bug: DefaultJavaPrettyPrinter misses line breaks with enums

[SirYwell]

I found some issues when writing enums:

1. If an enum only contains enum values but no other type members, code like

enum SimpleEnum {
    CONSTANT
}

is transformed into

enum SimpleEnum {

    CONSTANT;}

This comes from the printList call here:

spoon/src/main/java/spoon/reflect/visitor/DefaultJavaPrettyPrinter.java

Line 753 in e8c0d1b

elementPrinterHelper.printList(ctEnum.getEnumValues(),

It writes a line break before each enum value but does not add one after the ;. This isn't a problem if there are any other type members to write because ElementPrinterHelper#writeElementList will add the line break (although there is no empty line then, but that breaks a test here due to the expected output:

spoon/src/test/java/spoon/test/prettyprinter/DefaultPrettyPrinterTest.java

Lines 303 to 311 in cd339e2

	"public enum ENUM {" + nl + nl
	+ " E1(TypeIdentifierCollision.globalField, TypeIdentifierCollision.ENUM.E1);" + nl
	+ " final int NUM;" + nl + nl
	+ " final Enum<?> e;" + nl + nl
	+ " private ENUM(int num, Enum<?> e) {" + nl
	+ " NUM = num;" + nl
	+ " this.e = e;" + nl
	+ " }" + nl
	+ "}";

)

Only writing a new line if enum values were written but no type members makes it work.

2. Using preserveLineNumbers writes an initial code

enum AlmostEmptyEnum {
    ;
    @Override
    public void toString() {
        return name().toLowerCase();
    }
}

as

enum AlmostEmptyEnum {
    ;
    @Override
    public void toString() {
        return name().toLowerCase();
    }}

This only happens with that option, without the option it looks like

enum AlmostEmptyEnum {
    ;

    @Override
    public void toString() {
        return name().toLowerCase();
    }
}

Note that without preserving line numbers, a new line is added before the method. This line is not added with that option but due to

spoon/src/main/java/spoon/reflect/visitor/ElementPrinterHelper.java

Lines 185 to 187 in 2fff4c5

	if (!env.isPreserveLineNumbers()) {
	printer.writeln();
	}

the last line break is still skipped (this might be an issue with normal classes too(?)).

Another - rather unrelated - issue I encountered with printing of enum values is that an enum

enum SimpleEnum {
    CONSTANT {

    }
}

is written as

enum SimpleEnum {

    CONSTANT() {};}

The added () and the ; also appear with the Sniper printer.

---

Edit

The added () come from the !isImplicit check here

spoon/src/main/java/spoon/reflect/visitor/DefaultJavaPrettyPrinter.java

Lines 795 to 797 in e8c0d1b

	CtConstructorCall<?> constructorCall = (CtConstructorCall<?>) enumValue.getDefaultExpression();
	if (!constructorCall.isImplicit()) {
	elementPrinterHelper.printList(constructorCall.getArguments(), null, false, "(", false, false, ",", true, false, ")", expr -> scan(expr));

which indicates that the default expression is not implicit but it is handled as if the constructor is not implicit.

[slarse]

I've also noted some funky printing of enums at times. This clearly needs some work.