Fix vector for 0-length span (#9244)

spacy/tests/doc/test_span.py

@@ -5,7 +5,9 @@ from spacy.attrs import ORTH, LENGTH
 from spacy.tokens import Doc, Span, Token
 from spacy.vocab import Vocab
 from spacy.util import filter_spans
+from thinc.api import get_current_ops
 
+from ..util import add_vecs_to_vocab
 from .test_underscore import clean_underscore  # noqa: F401
 
 
@@ -412,3 +414,23 @@ def test_sent(en_tokenizer):
     assert not span.doc.has_annotation("SENT_START")
     with pytest.raises(ValueError):
         span.sent
+
+
+def test_span_with_vectors(doc):
+    ops = get_current_ops()
+    prev_vectors = doc.vocab.vectors
+    vectors = [
+        ("apple", ops.asarray([1, 2, 3])),
+        ("orange", ops.asarray([-1, -2, -3])),
+        ("And", ops.asarray([-1, -1, -1])),
+        ("juice", ops.asarray([5, 5, 10])),
+        ("pie", ops.asarray([7, 6.3, 8.9])),
+    ]
+    add_vecs_to_vocab(doc.vocab, vectors)
+    # 0-length span
+    assert_array_equal(ops.to_numpy(doc[0:0].vector), numpy.zeros((3, )))
+    # longer span with no vector
+    assert_array_equal(ops.to_numpy(doc[0:4].vector), numpy.zeros((3, )))
+    # single-token span with vector
+    assert_array_equal(ops.to_numpy(doc[10:11].vector), [-1, -1, -1])
+    doc.vocab.vectors = prev_vectors

spacy/tokens/span.pyx

@@ -474,7 +474,11 @@ cdef class Span:
         if "vector" in self.doc.user_span_hooks:
             return self.doc.user_span_hooks["vector"](self)
         if self._vector is None:
-            self._vector = sum(t.vector for t in self) / len(self)
+            if not len(self):
+                xp = get_array_module(self.vocab.vectors.data)
+                self._vector = xp.zeros((self.vocab.vectors_length,), dtype="f")
+            else:
+                self._vector = sum(t.vector for t in self) / len(self)
         return self._vector
 
     @property