trig Parser now raises SyntaxError, when finding nested graphs

[WhiteGobo]

Summary of changes

When loading trig-graph-bad-07.trig an exception should be raised.
I implemented a normal SyntaxError for this occasion.

The xfail for the corresponding test was removed.

Checklist

• Checked that there aren't other open pull requests for
  the same change.
• Checked that all tests and type checking passes.
• If the change has a potential impact on users of this project:
  • Updated relevant documentation to avoid inaccuracies.
  • Considered adding additional documentation.
• Considered granting push permissions to the PR branch,
  so maintainers can fix minor issues and keep your PR up to date.

[WhiteGobo]

I havent checked if the Syntaxerror should be subclassed.

[coveralls]

coverage: 90.901% (+0.01%) from 90.891% when pulling a6ca291 on WhiteGobo:trig-xfail-no-nested-graphs into 8582691 on RDFLib:main.

[aucampia]

pre-commit.ci autofix

[aucampia]

Thanks for the PR @WhiteGobo - I will check it in a bit more detail a bit later tonight but it looks good at a glance.

One concern may be that people prefer more lax parsers, but that can go too far [ref], and in this case, I definitely would much rather have the default be compliant with the spec and if someone wants it more lax we can consider adding an option to control parser behaviour to make it more lax; however, it is hard to see who would want it in this case.

[aucampia]

For reference, this is the test file in question:

rdflib/test/data/suites/w3c/trig/trig-graph-bad-07.trig

Lines 1 to 9 in 6f53455

	# GRAPH tests
	PREFIX : <http://example/>
	# GRAPH and a triples block.
	GRAPH :g {
	:s :p :o .
	GRAPH :g1 { :s1 :p1 :o1 }
	}

[aucampia]

I'm going to fix the two issues I noted in comments on your branch.

[aucampia]

I'm going to fix the two issues I noted in comments on your branch.

done now.

[aucampia]

Thanks for the fix, I'm not sure what was happening with the triples when nested graphs were encountered, but it could not have been good.

I will merge later this week if there is no more feedback.

[WhiteGobo]

Thx for the review. Ive felt really lost, when working on the Trig- and Notation3-Parser. I worked more with trial and error, than thinking:) Im much more confident with the parsers, that are written with pyparsing.

[aucampia]

Thx for the review. Ive felt really lost, when working on the Trig- and Notation3-Parser. I worked more with trial and error, than thinking:) Im much more confident with the parsers, that are written with pyparsing.

We really should get rid of the hand-written parsers, I don't like working on it either. I think using https://github.com/lark-parser/lark would be best, as that allows generating parsers that don't need any runtime dependencies, but PyParsing is already a lot easier.