Don't raise error if set_extension has getter and setter (closes #2177)

Improve error messages, raise error if setter is specified without a getter and compare against _unset to allow default=None. Also add more tests.

spacy/errors.py

@@ -218,8 +218,8 @@ class Errors(object):
     E082 = ("Error deprojectivizing parse: number of heads ({n_heads}), "
             "projective heads ({n_proj_heads}) and labels ({n_labels}) do not "
             "match.")
-    E083 = ("Error setting extension: only one of default, getter, setter and "
+    E083 = ("Error setting extension: only one of `default`, `method`, or "
-            "method is allowed. {n_args} keyword arguments were specified.")
+            "`getter` (plus optional `setter`) is allowed. Got: {nr_defined}")
     E084 = ("Error assigning label ID {label} to span: not in StringStore.")
     E085 = ("Can't create lexeme for string '{string}'.")
     E086 = ("Error deserializing lexeme '{string}': orth ID {orth_id} does "
@@ -233,6 +233,12 @@ class Errors(object):
             "`nlp.max_length` limit. The limit is in number of characters, so "
             "you can check whether your inputs are too long by checking "
             "`len(text)`.")
+    E089 = ("Extensions can't have a setter argument without a getter "
+            "argument. Check the keyword arguments on `set_extension`.")
+    E090 = ("Extension '{name}' already exists on {obj}. To overwrite the "
+            "existing extension, set `force=True` on `{obj}.set_extension`.")
+    E091 = ("Invalid extension attribute {name}: expected callable or None, "
+            "but got: {value}")
 
 
 @add_codes

spacy/tests/test_underscore.py

@@ -1,4 +1,11 @@
+# coding: utf-8
+from __future__ import unicode_literals
+
+import pytest
 from mock import Mock
+
+from ..vocab import Vocab
+from ..tokens.doc import Doc
 from ..tokens.underscore import Underscore
 
 
@@ -51,3 +58,36 @@ def test_token_underscore_method():
                                             None, None)
     token._ = Underscore(Underscore.token_extensions, token, start=token.idx)
     assert token._.hello() == 'cheese'
+
+
+@pytest.mark.parametrize('obj', [
+    Doc(Vocab(), words=['hello', 'world']),
+    Doc(Vocab(), words=['hello', 'world'])[1],
+    Doc(Vocab(), words=['hello', 'world'])[0:2]])
+def test_underscore_raises_for_dup(obj):
+    obj.set_extension('test', default=None)
+    with pytest.raises(ValueError):
+        obj.set_extension('test', default=None)
+
+
+@pytest.mark.parametrize('invalid_kwargs', [
+    {'getter': None, 'setter': lambda: None},
+    {'default': None, 'method': lambda: None, 'getter': lambda: None},
+    {'setter': lambda: None},
+    {'default': None, 'method': lambda: None},
+    {'getter': True}])
+def test_underscore_raises_for_invalid(invalid_kwargs):
+    doc = Doc(Vocab(), words=['hello', 'world'])
+    with pytest.raises(ValueError):
+        doc.set_extension('test', **invalid_kwargs, force=True)
+
+
+@pytest.mark.parametrize('valid_kwargs', [
+    {'getter': lambda: None},
+    {'getter': lambda: None, 'setter': lambda: None},
+    {'default': 'hello'},
+    {'default': None},
+    {'method': lambda: None}])
+def test_underscore_accepts_valid(valid_kwargs):
+    doc = Doc(Vocab(), words=['hello', 'world'])
+    doc.set_extension('test', **valid_kwargs, force=True)

spacy/tokens/doc.pyx

@@ -33,7 +33,7 @@ from ..util import normalize_slice
 from ..compat import is_config, copy_reg, pickle, basestring_
 from ..errors import Errors, Warnings, deprecation_warning
 from .. import util
-from .underscore import Underscore
+from .underscore import Underscore, get_ext_args
 from ._retokenize import Retokenizer
 
 DEF PADDING = 5
@@ -95,12 +95,10 @@ cdef class Doc:
                       spaces=[True, False, False])
     """
     @classmethod
-    def set_extension(cls, name, default=None, method=None,
+    def set_extension(cls, name, **kwargs):
-                      getter=None, setter=None):
+        if cls.has_extension(name) and not kwargs.get('force', False):
-        nr_defined = sum(t is not None for t in (default, getter, setter, method))
+            raise ValueError(Errors.E090.format(name=name, obj='Doc'))
-        if nr_defined != 1:
+        Underscore.doc_extensions[name] = get_ext_args(**kwargs)
-            raise ValueError(Errors.E083.format(n_args=nr_defined))
-        Underscore.doc_extensions[name] = (default, method, getter, setter)
 
     @classmethod
     def get_extension(cls, name):

spacy/tokens/span.pyx

@@ -17,15 +17,16 @@ from ..attrs cimport IS_PUNCT, IS_SPACE
 from ..lexeme cimport Lexeme
 from ..compat import is_config
 from ..errors import Errors, TempErrors
-from .underscore import Underscore
+from .underscore import Underscore, get_ext_args
 
 
 cdef class Span:
     """A slice from a Doc object."""
     @classmethod
-    def set_extension(cls, name, default=None, method=None,
+    def set_extension(cls, name, **kwargs):
-                      getter=None, setter=None):
+        if cls.has_extension(name) and not kwargs.get('force', False):
-        Underscore.span_extensions[name] = (default, method, getter, setter)
+            raise ValueError(Errors.E090.format(name=name, obj='Span'))
+        Underscore.span_extensions[name] = get_ext_args(**kwargs)
 
     @classmethod
     def get_extension(cls, name):

spacy/tokens/token.pyx

@@ -21,16 +21,17 @@ from ..attrs cimport LENGTH, CLUSTER, LEMMA, POS, TAG, DEP
 from ..compat import is_config
 from ..errors import Errors
 from .. import util
-from .underscore import Underscore
+from .underscore import Underscore, get_ext_args
 
 
 cdef class Token:
     """An individual token – i.e. a word, punctuation symbol, whitespace,
     etc."""
     @classmethod
-    def set_extension(cls, name, default=None, method=None,
+    def set_extension(cls, name, **kwargs):
-                      getter=None, setter=None):
+        if cls.has_extension(name) and not kwargs.get('force', False):
-        Underscore.token_extensions[name] = (default, method, getter, setter)
+            raise ValueError(Errors.E090.format(name=name, obj='Token'))
+        Underscore.token_extensions[name] = get_ext_args(**kwargs)
 
     @classmethod
     def get_extension(cls, name):

spacy/tokens/underscore.py

@@ -54,3 +54,24 @@ class Underscore(object):
 
     def _get_key(self, name):
         return ('._.', name, self._start, self._end)
+
+
+def get_ext_args(**kwargs):
+    """Validate and convert arguments. Reused in Doc, Token and Span."""
+    default = kwargs.get('default')
+    getter = kwargs.get('getter')
+    setter = kwargs.get('setter')
+    method = kwargs.get('method')
+    if getter is None and setter is not None:
+        raise ValueError(Errors.E089)
+    valid_opts = ('default' in kwargs, method is not None, getter is not None)
+    nr_defined = sum(t is True for t in valid_opts)
+    if nr_defined != 1:
+        raise ValueError(Errors.E083.format(nr_defined=nr_defined))
+    if setter is not None and not hasattr(setter, '__call__'):
+        raise ValueError(Errors.E091.format(name='setter', value=repr(setter)))
+    if getter is not None and not hasattr(getter, '__call__'):
+        raise ValueError(Errors.E091.format(name='getter', value=repr(getter)))
+    if method is not None and not hasattr(method, '__call__'):
+        raise ValueError(Errors.E091.format(name='method', value=repr(method)))
+    return (default, method, getter, setter)