xarray Image plot fails with datashade=True

[michaelaye]

ALL software version info

xarray 0.17.0
hvplot 0.7.0
holoviews 1.14.1
bokeh 2.2.3
python 3.8.x
notebook 6.2
OS: PopOS(Ubuntu) 20.10
Browser Brave (Chrome)

Description of expected behavior and the observed behavior

Like for xarray.hvplot.scatter in the docs, using the datashade option should work for Image rasters.
Instead it throws a huge traceback.

Complete, minimal, self-contained example code that reproduces the issue

arr = xr.DataArray(
    np.arange(10000).reshape(100, 100),
    dims=("x", "y"),
    coords={"x": np.arange(100), "y": np.arange(100)},
)
arr.hvplot()
arr.hvplot(datashade=True)

Stack traceback and/or browser JavaScript console output

WARNING:param.dynamic_operation: Callable raised "AttributeError("'DataArray' object has no attribute '_file_obj'")".
Invoked as dynamic_operation(height=300, scale=1.0, width=700, x_range=None, y_range=None)
WARNING:param.dynamic_operation: Callable raised "AttributeError("'DataArray' object has no attribute '_file_obj'")".
Invoked as dynamic_operation(height=300, scale=1.0, width=700, x_range=None, y_range=None)

AttributeError Traceback (most recent call last)
~/miniconda3/envs/py38/lib/python3.8/site-packages/IPython/core/formatters.py in call(self, obj, include, exclude)
968
969 if method is not None:
--> 970 return method(include=include, exclude=exclude)
971 return None
972 else:

~/miniconda3/envs/py38/lib/python3.8/site-packages/holoviews/core/dimension.py in repr_mimebundle(self, include, exclude)
1314 combined and returned.
1315 """
-> 1316 return Store.render(self)
1317
1318

~/miniconda3/envs/py38/lib/python3.8/site-packages/holoviews/core/options.py in render(cls, obj)
1403 data, metadata = {}, {}
1404 for hook in hooks:
-> 1405 ret = hook(obj)
1406 if ret is None:
1407 continue

~/miniconda3/envs/py38/lib/python3.8/site-packages/holoviews/ipython/display_hooks.py in pprint_display(obj)
280 if not ip.display_formatter.formatters['text/plain'].pprint:
281 return None
--> 282 return display(obj, raw_output=True)
283
284

~/miniconda3/envs/py38/lib/python3.8/site-packages/holoviews/ipython/display_hooks.py in display(obj, raw_output, **kwargs)
256 elif isinstance(obj, (HoloMap, DynamicMap)):
257 with option_state(obj):
--> 258 output = map_display(obj)
259 elif isinstance(obj, Plot):
260 output = render(obj)

~/miniconda3/envs/py38/lib/python3.8/site-packages/holoviews/ipython/display_hooks.py in wrapped(element)
144 try:
145 max_frames = OutputSettings.options['max_frames']
--> 146 mimebundle = fn(element, max_frames=max_frames)
147 if mimebundle is None:
148 return {}, {}

~/miniconda3/envs/py38/lib/python3.8/site-packages/holoviews/ipython/display_hooks.py in map_display(vmap, max_frames)
204 return None
205
--> 206 return render(vmap)
207
208

~/miniconda3/envs/py38/lib/python3.8/site-packages/holoviews/ipython/display_hooks.py in render(obj, **kwargs)
66 renderer = renderer.instance(fig='png')
67
---> 68 return renderer.components(obj, **kwargs)
69
70

~/miniconda3/envs/py38/lib/python3.8/site-packages/holoviews/plotting/renderer.py in components(self, obj, fmt, comm, **kwargs)
408 doc = Document()
409 with config.set(embed=embed):
--> 410 model = plot.layout._render_model(doc, comm)
411 if embed:
412 return render_model(model, comm)

~/miniconda3/envs/py38/lib/python3.8/site-packages/panel/viewable.py in _render_model(self, doc, comm)
422 if comm is None:
423 comm = state._comm_manager.get_server_comm()
--> 424 model = self.get_root(doc, comm)
425
426 if config.embed:

~/miniconda3/envs/py38/lib/python3.8/site-packages/panel/viewable.py in get_root(self, doc, comm, preprocess)
480 """
481 doc = init_doc(doc)
--> 482 root = self._get_model(doc, comm=comm)
483 if preprocess:
484 self._preprocess(root)

~/miniconda3/envs/py38/lib/python3.8/site-packages/panel/layout/base.py in _get_model(self, doc, root, parent, comm)
110 if root is None:
111 root = model
--> 112 objects = self._get_objects(model, [], doc, root, comm)
113 props = dict(self._init_properties(), objects=objects)
114 model.update(**self._process_param_change(props))

~/miniconda3/envs/py38/lib/python3.8/site-packages/panel/layout/base.py in _get_objects(self, model, old_objects, doc, root, comm)
100 else:
101 try:
--> 102 child = pane._get_model(doc, root, model, comm)
103 except RerenderError:
104 return self._get_objects(model, current_objects[:i], doc, root, comm)

~/miniconda3/envs/py38/lib/python3.8/site-packages/panel/pane/holoviews.py in _get_model(self, doc, root, parent, comm)
239 plot = self.object
240 else:
--> 241 plot = self._render(doc, comm, root)
242
243 plot.pane = self

~/miniconda3/envs/py38/lib/python3.8/site-packages/panel/pane/holoviews.py in _render(self, doc, comm, root)
304 kwargs['comm'] = comm
305
--> 306 return renderer.get_plot(self.object, **kwargs)
307
308 def _cleanup(self, root):

~/miniconda3/envs/py38/lib/python3.8/site-packages/holoviews/plotting/bokeh/renderer.py in get_plot(self_or_cls, obj, doc, renderer, **kwargs)
71 combining the bokeh model with another plot.
72 """
---> 73 plot = super(BokehRenderer, self_or_cls).get_plot(obj, doc, renderer, **kwargs)
74 if plot.document is None:
75 plot.document = Document() if self_or_cls.notebook_context else curdoc()

~/miniconda3/envs/py38/lib/python3.8/site-packages/holoviews/plotting/renderer.py in get_plot(self_or_cls, obj, doc, renderer, comm, **kwargs)
218
219 # Initialize DynamicMaps with first data item
--> 220 initialize_dynamic(obj)
221
222 if not renderer:

~/miniconda3/envs/py38/lib/python3.8/site-packages/holoviews/plotting/util.py in initialize_dynamic(obj)
250 continue
251 if not len(dmap):
--> 252 dmap[dmap._initial_key()]
253
254

~/miniconda3/envs/py38/lib/python3.8/site-packages/holoviews/core/spaces.py in getitem(self, key)
1329 # Not a cross product and nothing cached so compute element.
1330 if cache is not None: return cache
-> 1331 val = self._execute_callback(*tuple_key)
1332 if data_slice:
1333 val = self._dataslice(val, data_slice)

~/miniconda3/envs/py38/lib/python3.8/site-packages/holoviews/core/spaces.py in _execute_callback(self, *args)
1098
1099 with dynamicmap_memoization(self.callback, self.streams):
-> 1100 retval = self.callback(*args, **kwargs)
1101 return self._style(retval)
1102

~/miniconda3/envs/py38/lib/python3.8/site-packages/holoviews/core/spaces.py in call(self, *args, **kwargs)
712
713 try:
--> 714 ret = self.callable(*args, **kwargs)
715 except KeyError:
716 # KeyError is caught separately because it is used to signal

~/miniconda3/envs/py38/lib/python3.8/site-packages/holoviews/util/init.py in dynamic_operation(*key, **kwargs)
1016
1017 def dynamic_operation(*key, **kwargs):
-> 1018 key, obj = resolve(key, kwargs)
1019 return apply(obj, *key, **kwargs)
1020

~/miniconda3/envs/py38/lib/python3.8/site-packages/holoviews/util/init.py in resolve(key, kwargs)
1005 elif isinstance(map_obj, DynamicMap) and map_obj._posarg_keys and not key:
1006 key = tuple(kwargs[k] for k in map_obj._posarg_keys)
-> 1007 return key, map_obj[key]
1008
1009 def apply(element, *key, **kwargs):

~/miniconda3/envs/py38/lib/python3.8/site-packages/holoviews/core/spaces.py in getitem(self, key)
1329 # Not a cross product and nothing cached so compute element.
1330 if cache is not None: return cache
-> 1331 val = self._execute_callback(*tuple_key)
1332 if data_slice:
1333 val = self._dataslice(val, data_slice)

~/miniconda3/envs/py38/lib/python3.8/site-packages/holoviews/core/spaces.py in _execute_callback(self, *args)
1098
1099 with dynamicmap_memoization(self.callback, self.streams):
-> 1100 retval = self.callback(*args, **kwargs)
1101 return self._style(retval)
1102

~/miniconda3/envs/py38/lib/python3.8/site-packages/holoviews/core/spaces.py in call(self, *args, **kwargs)
712
713 try:
--> 714 ret = self.callable(*args, **kwargs)
715 except KeyError:
716 # KeyError is caught separately because it is used to signal

~/miniconda3/envs/py38/lib/python3.8/site-packages/holoviews/util/init.py in dynamic_operation(*key, **kwargs)
1017 def dynamic_operation(*key, **kwargs):
1018 key, obj = resolve(key, kwargs)
-> 1019 return apply(obj, *key, **kwargs)
1020
1021 operation = self.p.operation

~/miniconda3/envs/py38/lib/python3.8/site-packages/holoviews/util/init.py in apply(element, *key, **kwargs)
1009 def apply(element, *key, **kwargs):
1010 kwargs = dict(util.resolve_dependent_kwargs(self.p.kwargs), **kwargs)
-> 1011 processed = self._process(element, key, kwargs)
1012 if (self.p.link_dataset and isinstance(element, Dataset) and
1013 isinstance(processed, Dataset) and processed._dataset is None):

~/miniconda3/envs/py38/lib/python3.8/site-packages/holoviews/util/init.py in _process(self, element, key, kwargs)
991 elif isinstance(self.p.operation, Operation):
992 kwargs = {k: v for k, v in kwargs.items() if k in self.p.operation.param}
--> 993 return self.p.operation.process_element(element, key, **kwargs)
994 else:
995 return self.p.operation(element, **kwargs)

~/miniconda3/envs/py38/lib/python3.8/site-packages/holoviews/core/operation.py in process_element(self, element, key, **params)
192 self.p = param.ParamOverrides(self, params,
193 allow_extra_keywords=self._allow_extra_keywords)
--> 194 return self._apply(element, key)
195
196

~/miniconda3/envs/py38/lib/python3.8/site-packages/holoviews/core/operation.py in _apply(self, element, key)
139 if not in_method:
140 element._in_method = True
--> 141 ret = self._process(element, key)
142 if hasattr(element, '_in_method') and not in_method:
143 element._in_method = in_method

~/miniconda3/envs/py38/lib/python3.8/site-packages/holoviews/operation/datashader.py in _process(self, element, key)
1496
1497 def _process(self, element, key=None):
-> 1498 agg = rasterize._process(self, element, key)
1499 shaded = shade._process(self, agg, key)
1500 return shaded

~/miniconda3/envs/py38/lib/python3.8/site-packages/holoviews/operation/datashader.py in _process(self, element, key)
1475 if k in transform.param})
1476 op._precomputed = self._precomputed
-> 1477 element = element.map(op, predicate)
1478 self._precomputed = op._precomputed
1479

~/miniconda3/envs/py38/lib/python3.8/site-packages/holoviews/core/data/init.py in pipelined_fn(*args, **kwargs)
199
200 try:
--> 201 result = method_fn(*args, **kwargs)
202 if PipelineMeta.disable:
203 return result

~/miniconda3/envs/py38/lib/python3.8/site-packages/holoviews/core/data/init.py in map(self, *args, **kwargs)
1214
1215 def map(self, *args, **kwargs):
-> 1216 return super(Dataset, self).map(*args, **kwargs)
1217 map.doc = LabelledData.map.doc
1218

~/miniconda3/envs/py38/lib/python3.8/site-packages/holoviews/core/dimension.py in map(self, map_fn, specs, clone)
707 return deep_mapped
708 else:
--> 709 return map_fn(self) if applies else self
710
711

~/miniconda3/envs/py38/lib/python3.8/site-packages/holoviews/core/operation.py in call(self, element, **kwargs)
212 elif ((self._per_element and isinstance(element, Element)) or
213 (not self._per_element and isinstance(element, ViewableElement))):
--> 214 return self._apply(element)
215 elif 'streams' not in kwargs:
216 kwargs['streams'] = self.p.streams

~/miniconda3/envs/py38/lib/python3.8/site-packages/holoviews/core/operation.py in _apply(self, element, key)
139 if not in_method:
140 element._in_method = True
--> 141 ret = self._process(element, key)
142 if hasattr(element, '_in_method') and not in_method:
143 element._in_method = in_method

~/miniconda3/envs/py38/lib/python3.8/site-packages/holoviews/operation/datashader.py in _process(self, element, key)
937 agg_fn = self._get_aggregator(element, add_field=False)
938 for vd, xarr in arrays.items():
--> 939 rarray = cvs.raster(xarr, upsample_method=interp,
940 downsample_method=agg_fn)
941

~/miniconda3/envs/py38/lib/python3.8/site-packages/datashader/core.py in raster(self, source, layer, upsample_method, downsample_method, nan_value, agg, interpolate, chunksize, max_mem)
1131 dims = [ydim, xdim]
1132 attrs = dict(res=res[0])
-> 1133 if source._file_obj is not None and hasattr(source._file_obj, 'nodata'):
1134 attrs['nodata'] = source._file_obj.nodata
1135

~/miniconda3/envs/py38/lib/python3.8/site-packages/xarray/core/common.py in getattr(self, name)
237 with suppress(KeyError):
238 return source[name]
--> 239 raise AttributeError(
240 "{!r} object has no attribute {!r}".format(type(self).name, name)
241 )

AttributeError: 'DataArray' object has no attribute '_file_obj'

Screenshots or screencasts of the bug in action

[michaelaye]

This looks really involved but is maybe simpler than it looks?

In datashader/core.py I'd change lines from 1133:

if source._file_obj is not None and hasattr(source._file_obj, 'nodata'):
            attrs['nodata'] = source._file_obj.nodata

to

if hasattr(source, "_file_obj") and source._file_obj is not None and hasattr(source._file_obj, 'nodata'):
            attrs['nodata'] = source._file_obj.nodata

unless the underlying issue is that source really should have an _file_obj and it should be set to None, instead of being missing?

[jbednar]

From https://github.com/pydata/xarray/pull/4809/files#r557628298 it looks to me like _file_obj is no longer expected to exist at all, with that object stuffed inside a closure and really, clearly not being meant to be used. I would assume that we need to fix our code to find the nodata attribute some other more reliable way. I don't know where we were supposed to find it if not on _file_obj, though!

Hello,

I do experience the same issue using:
xarray 0.17.0
hvplot 0.7.0
holoviews 1.14.1
bokeh 2.2.3
geoviews 1.8.1
python 3.8.5
notebook 6.2.0
OS: Ubuntu 18.04
Google Chrome (Chromium)

Where I use the hvplot.rgb(), adding rasterize=True generates the error below.

---

WARNING:param.dynamic_operation: Callable raised "AttributeError("'DataArray' object has no attribute '_file_obj'")".
Invoked as dynamic_operation(height=400, scale=1.0, width=400, x_range=None, y_range=None)

AttributeError Traceback (most recent call last)
/usr/local/lib/python3.8/dist-packages/IPython/core/formatters.py in call(self, obj, include, exclude)
968
969 if method is not None:
--> 970 return method(include=include, exclude=exclude)
971 return None
972 else:

/usr/local/lib/python3.8/dist-packages/holoviews/core/dimension.py in repr_mimebundle(self, include, exclude)
1314 combined and returned.
1315 """
-> 1316 return Store.render(self)
1317
1318

/usr/local/lib/python3.8/dist-packages/holoviews/core/options.py in render(cls, obj)
1403 data, metadata = {}, {}
1404 for hook in hooks:
-> 1405 ret = hook(obj)
1406 if ret is None:
1407 continue

/usr/local/lib/python3.8/dist-packages/holoviews/ipython/display_hooks.py in pprint_display(obj)
280 if not ip.display_formatter.formatters['text/plain'].pprint:
281 return None
--> 282 return display(obj, raw_output=True)
283
284

/usr/local/lib/python3.8/dist-packages/holoviews/ipython/display_hooks.py in display(obj, raw_output, **kwargs)
256 elif isinstance(obj, (HoloMap, DynamicMap)):
257 with option_state(obj):
--> 258 output = map_display(obj)
259 elif isinstance(obj, Plot):
260 output = render(obj)

/usr/local/lib/python3.8/dist-packages/holoviews/ipython/display_hooks.py in wrapped(element)
144 try:
145 max_frames = OutputSettings.options['max_frames']
--> 146 mimebundle = fn(element, max_frames=max_frames)
147 if mimebundle is None:
148 return {}, {}

/usr/local/lib/python3.8/dist-packages/holoviews/ipython/display_hooks.py in map_display(vmap, max_frames)
204 return None
205
--> 206 return render(vmap)
207
208

/usr/local/lib/python3.8/dist-packages/holoviews/ipython/display_hooks.py in render(obj, **kwargs)
66 renderer = renderer.instance(fig='png')
67
---> 68 return renderer.components(obj, **kwargs)
69
70

/usr/local/lib/python3.8/dist-packages/holoviews/plotting/renderer.py in components(self, obj, fmt, comm, **kwargs)
408 doc = Document()
409 with config.set(embed=embed):
--> 410 model = plot.layout._render_model(doc, comm)
411 if embed:
412 return render_model(model, comm)

/usr/local/lib/python3.8/dist-packages/panel/viewable.py in _render_model(self, doc, comm)
422 if comm is None:
423 comm = state._comm_manager.get_server_comm()
--> 424 model = self.get_root(doc, comm)
425
426 if config.embed:

/usr/local/lib/python3.8/dist-packages/panel/viewable.py in get_root(self, doc, comm, preprocess)
480 """
481 doc = init_doc(doc)
--> 482 root = self._get_model(doc, comm=comm)
483 if preprocess:
484 self._preprocess(root)

/usr/local/lib/python3.8/dist-packages/panel/layout/base.py in _get_model(self, doc, root, parent, comm)
110 if root is None:
111 root = model
--> 112 objects = self._get_objects(model, [], doc, root, comm)
113 props = dict(self._init_properties(), objects=objects)
114 model.update(**self._process_param_change(props))

/usr/local/lib/python3.8/dist-packages/panel/layout/base.py in _get_objects(self, model, old_objects, doc, root, comm)
100 else:
101 try:
--> 102 child = pane._get_model(doc, root, model, comm)
103 except RerenderError:
104 return self._get_objects(model, current_objects[:i], doc, root, comm)

/usr/local/lib/python3.8/dist-packages/panel/pane/holoviews.py in _get_model(self, doc, root, parent, comm)
239 plot = self.object
240 else:
--> 241 plot = self._render(doc, comm, root)
242
243 plot.pane = self

/usr/local/lib/python3.8/dist-packages/panel/pane/holoviews.py in _render(self, doc, comm, root)
304 kwargs['comm'] = comm
305
--> 306 return renderer.get_plot(self.object, **kwargs)
307
308 def _cleanup(self, root):

/usr/local/lib/python3.8/dist-packages/holoviews/plotting/bokeh/renderer.py in get_plot(self_or_cls, obj, doc, renderer, **kwargs)
71 combining the bokeh model with another plot.
72 """
---> 73 plot = super(BokehRenderer, self_or_cls).get_plot(obj, doc, renderer, **kwargs)
74 if plot.document is None:
75 plot.document = Document() if self_or_cls.notebook_context else curdoc()

/usr/local/lib/python3.8/dist-packages/holoviews/plotting/renderer.py in get_plot(self_or_cls, obj, doc, renderer, comm, **kwargs)
218
219 # Initialize DynamicMaps with first data item
--> 220 initialize_dynamic(obj)
221
222 if not renderer:

/usr/local/lib/python3.8/dist-packages/holoviews/plotting/util.py in initialize_dynamic(obj)
250 continue
251 if not len(dmap):
--> 252 dmap[dmap._initial_key()]
253
254

/usr/local/lib/python3.8/dist-packages/holoviews/core/spaces.py in getitem(self, key)
1329 # Not a cross product and nothing cached so compute element.
1330 if cache is not None: return cache
-> 1331 val = self._execute_callback(*tuple_key)
1332 if data_slice:
1333 val = self._dataslice(val, data_slice)

/usr/local/lib/python3.8/dist-packages/holoviews/core/spaces.py in _execute_callback(self, *args)
1098
1099 with dynamicmap_memoization(self.callback, self.streams):
-> 1100 retval = self.callback(*args, **kwargs)
1101 return self._style(retval)
1102

/usr/local/lib/python3.8/dist-packages/holoviews/core/spaces.py in call(self, *args, **kwargs)
712
713 try:
--> 714 ret = self.callable(*args, **kwargs)
715 except KeyError:
716 # KeyError is caught separately because it is used to signal

/usr/local/lib/python3.8/dist-packages/holoviews/util/init.py in dynamic_operation(*key, **kwargs)
1016
1017 def dynamic_operation(*key, **kwargs):
-> 1018 key, obj = resolve(key, kwargs)
1019 return apply(obj, *key, **kwargs)
1020

/usr/local/lib/python3.8/dist-packages/holoviews/util/init.py in resolve(key, kwargs)
1005 elif isinstance(map_obj, DynamicMap) and map_obj._posarg_keys and not key:
1006 key = tuple(kwargs[k] for k in map_obj._posarg_keys)
-> 1007 return key, map_obj[key]
1008
1009 def apply(element, *key, **kwargs):

/usr/local/lib/python3.8/dist-packages/holoviews/core/spaces.py in getitem(self, key)
1329 # Not a cross product and nothing cached so compute element.
1330 if cache is not None: return cache
-> 1331 val = self._execute_callback(*tuple_key)
1332 if data_slice:
1333 val = self._dataslice(val, data_slice)

/usr/local/lib/python3.8/dist-packages/holoviews/core/spaces.py in _execute_callback(self, *args)
1098
1099 with dynamicmap_memoization(self.callback, self.streams):
-> 1100 retval = self.callback(*args, **kwargs)
1101 return self._style(retval)
1102

/usr/local/lib/python3.8/dist-packages/holoviews/core/spaces.py in call(self, *args, **kwargs)
712
713 try:
--> 714 ret = self.callable(*args, **kwargs)
715 except KeyError:
716 # KeyError is caught separately because it is used to signal

/usr/local/lib/python3.8/dist-packages/holoviews/util/init.py in dynamic_operation(*key, **kwargs)
1017 def dynamic_operation(*key, **kwargs):
1018 key, obj = resolve(key, kwargs)
-> 1019 return apply(obj, *key, **kwargs)
1020
1021 operation = self.p.operation

/usr/local/lib/python3.8/dist-packages/holoviews/util/init.py in apply(element, *key, **kwargs)
1009 def apply(element, *key, **kwargs):
1010 kwargs = dict(util.resolve_dependent_kwargs(self.p.kwargs), **kwargs)
-> 1011 processed = self._process(element, key, kwargs)
1012 if (self.p.link_dataset and isinstance(element, Dataset) and
1013 isinstance(processed, Dataset) and processed._dataset is None):

/usr/local/lib/python3.8/dist-packages/holoviews/util/init.py in _process(self, element, key, kwargs)
991 elif isinstance(self.p.operation, Operation):
992 kwargs = {k: v for k, v in kwargs.items() if k in self.p.operation.param}
--> 993 return self.p.operation.process_element(element, key, **kwargs)
994 else:
995 return self.p.operation(element, **kwargs)

/usr/local/lib/python3.8/dist-packages/holoviews/core/operation.py in process_element(self, element, key, **params)
192 self.p = param.ParamOverrides(self, params,
193 allow_extra_keywords=self._allow_extra_keywords)
--> 194 return self._apply(element, key)
195
196

/usr/local/lib/python3.8/dist-packages/holoviews/core/operation.py in _apply(self, element, key)
139 if not in_method:
140 element._in_method = True
--> 141 ret = self._process(element, key)
142 if hasattr(element, '_in_method') and not in_method:
143 element._in_method = in_method

/usr/local/lib/python3.8/dist-packages/holoviews/operation/datashader.py in _process(self, element, key)
1475 if k in transform.param})
1476 op._precomputed = self._precomputed
-> 1477 element = element.map(op, predicate)
1478 self._precomputed = op._precomputed
1479

/usr/local/lib/python3.8/dist-packages/holoviews/core/data/init.py in pipelined_fn(*args, **kwargs)
199
200 try:
--> 201 result = method_fn(*args, **kwargs)
202 if PipelineMeta.disable:
203 return result

/usr/local/lib/python3.8/dist-packages/holoviews/core/data/init.py in map(self, *args, **kwargs)
1214
1215 def map(self, *args, **kwargs):
-> 1216 return super(Dataset, self).map(*args, **kwargs)
1217 map.doc = LabelledData.map.doc
1218

/usr/local/lib/python3.8/dist-packages/holoviews/core/dimension.py in map(self, map_fn, specs, clone)
707 return deep_mapped
708 else:
--> 709 return map_fn(self) if applies else self
710
711

/usr/local/lib/python3.8/dist-packages/holoviews/core/operation.py in call(self, element, **kwargs)
212 elif ((self._per_element and isinstance(element, Element)) or
213 (not self._per_element and isinstance(element, ViewableElement))):
--> 214 return self._apply(element)
215 elif 'streams' not in kwargs:
216 kwargs['streams'] = self.p.streams

/usr/local/lib/python3.8/dist-packages/holoviews/core/operation.py in _apply(self, element, key)
139 if not in_method:
140 element._in_method = True
--> 141 ret = self._process(element, key)
142 if hasattr(element, '_in_method') and not in_method:
143 element._in_method = in_method

/usr/local/lib/python3.8/dist-packages/holoviews/operation/datashader.py in _process(self, element, key)
937 agg_fn = self._get_aggregator(element, add_field=False)
938 for vd, xarr in arrays.items():
--> 939 rarray = cvs.raster(xarr, upsample_method=interp,
940 downsample_method=agg_fn)
941

/usr/local/lib/python3.8/dist-packages/datashader/core.py in raster(self, source, layer, upsample_method, downsample_method, nan_value, agg, interpolate, chunksize, max_mem)
1131 dims = [ydim, xdim]
1132 attrs = dict(res=res[0])
-> 1133 if source._file_obj is not None and hasattr(source._file_obj, 'nodata'):
1134 attrs['nodata'] = source._file_obj.nodata
1135

/usr/local/lib/python3.8/dist-packages/xarray/core/common.py in getattr(self, name)
237 with suppress(KeyError):
238 return source[name]
--> 239 raise AttributeError(
240 "{!r} object has no attribute {!r}".format(type(self).name, name)
241 )

AttributeError: 'DataArray' object has no attribute '_file_obj'
:DynamicMap []

[jbednar]

@dev-eo , you should be able to avoid the problem by pinning xarray<0.17.0. We don't have a proper fix yet, other than that.

[scottyhq]

just hit the same thing. @philippjfr @jbednar in case it helps, this issue has been cropping up in other libraries with xarray as a dependency (see corteva/rioxarray#254, intake/intake-xarray#99 (comment)). There are some pretty big changes with backend I/O and indexing, so it might be good to add a test environment against xarray master.

[philippjfr]

Closing since this is an upstream issue in datashader (see holoviz/datashader#990). Upstream testing of the master branch of all supported data backends seems like a good idea though. Could one of you file an issue about that?