Update doc for DescendantToken

[timurt]

https://checkstyle.org/config_misc.html#DescendantToken

Add example for each existing config to show what code is ok and what code cause violation.
Good example is https://checkstyle.org/config_naming.html#AbstractClassName

please play with module/Check by means of https://checkstyle.org/cmdline.html to understand how it works.

---

PLEASE READ https://github.com/checkstyle/checkstyle/wiki/Good-practice-on-how-to-update-examples

[romani]

No assignments, just make comment "I am on it" and send PR

[athuma]

Hi @romani i am new to open source and would like to contribute i am familiar with java but i don't know where to start can you please help me with how to start?

[romani]

Please read https://github.com/checkstyle/checkstyle/wiki/To-GSoC-participant

[athuma]

@romani i have gone through it and i think i can do spellcheck of Identifiers by english dictionary project will be submitting my application through GSOC thanks for your help

[athuma]

i am working on this issue

[athuma]

@romani i am not getting how should i pass the xml file for checking the case for switch statement in this issue

i have attached the file i am passing but getting error "unable to parse configuration stream"
can you please help me

[romani]

I did wrong link pasting. Fixed.
Please fix several issues to prove that you can resolve issues quickly enough.
Please follow https://github.com/checkstyle/checkstyle/wiki/To-GSoC-participant
Amount of merged Pull Requests is most valuable criteria for selection in summer.

Here is example how to run CLI https://checkstyle.org/report_issue.html#How_to_report_a_bug.3F

[athuma]

@romani getting error like this

[nrmancuso]

@athuma it is very difficult the read screenshots, usually it is much better to share as copy pasted code blocks of output (see our bug report template as an example).

[romani]

Reading is ok, but most critical that we can not reuse your config as is to reproduce quickly issue on our side.

[athuma]

Athu@Atharv MINGW64 ~/Desktop

$ cat Switch.java

package basic;

public class Switch {

public static void main(String[] args) {
        int x=1;
        switch(x)
        {
        case 1: System.out.println("hi");
        break;
        }

}

}

Athu@Atharv MINGW64 ~/Desktop

$ cat file.xml

<?xml version="1.0"?>
<!DOCTYPE module PUBLIC
      "-//Checkstyle//DTD Check Configuration 1.3//EN" 
      "https://checkstyle.org/dtds/configuration_1_3.dtd">
<module name="Checker">
	<module name="TreeWalker">
		<module name="DescendantToken">
			<property name="tokens" value="LITERAL SWITCH"/>
			<property name="maximumdepth" value="2"/>
			<property name="limitedtokens" value="LITERAL_DEFAULT"/>
			<property name="minimumnumber" value="1"/>
		</module>
	</module>
</module>

Athu@Atharv MINGW64 ~/Desktop

$ java -jar checkstyle-10.8.0-all.jar -c file.xml Switch.java

com.puppycrawl.tools.checkstyle.api.CheckstyleException: unable to parse configuration stream - Content is not allowed in prolog.:1:1
at com.puppycrawl.tools.checkstyle.ConfigurationLoader.loadConfiguration(ConfigurationLoader.java:321)
at com.puppycrawl.tools.checkstyle.ConfigurationLoader.loadConfiguration(ConfigurationLoader.java:266)
at com.puppycrawl.tools.checkstyle.Main.runCheckstyle(Main.java:380)
at com.puppycrawl.tools.checkstyle.Main.runCli(Main.java:338)
at com.puppycrawl.tools.checkstyle.Main.execute(Main.java:195)
at com.puppycrawl.tools.checkstyle.Main.main(Main.java:130)
Caused by: org.xml.sax.SAXParseException; systemId: file:/C:/Users/Athu/Desktop/file.xml; lineNumber: 1; columnNumber: 1; Content is not allowed in prolog.
at java.xml/com.sun.org.apache.xerces.internal.util.ErrorHandlerWrapper.createSAXParseException(ErrorHandlerWrapper.java:204)
at java.xml/com.sun.org.apache.xerces.internal.util.ErrorHandlerWrapper.fatalError(ErrorHandlerWrapper.java:178)
at java.xml/com.sun.org.apache.xerces.internal.impl.XMLErrorReporter.reportError(XMLErrorReporter.java:400)
at java.xml/com.sun.org.apache.xerces.internal.impl.XMLErrorReporter.reportError(XMLErrorReporter.java:327)
at java.xml/com.sun.org.apache.xerces.internal.impl.XMLScanner.reportFatalError(XMLScanner.java:1465)
at java.xml/com.sun.org.apache.xerces.internal.impl.XMLDocumentScannerImpl$PrologDriver.next(XMLDocumentScannerImpl.java:978)
at java.xml/com.sun.org.apache.xerces.internal.impl.XMLDocumentScannerImpl.next(XMLDocumentScannerImpl.java:605)
at java.xml/com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl.scanDocument(XMLDocumentFragmentScannerImpl.java:542)
at java.xml/com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(XML11Configuration.java:889)
at java.xml/com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(XML11Configuration.java:825)
at java.xml/com.sun.org.apache.xerces.internal.parsers.XMLParser.parse(XMLParser.java:141)
at java.xml/com.sun.org.apache.xerces.internal.parsers.AbstractSAXParser.parse(AbstractSAXParser.java:1224)
at java.xml/com.sun.org.apache.xerces.internal.jaxp.SAXParserImpl$JAXPSAXParser.parse(SAXParserImpl.java:637)
at com.puppycrawl.tools.checkstyle.XmlLoader.parseInputSource(XmlLoader.java:81)
at com.puppycrawl.tools.checkstyle.ConfigurationLoader.parseInputSource(ConfigurationLoader.java:196)
at com.puppycrawl.tools.checkstyle.ConfigurationLoader.loadConfiguration(ConfigurationLoader.java:315)
... 5 more
Checkstyle ends with 1 errors.

@romani @nrmancuso

[romani]

@athuma, please try to remove content from xml file to see what symbol damage xml parsing. There might be some invisible symbol.

I can not spot a problem, so it means we need brute force.

[romani]

See example of execution at #2507

[athuma]

$ cat Switch.java
package basic;

public class Switch {

    public static void main(String[] args) {
            int x=1;
            switch(x)
            {
            case 1: System.out.println("hi");
            break;
            }

    }

}

Athu@Atharv MINGW64 ~/Desktop

$ cat file.xml

<?xml version="1.0"?>
<!DOCTYPE module PUBLIC
      "-//Checkstyle//DTD Check Configuration 1.3//EN"
      "https://checkstyle.org/dtds/configuration_1_3.dtd">
<module name="Checker">
  <module name="TreeWalker">
    <module name="DescendantToken">
        <property name="tokens" value="LITERAL_SWITCH"/>
         <property name="maximumDepth" value="2"/>
         <property name="limitedTokens" value="LITERAL_DEFAULT"/>
        <property name="minimumNumber" value="1"/>
    </module>
  </module>
</module>

Athu@Atharv MINGW64 ~/Desktop

$ java -jar checkstyle-10.8.0-all.jar -c file.xml Switch.java

Starting audit...
[ERROR] C:\Users\Athu\Desktop\Switch.java:7:17: Count of 0 for 'LITERAL_SWITCH' descendant 'LITERAL_DEFAULT' is less than minimum count 1. [DescendantToken]
Audit done.
Checkstyle ends with 1 errors.

For Switch with default case :

Athu@Atharv MINGW64 ~/Desktop
$ cat Switch.java
package basic;

public class Switch {

    public static void main(String[] args) {
            int x=1;
            switch(x)
            {
            case 1: System.out.println("hi");
            break;
            default: System.out.println("Default case");
            break;
            }

    }

}

Athu@Atharv MINGW64 ~/Desktop
$ java -jar checkstyle-10.8.0-all.jar -c file.xml Switch.java
Starting audit...
Audit done.

I think this is correct and working out good with no changes in xml it automatically worked today please check this so that i can raise a pull @romani

[romani]

Please send PR

[navyakarna]

can i work on this issue

[Rishabh7798]

I want to work on this issue please assign me this task

[romani]

@Rishabh7798 , just send a pull request.
looks like we lost connection to contributors above.

[ShivamPandey00]

I am on it

[ShivamPandey00]

@romani @nrmancuso there are total 17 config check. Do we need add example for each config ?

[romani]

Yes

[nrmancuso]

@romani I think we can make exception and allow different code for each example for this check, to allow user to focus only on what is important

[romani]

For this check it is ok to have different java code for all configs

[romani]

Fix is merged