support scala3 with slick

[pjfanning]

• relates to pekko-projection-slick scala 3 support? #110
• the scala file changes were all due to code that wouldn't compile in Scala 3
• link validator issue is unrelated to these changes

[pjfanning]

there is an example test class in the jdocs package that Scala 3 won't allow to access this package private class

[He-Pin]

Lgtm

[Roiocam]

LGTM

[Roiocam]

I am not sure it was a good idea to directly use config rather than db instance and profile.

Are these harmful for tests?

[He-Pin]

That should be fine, just lost some typesafety

[pjfanning]

val db: P#Backend#Database does not compile in Scala 3 and I couldn't find any alternative that compiles either.

These classes are internal classes. I don't see it being a problem changing them. The constructor was like this before but was changed.

[He-Pin]

yes, I think this change is fine.

[Roiocam]

We initialized it but didn't close it, would it be better to use lazy in this field?

These changes didn't seem harmless, maybe there is a issue hidden in the shadows.

https://github.com/slick/slick/blob/b878d45556fb6b4799e62a5d3c08364def51a89f/slick/src/main/scala/slick/basic/DatabaseConfig.scala#L15-L18

https://github.com/apache/pekko-persistence-jdbc/blob/c3621706de0b43bbb0f60d224d784085fa3197cf/core/src/main/scala/org/apache/pekko/persistence/jdbc/db/SlickDatabase.scala#L106-L118

[pjfanning]

The db instance is used instantly in the class. So I don't think making it lazy will help.
There is no lifecycle management in these classes so I don't know where we can add something to close the db instance. If anyone has any ideas that would be great.

[Roiocam]

my second link maybe helpful, it uses the system shutdown hook for instance closing.

I think they only use it when OffsetStore method call? Otherwise it only created but won't be used.

I mean the config.db is a method call too... you could lazily call it. Kind of like we got the method like:

< private Database db = instanceDB(); // initialize immediately
> private Database db; // won't initialize in creation.


> public getDB(){
>  if (db == null){
>     db = instanceDB(); // initialize here.
>  }
>  return db;
> }

public void something_operation() {
< return db.call();
> return getDB().call();
}

[pjfanning]

I've created #168

• this PR does not introduce the db close issue - it is a pre-existing issue
• it is also a complicated pre-existing issue - and I believe that there is no simple solution
• I do believe that the issue should be fixed separately and not bundled into this PR

[pjfanning]

I have changed the code not to eagerly call dbConfig.db.

[Roiocam]

I do believe that the issue should be fixed separately and not bundled into this PR

fair to me.

[Roiocam]

can you open an issue for this? rather than a discussion, i think people want to be find it on the issues? thanks~

[pjfanning]

created #172

[laglangyue]

lgtm