Summarize visualizer breaks on columnless metadata

[thermokarst]

Bug Description
Providing ID-only sample metadata to summarize breaks.

Expected behavior
We should still error out, but in a more controlled fashion.

Screenshots

/home/wanghuilin/miniconda3/envs/qiime2/lib/python3.6/site-packages/q2_feature_table/_summarize/_visualizer.py:122: FutureWarning: The signature of Series.to_csv was aligned to that of DataFrame.to_csv, and argument ‘header’ will change its default value from False to True: please pass an explicit value to suppress this warning.
os.path.join(output_dir, ‘sample-frequency-detail.csv’))
/home/wanghuilin/miniconda3/envs/qiime2/lib/python3.6/site-packages/q2_feature_table/_summarize/_visualizer.py:124: FutureWarning: The signature of Series.to_csv was aligned to that of DataFrame.to_csv, and argument ‘header’ will change its default value from False to True: please pass an explicit value to suppress this warning.
os.path.join(output_dir, ‘feature-frequency-detail.csv’))
Traceback (most recent call last):
File “/home/wanghuilin/miniconda3/envs/qiime2/lib/python3.6/site-packages/q2cli/commands.py”, line 328, in call
results = action(**arguments)
File “</home/wanghuilin/miniconda3/envs/qiime2/lib/python3.6/site-packages/decorator.py:decorator-gen-326>”, line 2, in summarize
File “/home/wanghuilin/miniconda3/envs/qiime2/lib/python3.6/site-packages/qiime2/sdk/action.py”, line 245, in bound_callable
output_types, provenance)
File “/home/wanghuilin/miniconda3/envs/qiime2/lib/python3.6/site-packages/qiime2/sdk/action.py”, line 452, in callable_executor
ret_val = self._callable(output_dir=temp_dir, **view_args)
File “/home/wanghuilin/miniconda3/envs/qiime2/lib/python3.6/site-packages/q2_feature_table/_summarize/_visualizer.py”, line 156, in summarize
sample_frequencies
File “/home/wanghuilin/miniconda3/envs/qiime2/lib/python3.6/site-packages/q2_feature_table/_summarize/_vega_spec.py”, line 106, in vega_spec
‘value’: metadata_categories[0]
IndexError: list index out of range

References

1. Forum

[thermokarst]

BTW, for anyone interested in tackling this, I think adding a simple check around here will do it:

q2-feature-table/q2_feature_table/_summarize/_visualizer.py

Lines 153 to 158 in a5dc41b

	if sample_metadata is not None:
	context.update({'vega_spec':
	json.dumps(vega_spec(sample_metadata,
	sample_frequencies
	))
	})

    if sample_metadata is not None and sample_metadata.column_count > 0:

What isn't clear to me is if we should error or not. I guess if someone provides ID-only we could still show them the interactive viz, although it doesnt have much utility.

Another potential solution is to do what we do in q2-taxa's barplot viz - "demote" the ID column to a vanilla metadata column.