Error parsing simple DESCRIBE query

[johnstonskj]

A simple query of the form DESCRIBE <http://example.org/> results in the following stacktrace.

  File "/Users/simonjo/anaconda/lib/python3.5/site-packages/rdflib/plugins/sparql/processor.py", line 75, in query
    query = translateQuery(parsetree, base, initNs)
  File "/Users/simonjo/anaconda/lib/python3.5/site-packages/rdflib/plugins/sparql/algebra.py", line 766, in translateQuery
    P, PV = translate(q[1])
  File "/Users/simonjo/anaconda/lib/python3.5/site-packages/rdflib/plugins/sparql/algebra.py", line 549, in translate
    M = translateGroupGraphPattern(q.where)
  File "/Users/simonjo/anaconda/lib/python3.5/site-packages/rdflib/plugins/sparql/algebra.py", line 269, in translateGroupGraphPattern
    if graphPattern.name == 'SubSelect':
AttributeError: 'NoneType' object has no attribute 'name'

The call to translateGroupGraphPattern in algebra.py states incorrectly that queries always include a where clause. This is not the case for DESCRIBE, see SPARQL 1.1 section 16.4.1 (SPARQL 1.0 section 10.4.1) "Explicit IRIs".

rdflib/rdflib/plugins/sparql/algebra.py

Lines 550 to 551 in 300db62

	# all query types have a where part
	M = translateGroupGraphPattern(q.where)

[luckyagarwal]

@johnstonskj the above issue has now been fixed.

[aucampia]

See also:

• DESCRIBE query not working #479
• Earlier attempt to fix it: master...gjhiggins:fix-for-issue813-sparql-describe

[ms1901]

Hey, I am working to resolve this issue and will be sending a PR soon.

[ghost]

Hey, I am working to resolve this issue and will be sending a PR soon.

Please note the existing ongoing work on this same issue in #479 and the previous partial implementation in https://github.com/gjhiggins/rdflib/commit/5fb6f43e6b1d2264ac5015c260b32fc4e7dbf240

[aucampia]

This was implemented in #2221 and should now be working. Please confirm if you can.

I will close this issue in some weeks if there is no further feedback.

[aucampia]

Closing this as DESCRIBE was implemented.