mercurial/error.py

hgweb: refactor 304 handling code

We had generic code in wsgirequest for handling HTTP 304 responses.
We also had a special case for it in the catch all exception handler
in the WSGI application.

We only ever raise 304 in one place. So, we don't need to treat it
specially in the catch all exception handler.

But it is useful to validate behavior of 304 responses. We port the
code that sends a 304 to use the new response API. We then move the
code for screening 304 sanity into the new response API.

As part of doing so, we discovered that we would send
Content-Length: 0. This is not allowed. So, we fix our response code
to not emit that header for empty response bodies.

Differential Revision: https://phab.mercurial-scm.org/D2794

# error.py - Mercurial exceptions
#
# Copyright 2005-2008 Matt Mackall <[e-mail]>
#
# This software may be used and distributed according to the terms of the
# GNU General Public License version 2 or any later version.

"""Mercurial exceptions.

This allows us to catch exceptions at higher levels without forcing
imports.
"""

from __future__ import absolute_import

# Do not import anything but pycompat here, please
from . import pycompat

def _tobytes(exc):
    """Byte-stringify exception in the same way as BaseException_str()"""
    if not exc.args:
        return b''
    if len(exc.args) == 1:
        return pycompat.bytestr(exc.args[0])
    return b'(%s)' % b', '.join(b"'%s'" % pycompat.bytestr(a) for a in exc.args)

class Hint(object):
    """Mix-in to provide a hint of an error

    This should come first in the inheritance list to consume a hint and
    pass remaining arguments to the exception class.
    """
    def __init__(self, *args, **kw):
        self.hint = kw.pop(r'hint', None)
        super(Hint, self).__init__(*args, **kw)

class RevlogError(Hint, Exception):
    __bytes__ = _tobytes

class FilteredIndexError(IndexError):
    __bytes__ = _tobytes

class LookupError(RevlogError, KeyError):
    def __init__(self, name, index, message):
        self.name = name
        self.index = index
        # this can't be called 'message' because at least some installs of
        # Python 2.6+ complain about the 'message' property being deprecated
        self.lookupmessage = message
        if isinstance(name, bytes) and len(name) == 20:
            from .node import short
            name = short(name)
        RevlogError.__init__(self, '%s@%s: %s' % (index, name, message))

    def __bytes__(self):
        return RevlogError.__bytes__(self)

    def __str__(self):
        return RevlogError.__str__(self)

class FilteredLookupError(LookupError):
    pass

class ManifestLookupError(LookupError):
    pass

class CommandError(Exception):
    """Exception raised on errors in parsing the command line."""
    __bytes__ = _tobytes

class InterventionRequired(Hint, Exception):
    """Exception raised when a command requires human intervention."""
    __bytes__ = _tobytes

class Abort(Hint, Exception):
    """Raised if a command needs to print an error and exit."""
    __bytes__ = _tobytes

class HookLoadError(Abort):
    """raised when loading a hook fails, aborting an operation

    Exists to allow more specialized catching."""

class HookAbort(Abort):
    """raised when a validation hook fails, aborting an operation

    Exists to allow more specialized catching."""

class ConfigError(Abort):
    """Exception raised when parsing config files"""

class UpdateAbort(Abort):
    """Raised when an update is aborted for destination issue"""

class MergeDestAbort(Abort):
    """Raised when an update is aborted for destination issues"""

class NoMergeDestAbort(MergeDestAbort):
    """Raised when an update is aborted because there is nothing to merge"""

class ManyMergeDestAbort(MergeDestAbort):
    """Raised when an update is aborted because destination is ambiguous"""

class ResponseExpected(Abort):
    """Raised when an EOF is received for a prompt"""
    def __init__(self):
        from .i18n import _
        Abort.__init__(self, _('response expected'))

class OutOfBandError(Hint, Exception):
    """Exception raised when a remote repo reports failure"""
    __bytes__ = _tobytes

class ParseError(Hint, Exception):
    """Raised when parsing config files and {rev,file}sets (msg[, pos])"""
    __bytes__ = _tobytes

class PatchError(Exception):
    __bytes__ = _tobytes

class UnknownIdentifier(ParseError):
    """Exception raised when a {rev,file}set references an unknown identifier"""

    def __init__(self, function, symbols):
        from .i18n import _
        ParseError.__init__(self, _("unknown identifier: %s") % function)
        self.function = function
        self.symbols = symbols

class RepoError(Hint, Exception):
    __bytes__ = _tobytes

class RepoLookupError(RepoError):
    pass

class FilteredRepoLookupError(RepoLookupError):
    pass

class CapabilityError(RepoError):
    pass

class RequirementError(RepoError):
    """Exception raised if .hg/requires has an unknown entry."""

class StdioError(IOError):
    """Raised if I/O to stdout or stderr fails"""

    def __init__(self, err):
        IOError.__init__(self, err.errno, err.strerror)

    # no __bytes__() because error message is derived from the standard IOError

class UnsupportedMergeRecords(Abort):
    def __init__(self, recordtypes):
        from .i18n import _
        self.recordtypes = sorted(recordtypes)
        s = ' '.join(self.recordtypes)
        Abort.__init__(
            self, _('unsupported merge state records: %s') % s,
            hint=_('see https://mercurial-scm.org/wiki/MergeStateRecords for '
                   'more information'))

class UnknownVersion(Abort):
    """generic exception for aborting from an encounter with an unknown version
    """

    def __init__(self, msg, hint=None, version=None):
        self.version = version
        super(UnknownVersion, self).__init__(msg, hint=hint)

class LockError(IOError):
    def __init__(self, errno, strerror, filename, desc):
        IOError.__init__(self, errno, strerror, filename)
        self.desc = desc

    # no __bytes__() because error message is derived from the standard IOError

class LockHeld(LockError):
    def __init__(self, errno, filename, desc, locker):
        LockError.__init__(self, errno, 'Lock held', filename, desc)
        self.locker = locker

class LockUnavailable(LockError):
    pass

# LockError is for errors while acquiring the lock -- this is unrelated
class LockInheritanceContractViolation(RuntimeError):
    __bytes__ = _tobytes

class ResponseError(Exception):
    """Raised to print an error with part of output and exit."""
    __bytes__ = _tobytes

class UnknownCommand(Exception):
    """Exception raised if command is not in the command table."""
    __bytes__ = _tobytes

class AmbiguousCommand(Exception):
    """Exception raised if command shortcut matches more than one command."""
    __bytes__ = _tobytes

# derived from KeyboardInterrupt to simplify some breakout code
class SignalInterrupt(KeyboardInterrupt):
    """Exception raised on SIGTERM and SIGHUP."""

class SignatureError(Exception):
    __bytes__ = _tobytes

class PushRaced(RuntimeError):
    """An exception raised during unbundling that indicate a push race"""
    __bytes__ = _tobytes

class ProgrammingError(Hint, RuntimeError):
    """Raised if a mercurial (core or extension) developer made a mistake"""
    __bytes__ = _tobytes

class WdirUnsupported(Exception):
    """An exception which is raised when 'wdir()' is not supported"""
    __bytes__ = _tobytes

# bundle2 related errors
class BundleValueError(ValueError):
    """error raised when bundle2 cannot be processed"""
    __bytes__ = _tobytes

class BundleUnknownFeatureError(BundleValueError):
    def __init__(self, parttype=None, params=(), values=()):
        self.parttype = parttype
        self.params = params
        self.values = values
        if self.parttype is None:
            msg = 'Stream Parameter'
        else:
            msg = parttype
        entries = self.params
        if self.params and self.values:
            assert len(self.params) == len(self.values)
            entries = []
            for idx, par in enumerate(self.params):
                val = self.values[idx]
                if val is None:
                    entries.append(val)
                else:
                    entries.append("%s=%r" % (par, val))
        if entries:
            msg = '%s - %s' % (msg, ', '.join(entries))
        ValueError.__init__(self, msg)

class ReadOnlyPartError(RuntimeError):
    """error raised when code tries to alter a part being generated"""
    __bytes__ = _tobytes

class PushkeyFailed(Abort):
    """error raised when a pushkey part failed to update a value"""

    def __init__(self, partid, namespace=None, key=None, new=None, old=None,
                 ret=None):
        self.partid = partid
        self.namespace = namespace
        self.key = key
        self.new = new
        self.old = old
        self.ret = ret
        # no i18n expected to be processed into a better message
        Abort.__init__(self, 'failed to update value for "%s/%s"'
                       % (namespace, key))

class CensoredNodeError(RevlogError):
    """error raised when content verification fails on a censored node

    Also contains the tombstone data substituted for the uncensored data.
    """

    def __init__(self, filename, node, tombstone):
        from .node import short
        RevlogError.__init__(self, '%s:%s' % (filename, short(node)))
        self.tombstone = tombstone

class CensoredBaseError(RevlogError):
    """error raised when a delta is rejected because its base is censored

    A delta based on a censored revision must be formed as single patch
    operation which replaces the entire base with new content. This ensures
    the delta may be applied by clones which have not censored the base.
    """

class InvalidBundleSpecification(Exception):
    """error raised when a bundle specification is invalid.

    This is used for syntax errors as opposed to support errors.
    """
    __bytes__ = _tobytes

class UnsupportedBundleSpecification(Exception):
    """error raised when a bundle specification is not supported."""
    __bytes__ = _tobytes

class CorruptedState(Exception):
    """error raised when a command is not able to read its state from file"""
    __bytes__ = _tobytes

class PeerTransportError(Abort):
    """Transport-level I/O error when communicating with a peer repo."""

class InMemoryMergeConflictsError(Exception):
    """Exception raised when merge conflicts arose during an in-memory merge."""
    __bytes__ = _tobytes