text: reduce lang. specific mecab-ko (#2456)

* text: reduce lang. specific `mecab-ko`
* mecab-ko for testing
* Add skips for TestSacreBLEUScore for ko-mecab

---------

Co-authored-by: daniel.stancl <daniel.stancl@rossum.ai>

requirements/text.txt

@@ -6,7 +6,5 @@ tqdm >=4.41.0, <4.67.0
 regex >=2021.9.24, <=2023.12.25
 transformers >4.4.0, <4.40.0
 mecab-python3 >=1.0.6, <1.1.0
-mecab-ko >=1.0.0, <1.1.0
-mecab-ko-dic >=1.0.0, <1.1.0
 ipadic >=1.0.0, <1.1.0
 sentencepiece >=0.2.0, <0.3.0

requirements/text_test.txt

@@ -6,3 +6,6 @@ rouge-score >0.1.0, <=0.1.2
 bert_score ==0.3.13
 huggingface-hub <0.23
 sacrebleu >=2.3.0, <2.5.0
+
+mecab-ko >=1.0.0, <1.1.0
+mecab-ko-dic >=1.0.0, <1.1.0

tests/unittests/text/test_sacre_bleu.py

@@ -16,6 +16,7 @@
 from typing import Sequence
 
 import pytest
+from lightning_utilities.core.imports import RequirementCache
 from torch import Tensor, tensor
 from torchmetrics.functional.text.sacre_bleu import AVAILABLE_TOKENIZERS, _TokenizersLiteral, sacre_bleu_score
 from torchmetrics.text.sacre_bleu import SacreBLEUScore
@@ -51,6 +52,8 @@ class TestSacreBLEUScore(TextTester):
     @pytest.mark.parametrize("ddp", [pytest.param(True, marks=pytest.mark.DDP), False])
     def test_bleu_score_class(self, ddp, preds, targets, tokenize, lowercase):
         """Test class implementation of metric."""
+        if _should_skip_tokenizer(tokenize):
+            pytest.skip(reason="`ko-mecab` tokenizer requires  `mecab-ko` package to be installed")
         if tokenize == "flores200":
             pytest.skip("flores200 tests are flaky")  # TODO: figure out why
 
@@ -68,6 +71,9 @@ def test_bleu_score_class(self, ddp, preds, targets, tokenize, lowercase):
 
     def test_bleu_score_functional(self, preds, targets, tokenize, lowercase):
         """Test functional implementation of metric."""
+        if _should_skip_tokenizer(tokenize):
+            pytest.skip(reason="`ko-mecab` tokenizer requires  `mecab-ko` package to be installed")
+
         metric_args = {"tokenize": tokenize, "lowercase": lowercase}
         original_sacrebleu = partial(_reference_sacre_bleu, tokenize=tokenize, lowercase=lowercase)
 
@@ -81,6 +87,9 @@ def test_bleu_score_functional(self, preds, targets, tokenize, lowercase):
 
     def test_bleu_score_differentiability(self, preds, targets, tokenize, lowercase):
         """Test the differentiability of the metric, according to its `is_differentiable` attribute."""
+        if _should_skip_tokenizer(tokenize):
+            pytest.skip(reason="`ko-mecab` tokenizer requires  `mecab-ko` package to be installed")
+
         metric_args = {"tokenize": tokenize, "lowercase": lowercase}
 
         self.run_differentiability_test(
@@ -122,6 +131,7 @@ def test_tokenize_ja_mecab():
     assert sacrebleu(preds, targets) == _reference_sacre_bleu(preds, targets, tokenize="ja-mecab", lowercase=False)
 
 
+@pytest.mark.skipif(not RequirementCache("mecab-ko"), reason="this test requires `mecab-ko` package to be installed")
 def test_tokenize_ko_mecab():
     """Test that `ja-mecab` tokenizer works on a Japanese text in alignment with the SacreBleu implementation."""
     sacrebleu = SacreBLEUScore(tokenize="ko-mecab")
@@ -134,3 +144,7 @@ def test_tokenize_ko_mecab():
 def test_equivalence_of_available_tokenizers_and_annotation():
     """Test equivalence of SacreBLEU available tokenizers and corresponding type annotation."""
     assert set(AVAILABLE_TOKENIZERS) == set(_TokenizersLiteral.__args__)
+
+
+def _should_skip_tokenizer(tokenizer: _TokenizersLiteral) -> bool:
+    return tokenizer == "ko-mecab" and not RequirementCache("mecab-ko")