Fix PolarAxes.format() silently dropping xlabel/ylabel

ultraplot/axes/polar.py

@@ -82,6 +82,13 @@
 thetaformatter_kw, rformatter_kw : dict-like, optional
     The azimuthal and radial label formatter settings. Passed to
     `~ultraplot.constructor.Formatter`.
+xlabel, ylabel : str, optional
+    The x and y axis labels. Applied with `~matplotlib.axes.Axes.set_xlabel`
+    and `~matplotlib.axes.Axes.set_ylabel`.
+xlabel_kw, ylabel_kw : dict-like, optional
+    Additional axis label settings applied with `~matplotlib.axes.Axes.set_xlabel`
+    and `~matplotlib.axes.Axes.set_ylabel`. See also `labelpad`, `labelcolor`,
+    `labelsize`, and `labelweight`.
 color : color-spec, default: :rc:`meta.color`
     Color for the axes edge. Propagates to `labelcolor` unless specified
     otherwise (similar to :func:`~ultraplot.axes.CartesianAxes.format`).
@@ -212,6 +219,23 @@ def _update_locators(
             else:
                 axis.set_minor_locator(loc)
 
+    def _update_labels(self, x, *args, **kwargs):
+        """
+        Apply axis labels via `set_xlabel` / `set_ylabel`.
+        """
+        # NOTE: Critical to test whether arguments are None or else this
+        # will set isDefault_label to False every time format() is called.
+        kwargs = rc._get_label_props(**kwargs)
+        no_args = all(a is None for a in args)
+        no_kwargs = all(v is None for v in kwargs.values())
+        if no_args and no_kwargs:
+            return
+        setter = getattr(self, f"set_{x}label")
+        getter = getattr(self, f"get_{x}label")
+        if no_args:  # otherwise label text is reset!
+            args = (getter(),)
+        setter(*args, **kwargs)
+
     @docstring._snippet_manager
     def format(
         self,
@@ -256,6 +280,10 @@ def format(
         labelsize=None,
         labelcolor=None,
         labelweight=None,
+        xlabel=None,
+        ylabel=None,
+        xlabel_kw=None,
+        ylabel_kw=None,
         **kwargs,
     ):
         """
@@ -335,6 +363,8 @@ def format(
                 formatter_kw,
                 minorlocator,
                 minorlocator_kw,
+                label,
+                label_kw,
             ) in zip(
                 ("x", "y"),
                 (thetamin, rmin),
@@ -349,6 +379,8 @@ def format(
                 (thetaformatter_kw, rformatter_kw),
                 (thetaminorlocator, rminorlocator),
                 (thetaminorlocator_kw, rminorlocator_kw),
+                (xlabel, ylabel),
+                (xlabel_kw, ylabel_kw),
             ):
                 # Axis limits
                 self._update_limits(x, min_=min_, max_=max_, lim=lim)
@@ -382,6 +414,16 @@ def format(
                     x, formatter=formatter, formatter_kw=formatter_kw
                 )
 
+                # Axis label
+                kw = dict(
+                    labelpad=labelpad,
+                    color=labelcolor,
+                    size=labelsize,
+                    weight=labelweight,
+                )
+                kw.update(label_kw or {})
+                self._update_labels(x, label, **kw)
+
         # Parent format method
         super().format(rc_kw=rc_kw, rc_mode=rc_mode, **kwargs)
 

ultraplot/figure.py

@@ -3277,11 +3277,15 @@ def format(
         if skip_axes:  # avoid recursion
             return
 
-        # Remove all keywords that are not in the allowed signature parameters
+        # Collect each class's matching kwargs without popping, then drop the union —
+        # shared params (e.g. xlabel/ylabel, accepted by both CartesianAxes and
+        # PolarAxes) need to reach every matching class.
         kws = {
-            cls: _pop_params(kwargs, sig)
+            cls: {k: kwargs[k] for k in sig.parameters if kwargs.get(k) is not None}
             for cls, sig in paxes.Axes._format_signatures.items()
         }
+        for k in {k for cls_kw in kws.values() for k in cls_kw}:
+            kwargs.pop(k, None)
         classes = set()  # track used dictionaries
 
         def _axis_has_share_label_text(ax, axis):
@@ -3314,11 +3318,14 @@ def _axis_has_label_text(ax, axis):
                     kw.pop("ylabel", None)
             ax.format(rc_kw=rc_kw, rc_mode=rc_mode, skip_figure=True, **kw, **kwargs)
             ax.number = store_old_number
-        # Warn unused keyword argument(s)
+        # Warn unused keyword argument(s). Shared params (those in multiple
+        # signatures) are considered "used" if any matched class consumed them.
+        used_keys = {k for cls in classes for k in kws[cls]}
         kw = {
             key: value
             for name in kws.keys() - classes
             for key, value in kws[name].items()
+            if key not in used_keys
         }
         if kw:
             warnings._warn_ultraplot(

ultraplot/tests/test_projections.py

@@ -154,6 +154,16 @@ def test_polar_projections():
     return fig
 
 
+def test_polar_format_labels():
+    """
+    ax.format(xlabel=..., ylabel=...) must forward to set_xlabel/set_ylabel.
+    """
+    fig, ax = uplt.subplots(proj="polar")
+    ax.format(xlabel="xlabel", ylabel="ylabel")
+    assert ax.get_xlabel() == "xlabel"
+    assert ax.get_ylabel() == "ylabel"
+
+
 def test_sharing_axes():
     """
     Test sharing axes for GeoAxes