Fix: Handle Russian preposition "с" in date parsing and add tests (#1261)

Fix: Handle Russian preposition "с" in date parsing and add tests

Author: serhii73

dateparser/search/__init__.py

@@ -57,6 +57,8 @@ def search_dates(
      ('on May 6th 2004', datetime.datetime(2004, 5, 6, 0, 0))]
 
     """
+    text = _search_with_detection.preprocess_text(text, languages)
+
     result = _search_with_detection.search_dates(
         text=text,
         languages=languages,

dateparser/search/search.py

@@ -295,3 +295,10 @@ def search_dates(
                 language_shortname, text, settings=settings
             ),
         }
+
+    def preprocess_text(self, text, languages):
+        """Preprocess text to handle language-specific quirks."""
+        if languages and "ru" in languages:
+            # Replace "с" (from) before numbers with a placeholder
+            text = re.sub(r"\bс\s+(?=\d)", "[FROM] ", text)
+        return text

tests/test_search.py

@@ -1090,3 +1090,16 @@ def test_date_search_function_invalid_language_code(self, text, languages):
             text=text, languages=languages, error_type=ValueError
         )
         self.check_error_message("Unknown language(s): 'unknown language code'")
+
+    def test_search_dates_with_prepositions(self):
+        """Test `search_dates` for parsing Russian date ranges with prepositions and language detection."""
+        result = search_dates(
+            "Сервис будет недоступен с 12 января по 30 апреля.",
+            add_detected_language=True,
+            languages=["ru"],
+        )
+        expected = [
+            ("12 января", datetime.datetime(2025, 1, 12, 0, 0), "ru"),
+            ("30 апреля", datetime.datetime(2025, 4, 30, 0, 0), "ru"),
+        ]
+        assert result == expected