Fix saving Panel objects with hvplot.save

hvplot/utilities.py

@@ -6,7 +6,64 @@
 
 output = _hv.output
 
-save = _hv.save
+
+def save(obj, filename, fmt='auto', backend=None, resources='cdn', toolbar=None, title=None, **kwargs):
+    """
+    Saves the supplied object to file.
+
+    This function delegates saving to `holoviews.util.save` when the
+    object is a HoloViews element, which is the type of object mostly
+    created by hvPlot. This function inherits the same signature and
+    docstring below. However, in some cases hvPlot creates Panel objects,
+    in which case saving is delegated to the method `panel.io.Viewable.save`.
+    It shares a few common parameters with `holoviews.util.save`, and extra
+    parameters can be passed as kwargs.
+
+    The available output formats depend on the backend being used. By
+    default and if the filename is a string the output format will be
+    inferred from the file extension. Otherwise an explicit format
+    will need to be specified. For ambiguous file extensions such as
+    html it may be necessary to specify an explicit fmt to override
+    the default, e.g. in the case of 'html' output the widgets will
+    default to fmt='widgets', which may be changed to scrubber widgets
+    using fmt='scrubber'.
+
+    Arguments
+    ---------
+    obj: HoloViews object
+        The HoloViews object to save to file
+    filename: string or IO object
+        The filename or BytesIO/StringIO object to save to
+    fmt: string
+        The format to save the object as, e.g. png, svg, html, or gif
+        and if widgets are desired either 'widgets' or 'scrubber'
+    backend: string
+        A valid HoloViews rendering backend, e.g. bokeh or matplotlib
+    resources: string or bokeh.resource.Resources
+        Bokeh resources used to load bokehJS components. Defaults to
+        CDN, to embed resources inline for offline usage use 'inline'
+        or bokeh.resources.INLINE.
+    toolbar: bool or None
+        Whether to include toolbars in the exported plot. If None,
+        display the toolbar unless fmt is `png` and backend is `bokeh`.
+        If `True`, always include the toolbar.  If `False`, do not include the
+        toolbar.
+    title: string
+        Custom title for exported HTML file
+    **kwargs: dict
+        Additional keyword arguments passed to the renderer,
+        e.g. fps for animations
+    """
+    if isinstance(obj, _hv.core.Dimensioned):
+        _hv.save(
+            obj, filename, fmt=fmt, backend=backend, resources=resources,
+            toolbar=toolbar, title=title, **kwargs
+        )
+    elif isinstance(obj, _pn.layout.Panel):
+        obj.save(filename, resources=resources, title=title, **kwargs)
+    else:
+        raise TypeError(f"Saving not supported for objects of type {type(obj)!r}")
+
 
 def show(obj, title=None, port=0, **kwargs):
     """