Add a config converter for enums

[dmlloyd]

Description
Add a converter for enums that would translate between the idiomatic Java enum syntax and the idiomatic skewered-lowercase syntax of configuration. For example:

Java enum constant name	Canonical equivalent
DISCARD	discard
READ_UNCOMMITTED	read-uncommitted
SIGUSR1	sigusr1
TrendBreaker	trend-breaker
MAKING_LifeDifficult	making-life-difficult
YeOldeJBoss	ye-olde-jboss

Hyphens and underscores would be interchangeable on input. Values would be case-insensitive. Note the special exception JBoss is always treated as a whole word (see io.quarkus.deployment.util.StringUtil).

[machi1990]

Hi @dmlloyd
I was giving this a thought and I have got a question regarding the conversion.
What happens when converting the following values:

• makingLifeDifficult: is it making-life-difficult?
• READ__UNCOMMITTED: is it read-committed or read--committed?

[dmlloyd]

I would say:

• makingLifeDifficult would be making-life-difficult as you say
• READ__UNCOMMITTED could go either way (whichever way is easier to specify): such a constant is so poorly named that it probably should be changed. :)

[machi1990]

@dmlloyd thanks for the clarifications.

So I have given this a thought and gave it a go here

• Some enums are not / need not to be in skewCase e.g Protocol cf ServerSslConfig.java, I thought of adding an option skewCase for @ConfigItem to opt out the conversion.
• Some modifications had to be done for ObjectConfigType OptionalObjectConfigType and ObjectListConfigType as I could not find a way to make it by implementing a MP Config Converter. Did you have something similar in mind? Or is there a way to make it simple?

[dmlloyd]

@dmlloyd thanks for the clarifications.

So I have given this a thought and gave it a go here

• Some enums are not / need not to be in skewCase e.g Protocol cf ServerSslConfig.java, I thought of adding an option skewCase for @ConfigItem to opt out the conversion.

You're right, we do need a way to opt out. Maybe hyphenate-values is a better name? But it only applies to enum properties, so maybe a separate @Hyphenate(false) is better. We could give an error if the @Hyphenate annotation is given on non-enum properties.

• Some modifications had to be done for ObjectConfigType OptionalObjectConfigType and ObjectListConfigType as I could not find a way to make it by implementing a MP Config Converter. Did you have something similar in mind? Or is there a way to make it simple?

I think your approach is correct, generally speaking.

[machi1990]

You're right, we do need a way to opt out. Maybe hyphenate-values is a better name? But it only applies to enum properties, so maybe a separate @Hyphenate(false) is better. We could give an error if the @Hyphenate annotation is given on non-enum properties.

Re: skewCase I was not sure about the naming either so I decided to went to the very end of my approach. Finally, I like what you propose better regarding an @Hypenate annotation.
I will go along that line and allow opting in for hypnated-values by @Hyphenate(true). The default value is false.

• Some modifications had to be done for ObjectConfigType OptionalObjectConfigType and ObjectListConfigType as I could not find a way to make it by implementing a MP Config Converter. Did you have something similar in mind? Or is there a way to make it simple?

I think your approach is correct, generally speaking.

Okay, let me prepare a commit and open a draft PR so that we can continue with the discussion there.