Enable additional Error Prone checks which are disabled by default
Description
Some of them also enforce additional Google Java Format requirements which are not handled by google-java-format, such as disallowing wildcard imports.
Not all experimental checks have been listed because some are not applicable, such as Dependency Injection framework checks, or checks related to Guava's immutable collections (since Gson's main code does not have a dependency on Guava).
Other checks have been omitted because they are probably not relevant (this was a subjective choice), or would require larger refactoring or would flag issues with the public API, which cannot be changed easily.
Open questions:
Are some of the Error Prone checks too strict?
Should some of the checks be disabled for test code?
Though might not be easily possible without separate testCompile configuration, which duplicates configuration, or without disabling all Error Prone checks for a certain file path. There are also the (undocumented?) flags -XepCompilingTestOnlyCode and -XepCompilingPubliclyVisibleCode, but it is not clear which checks consider them, and it would probably still be necessary to have a separate testCompile configuration then which sets these flags.
Checklist
[x] New code follows the Google Java Style Guide\
This is automatically checked by mvn verify, but can also be checked on its own using mvn spotless:check.\
Style violations can be fixed using mvn spotless:apply; this can be done in a separate commit to verify that it did not cause undesired changes.
[ ] If necessary, new public API validates arguments, for example rejects null
[ ] New public API has Javadoc
[ ] Javadoc uses @since $next-version$
($next-version$ is a special placeholder which is automatically replaced during release)
[ ] If necessary, new unit tests have been added
[ ] Assertions in unit tests use Truth, see existing tests
[ ] No JUnit 3 features are used (such as extending class TestCase)
[ ] If this pull request fixes a bug, a new test was added for a situation which failed previously and is now fixed
[x] mvn clean verify javadoc:jar passes without errors
Purpose
Enable additional Error Prone checks which are disabled by default
Description
Some of them also enforce additional Google Java Format requirements which are not handled by google-java-format, such as disallowing wildcard imports.
Not all experimental checks have been listed because some are not applicable, such as Dependency Injection framework checks, or checks related to Guava's immutable collections (since Gson's main code does not have a dependency on Guava).
Other checks have been omitted because they are probably not relevant (this was a subjective choice), or would require larger refactoring or would flag issues with the public API, which cannot be changed easily.
Open questions:
testCompileconfiguration, which duplicates configuration, or without disabling all Error Prone checks for a certain file path. There are also the (undocumented?) flags-XepCompilingTestOnlyCodeand-XepCompilingPubliclyVisibleCode, but it is not clear which checks consider them, and it would probably still be necessary to have a separatetestCompileconfiguration then which sets these flags.Checklist
mvn verify, but can also be checked on its own usingmvn spotless:check.\ Style violations can be fixed usingmvn spotless:apply; this can be done in a separate commit to verify that it did not cause undesired changes.null@since $next-version$(
$next-version$is a special placeholder which is automatically replaced during release)TestCase)mvn clean verify javadoc:jarpasses without errors