Stop Shortening Underscore in Enum Value

[tao-qian]

"__" is a valid value for enum, but it is shortened to "" in AbstractJavaCodegen. In fact, "" shouldn't be used because it may not be supported in the future according to this post http://stackoverflow.com/questions/34521690/why-is-a-single-underscore-character-an-illegal-name-for-a-lambda-parameter.

For the following field:

"state": {
  "type": "string",
  "enum": [
    "GOOD",
    "BAD",
    "__"
  ]
}

The generated enum is

  public enum StateEnum {
    GOOD("GOOD"),
    BAD("BAD"),
    _("__");

    private String value;

    StateEnum(String value) {
      this.value = value;
    }

    @Override
    @JsonValue
    public String toString() {
      return value;
    }
  }

I am also getting the following compiler warning when using Java 8:

[WARNING]   (use of '_' as an identifier might not be supported in releases after Java SE 8)

[wing328]

@qtstc what about mapping __ to DOUBLE_UNDERSCORE instead?

There's similar request to map symbol (e.g. #, @, &, etc) to enum value.

[tao-qian]

@wing328 I think given that "__" is a valid identifier in Java, just like "o1" or "user", we shouldn't modify it just for readability in a one-off case.
I agree that we need to deal with other symbols though. And I think what the code does right now (e.g. replacing those symbols with "_") is simple and reasonable.

[wing328]

@qtstc Thanks for writing the test case to cover the change. Can you put it under modules/swagger-codegen/src/test/java/io/swagger/codegen/java instead? I think that's folder where developers expect to find Java-related test cases.

[tao-qian]

@wing328 moved the file to modules/swagger-codegen/src/test/java/io/swagger/codegen/java