Java 14 SwitchExpression Check Support validation: WhitespaceAroundCheck

[nrmancuso]

Child of #8658
Check documentation: https://checkstyle.sourceforge.io/config_whitespace.html#WhitespaceAround

Checks that a token is surrounded by whitespace.

➜  src /usr/lib/jvm/java-14-openjdk/bin/javac --enable-preview --source 14 TestClass.java                               
➜  src cat config.xml 
<?xml version="1.0"?>
<!DOCTYPE module PUBLIC
        "-//Checkstyle//DTD Checkstyle Configuration 1.3//EN"
        "https://checkstyle.org/dtds/configuration_1_3.dtd">
<module name="Checker">
    <module name="TreeWalker">
        <module name="WhitespaceAround"/>
    </module>
</module>
➜  src cat TestClass.java 
public class TestClass {

    int howMany1(int k) {
        int x = 2;
        int number = 42;
        boolean bool = false;
        switch (k) {
            case 1:
                int y= (2); // violation
                break;
            case 2:{ // violation
                int otherNumber = 42;
                int z = x + 2;
                x = z;
                break;
            }
            case (3 ):{ // violation
                if(bool = true) { // violation
                }
                int a = x + 3;
                x = a;
                break;
            }
            default:
                int b = 4;
                x = b;
        }
        return x;
    }

    int howMany2(int k) {
        int x = 2;
        int number = 42;
        boolean bool = false;
        return switch (k) {
            case 1 ->{ // violation x2
                int y= (2); // violation
                yield y;
            }
            case ( 2) ->{ // violation x2
                int otherNumber = 42;
                int z = ( x + 2); 
                yield ( otherNumber); 
            }
            case (3 ) ->{ // violation x2
                if(bool = true ) { // violation
                }
                int a = x + 3;
                x = a;
                yield a;
            }
            default -> {
                int b = (2 ); 
                yield b;
            }
        };
    }

    int howMany3(int x) {
        int inner = 8;
        boolean bool = false;
        return switch (x) {
            case 1:
                int y= (2); // violation
                yield y;
            case 2:{ // violation
                int otherNumber = 42;
                int z = inner = x + 2;
                x = z;
                yield (otherNumber);
            }
            case (3 ): //violation
                if(bool = true ) { // violation
                }
                int a = x + 3;
                x = a;
                yield a;
            default:
                int b = (2 ); 
                yield b;
        };
    }

}
➜  src java -jar /home/nick/IdeaProjects/checkstyle/target/checkstyle-8.36-SNAPSHOT-all.jar -c config.xml TestClass.java
Starting audit...
[ERROR] /home/nick/Desktop/enhanced-switch/src/TestClass.java:9:22: '=' is not preceded with whitespace. [WhitespaceAround]
[ERROR] /home/nick/Desktop/enhanced-switch/src/TestClass.java:11:20: '{' is not preceded with whitespace. [WhitespaceAround]
[ERROR] /home/nick/Desktop/enhanced-switch/src/TestClass.java:17:23: '{' is not preceded with whitespace. [WhitespaceAround]
[ERROR] /home/nick/Desktop/enhanced-switch/src/TestClass.java:18:17: 'if' is not followed by whitespace. [WhitespaceAround]
[ERROR] /home/nick/Desktop/enhanced-switch/src/TestClass.java:36:20: '->' is not followed by whitespace. [WhitespaceAround]
[ERROR] /home/nick/Desktop/enhanced-switch/src/TestClass.java:36:22: '{' is not preceded with whitespace. [WhitespaceAround]
[ERROR] /home/nick/Desktop/enhanced-switch/src/TestClass.java:37:22: '=' is not preceded with whitespace. [WhitespaceAround]
[ERROR] /home/nick/Desktop/enhanced-switch/src/TestClass.java:40:23: '->' is not followed by whitespace. [WhitespaceAround]
[ERROR] /home/nick/Desktop/enhanced-switch/src/TestClass.java:40:25: '{' is not preceded with whitespace. [WhitespaceAround]
[ERROR] /home/nick/Desktop/enhanced-switch/src/TestClass.java:45:23: '->' is not followed by whitespace. [WhitespaceAround]
[ERROR] /home/nick/Desktop/enhanced-switch/src/TestClass.java:45:25: '{' is not preceded with whitespace. [WhitespaceAround]
[ERROR] /home/nick/Desktop/enhanced-switch/src/TestClass.java:46:17: 'if' is not followed by whitespace. [WhitespaceAround]
[ERROR] /home/nick/Desktop/enhanced-switch/src/TestClass.java:64:22: '=' is not preceded with whitespace. [WhitespaceAround]
[ERROR] /home/nick/Desktop/enhanced-switch/src/TestClass.java:66:20: '{' is not preceded with whitespace. [WhitespaceAround]
[ERROR] /home/nick/Desktop/enhanced-switch/src/TestClass.java:73:17: 'if' is not followed by whitespace. [WhitespaceAround]
Audit done.
Checkstyle ends with 15 errors.

This check works as intended, so I think that we can close this issue. The switch rule with a LAMBDA should count as two, since unlike the COLON in a regular switch, it should have whitespace around it.