Block lemmatization of base-form adjectives

Fixes check that an adjective is a base form (as opposed to a
comparative or superlative), so that it's not lemmatized.
e.g. inner -!> inn. Closes #912.

spacy/lemmatizer.py

@@ -7,6 +7,8 @@ import ujson as json
 from .en.lemmatizer import INDEX, EXC, RULES
 from .symbols import POS, NOUN, VERB, ADJ, PUNCT
 from .symbols import VerbForm_inf, VerbForm_none
+from .symbols import Number_sing
+from .symbols import Degree_pos
 
 
 class Lemmatizer(object):
@@ -42,6 +44,7 @@ class Lemmatizer(object):
     def is_base_form(self, univ_pos, morphology=None):
         '''Check whether we're dealing with an uninflected paradigm, so we can
         avoid lemmatization entirely.'''
+        print("Is base form?", univ_pos, morphology)
         morphology = {} if morphology is None else morphology
         others = [key for key in morphology if key not in (POS, 'number', 'pos', 'verbform')]
         true_morph_key = morphology.get('morph', 0)
@@ -49,7 +52,10 @@ class Lemmatizer(object):
             return True
         elif univ_pos == 'verb' and morphology.get('verbform') == 'inf' and not others:
             return True
-        elif true_morph_key in (VerbForm_inf, VerbForm_none):
+        elif univ_pos == 'adj' and morphology.get('Degree') == 'pos':
+            return True
+        elif true_morph_key in \
+            (VerbForm_inf, VerbForm_none, Number_sing, Degree_pos):
             return True
         else:
             return False

spacy/tests/regression/test_issue912.py

@@ -0,0 +1,14 @@
+# coding: utf8
+from __future__ import unicode_literals
+
+import pytest
+from ...tokens import Doc
+
+
+@pytest.mark.parametrize('text,tag,lemma', [("inner", "JJ", "inner")])
+def test_issue912(en_vocab, text, tag, lemma):
+    '''Test base-forms of adjectives are preserved.'''
+    doc = Doc(en_vocab, words=[text])
+    doc[0].tag_ = tag
+    assert doc[0].lemma_ == lemma
+