Validate pos values when creating Doc (#9148)

* Validate pos values when creating Doc

* Add clear error when setting invalid pos

This also changes the error language slightly.

* Fix variable name

* Update spacy/tokens/doc.pyx

* Test that setting invalid pos raises an error

Co-authored-by: Sofie Van Landeghem <svlandeg@users.noreply.github.com>

spacy/errors.py

@@ -871,6 +871,8 @@ class Errors:
              "the documentation:\nhttps://spacy.io/usage/models")
     E1020 = ("No `epoch_resume` value specified and could not infer one from "
              "filename. Specify an epoch to resume from.")
+    E1021 = ("`pos` value \"{pp}\" is not a valid Universal Dependencies tag. "
+             "Non-UD tags should use the `tag` property.")
 
 
 # Deprecated model shortcuts, only used in errors and warnings

spacy/tests/doc/test_creation.py

@@ -70,3 +70,10 @@ def test_create_with_heads_and_no_deps(vocab):
     heads = list(range(len(words)))
     with pytest.raises(ValueError):
         Doc(vocab, words=words, heads=heads)
+
+
+def test_create_invalid_pos(vocab):
+    words = "I like ginger".split()
+    pos = "QQ ZZ XX".split()
+    with pytest.raises(ValueError):
+        Doc(vocab, words=words, pos=pos)

spacy/tests/doc/test_token_api.py

@@ -202,6 +202,10 @@ def test_set_pos():
     doc[1].pos = VERB
     assert doc[1].pos_ == "VERB"
 
+def test_set_invalid_pos():
+    doc = Doc(Vocab(), words=["hello", "world"])
+    with pytest.raises(ValueError):
+        doc[0].pos_ = "blah"
 
 def test_tokens_sent(doc):
     """Test token.sent property"""

spacy/tokens/doc.pyx

@@ -30,6 +30,7 @@ from ..compat import copy_reg, pickle
 from ..errors import Errors, Warnings
 from ..morphology import Morphology
 from .. import util
+from .. import parts_of_speech
 from .underscore import Underscore, get_ext_args
 from ._retokenize import Retokenizer
 from ._serialize import ALL_ATTRS as DOCBIN_ALL_ATTRS
@@ -285,6 +286,10 @@ cdef class Doc:
                     sent_starts[i] = -1
                 elif sent_starts[i] is None or sent_starts[i] not in [-1, 0, 1]:
                     sent_starts[i] = 0
+        if pos is not None:
+            for pp in set(pos):
+                if pp not in parts_of_speech.IDS:
+                    raise ValueError(Errors.E1021.format(pp=pp))
         ent_iobs = None
         ent_types = None
         if ents is not None:

spacy/tokens/token.pyx

@@ -867,6 +867,8 @@ cdef class Token:
             return parts_of_speech.NAMES[self.c.pos]
 
         def __set__(self, pos_name):
+            if pos_name not in parts_of_speech.IDS:
+                raise ValueError(Errors.E1021.format(pp=pos_name))
             self.c.pos = parts_of_speech.IDS[pos_name]
 
     property tag_: