator[None, None, None]:
        wrap_pytest_function_for_tracing(pyfuncitem)
        yield


def wrap_pytest_function_for_tracing(pyfuncitem):
    """Change the Python function object of the given Function item by a
    wrapper which actually enters pdb before calling the python function
    itself, effectively leaving the user in the pdb prompt in the first
    statement of the function."""
    _pdb = pytestPDB._init_pdb("runcall")
    testfunction = pyfuncitem.obj

    # we can't just return `partial(pdb.runcall, testfunction)` because (on
    # python < 3.7.4) runcall's first param is `func`, which means we'd get
    # an exception if one of the kwargs to testfunction was called `func`.
    @functools.wraps(testfunction)
    def wrapper(*args, **kwargs):
        func = functools.partial(testfunction, *args, **kwargs)
        _pdb.runcall(func)

    pyfuncitem.obj = wrapper


def maybe_wrap_pytest_function_for_tracing(pyfuncitem):
    """Wrap the given pytestfunct item for tracing support if --trace was given in
    the command line."""
    if pyfuncitem.config.getvalue("trace"):
        wrap_pytest_function_for_tracing(pyfuncitem)


def _enter_pdb(
    node: Node, excinfo: ExceptionInfo[BaseException], rep: BaseReport
) -> BaseReport:
    # XXX we re-use the TerminalReporter's terminalwriter
    # because this seems to avoid some encoding related troubles
    # for not completely clear reasons.
    tw = node.config.pluginmanager.getplugin("terminalreporter")._tw
    tw.line()

    showcapture = node.config.option.showcapture

    for sectionname, content in (
        ("stdout", rep.capstdout),
        ("stderr", rep.capstderr),
        ("log", rep.caplog),
    ):
        if showcapture in (sectionname, "all") and content:
            tw.sep(">", "captured " + sectionname)
            if content[-1:] == "\n":
                content = content[:-1]
            tw.line(content)

    tw.sep(">", "traceback")
    rep.toterminal(tw)
    tw.sep(">", "entering PDB")
    tb = _postmortem_traceback(excinfo)
    rep._pdbshown = True  # type: ignore[attr-defined]
    post_mortem(tb)
    return rep


def _postmortem_traceback(excinfo: ExceptionInfo[BaseException]) -> types.TracebackType:
    from doctest import UnexpectedException

    if isinstance(excinfo.value, UnexpectedException):
        # A doctest.UnexpectedException is not useful for post_mortem.
        # Use the underlying exception instead:
        return excinfo.value.exc_info[2]
    elif isinstance(excinfo.value, ConftestImportFailure):
        # A config.ConftestImportFailure is not useful for post_mortem.
        # Use the underlying exception instead:
        return excinfo.value.excinfo[2]
    else:
        assert excinfo._excinfo is not None
        return excinfo._excinfo[2]


def post_mortem(t: types.TracebackType) -> None:
    p = pytestPDB._init_pdb("post_mortem")
    p.reset()
    p.interaction(None, t)
    if p.quitting:
        outcomes.exit("Quitting debugger")