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[otConverters] must also implement _LazyList.__radd__

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We can't set, e.g. `__radd__ = NotImplemented` as it's not a callable.
NotImplemented is what is returned from a rich comparison method
when self doesn't know how to compare with the other object.

_LazyList object may also occur on the right hand side of a `+`
operator, when the left operand is a list. Also in this case we
want to first unpack the _LazyList and return a new list containing
elements from both.
This commit is contained in:
Cosimo Lupo 2017-08-18 15:53:56 +01:00
parent 6ef48bd26f
commit 1aef1683df
1 changed files with 18 additions and 7 deletions
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25
Lib/fontTools/ttLib/tables/otConverters.py
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@ -70,15 +70,18 @@ def buildConverters(tableSpec, tableNamespace):
class _MissingItem(tuple): class _MissingItem(tuple):
__slots__ = () __slots__ = ()
try: try:
from collections import UserList from collections import UserList
except: except ImportError:
from UserList import UserList from UserList import UserList
class _LazyList(UserList): class _LazyList(UserList):
def __getslice__(self, i, j): def __getslice__(self, i, j):
return self.__getitem__(slice(i, j)) return self.__getitem__(slice(i, j))
def __getitem__(self, k): def __getitem__(self, k):
if isinstance(k, slice): if isinstance(k, slice):
indices = range(*k.indices(len(self))) indices = range(*k.indices(len(self)))
@ -89,13 +92,21 @@ class _LazyList(UserList):
item = self.conv.read(self.reader, self.font, {}) item = self.conv.read(self.reader, self.font, {})
self.data[k] = item self.data[k] = item
return item return item
def __add__(self, other): def __add__(self, other):
if isinstance(other, UserList): if isinstance(other, _LazyList):
other = other[:] other = list(other)
return self[:] + other elif isinstance(other, list):
# Not needed currently pass
__radd__ = NotImplemented else:
__iadd__ = NotImplemented return NotImplemented
return list(self) + other
def __radd__(self, other):
if not isinstance(other, list):
return NotImplemented
return other + list(self)
class BaseConverter(object): class BaseConverter(object):