Add default option to MorphAnalysis.get (#12545)

* Add default to MorphAnalysis.get

Similar to `dict`, allow a `default` option for `MorphAnalysis.get` for
the user to provide a default return value if the field is not found.
The default return value remains `[]`, which is not the same as
`dict.get`, but is already established as this method's default return
value with the return type `List[str]`. However the new `default` option
does not enforce that the user-provided default is actually `List[str]`.

* Restore test case

spacy/tests/doc/test_morphanalysis.py

@@ -33,6 +33,8 @@ def test_token_morph_key(i_has):
 def test_morph_props(i_has):
     assert i_has[0].morph.get("PronType") == ["prs"]
     assert i_has[1].morph.get("PronType") == []
+    assert i_has[1].morph.get("AsdfType", ["asdf"]) == ["asdf"]
+    assert i_has[1].morph.get("AsdfType", default=["asdf", "qwer"]) == ["asdf", "qwer"]
 
 
 def test_morph_iter(i_has):

spacy/tokens/morphanalysis.pyi

@@ -1,4 +1,4 @@
-from typing import Any, Dict, Iterator, List, Union
+from typing import Any, Dict, Iterator, List, Optional, Union
 from ..vocab import Vocab
 
 class MorphAnalysis:
@@ -13,7 +13,7 @@ class MorphAnalysis:
     def __hash__(self) -> int: ...
     def __eq__(self, other: MorphAnalysis) -> bool: ...  # type: ignore[override]
     def __ne__(self, other: MorphAnalysis) -> bool: ...  # type: ignore[override]
-    def get(self, field: Any) -> List[str]: ...
+    def get(self, field: Any, default: Optional[List[str]]) -> List[str]: ...
     def to_json(self) -> str: ...
     def to_dict(self) -> Dict[str, str]: ...
     def __str__(self) -> str: ...

spacy/tokens/morphanalysis.pyx

@@ -58,10 +58,14 @@ cdef class MorphAnalysis:
     def __ne__(self, other):
         return self.key != other.key
 
-    def get(self, field):
+    def get(self, field, default=None):
         """Retrieve feature values by field."""
         cdef attr_t field_id = self.vocab.strings.as_int(field)
         cdef np.ndarray results = get_by_field(&self.c, field_id)
+        if len(results) == 0:
+            if default is None:
+                default = []
+            return default
         features = [self.vocab.strings[result] for result in results]
         return [f.split(Morphology.FIELD_SEP)[1] for f in features]
 

website/docs/api/morphology.mdx

@@ -213,10 +213,11 @@ Retrieve values for a feature by field.
 > assert morph.get("Feat1") == ["Val1", "Val2"]
 > ```
 
-| Name        | Description                                      |
+| Name                                   | Description                                                                                                                    |
-| ----------- | ------------------------------------------------ |
+| -------------------------------------- | ------------------------------------------------------------------------------------------------------------------------------ |
-| `field`     | The field to retrieve. ~~str~~                   |
+| `field`                                | The field to retrieve. ~~str~~                                                                                                 |
-| **RETURNS** | A list of the individual features. ~~List[str]~~ |
+| `default` <Tag variant="new">3.6</Tag> | The value to return if the field is not present. If unset or `None`, the default return value is `[]`. ~~Optional[List[str]]~~ |
+| **RETURNS**                            | A list of the individual features. ~~List[str]~~                                                                               |
 
 ### MorphAnalysis.to_dict {id="morphanalysis-to_dict",tag="method"}