[Cobertura-devel] Ability to enable/disable code complexity calculator

[Timo <Mai...@gm...>]

Hello everyone,

I am currently developing a project using Java 8 and want to check the
code coverage of my tests. As you know, Cobertura does not fully
support Java 8 because JavaNCSS cannot parse Java 8 source code. The
coverage reporting does seem to work flawlessly, however the
complexity calcuation fails with an unpleasant exception from
JavaNCSS. Since I do not care about the complexity reporting right
now, I would like to be able to disable it and use Cobertura for code
coverage reporting only. As I was searching for a way to do that I
discovered this feature in the roadmap [1]. So I thought I would give
the source code of Cobertura a look and see how it could be
implemented.

First of all, I am not sure I understand all design/architecture
desicions in Cobertura. That being said, here is my rough proposal how
to implement enabling/disabling the code complexity calculator:

Preparations
- To make Cobertura's reporting flexible and maintainable, I would
like to separate data, view and logic. Currently, the various classes
generating output (e.g. HTMLReport) mix it all together. Let's call
HTMLReport etc. "OutputReports" to distinguish them from
net.sourceforge.cobertura.reporting.Report.
- There should be a class that can hold complexity information,
without any logic. Not the ComplexityCalculator, but something that is
filled using the ComplexityCalculator. This way we can separate logic
from data and OutputReports do not have to know about the
ComplexityCalculator. Let's call this class "ComplexityData".
- Cobertura should use a template engine like Velocity or Freemarker
to generate output. This way we can easily implement reports with or
without complexity information and even "themes" in some future
version.
- There should be a ReportingTask, much like the CheckCoverageTask,
that creates the NativeReport. The ComplexityCalculator and the
ComplexityData object should be created there. Only the ComplexityData
object should be passed to the NativeReport.

Once the preparations are done, we can implement the switch:
- Add a Metric enum with two values: COVERAGE and COMPLEXITY
- Add a method to the Report interface: hasMetric(Metric)
- Use that method in the ReportFormatStrategy implementations to
decide which OutputReport to use
- Implement OutputReports without complexity information
- Add a method named "coverageOnly" to the DSL which sets an internal boolean.
- When report() is called, the boolean is passed to the ReportingTask
which returns a report with or without complexity information. The
default is to calculate both coverage and complexity to stay API
compatible with earlier versions.

What do you think?

Greetings from Germany
Timo


[1] https://github.com/cobertura/cobertura/wiki/Roadmap