Allow marks to be withheld from legend

seaborn/_core/plot.py

@@ -1562,12 +1562,15 @@ def _update_legend_contents(
                     schema.append(entry)
 
         # Second pass, generate an artist corresponding to each value
-        contents = []
+        contents: list[tuple[tuple[str, str | int], Any, list[str]]] = []
         for key, variables, (values, labels) in schema:
             artists = []
             for val in values:
-                artists.append(mark._legend_artist(variables, val, scales))
-            contents.append((key, artists, labels))
+                artist = mark._legend_artist(variables, val, scales)
+                if artist is not None:
+                    artists.append(artist)
+            if contents:
+                contents.append((key, artists, labels))
 
         self._legend_contents.extend(contents)
 

seaborn/_marks/base.py

@@ -217,8 +217,8 @@ def _plot(
     def _legend_artist(
         self, variables: list[str], value: Any, scales: dict[str, Scale],
     ) -> Artist:
-        # TODO return some sensible default?
-        raise NotImplementedError
+
+        return None
 
 
 def resolve_properties(

seaborn/_marks/text.py

@@ -1,11 +1,9 @@
 from __future__ import annotations
 from collections import defaultdict
 from dataclasses import dataclass
-from typing import Any
 
 import numpy as np
 import matplotlib as mpl
-from matplotlib.artist import Artist
 
 from seaborn._marks.base import (
     Mark,
@@ -17,7 +15,6 @@
     resolve_color,
     document_properties,
 )
-from seaborn._core.scales import Scale
 
 
 @document_properties
@@ -31,7 +28,6 @@ class Text(Mark):
     .. include:: ../docstrings/objects.Text.rst
 
     """
-
     text: MappableString = Mappable("")
     color: MappableColor = Mappable("k")
     alpha: MappableFloat = Mappable(1)
@@ -62,10 +58,3 @@ def _plot(self, split_gen, scales, orient):
 
         for ax, ax_vals in ax_data.items():
             ax.update_datalim(np.array(ax_vals))
-
-    def _legend_artist(
-        self, variables: list[str], value: Any, scales=dict[str, Scale],
-    ) -> Artist:
-
-        # TODO
-        return mpl.lines.Line2D([], [])

tests/_core/test_plot.py

@@ -1981,8 +1981,17 @@ def test_anonymous_title(self, xy):
         legend, = p._figure.legends
         assert legend.get_title().get_text() == ""
 
+    def test_legendless_mark(self, xy):
 
-class TestHelpers:
+        class NoLegendMark(MockMark):
+            def _legend_artist(self, variables, value, scales):
+                return None
+
+        p = Plot(**xy, color=["a", "b", "c", "d"]).add(NoLegendMark()).plot()
+        assert not p._figure.legends
+
+
+class TestDefaultObject:
 
     def test_default_repr(self):