[MCHECKSTYLE-397] support ${config_loc} on checkstyle xml

[qxo]

we can use config_loc as: ${config_loc}/suppressions.xml.

with this PR, we can use same checkstyle.xml which contains ${config_loc}

for eclipsecs ${config_loc} is a variable of Eclipse and it will refer to the same directory where the checkstyle.xml is present.
ref: https://checkstyle.org/eclipse-cs/#!/properties

https://issues.apache.org/jira/projects/MCHECKSTYLE/issues/MCHECKSTYLE-397

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[qxo]

mvn -Prun-its clean verify failed on my PC because my network issue:

javax.net.ssl.SSLException: Connection reset
    at sun.security.ssl.Alert.createSSLException (Alert.java:127)
    at sun.security.ssl.TransportContext.fatal (TransportContext.java:321)
    at sun.security.ssl.TransportContext.fatal (TransportContext.java:264)
    at sun.security.ssl.TransportContext.fatal (TransportContext.java:259)
    at sun.security.ssl.SSLTransport.decode (SSLTransport.java:137)
    at sun.security.ssl.SSLSocketImpl.decode (SSLSocketImpl.java:1152)

[elharo]

This could use some tests.

[lrozenblyum]

@bmarwell @elharo it's really a nice feature to have in the plug-in.
Currently enabling suppressions for a Maven multi-module project is much more complex than it could be.
${config_loc} support should enable seamless experience for Checkstyle users.

So could I for example continue work on this feature if it has chances for merge?
As I understand this pull request remarks should be solved?

[jira-importer]

Resolve #309

[Copilot]

Pull Request Overview

This PR adds support for the ${config_loc} property in Checkstyle configurations, mirroring the behavior of the Eclipse Checkstyle plugin (eclipsecs). This allows Checkstyle configuration files to reference other resources (like suppression files) relative to the config file's directory.

• Extracts the directory path from the config location and sets it as the config_loc property
• Enables relative path references in Checkstyle configurations using ${config_loc}

---

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[Copilot]

The code only handles forward slash / as a path separator, but Windows systems use backslash \. This will cause the config_loc property to be incorrectly set on Windows when the config location contains backslashes. Consider using Math.max(configLocation.lastIndexOf('/'), configLocation.lastIndexOf('\\')) to handle both path separators, or use a platform-independent approach.

Suggested change

	final int idx = configLocation.lastIndexOf( '/' );
	final int idx = Math.max(configLocation.lastIndexOf('/'), configLocation.lastIndexOf('\\'));

[Copilot]

Potential NullPointerException: The code doesn't check if configLocation is null before calling lastIndexOf(). While getConfigFile() is currently called before this method in getConfiguration(), this creates a fragile implicit dependency. Add a null check to make the code more robust: if (configLocation != null) { ... }.

Suggested change

	final int idx = configLocation.lastIndexOf( '/' );
	final String configLoc;
	if ( idx == -1 )
	{
	configLoc = "";
	}
	else
	{
	configLoc = configLocation.substring( 0, idx );
	final String configLoc;
	if (configLocation != null)
	{
	final int idx = configLocation.lastIndexOf( '/' );
	if ( idx == -1 )
	{
	configLoc = "";
	}
	else
	{
	configLoc = configLocation.substring( 0, idx );
	}
	}
	else
	{
	configLoc = "";

[Copilot]

Grammatical error in comment: "so we config such as" should be "so we can configure such as" or "allowing configuration such as".

Suggested change

	// so we config such as `${config_loc}/checkstyle-suppressions.xml`
	// so we can configure paths such as `${config_loc}/checkstyle-suppressions.xml`

[Copilot]

The comment should follow standard Java comment conventions. The variable reference ${config_loc} and the purpose of this code would be clearer with improved documentation. Consider: "Sets the config_loc property to the directory portion of configLocation. This allows Checkstyle configurations to reference the config directory using ${config_loc}, similar to Eclipse CS plugin behavior."

Suggested change

	//${config_loc} for the origin dir of the configLocation, just like eclipsecs
	// so we config such as `${config_loc}/checkstyle-suppressions.xml`
	/*
	* Sets the config_loc property to the directory portion of configLocation.
	* This allows Checkstyle configurations to reference the config directory using ${config_loc},
	* similar to Eclipse CS plugin behavior.
	*/