Cobertura: missing support for function coverage

[RoadTrain]

Currently Cobertura reporter does not fill the <methods> element, leaving it blank. The reasoning for that is as folows:

gcovr/gcovr/formats/cobertura/write.py

Lines 73 to 75 in f42ab8f

	# The Cobertura DTD requires a methods section, which isn't
	# trivial to get from gcov (so we will leave it blank)
	etree.SubElement(c, "methods")

I'm not sure if this rationale still holds? By looking at JSON output there seems to be a list of functions for each file, including their line numbers.

So probably the Cobertura reporter can be updated to support functions?
If so, then the correct output would be as follows:

		<methods>
			<method name="func1"  hits="7"  signature="(signature1)" >
				<lines><line number="40"  hits="7" /></lines>
			</method>
			<method name="func2"  hits="0"  signature="(signature2)" >
				<lines><line number="8"  hits="0" /></lines>
			</method>
		</methods>

[Spacetown]

Currently Cobertura reporter does not fill the <methods> element, leaving it blank. The reasoning for that is as folows:

gcovr/gcovr/formats/cobertura/write.py

Lines 73 to 75 in f42ab8f

	# The Cobertura DTD requires a methods section, which isn't
	# trivial to get from gcov (so we will leave it blank)
	etree.SubElement(c, "methods")

I'm not sure if this rationale still holds? By looking at JSON output there seems to be a list of functions for each file, including their line numbers.

It still true since we do not have full information needed for the report.

So probably the Cobertura reporter can be updated to support functions? If so, then the correct output would be as follows:

		<methods>
			<method name="func1"  hits="7"  signature="(signature1)" >
				<lines><line number="40"  hits="7" /></lines>
			</method>
			<method name="func2"  hits="0"  signature="(signature2)" >
				<lines><line number="8"  hits="0" /></lines>
			</method>
		</methods>

This example is invalid according to the DTD:

gcovr/gcovr/tests/cobertura.coverage-04.dtd

Lines 41 to 46 in f42ab8f

	<!ELEMENT method (lines)>
	<!ATTLIST method name CDATA #REQUIRED>
	<!ATTLIST method signature CDATA #REQUIRED>
	<!ATTLIST method line-rate CDATA #REQUIRED>
	<!ATTLIST method branch-rate CDATA #REQUIRED>
	<!ATTLIST method complexity CDATA #REQUIRED>

The hitsis not valid here but a line-rate, branch-rateand complexity is required. This information is completely missing, we only have a block-rate.

Related #654 .

[RoadTrain]

For the record, my example was from the cobertura report generated by istanbuljs. It is indeed not compliant with the spec, but it's working with report parsers and visualizers that we have tried (namely, ReportGenerator).

Of course I would like for gcovr to be compliant with the spec, and I'm looking forward for this kind of support.
Thanks!

[Spacetown]

There is already an issue since Apr 2021 related to the wrong report format, see istanbuljs/istanbuljs#603.

ReportGenerator doesn't validate input against the DTD. It only uses the expected arguments and ignores additional ones. The reports generated by the tool are DTD conform.

[RoadTrain]

Well, apparently there's an alternative spec, which is less strict: https://github.com/cobertura/cobertura/blob/master/cobertura/src/site/htdocs/xml/coverage-loose.dtd
Anyway, I think it's better to conform to the stricter spec.