MNT: Deprecate date_ticker_factory (matplotlib#23081)

* Deprecate date_ticker_factory

* Update doc/api/next_api_changes/deprecations/23081-OG.rst

Co-authored-by: Tim Hoffmann <[email protected]>

Co-authored-by: Tim Hoffmann <[email protected]>

Author: oscargus

doc/api/next_api_changes/deprecations/23081-OG.rst

@@ -0,0 +1,8 @@
+``date_ticker_factory`` deprecated
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+The ``date_ticker_factory`` method in the `matplotlib.dates` module is
+deprecated. Instead use `~.AutoDateLocator` and `~.AutoDateFormatter` for a
+more flexible and scalable locator and formatter.
+
+If you need the exact ``date_ticker_factory`` behavior, please copy the code.

lib/matplotlib/dates.py

@@ -1782,6 +1782,8 @@ def num2epoch(d):
     return np.asarray(d) * SEC_PER_DAY - dt
 
 
+@_api.deprecated("3.6", alternative="`AutoDateLocator` and `AutoDateFormatter`"
+                 " or vendor the code")
 def date_ticker_factory(span, tz=None, numticks=5):
     """
     Create a date locator with *numticks* (approx) and a date formatter

lib/matplotlib/tests/test_dates.py

@@ -1319,8 +1319,9 @@ def test_concise_formatter_call():
                           (200, mdates.MonthLocator),
                           (2000, mdates.YearLocator)))
 def test_date_ticker_factory(span, expected_locator):
-    locator, _ = mdates.date_ticker_factory(span)
-    assert isinstance(locator, expected_locator)
+    with pytest.warns(_api.MatplotlibDeprecationWarning):
+        locator, _ = mdates.date_ticker_factory(span)
+        assert isinstance(locator, expected_locator)
 
 
 def test_usetex_newline():