Deprecate auto-removal of grid by pcolor/pcolormesh.

Author: anntzer

doc/api/next_api_changes/deprecations/15604-AL.rst

@@ -0,0 +1,5 @@
+Auto-removal of grids by `~.Axes.pcolor` and `~.Axes.pcolormesh`
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+`~.Axes.pcolor` and `~.Axes.pcolormesh` currently remove any visible axes major
+grid.  This behavior is deprecated; please explicitly call ``ax.grid(False)``
+to remove the grid.

lib/matplotlib/axes/_axes.py

@@ -5721,6 +5721,15 @@ def _interp_grid(X):
         C = cbook.safe_masked_invalid(C)
         return X, Y, C, shading
 
+    def _pcolor_grid_deprecation_helper(self):
+        if any(axis._major_tick_kw["gridOn"]
+               for axis in self._get_axis_list()):
+            _api.warn_deprecated(
+                "3.5", message="Auto-removal of grids by pcolor() and "
+                "pcolormesh() is deprecated since %(since)s and will be "
+                "removed %(removal)s; please call grid(False) first.")
+        self.grid(False)
+
     @_preprocess_data()
     @docstring.dedent_interpd
     def pcolor(self, *args, shading=None, alpha=None, norm=None, cmap=None,
@@ -5936,7 +5945,7 @@ def pcolor(self, *args, shading=None, alpha=None, norm=None, cmap=None,
         collection.set_cmap(cmap)
         collection.set_norm(norm)
         collection._scale_norm(norm, vmin, vmax)
-        self.grid(False)
+        self._pcolor_grid_deprecation_helper()
 
         x = X.compressed()
         y = Y.compressed()
@@ -6173,8 +6182,7 @@ def pcolormesh(self, *args, alpha=None, norm=None, cmap=None, vmin=None,
         collection.set_cmap(cmap)
         collection.set_norm(norm)
         collection._scale_norm(norm, vmin, vmax)
-
-        self.grid(False)
+        self._pcolor_grid_deprecation_helper()
 
         # Transform from native to data coordinates?
         t = collection._transform