Improving enum capabilities

[elifKurtay]

Implementation of this issue.

• using Java/Kotlin enum constant definition.
• checking enum constant naming.
• adding fields, properties, constructors and methods to enums.
• a private all fields constructor needs to be added on enums with constant object values.

Generated enum class example:

package io.micronaut.sourcegen.example;

import java.lang.String;

public enum MyEnum2 {

  A(0),
  B(1),
  C(2);

  public int myValue;

  private MyEnum2(int myValue) {
    this.myValue = myValue;
  }

  public String myName() {
    return this.toString();
  }
}

From the following definition:

EnumDef enumDef = EnumDef.builder(enumClassName)
            .addModifiers(Modifier.PUBLIC)
            .addEnumConstant("A", ExpressionDef.constant(0))
            .addEnumConstant("B", ExpressionDef.constant(1))
            .addEnumConstant("C", ExpressionDef.constant(2))
            .addField(FieldDef.builder("myValue").ofType(TypeDef.Primitive.INT).addModifiers(Modifier.PUBLIC).build())
            .addMethod(MethodDef.builder("myName")
                .addModifiers(Modifier.PUBLIC)
                .returns(TypeDef.STRING)
                .build((aThis, parameters) ->
                    aThis.invoke("toString", TypeDef.STRING, List.of()).returning()))
            .addAllFieldsConstructor(Modifier.PRIVATE)
            .build();

[dstepanov]

That example doesn't make sense. It should be:

     .addEnumConstant(constant("active"))

[dstepanov]

For enums we should add the concept of fields, properties and constructors we already have (which we already have because of methods)