What is the use case for a configuration settings if it does not allow to change the value ? this is why the enum node enforces having a choice currently

@stof apparently, @ro0NL starts with a proper parameter with several values, which is enum-compatible.

However, the values of this parameter change frequently and sometimes they remove all values except one. Obviously at this point the parameter is not an enumeration, but it was previously and it will be again in the future.

It's a pity that Symfony doesn't support 1-value enums, because they must change their application config when updating that parameter.

At first sight, this feature request looks legit. It would be nice to know the behavior of "1 element enums" in other languages and technologies (Java, Python, MySQL, etc.)

For MySQL it works;

CREATE TABLE `test` (
    `test` ENUM('a') NOT NULL
);

Some extra info;

• https://en.wikipedia.org/wiki/Enumerated_type

  • No info about single values as far as i can see

• https://msdn.microsoft.com/en-us/library/ms229058(v=vs.110).aspx

  X AVOID publicly exposing enums with only one value.

• http://en.cppreference.com/w/c/language/enum

  where enumerator-list is a comma-separated list (with trailing comma permitted) (since C99) of enumerators

@stof the use case is we currently only support 1 option of the enum (implementation-wise that is), as soon as other options are implemented we want to expand the enum with the newly implemented options, i.e. make them available for configuration.

In case this feature request is accepted, there is a pull request to implement it: #15433.

I see no real reason (apart from ideology) to prevent single element enums. This seems like a pretty standard way to be forward-compatible. So no real reason to arbitrarily prevent it IMHO.