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From Andres Almiray <>
Subject Groovy and code coverage
Date Fri, 08 Sep 2017 09:41:18 GMT
Hello everyone,

As you may be aware there are only a few choices in the Java pace that can
be used for code coverage, JaCoCo being the one that gives the most
accurate results. While it's easy to setup JaCoco for Groovy sources there
are times where the tool reports no coverage for some lines of code that
should not have been counted for coverage in the first case, these are some
of the methods coming from GroovyObject and AST transformations,
specifically `getProperty`, `setProperty`, `getMetaClass`, and

I had a chat with Marc Hoffmann yesterday about this situation, which is a
topic we've discussed a few times in the past. I've got some good news,
Groovy is not alone in this problem, the Lombok project has suffered the
same fate which has prompted them to seek a solution. The alternative they
came up with is to have Lombok identified generated code that should not be
covered with a special annotation (@lombok.Generated), JaCoCo has a
filtering feature (not yet public) that can identify elements annotated
with said annotation and skip them from coverage reports. See

This feature will be available for consumption in the next releases of
Lombok (1.16.8+) and JaCoCo (0.7.9+).

Given this, Marc suggested that Groovy could follow the same idea and
provide an annotation that JaCoCo can identify, say for example

If such annotation were to be added to Groovy we would need (at least) the
following steps too:
 - update compiler to annotate `getProperty`, `setProperty`,
`getMetaClass`, and `invokeMethod` when the class does not explicitly
defines any of those methods.
 - review and update all core AST xforms that generate methods that should
be skipped from coverage.
 - document the usage of this annotation and encourage AST xform developers
to use it once they upgrade.

Would be great to have this feature in the 2.6.0 release if possible.


Java Champion; Groovy Enthusiast
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those who don't.
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