<!--- Provide a general summary of your changes in the title. -->
## Description
This PR adds the abilility to override custom extension attributes during merging. This will only work for attributes that are writable, i.e. attributes registered with a default value like `default=False` or attribute that have both a getter *and* a setter implemented.
```python
Token.set_extension('is_musician', default=False)
doc = nlp("I like David Bowie.")
with doc.retokenize() as retokenizer:
attrs = {"LEMMA": "David Bowie", "_": {"is_musician": True}}
retokenizer.merge(doc[2:4], attrs=attrs)
assert doc[2].text == "David Bowie"
assert doc[2].lemma_ == "David Bowie"
assert doc[2]._.is_musician
```
### Types of change
enhancement
## Checklist
<!--- Before you submit the PR, go over this checklist and make sure you can
tick off all the boxes. [] -> [x] -->
- [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.
* Keep TextCategorizer default model same as v2.0
* Add option 'architecture' that allows "simple_cnn" to switch to
simpler model.
* Add option exclusive_classes, defaulting to False. If set to True,
the model treats classes as mutually exclusive, i.e. only one class can
be true per instance.
* splitting up latin unicode interval
* removing hyphen as infix for French
* adding failing test for issue 1235
* test for issue #3002 which now works
* partial fix for issue #2070
* keep the hyphen as infix for French (as it was)
* restore french expressions with hyphen as infix (as it was)
* added succeeding unit test for Issue #2656
* Fix issue #2822 with custom Italian exception
* Fix issue #2926 by allowing numbers right before infix /
* splitting up latin unicode interval
* removing hyphen as infix for French
* adding failing test for issue 1235
* test for issue #3002 which now works
* partial fix for issue #2070
* keep the hyphen as infix for French (as it was)
* restore french expressions with hyphen as infix (as it was)
* added succeeding unit test for Issue #2656
* Fix issue #2822 with custom Italian exception
* Fix issue #2926 by allowing numbers right before infix /
* remove duplicate
* remove xfail for Issue #2179 fixed by Matt
* adjust documentation and remove reference to regex lib
* Fix matching on extension attrs and predicates
* Fix detection of match_id when using extension attributes. The match
ID is stored as the last entry in the pattern. We were checking for this
with nr_attr == 0, which didn't account for extension attributes.
* Fix handling of predicates. The wrong count was being passed through,
so even patterns that didn't have a predicate were being checked.
* Fix regex pattern
* Fix matcher set value test
* Change retokenize.split() API for heads
* Pass lists as values for attrs in split
* Fix test_doc_split filename
* Add error for mismatched tokens after split
* Raise error if new tokens don't match text
* Fix doc test
* Fix error
* Move deps under attrs
* Fix split tests
* Fix retokenize.split
* Add base classes for more languages
* Add test for language class initialization
Make sure language can be initialize – otherwise, it's difficult to catch serious errors in the test suite, because languages are lazy-loaded
* Add split one token into several (resolves#2838)
* Improve error message for token splitting
* Make retokenizer.split() tests use a Token object
Change retokenizer.split() to use a Token object, instead of an index.
* Pass Token into retokenize.split()
Tweak retokenize.split() API so that we pass the `Token` object, not the index.
* Fix token.idx in retokenize.split()
* Test that token.idx is correct after split
* Fix token.idx for split tokens
* Fix retokenize.split()
* Fix retokenize.split
* Fix retokenize.split() test
Otherwise, the true error that happens within a Language subclass is swallowed, because if it's imported lazily like that, it'll always be an ImportError
* Add custom MatchPatternError
* Improve validators and add validation option to Matcher
* Adjust formatting
* Never validate in Matcher within PhraseMatcher
If we do decide to make validate default to True, the PhraseMatcher's Matcher shouldn't ever validate. Here, we create the patterns automatically anyways (and it's currently unclear whether the validation has performance impacts at a very large scale).
In most cases, the PhraseMatcher will match on the verbatim token text or as of v2.1, sometimes the lowercase text. This means that we only need a tokenized Doc, without any other attributes.
If phrase patterns are created by processing large terminology lists with the full `nlp` object, this easily can make things a lot slower, because all components will be applied, even if we don't actually need the attributes they set (like part-of-speech tags, dependency labels).
The warning message also includes a suggestion to use nlp.make_doc or nlp.tokenizer.pipe for even faster processing. For now, the validation has to be enabled explicitly by setting validate=True.
