Improve Italian & Urdu tokenization accuracy (explosion#3228)

## Description

1. Added the same infix rule as in French (`d'une`, `j'ai`) for Italian (`c'è`, `l'ha`), bringing F-score on `it_isdt-ud-train.txt` from 96% to 99%. Added unit test to check this behaviour.

2. Added specific Urdu punctuation character as suffix, improving F-score on `ur_udtb-ud-train.txt` from 94% to 100%. Added unit test to check this behaviour.

### Types of change
Enhancement of Italian & Urdu tokenization

## Checklist
- [x] I have submitted the spaCy Contributor Agreement.
- [x] I ran the tests, and all new and existing tests passed.
- [x] My changes don't require a change to the documentation, or if they do, I've added all required information.

spacy/lang/it/__init__.py

@@ -11,6 +11,8 @@
 from ...attrs import LANG, NORM
 from ...util import update_exc, add_lookups
 
+from .punctuation import TOKENIZER_INFIXES
+
 
 class ItalianDefaults(Language.Defaults):
     lex_attr_getters = dict(Language.Defaults.lex_attr_getters)
@@ -22,6 +24,7 @@ class ItalianDefaults(Language.Defaults):
     stop_words = STOP_WORDS
     lemma_lookup = LOOKUP
     tag_map = TAG_MAP
+    infixes = TOKENIZER_INFIXES
 
 
 class Italian(Language):

spacy/lang/it/punctuation.py

@@ -0,0 +1,15 @@
+# coding: utf8
+from __future__ import unicode_literals
+
+from ..punctuation import TOKENIZER_INFIXES
+from ..char_classes import ALPHA
+
+
+ELISION = " ' ’ ".strip().replace(" ", "").replace("\n", "")
+
+
+_infixes = TOKENIZER_INFIXES + [
+    r"(?<=[{a}][{el}])(?=[{a}])".format(a=ALPHA, el=ELISION)
+]
+
+TOKENIZER_INFIXES = _infixes

spacy/lang/ur/__init__.py

@@ -9,6 +9,8 @@
 from ...language import Language
 from ...attrs import LANG
 
+from .punctuation import TOKENIZER_SUFFIXES
+
 
 class UrduDefaults(Language.Defaults):
     lex_attr_getters = dict(Language.Defaults.lex_attr_getters)
@@ -18,6 +20,7 @@ class UrduDefaults(Language.Defaults):
     tokenizer_exceptions = BASE_EXCEPTIONS
     tag_map = TAG_MAP
     stop_words = STOP_WORDS
+    suffixes = TOKENIZER_SUFFIXES
 
 
 class Urdu(Language):

spacy/lang/ur/punctuation.py

@@ -0,0 +1,10 @@
+# coding: utf8
+from __future__ import unicode_literals
+
+from ..punctuation import TOKENIZER_SUFFIXES
+
+
+_suffixes = TOKENIZER_SUFFIXES + ["۔"]
+
+
+TOKENIZER_SUFFIXES = _suffixes

spacy/tests/conftest.py

@@ -65,6 +65,11 @@ def id_tokenizer():
     return get_lang_class("id").Defaults.create_tokenizer()
 
 
+@pytest.fixture(scope="session")
+def it_tokenizer():
+    return get_lang_class("it").Defaults.create_tokenizer()
+
+
 @pytest.fixture(scope="session")
 def sv_tokenizer():
     return get_lang_class("sv").Defaults.create_tokenizer()

spacy/tests/lang/ca/test_prefix_suffix_infix.py

@@ -11,3 +11,4 @@ def test_contractions(ca_tokenizer, text, expected_tokens):
     """ Test that the contractions are split into two tokens"""
     tokens = ca_tokenizer(text)
     assert len(tokens) == 2
+    assert [t.text for t in tokens] == expected_tokens

spacy/tests/lang/it/test_prefix_suffix_infix.py

@@ -0,0 +1,14 @@
+# coding: utf-8
+from __future__ import unicode_literals
+
+import pytest
+
+
+@pytest.mark.parametrize(
+    "text,expected_tokens", [("c'è", ["c'", "è"]), ("l'ha", ["l'", "ha"])]
+)
+def test_contractions(it_tokenizer, text, expected_tokens):
+    """ Test that the contractions are split into two tokens"""
+    tokens = it_tokenizer(text)
+    assert len(tokens) == 2
+    assert [t.text for t in tokens] == expected_tokens

spacy/tests/lang/ur/test_prefix_suffix_infix.py

@@ -0,0 +1,13 @@
+# coding: utf-8
+from __future__ import unicode_literals
+
+import pytest
+
+
+@pytest.mark.parametrize(
+    "text", ['ہےں۔', 'کیا۔']
+)
+def test_contractions(ur_tokenizer, text):
+    """Test specific Urdu punctuation character"""
+    tokens = ur_tokenizer(text)
+    assert len(tokens) == 2

spacy/tests/lang/ur/test_text.py

@@ -10,7 +10,7 @@ def test_ur_tokenizer_handles_long_text(ur_tokenizer):
      کہ ایک عدد ٹیلی ویژن ہی کیوں نہ خرید لیں ، سوچا ورلڈ کپ ہی دیکھیں گے۔اپنے پاکستان کے کھلاڑیوں کو دیکھ کر
     ورلڈ کپ دیکھنے کا حوصلہ ہی نہ رہا تو اب یوں ہی ادھر اُدھر کے چینل گھمانے لگ پڑتے ہیں۔"""
     tokens = ur_tokenizer(text)
-    assert len(tokens) == 77
+    assert len(tokens) == 78
 
 
 @pytest.mark.parametrize("text,length", [("تحریر باسط حبیب", 3), ("میرا پاکستان", 2)])