Upgrade to Checkstyle 8.21

[snicoll]

This project uses the latest checkstyle release at that time (8.21). Trying to use 0.0.12 with that version on the initializr repository leads to:

Caused by: org.apache.maven.plugin.PluginExecutionException: Execution checkstyle-validation of goal org.apache.maven.plugins:maven-checkstyle-plugin:3.1.0:check failed: An API incompatibility was encountered while executing org.apache.maven.plugins:maven-checkstyle-plugin:3.1.0:check: java.lang.VerifyError: class io.spring.javaformat.checkstyle.SpringChecks overrides final method setTabWidth.(I)V
-----------------------------------------------------
realm =    plugin>org.apache.maven.plugins:maven-checkstyle-plugin:3.1.0

This can be reproduced by upgrading the checkstyle version locally

[wilkinsona]

It was added in 8.19.

[snicoll]

Would it be possible to add an integration test in this project or something? The project currently build with that version and I'd expect it to fail.

[rajadilipkolli]

Any temporary solution ?

[wilkinsona]

You'll have to use Checkstyle 8.18 or earlier for now.

[wilkinsona]

8.21 has changed how try-with-resources is treated and the formatter and Checkstyle now disagree. The formatter produces this:

try (InputStream foo = getInputStreamFor("foo"); InputStream bar = getInputStreamFor("bar")) {
   // …
}

Checkstyle reports an error due to multiple statements:

[ERROR] src/test/java/org/springframework/boot/configurationmetadata/ConfigurationMetadataRepositoryJsonBuilderTests.java:[66,64] (coding) OneStatementPerLine: Only one statement per line allowed.
[ERROR] src/test/java/org/springframework/boot/configurationmetadata/ConfigurationMetadataRepositoryJsonBuilderTests.java:[79,64] (coding) OneStatementPerLine: Only one statement per line allowed.
[ERROR] src/test/java/org/springframework/boot/configurationmetadata/ConfigurationMetadataRepositoryJsonBuilderTests.java:[92,64] (coding) OneStatementPerLine: Only one statement per line allowed.
[ERROR] src/test/java/org/springframework/boot/configurationmetadata/ConfigurationMetadataRepositoryJsonBuilderTests.java:[138,64] (coding) OneStatementPerLine: Only one statement per line allowed.

A change in Checkstyle is being discussed and a PR has been proposed. AIUI, the proposed change will mean that an error is no longer reported by default with a property to turn it on.

I'm not sure if we should:

1. wait for a new Checkstyle release
2. change the formatter to split the code onto multiple lines
3. do something else

[philwebb]

Changing the formatter is never easy so I'm tempted to fix it at checkstyle. Perhaps we can create our own local copy of that rule until the 8.22 is released.

[wilkinsona]

There are only a handful of places in Boot that are affected. See parts of this commit. Another option could be to live with it and avoid having our own interim copy of the rule.

[philwebb]

I think I prefer the multiple try blocks anyway, they seem a bit easier to read.