datasource/sbt-plugin doesn't support registries that doesn't allow dir listing

[pnordh]

Tell us more.

Same issue reported for the sbt-package datasource in:

• Private gitlab maven repository doesn't work with sbt-package datasource #16761
• sbt datasource incompatible with non directory listable repositories #18589

... which was fixed by falling back to the maven datasource (parses versions available in a package's maven-metadata.xml) if it failed to list registry directories in:

• feat(sbt-package): Fallback to Maven datasource for GitLab packages #16817
• fix(datasource/sbt-package): Fallbacks to maven when no sbt directory listing available #18590

I'm thinking the same fix should be applicable for the sbt-plugin datasource (I'm working on it, including reproduction).

What do you think?

[MPV]

cc @sschoebinger @zharinov @fernandomora as you worked on the previous implementations (linked above)

[MPV]

There's a first draft over here:

• pnordh@f87568d

...however it doesn't fully handle the oddities of versioning of sbt-plugins such as:

differences in maven path for plugins published by sbt >= 1.9, which includes the extra attributes scalaVersion and sbtVersion

i.e. a scala package:
com/myorg/myproject/0.1.0-SNAPSHOT/myproject-0.1.0-SNAPSHOT.pom

versus an sbt plugin:
com/myorg/myplugin_2.12_1.0/1.0.0/myplugin_2.12_1.0-1.0.0.pom

Ideas welcome. 🙏