Added Italian POS-aware lemmatizer. (#8079)

* Added Italian POS-aware lemmatizer.

Also added the code used to build the lookup tables by POS.

* Create gtoffoli.md

* Add imports and format

* Remove helper script

* Use lemma_lookup instead of lemma_lookup_legacy

Co-authored-by: Adriane Boyd <adrianeboyd@gmail.com>

.github/contributors/gtoffoli.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 UG (haftungsbeschränkt)](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
+example_user would create the file `.github/contributors/example_user.md`.
+
+Read this agreement carefully before signing. These terms and conditions
+constitute a binding legal agreement.
+
+## Contributor Agreement
+
+1. The term "contribution" or "contributed materials" means any source code,
+object code, patch, tool, sample, graphic, specification, manual,
+documentation, or any other material posted or submitted by you to the project.
+
+2. With respect to any worldwide copyrights, or copyright applications and
+registrations, in your contribution:
+
+    * you hereby assign to us joint ownership, and to the extent that such
+    assignment is or becomes invalid, ineffective or unenforceable, you hereby
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+    copyrights. This includes, at our option, the right to sublicense these same
+    rights to third parties through multiple levels of sublicensees or other
+    licensing arrangements;
+
+    * you agree that each of us can do all things in relation to your
+    contribution as if each of us were the sole owners, and if one of us makes
+    a derivative work of your contribution, the one who makes the derivative
+    work (or has it made will be the sole owner of that derivative work;
+
+    * you agree that you will not assert any moral rights in your contribution
+    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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+    * to the best of your knowledge, each contribution will not violate any
+    third party's copyrights, trademarks, patents, or other intellectual
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+
+    * each contribution shall be in compliance with U.S. export control laws and
+    other applicable export and import laws. You agree to notify us if you
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+    participation in the project, including the fact that you have signed the SCA.
+
+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                           | Giovanni Toffoli         |
+| Company name (if applicable)   |                          |
+| Title or role (if applicable)  |                          |
+| Date                           | 2021-05-12               |
+| GitHub username                | gtoffoli                 |
+| Website (optional)             |                          |

spacy/lang/it/__init__.py

@@ -1,7 +1,11 @@
+from typing import Optional
+from thinc.api import Model
+
 from .stop_words import STOP_WORDS
 from .tokenizer_exceptions import TOKENIZER_EXCEPTIONS
 from .punctuation import TOKENIZER_PREFIXES, TOKENIZER_INFIXES
 from ...language import Language
+from .lemmatizer import ItalianLemmatizer
 
 
 class ItalianDefaults(Language.Defaults):
@@ -16,4 +20,16 @@ class Italian(Language):
     Defaults = ItalianDefaults
 
 
+@Italian.factory(
+    "lemmatizer",
+    assigns=["token.lemma"],
+    default_config={"model": None, "mode": "pos_lookup", "overwrite": False},
+    default_score_weights={"lemma_acc": 1.0},
+)
+def make_lemmatizer(
+    nlp: Language, model: Optional[Model], name: str, mode: str, overwrite: bool
+):
+    return ItalianLemmatizer(nlp.vocab, model, name, mode=mode, overwrite=overwrite)
+
+
 __all__ = ["Italian"]

spacy/lang/it/lemmatizer.py

@@ -0,0 +1,132 @@
+from typing import List, Dict, Tuple
+
+from ...pipeline import Lemmatizer
+from ...tokens import Token
+
+
+
+class ItalianLemmatizer(Lemmatizer):
+    """This lemmatizer was adapted from the Polish one (version of April 2021).
+    It implements lookup lemmatization based on the morphological lexicon
+    morph-it (Baroni and Zanchetta). The table lemma_lookup with non-POS-aware
+    entries is used as a backup for words that aren't handled by morph-it."""
+    @classmethod
+    def get_lookups_config(cls, mode: str) -> Tuple[List[str], List[str]]:
+        if mode == "pos_lookup":
+            required = [
+                "lemma_lookup_num",
+                "lemma_lookup_det",
+                "lemma_lookup_adp",
+                "lemma_lookup_adj",
+                "lemma_lookup_noun",
+                "lemma_lookup_pron",
+                "lemma_lookup_verb",
+                "lemma_lookup_aux",
+                "lemma_lookup_adv",
+                "lemma_lookup_other",
+                "lemma_lookup",
+            ]
+            return (required, [])
+        else:
+            return super().get_lookups_config(mode)
+
+    def pos_lookup_lemmatize(self, token: Token) -> List[str]:
+        string = token.text
+        univ_pos = token.pos_
+        morphology = token.morph.to_dict()
+        lookup_pos = univ_pos.lower()
+        if univ_pos == "PROPN":
+            lookup_pos = "noun"
+        elif univ_pos == "PART":
+            lookup_pos = "pron"
+        lookup_table = self.lookups.get_table("lemma_lookup_" + lookup_pos, {})
+        if univ_pos == "NOUN":
+            return self.lemmatize_noun(string, morphology, lookup_table)
+        else:
+            if univ_pos != "PROPN":
+                string = string.lower()
+            if univ_pos == "DET":
+                return self.lemmatize_det(string, morphology, lookup_table)
+            elif univ_pos == "PRON":
+                return self.lemmatize_pron(string, morphology, lookup_table)
+            elif univ_pos == "ADP":
+                return self.lemmatize_adp(string, morphology, lookup_table)
+            elif univ_pos == "ADJ":
+                return self.lemmatize_adj(string, morphology, lookup_table)
+            else:
+                lemma = lookup_table.get(string, "")
+        if not lemma:
+            lookup_table = self.lookups.get_table("lemma_lookup_other")
+            lemma = lookup_table.get(string, "")
+        if not lemma:
+            lookup_table = self.lookups.get_table(
+                "lemma_lookup"
+            )  # "legacy" lookup table
+            lemma = lookup_table.get(string, string.lower())
+        return [lemma]
+
+    def lemmatize_det(
+        self, string: str, morphology: dict, lookup_table: Dict[str, str]
+    ) -> List[str]:
+        if string in [
+            "l'",
+            "lo",
+            "la",
+            "i",
+            "gli",
+            "le",
+        ]:
+            return ["il"]
+        if string in ["un'", "un", "una"]:
+            return ["uno"]
+        return [lookup_table.get(string, string)]
+
+    def lemmatize_pron(
+        self, string: str, morphology: dict, lookup_table: Dict[str, str]
+    ) -> List[str]:
+        if string in [
+            "l'",
+            "li",
+            "la",
+            "gli",
+            "le",
+        ]:
+            return ["lo"]
+        if string in ["un'", "un", "una"]:
+            return ["uno"]
+        lemma = lookup_table.get(string, string)
+        if lemma == "alcun":
+            lemma = "alcuno"
+        elif lemma == "qualcun":
+            lemma = "qualcuno"
+        return [lemma]
+
+    def lemmatize_adp(
+        self, string: str, morphology: dict, lookup_table: Dict[str, str]
+    ) -> List[str]:
+        if string == "d'":
+            return ["di"]
+        return [lookup_table.get(string, string)]
+
+    def lemmatize_adj(
+        self, string: str, morphology: dict, lookup_table: Dict[str, str]
+    ) -> List[str]:
+        lemma = lookup_table.get(string, string)
+        if lemma == "alcun":
+            lemma = "alcuno"
+        elif lemma == "qualcun":
+            lemma = "qualcuno"
+        return [lemma]
+
+    def lemmatize_noun(
+        self, string: str, morphology: dict, lookup_table: Dict[str, str]
+    ) -> List[str]:
+        # this method is case-sensitive, in order to work
+        # for incorrectly tagged proper names
+        if string != string.lower():
+            if string.lower() in lookup_table:
+                return [lookup_table[string.lower()]]
+            elif string in lookup_table:
+                return [lookup_table[string]]
+            return [string.lower()]
+        return [lookup_table.get(string, string)]