fix: assume current year for formats without it (#1288)

Author: NTFSvolume

dateparser/date.py

@@ -19,6 +19,7 @@
     set_correct_day_from_settings,
     set_correct_month_from_settings,
 )
+from dateparser.utils.strptime import strptime as patched_strptime
 
 APOSTROPHE_LOOK_ALIKE_CHARS = [
     "\N{RIGHT SINGLE QUOTATION MARK}",  # '\u2019'
@@ -182,7 +183,7 @@ def parse_with_formats(date_string, date_formats, settings):
     period = "day"
     for date_format in date_formats:
         try:
-            date_obj = datetime.strptime(date_string, date_format)
+            date_obj = patched_strptime(date_string, date_format)
         except ValueError:
             continue
         else:

dateparser/utils/strptime.py

@@ -90,7 +90,34 @@ def patch_strptime():
 __strptime = patch_strptime()
 
 
-def strptime(date_string, format):
+def _prepare_format(date_string: str, og_format: str) -> tuple[str, str]:
+    # Adapted from std lib: https://github.com/python/cpython/blob/e34a5e33049ce845de646cf24a498766a2da3586/Lib/_strptime.py#L448
+    format = re.sub(r"([\\.^$*+?\(\){}\[\]|])", r"\\\1", og_format)
+    format = re.sub(r"\s+", r"\\s+", format)
+    format = re.sub(r"'", "['\u02bc]", format)
+    year_in_format = False
+    day_of_month_in_format = False
+
+    def repl(m: re.Match[str]) -> str:
+        format_char = m[1]
+        if format_char in ("Y", "y", "G"):
+            nonlocal year_in_format
+            year_in_format = True
+        elif format_char in ("d",):
+            nonlocal day_of_month_in_format
+            day_of_month_in_format = True
+
+        return ""
+
+    _ = re.sub(r"%[-_0^#]*[0-9]*([OE]?\\?.?)", repl, format)
+    if day_of_month_in_format and not year_in_format:
+        current_year = datetime.today().year
+        return f"{current_year} {date_string}", f"%Y {og_format}"
+    return date_string, og_format
+
+
+def strptime(date_string: str, format: str) -> datetime:
+    date_string, format = _prepare_format(date_string, format)
     obj = datetime(*__strptime(date_string, format)[:-3])
 
     if "%f" in format:

tests/test_parser.py

@@ -1,4 +1,5 @@
 from datetime import datetime, time
+import warnings
 
 from parameterized import param, parameterized
 
@@ -507,6 +508,30 @@ def then_error_is_raised_when_date_is_parsed(self, date_string):
         with self.assertRaises(ValueError):
             self.parser.parse(date_string, self.settings)
 
+    @parameterized.expand(
+        [
+            param(date_string="oct 14"),
+            param(date_string="14-October-2025"),
+            param(date_string="2024-11-27"),
+            param(date_string="tomorrow"),
+            param(date_string="1484823450"),
+            param(date_string="In two months"),
+        ]
+    )
+    def test_parser_does_not_raise_ambiguious_date_deprecation_warning(
+        self, date_string
+    ):
+        with warnings.catch_warnings(record=True) as w:
+            warnings.simplefilter("always")
+            self.when_date_is_parsed(date_string)
+            year_warnings = [
+                warn
+                for warn in w
+                if "day of month without a year specified is ambiguious"
+                in str(warn.message)
+            ]
+            self.assertEqual(len(year_warnings), 0)
+
 
 class TestTimeParser(BaseTestCase):
     @parameterized.expand(

tests/test_utils_strptime.py

@@ -1,6 +1,7 @@
 import locale
 from datetime import datetime
 from unittest import SkipTest
+import warnings
 
 from parameterized import param, parameterized
 
@@ -173,3 +174,67 @@ def test_parsing_date_should_fail_using_datetime_strptime_if_locale_is_non_engli
     def test_microseconds_are_parsed_correctly(self, date_string, fmt, expected):
         self.when_date_string_is_parsed(date_string, fmt)
         self.then_date_object_is(expected)
+
+    @parameterized.expand(
+        [
+            param(date_string="oct 14", fmt=r"%m %d"),
+            param(date_string="10-14", fmt=r"%b %d"),
+            param(date_string="12 Dec 10:30:55.000111", fmt="%d %b %H:%M:%S.%f"),
+            param(date_string="Wed 12 December 22:41", fmt="%a %d %B %H:%M"),
+        ]
+    )
+    def test_dates_with_no_year_do_not_raise_a_deprecation_warning(
+        self, date_string, fmt
+    ):
+        with warnings.catch_warnings(record=True) as w:
+            warnings.simplefilter("always")
+            self.when_date_string_is_parsed(date_string, fmt)
+            year_warnings = [
+                warn
+                for warn in w
+                if "day of month without a year specified is ambiguious"
+                in str(warn.message)
+            ]
+            self.assertEqual(len(year_warnings), 0)
+
+    @parameterized.expand(
+        [
+            param(
+                date_string="oct 14",
+                fmt=r"%b %d",
+                expected=datetime(2010, 10, 14, 0, 0),
+            ),
+            param(
+                date_string="10 14",
+                fmt=r"%m %d",
+                expected=datetime(2010, 10, 14, 0, 0),
+            ),
+            param(
+                date_string="14 Oct",
+                fmt=r"%d %b",
+                expected=datetime(2010, 10, 14, 0, 0),
+            ),
+            param(
+                "Monday 21 January",
+                "%A %d %B",
+                expected=datetime(2010, 1, 21, 0, 0),
+            ),
+            param(
+                "Tue 2 Mar",
+                "%a %d %b",
+                expected=datetime(2010, 3, 2, 0, 0),
+            ),
+            param(
+                "Friday 12 December 10:30",
+                "%A %d %B %H:%M",
+                expected=datetime(2010, 12, 12, 10, 30),
+            ),
+        ]
+    )
+    def test_dates_with_no_year_use_the_current_year(
+        self, date_string: str, fmt: str, expected: datetime
+    ):
+        self.when_date_string_is_parsed(date_string, fmt)
+        current_year = datetime.today().year
+        expected = expected.replace(year=current_year)
+        self.assertEqual(self.result, expected)