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from datetime import datetime, date
from decimal import Decimal
from json import JSONEncoder
# depending on the version WebOb might have 2 types of dicts
try:
# WebOb <= 1.1.1
from webob.multidict import MultiDict, UnicodeMultiDict
webob_dicts = (MultiDict, UnicodeMultiDict) # pragma: no cover
except ImportError: # pragma no cover
# WebOb >= 1.2
from webob.multidict import MultiDict
webob_dicts = (MultiDict,)
try:
from functools import singledispatch
except ImportError: # pragma: no cover
from singledispatch import singledispatch
try:
import sqlalchemy # noqa
try:
# SQLAlchemy 2.0 support
from sqlalchemy.engine import CursorResult as ResultProxy
from sqlalchemy.engine import Row as RowProxy
except ImportError:
from sqlalchemy.engine.result import ResultProxy, RowProxy
except ImportError:
# dummy classes since we don't have SQLAlchemy installed
class ResultProxy(object): # noqa
pass
class RowProxy(object): # noqa
pass
try:
from sqlalchemy.engine.cursor import LegacyCursorResult, LegacyRow
except ImportError: # pragma no cover
# dummy classes since we don't have SQLAlchemy installed
# or we're using SQLAlchemy < 1.4
class LegacyCursorResult(object): # noqa
pass
class LegacyRow(object): # noqa
pass
#
# encoders
#
def is_saobject(obj):
return hasattr(obj, '_sa_class_manager')
class GenericJSON(JSONEncoder):
'''
Generic JSON encoder. Makes several attempts to correctly JSONify
requested response objects.
'''
def default(self, obj):
'''
Converts an object and returns a ``JSON``-friendly structure.
:param obj: object or structure to be converted into a
``JSON``-ifiable structure
Considers the following special cases in order:
* object has a callable __json__() attribute defined
returns the result of the call to __json__()
* date and datetime objects
returns the object cast to str
* Decimal objects
returns the object cast to float
* SQLAlchemy objects
returns a copy of the object.__dict__ with internal SQLAlchemy
parameters removed
* SQLAlchemy ResultProxy objects
Casts the iterable ResultProxy into a list of tuples containing
the entire resultset data, returns the list in a dictionary
along with the resultset "row" count.
.. note:: {'count': 5, 'rows': [('Ed Jones',), ('Pete Jones',),
('Wendy Williams',), ('Mary Contrary',), ('Fred Smith',)]}
* SQLAlchemy RowProxy objects
Casts the RowProxy cursor object into a dictionary, probably
losing its ordered dictionary behavior in the process but
making it JSON-friendly.
* webob_dicts objects
returns webob_dicts.mixed() dictionary, which is guaranteed
to be JSON-friendly.
'''
if hasattr(obj, '__json__') and callable(obj.__json__):
return obj.__json__()
elif isinstance(obj, (date, datetime)):
return str(obj)
elif isinstance(obj, Decimal):
# XXX What to do about JSONEncoder crappy handling of Decimals?
# SimpleJSON has better Decimal encoding than the std lib
# but only in recent versions
return float(obj)
elif is_saobject(obj):
props = {}
for key in obj.__dict__:
if not key.startswith('_sa_'):
props[key] = getattr(obj, key)
return props
elif isinstance(obj, ResultProxy):
props = dict(rows=list(obj), count=obj.rowcount)
if props['count'] < 0:
props['count'] = len(props['rows'])
return props
elif isinstance(obj, LegacyCursorResult):
rows = [dict(row._mapping) for row in obj.fetchall()]
return {'count': len(rows), 'rows': rows}
elif isinstance(obj, LegacyRow):
return dict(obj._mapping)
elif isinstance(obj, RowProxy):
if obj.__class__.__name__ == 'Row':
# SQLAlchemy 2.0 support
obj = obj._mapping
return dict(obj)
elif isinstance(obj, webob_dicts):
return obj.mixed()
else:
return JSONEncoder.default(self, obj)
_default = GenericJSON()
def with_when_type(f):
# Add some backwards support for simplegeneric's API
f.when_type = f.register
return f
@with_when_type
@singledispatch
def jsonify(obj):
return _default.default(obj)
class GenericFunctionJSON(GenericJSON):
def default(self, obj):
return jsonify(obj)
_instance = GenericFunctionJSON()
def encode(obj):
return _instance.encode(obj)
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