Auto-unboxing issue in CheckstyleAuditListener

[tsjensen]

Sonar version: 7.6
Checkstyle sonar plugin verson: 4.18

Steps to reproduce or description of problem:

Run any check which reports line 0 for an issue. This used to be the required behavior for checks that flag the entire file, and have no relation to the AST. For example FileSetChecks.
I know there was a breaking change in checkstyle/checkstyle#6000, changing the "magic" line number to 1. This kind of neutralizes this problem.
BUT: I noticed the problem running custom checks at work. I would expect some custom checks to be around that haven't noticed checkstyle/checkstyle#6000.

The error caused is this:

Caused by: com.puppycrawl.tools.checkstyle.api.CheckstyleException: Exception was thrown while processing C:\path\to\File.java
        at com.puppycrawl.tools.checkstyle.Checker.processFiles(Checker.java:304)
        at com.puppycrawl.tools.checkstyle.Checker.process(Checker.java:217)
        at org.sonar.plugins.checkstyle.CheckstyleExecutor.executeWithClassLoader(CheckstyleExecutor.java:111)
        ... 71 more
Caused by: java.lang.NullPointerException
        at org.sonar.plugins.checkstyle.CheckstyleAuditListener.addError(CheckstyleAuditListener.java:106)
        at com.puppycrawl.tools.checkstyle.Checker.fireErrors(Checker.java:401)
        at com.puppycrawl.tools.checkstyle.Checker.processFiles(Checker.java:292)
        ... 73 more

I have already fixed this, it's a small thing. PR upcoming.

[rnveach]

Code is at

sonar-checkstyle/checkstyle-sonar-plugin/src/main/java/org/sonar/plugins/checkstyle/CheckstyleAuditListener.java

Line 106 in e167452

.at(currentResource.selectLine(getLineId(event)))

which does indeed return a class Integer

sonar-checkstyle/checkstyle-sonar-plugin/src/main/java/org/sonar/plugins/checkstyle/CheckstyleAuditListener.java

Line 160 in e167452

static Integer getLineId(AuditEvent event) {

I'm not sure why code would rather use null instead of 0. Seems odd.

sonar-checkstyle/checkstyle-sonar-plugin/src/main/java/org/sonar/plugins/checkstyle/CheckstyleAuditListener.java

Lines 164 to 166 in e167452

	// checkstyle returns 0 if there is no relation to a file content,
	// but we use null
	if (line != 0) {

I guess this is because it has to select a line and was expecting to not select anything with null. I would think this is the code we change to not return null but instead default to 1.

[rnveach]

This used to be the required behavior for checks that flag the entire file

So why wasn't this an issue in sonar before but it is now? Or was this always a problem and no one run checks that flagged line 0 to notice?