deprecate is_anchored, fix tests

Author: natmokval

pandas/_libs/tslibs/offsets.pyx

@@ -768,6 +768,12 @@ cdef class BaseOffset:
         >>> pd.DateOffset(2).is_anchored()
         False
         """
+        warnings.warn(
+            f"{type(self).__name__}.is_anchored() is deprecated and will be removed "
+            f"in a future version, please use {type(self).__name__}.n == 1 instead.",
+            FutureWarning,
+            stacklevel=find_stack_level(),
+        )
         return self.n == 1
 
     # ------------------------------------------------------------------
@@ -954,6 +960,12 @@ cdef class Tick(SingleConstructorOffset):
         return True
 
     def is_anchored(self) -> bool:
+        warnings.warn(
+            f"{type(self).__name__}.is_anchored() is deprecated and will be removed "
+            f"in a future version, please use False instead.",
+            FutureWarning,
+            stacklevel=find_stack_level(),
+        )
         return False
 
     # This is identical to BaseOffset.__hash__, but has to be redefined here
@@ -2663,6 +2675,13 @@ cdef class QuarterOffset(SingleConstructorOffset):
         return f"{self._prefix}-{month}"
 
     def is_anchored(self) -> bool:
+        warnings.warn(
+            f"{type(self).__name__}.is_anchored() is deprecated and will be removed "
+            f"in a future version, please use {type(self).__name__}.n == 1 "
+            f" and {type(self).__name__}.startingMonth is not None instead.",
+            FutureWarning,
+            stacklevel=find_stack_level(),
+        )
         return self.n == 1 and self.startingMonth is not None
 
     def is_on_offset(self, dt: datetime) -> bool:
@@ -3308,6 +3327,13 @@ cdef class Week(SingleConstructorOffset):
         self._cache = state.pop("_cache", {})
 
     def is_anchored(self) -> bool:
+        warnings.warn(
+            f"{type(self).__name__}.is_anchored() is deprecated and will be removed "
+            f"in a future version, please use {type(self).__name__}.n == 1 "
+            f" and {type(self).__name__}.weekday is not None instead.",
+            FutureWarning,
+            stacklevel=find_stack_level(),
+        )
         return self.n == 1 and self.weekday is not None
 
     @apply_wraps
@@ -3597,6 +3623,12 @@ cdef class FY5253Mixin(SingleConstructorOffset):
         self.variation = state.pop("variation")
 
     def is_anchored(self) -> bool:
+        warnings.warn(
+            f"{type(self).__name__}.is_anchored() is deprecated and will be removed "
+            f"in a future version, please use {type(self).__name__}.n == 1 instead.",
+            FutureWarning,
+            stacklevel=find_stack_level(),
+        )
         return (
             self.n == 1 and self.startingMonth is not None and self.weekday is not None
         )

pandas/tests/indexes/interval/test_interval_range.py

@@ -84,7 +84,7 @@ def test_constructor_timestamp(self, closed, name, freq, periods, tz):
         tm.assert_index_equal(result, expected)
 
         # GH 20976: linspace behavior defined from start/end/periods
-        if not breaks.freq.is_anchored() and tz is None:
+        if not breaks.freq.n == 1 and tz is None:
             # matches expected only for non-anchored offsets and tz naive
             # (anchored/DST transitions cause unequal spacing in expected)
             result = interval_range(

pandas/tests/tseries/offsets/test_ticks.py

@@ -339,7 +339,11 @@ def test_tick_equalities(cls):
 
 @pytest.mark.parametrize("cls", tick_classes)
 def test_tick_offset(cls):
-    assert not cls().is_anchored()
+    msg = f"{cls.__name__}.is_anchored() is deprecated and will be removed in a "
+    "future version, please use False instead."
+
+    with tm.assert_produces_warning(FutureWarning, match=msg):
+        assert not cls().is_anchored()
 
 
 @pytest.mark.parametrize("cls", tick_classes)