[Bug]: axhline and axvline do not take datelime limits

[scottshambaugh]

Bug summary

When setting xmax or xmin during an axhline call on a datetime axis, datetime limits are not accepted. This also happens with axvline.

Code for reproduction

import matplotlib.pyplot as plt
from datetime import datetime

fig, ax = plt.subplots()
start_date = datetime(2023, 5, 1)
end_date = datetime(2023, 5, 7)

ax.plot([start_date, end_date], [-1, 1])
ax.axhline(0, xmin=start_date, xmax=end_date)

Actual outcome

---------------------------------------------------------------------------
ValueError                                Traceback (most recent call last)
Cell In [16], line 9
      7 end_date = datetime(2023, 5, 7)
      8 ax.plot([start_date, end_date], [-1, 1])
----> 9 ax.axhline(0, xmin=start_date, xmax=end_date)

File ~/anaconda3/envs/py310/lib/python3.10/site-packages/matplotlib/axes/_axes.py:761, in Axes.axhline(self, y, xmin, xmax, **kwargs)
    710 @_docstring.dedent_interpd
    711 def axhline(self, y=0, xmin=0, xmax=1, **kwargs):
    712     """
    713     Add a horizontal line across the Axes.
    714 
   (...)
    759         >>> axhline(y=.5, xmin=0.25, xmax=0.75)
    760     """
--> 761     self._check_no_units([xmin, xmax], ['xmin', 'xmax'])
    762     if "transform" in kwargs:
    763         raise ValueError("'transform' is not allowed as a keyword "
    764                          "argument; axhline generates its own transform.")

File ~/anaconda3/envs/py310/lib/python3.10/site-packages/matplotlib/axes/_axes.py:851, in Axes._check_no_units(vals, names)
    849 for val, name in zip(vals, names):
    850     if not munits._is_natively_supported(val):
--> 851         raise ValueError(f"{name} must be a single scalar value, "
    852                          f"but got {val}")

ValueError: xmin must be a single scalar value, but got 2023-05-01 00:00:00

Expected outcome

The below, but with the horizontal line truncating at the limits.

Additional information

No response

Operating system

No response

Matplotlib Version

3.7.1

Matplotlib Backend

No response

Python version

3.10

Jupyter version

No response

Installation

pip

[story645]

I thought axhline and axvline only worked in axes coordinates by design. (ETA: and in the docs) Categorical doesn't work either with the same error messages

import matplotlib.pyplot as plt
fig, ax = plt.subplots()

ax.plot(['cat', 'hat', 'art'], ['cat', 'hat', 'art'])
ax.axvline(ymin='cat', ymax='hat')
ax.axhline(xmin='hat', xmax='art')

eta: like this example, the axvline and axhline have nothing to do with the data

fig, ax = plt.subplots()
ax.plot([0,5,10], [0,5,10])
ax.axvline(ymin=0, ymax=1)
ax.axhline(xmin=1, xmax=2)

[scottshambaugh]

Thank you @story645! This ended up being my misunderstanding, I should have used ax.hlines() instead, and that behaves as intended.