Add is_sent_end token property (#5375)

Reconstruction of the original PR #4697 by @MiniLau.

Removes unused `SENT_END` symbol and `IS_SENT_END` from `Matcher` schema
because the Matcher is only going to be able to support `IS_SENT_START`.

.github/contributors/MiniLau.md

@@ -0,0 +1,106 @@
+# spaCy contributor agreement
+
+This spaCy Contributor Agreement (**"SCA"**) is based on the
+[Oracle Contributor Agreement](http://www.oracle.com/technetwork/oca-405177.pdf).
+The SCA applies to any contribution that you make to any product or project
+managed by us (the **"project"**), and sets out the intellectual property rights
+you grant to us in the contributed materials. The term **"us"** shall mean
+[ExplosionAI GmbH](https://explosion.ai/legal). The term
+**"you"** shall mean the person or entity identified below.
+
+If you agree to be bound by these terms, fill in the information requested
+below and include the filled-in version with your first pull request, under the
+folder [`.github/contributors/`](/.github/contributors/). The name of the file
+should be your GitHub username, with the extension `.md`. For example, the user
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+
+Read this agreement carefully before signing. These terms and conditions
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+## Contributor Agreement
+
+1. The term "contribution" or "contributed materials" means any source code,
+object code, patch, tool, sample, graphic, specification, manual,
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+
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+
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+    contribution as if each of us were the sole owners, and if one of us makes
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+    against us, our licensees or transferees;
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+5. You covenant, represent, warrant and agree that:
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+    * Each contribution that you submit is and shall be an original work of
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+
+6. This SCA is governed by the laws of the State of California and applicable
+U.S. Federal law. Any choice of law rules will not apply.
+
+7. Please place an “x” on one of the applicable statement below. Please do NOT
+mark both statements:
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+    * [x] I am signing on behalf of myself as an individual and no other person
+    or entity, including my employer, has or will have rights with respect to my
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+    * [ ] I am signing on behalf of my employer or a legal entity and I have the
+    actual authority to contractually bind that entity.
+
+## Contributor Details
+
+| Field                          | Entry                |
+|------------------------------- | -------------------- |
+| Name                           |  Desausoi Laurent    |
+| Company name (if applicable)   |          /           |
+| Title or role (if applicable)  |          /           |
+| Date                           |  22 November 2019    |
+| GitHub username                |        MiniLau       |
+| Website (optional)             |          /           |

spacy/attrs.pxd

@@ -94,3 +94,4 @@ cdef enum attr_id_t:
     ENT_ID = symbols.ENT_ID
 
     IDX
+    SENT_END

spacy/attrs.pyx

@@ -88,6 +88,7 @@ IDS = {
     "ENT_KB_ID": ENT_KB_ID,
     "HEAD": HEAD,
     "SENT_START": SENT_START,
+    "SENT_END": SENT_END,
     "SPACY": SPACY,
     "PROB": PROB,
     "LANG": LANG,

spacy/errors.py

@@ -559,6 +559,8 @@ class Errors(object):
             "({curr_dim}).")
     E194 = ("Unable to aligned mismatched text '{text}' and words '{words}'.")
     E195 = ("Matcher can be called on {good} only, got {got}.")
+    E196 = ("Refusing to write to token.is_sent_end. Sentence boundaries can "
+            "only be fixed with token.is_sent_start.")
 
 
 @add_codes

spacy/tests/doc/test_token_api.py

@@ -181,6 +181,14 @@ def test_is_sent_start(en_tokenizer):
     doc.is_parsed = True
     assert len(list(doc.sents)) == 2
 
+def test_is_sent_end(en_tokenizer):
+    doc = en_tokenizer("This is a sentence. This is another.")
+    assert doc[4].is_sent_end is None
+    doc[5].is_sent_start = True
+    assert doc[4].is_sent_end is True
+    doc.is_parsed = True
+    assert len(list(doc.sents)) == 2
+
 
 def test_set_pos():
     doc = Doc(Vocab(), words=["hello", "world"])
@@ -205,6 +213,12 @@ def test_token0_has_sent_start_true():
     assert doc[1].is_sent_start is None
     assert not doc.is_sentenced
 
+def test_tokenlast_has_sent_end_true():
+    doc = Doc(Vocab(), words=["hello", "world"])
+    assert doc[0].is_sent_end is None
+    assert doc[1].is_sent_end is True
+    assert not doc.is_sentenced
+
 
 def test_token_api_conjuncts_chain(en_vocab):
     words = "The boy and the girl and the man went .".split()

spacy/tests/pipeline/test_sentencizer.py

@@ -14,7 +14,9 @@ def test_sentencizer(en_vocab):
     doc = sentencizer(doc)
     assert doc.is_sentenced
     sent_starts = [t.is_sent_start for t in doc]
+    sent_ends = [t.is_sent_end for t in doc]
     assert sent_starts == [True, False, True, False, False, False, False]
+    assert sent_ends == [False, True, False, False, False, False, True]
     assert len(list(doc.sents)) == 2
 
 
@@ -46,13 +48,14 @@ def test_sentencizer_empty_docs():
 
 
 @pytest.mark.parametrize(
-    "words,sent_starts,n_sents",
+    "words,sent_starts,sent_ends,n_sents",
     [
         # The expected result here is that the duplicate punctuation gets merged
         # onto the same sentence and no one-token sentence is created for them.
         (
             ["Hello", "!", ".", "Test", ".", ".", "ok"],
             [True, False, False, True, False, False, True],
+            [False, False, True, False, False, True, True],
             3,
         ),
         # We also want to make sure ¡ and ¿ aren't treated as sentence end
@@ -60,32 +63,36 @@ def test_sentencizer_empty_docs():
         (
             ["¡", "Buen", "día", "!", "Hola", ",", "¿", "qué", "tal", "?"],
             [True, False, False, False, True, False, False, False, False, False],
+            [False, False, False, True, False, False, False, False, False, True],
             2,
         ),
         # The Token.is_punct check ensures that quotes are handled as well
         (
             ['"', "Nice", "!", '"', "I", "am", "happy", "."],
             [True, False, False, False, True, False, False, False],
+            [False, False, False, True, False, False, False, True],
             2,
         ),
     ],
 )
-def test_sentencizer_complex(en_vocab, words, sent_starts, n_sents):
+def test_sentencizer_complex(en_vocab, words, sent_starts, sent_ends, n_sents):
     doc = Doc(en_vocab, words=words)
     sentencizer = Sentencizer()
     doc = sentencizer(doc)
     assert doc.is_sentenced
     assert [t.is_sent_start for t in doc] == sent_starts
+    assert [t.is_sent_end for t in doc] == sent_ends
     assert len(list(doc.sents)) == n_sents
 
 
 @pytest.mark.parametrize(
-    "punct_chars,words,sent_starts,n_sents",
+    "punct_chars,words,sent_starts,sent_ends,n_sents",
     [
         (
             ["~", "?"],
             ["Hello", "world", "~", "A", ".", "B", "."],
             [True, False, False, True, False, False, False],
+            [False, False, True, False, False, False, True],
             2,
         ),
         # Even thought it's not common, the punct_chars should be able to
@@ -94,16 +101,18 @@ def test_sentencizer_complex(en_vocab, words, sent_starts, n_sents):
             [".", "ö"],
             ["Hello", ".", "Test", "ö", "Ok", "."],
             [True, False, True, False, True, False],
+            [False, True, False, True, False, True],
             3,
         ),
     ],
 )
-def test_sentencizer_custom_punct(en_vocab, punct_chars, words, sent_starts, n_sents):
+def test_sentencizer_custom_punct(en_vocab, punct_chars, words, sent_starts, sent_ends, n_sents):
     doc = Doc(en_vocab, words=words)
     sentencizer = Sentencizer(punct_chars=punct_chars)
     doc = sentencizer(doc)
     assert doc.is_sentenced
     assert [t.is_sent_start for t in doc] == sent_starts
+    assert [t.is_sent_end for t in doc] == sent_ends
     assert len(list(doc.sents)) == n_sents
 
 

spacy/tokens/token.pyx

@@ -493,6 +493,28 @@ cdef class Token:
             else:
                 raise ValueError(Errors.E044.format(value=value))
 
+    property is_sent_end:
+        """A boolean value indicating whether the token ends a sentence.
+        `None` if unknown. Defaults to `True` for the last token in the `Doc`.
+
+        RETURNS (bool / None): Whether the token ends a sentence.
+            None if unknown.
+
+        DOCS: https://spacy.io/api/token#is_sent_end
+        """
+        def __get__(self):
+            if self.i + 1 == len(self.doc):
+                return True
+            elif self.doc[self.i+1].is_sent_start == None:
+                return None
+            elif self.doc[self.i+1].is_sent_start == True:
+                return True
+            else:
+                return False
+
+        def __set__(self, value):
+            raise ValueError(Errors.E196)
+
     @property
     def lefts(self):
         """The leftward immediate children of the word, in the syntactic

website/docs/api/token.md

@@ -352,7 +352,22 @@ property to `0` for the first word of the document.
 + assert doc[4].is_sent_start == True
 ```
 
-</Infobox>
+## Token.is_sent_end {#is_sent_end tag="property" new="2"}
+
+A boolean value indicating whether the token ends a sentence. `None` if
+unknown. Defaults to `True` for the last token in the `Doc`.
+
+> #### Example
+>
+> ```python
+> doc = nlp("Give it back! He pleaded.")
+> assert doc[3].is_sent_end
+> assert not doc[4].is_sent_end
+> ```
+
+| Name        | Type | Description                          |
+| ----------- | ---- | ------------------------------------ |
+| **RETURNS** | bool | Whether the token ends a sentence. |
 
 ## Token.has_vector {#has_vector tag="property" model="vectors"}