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Refactor exception classes #1129

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Refactor exception classes #1129

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156 changes: 7 additions & 149 deletions asyncpg/exceptions/_base.py
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Expand Up @@ -4,10 +4,11 @@
# This module is part of asyncpg and is released under
# the Apache 2.0 License: http://www.apache.org/licenses/LICENSE-2.0


import asyncpg
import sys
import textwrap
# PostgresMessageMeta imported for backward compatibility
from ._postgres_message import ( # noqa: F401
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You can add them to __all__. Then you won't need as and noqa.

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If I do that, then they will be imported with from ._base import * in asyncpg/exceptions/__init__.py, and then they will be accessible as asyncpg.PostgresMessage and asyncpg.PostgresMessageMeta

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Good point.

PostgresMessage as PostgresMessage,
PostgresMessageMeta as PostgresMessageMeta,
)


__all__ = ('PostgresError', 'FatalPostgresError', 'UnknownPostgresError',
Expand All @@ -18,150 +19,6 @@
'UnsupportedServerFeatureError')


def _is_asyncpg_class(cls):
modname = cls.__module__
return modname == 'asyncpg' or modname.startswith('asyncpg.')


class PostgresMessageMeta(type):

_message_map = {}
_field_map = {
'S': 'severity',
'V': 'severity_en',
'C': 'sqlstate',
'M': 'message',
'D': 'detail',
'H': 'hint',
'P': 'position',
'p': 'internal_position',
'q': 'internal_query',
'W': 'context',
's': 'schema_name',
't': 'table_name',
'c': 'column_name',
'd': 'data_type_name',
'n': 'constraint_name',
'F': 'server_source_filename',
'L': 'server_source_line',
'R': 'server_source_function'
}

def __new__(mcls, name, bases, dct):
cls = super().__new__(mcls, name, bases, dct)
if cls.__module__ == mcls.__module__ and name == 'PostgresMessage':
for f in mcls._field_map.values():
setattr(cls, f, None)

if _is_asyncpg_class(cls):
mod = sys.modules[cls.__module__]
if hasattr(mod, name):
raise RuntimeError('exception class redefinition: {}'.format(
name))

code = dct.get('sqlstate')
if code is not None:
existing = mcls._message_map.get(code)
if existing is not None:
raise TypeError('{} has duplicate SQLSTATE code, which is'
'already defined by {}'.format(
name, existing.__name__))
mcls._message_map[code] = cls

return cls

@classmethod
def get_message_class_for_sqlstate(mcls, code):
return mcls._message_map.get(code, UnknownPostgresError)


class PostgresMessage(metaclass=PostgresMessageMeta):

@classmethod
def _get_error_class(cls, fields):
sqlstate = fields.get('C')
return type(cls).get_message_class_for_sqlstate(sqlstate)

@classmethod
def _get_error_dict(cls, fields, query):
dct = {
'query': query
}

field_map = type(cls)._field_map
for k, v in fields.items():
field = field_map.get(k)
if field:
dct[field] = v

return dct

@classmethod
def _make_constructor(cls, fields, query=None):
dct = cls._get_error_dict(fields, query)

exccls = cls._get_error_class(fields)
message = dct.get('message', '')

# PostgreSQL will raise an exception when it detects
# that the result type of the query has changed from
# when the statement was prepared.
#
# The original error is somewhat cryptic and unspecific,
# so we raise a custom subclass that is easier to handle
# and identify.
#
# Note that we specifically do not rely on the error
# message, as it is localizable.
is_icse = (
exccls.__name__ == 'FeatureNotSupportedError' and
_is_asyncpg_class(exccls) and
dct.get('server_source_function') == 'RevalidateCachedQuery'
)

if is_icse:
exceptions = sys.modules[exccls.__module__]
exccls = exceptions.InvalidCachedStatementError
message = ('cached statement plan is invalid due to a database '
'schema or configuration change')

is_prepared_stmt_error = (
exccls.__name__ in ('DuplicatePreparedStatementError',
'InvalidSQLStatementNameError') and
_is_asyncpg_class(exccls)
)

if is_prepared_stmt_error:
hint = dct.get('hint', '')
hint += textwrap.dedent("""\

NOTE: pgbouncer with pool_mode set to "transaction" or
"statement" does not support prepared statements properly.
You have two options:

* if you are using pgbouncer for connection pooling to a
single server, switch to the connection pool functionality
provided by asyncpg, it is a much better option for this
purpose;

* if you have no option of avoiding the use of pgbouncer,
then you can set statement_cache_size to 0 when creating
the asyncpg connection object.
""")

dct['hint'] = hint

return exccls, message, dct

def as_dict(self):
dct = {}
for f in type(self)._field_map.values():
val = getattr(self, f)
if val is not None:
dct[f] = val
return dct


class PostgresError(PostgresMessage, Exception):
"""Base class for all Postgres errors."""

Expand Down Expand Up @@ -288,7 +145,8 @@ def new(cls, fields, query=None):
if exccls is PostgresLogMessage:
severity = dct.get('severity_en') or dct.get('severity')
if severity and severity.upper() == 'WARNING':
exccls = asyncpg.PostgresWarning
from . import PostgresWarning
exccls = PostgresWarning

if issubclass(exccls, (BaseException, Warning)):
msg = exccls(message_text)
Expand Down
153 changes: 153 additions & 0 deletions asyncpg/exceptions/_postgres_message.py
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@@ -0,0 +1,153 @@
# Copyright (C) 2016-present the asyncpg authors and contributors
# <see AUTHORS file>
#
# This module is part of asyncpg and is released under
# the Apache 2.0 License: http://www.apache.org/licenses/LICENSE-2.0

import sys
import textwrap


def _is_asyncpg_class(cls):
modname = cls.__module__
return modname == 'asyncpg' or modname.startswith('asyncpg.')


class PostgresMessageMeta(type):

_message_map = {}
_field_map = {
'S': 'severity',
'V': 'severity_en',
'C': 'sqlstate',
'M': 'message',
'D': 'detail',
'H': 'hint',
'P': 'position',
'p': 'internal_position',
'q': 'internal_query',
'W': 'context',
's': 'schema_name',
't': 'table_name',
'c': 'column_name',
'd': 'data_type_name',
'n': 'constraint_name',
'F': 'server_source_filename',
'L': 'server_source_line',
'R': 'server_source_function'
}

def __new__(mcls, name, bases, dct):
cls = super().__new__(mcls, name, bases, dct)
if cls.__module__ == mcls.__module__ and name == 'PostgresMessage':
for f in mcls._field_map.values():
setattr(cls, f, None)

if _is_asyncpg_class(cls):
mod = sys.modules[cls.__module__]
if hasattr(mod, name):
raise RuntimeError('exception class redefinition: {}'.format(
name))

code = dct.get('sqlstate')
if code is not None:
existing = mcls._message_map.get(code)
if existing is not None:
raise TypeError('{} has duplicate SQLSTATE code, which is'
'already defined by {}'.format(
name, existing.__name__))
mcls._message_map[code] = cls

return cls

@classmethod
def get_message_class_for_sqlstate(mcls, code):
from ._base import UnknownPostgresError
return mcls._message_map.get(code, UnknownPostgresError)


class PostgresMessage(metaclass=PostgresMessageMeta):

@classmethod
def _get_error_class(cls, fields):
sqlstate = fields.get('C')
return type(cls).get_message_class_for_sqlstate(sqlstate)

@classmethod
def _get_error_dict(cls, fields, query):
dct = {
'query': query
}

field_map = type(cls)._field_map
for k, v in fields.items():
field = field_map.get(k)
if field:
dct[field] = v

return dct

@classmethod
def _make_constructor(cls, fields, query=None):
dct = cls._get_error_dict(fields, query)

exccls = cls._get_error_class(fields)
message = dct.get('message', '')

# PostgreSQL will raise an exception when it detects
# that the result type of the query has changed from
# when the statement was prepared.
#
# The original error is somewhat cryptic and unspecific,
# so we raise a custom subclass that is easier to handle
# and identify.
#
# Note that we specifically do not rely on the error
# message, as it is localizable.
is_icse = (
exccls.__name__ == 'FeatureNotSupportedError' and
_is_asyncpg_class(exccls) and
dct.get('server_source_function') == 'RevalidateCachedQuery'
)

if is_icse:
exceptions = sys.modules[exccls.__module__]
exccls = exceptions.InvalidCachedStatementError
message = ('cached statement plan is invalid due to a database '
'schema or configuration change')

is_prepared_stmt_error = (
exccls.__name__ in ('DuplicatePreparedStatementError',
'InvalidSQLStatementNameError') and
_is_asyncpg_class(exccls)
)

if is_prepared_stmt_error:
hint = dct.get('hint', '')
hint += textwrap.dedent("""\

NOTE: pgbouncer with pool_mode set to "transaction" or
"statement" does not support prepared statements properly.
You have two options:

* if you are using pgbouncer for connection pooling to a
single server, switch to the connection pool functionality
provided by asyncpg, it is a much better option for this
purpose;

* if you have no option of avoiding the use of pgbouncer,
then you can set statement_cache_size to 0 when creating
the asyncpg connection object.
""")

dct['hint'] = hint

return exccls, message, dct

def as_dict(self):
dct = {}
for f in type(self)._field_map.values():
val = getattr(self, f)
if val is not None:
dct[f] = val
return dct