[SPARK-40654][PROTOBUF][FOLLOW-UP] Clean up SBT build in Proto component

[HyukjinKwon]

What changes were proposed in this pull request?

This PR cleans up the syntax, and properly copy protobuf assembly jar (currently it copies connect assembly jar by mistake).

Why are the changes needed?

For consistent code style, and correct SBT build.

Does this PR introduce any user-facing change?

No, this isn't released yet.

How was this patch tested?

CI in this PR should test it out.

[LuciferYang]

+1, LGTM

[LuciferYang]

hmm... should we add assemblyPackageScala and assemblyExcludedJars to SparkProtobuf module too, the assembly jar is a little fat

[debug] Including from cache: spark-tags_2.12-3.4.0-SNAPSHOT.jar
[debug] Including from cache: unused-1.0.0.jar
[debug] Including from cache: spark-protobuf_2.12-3.4.0-SNAPSHOT.jar
[debug] Including from cache: scala-collection-compat_2.12-2.2.0.jar
[debug] Including from cache: pmml-model-1.4.8.jar
[debug] Including from cache: protobuf-java-3.21.1.jar
[debug] Including from cache: guava-14.0.1.jar
[debug] Including from cache: scala-library-2.12.17.jar

for example, similar as SparkConnect module:

    // Exclude `scala-library` from assembly.
    (assembly / assemblyPackageScala / assembleArtifact) := false,

    // Exclude `pmml-model-*.jar`, `scala-collection-compat_*.jar`,
    // `spark-tags_*.jar`, "guava-*.jar" and `unused-1.0.0.jar` from assembly.
    (assembly / assemblyExcludedJars) := {
      val cp = (assembly / fullClasspath).value
      cp filter { v =>
        val name = v.data.getName
        name.startsWith("pmml-model-") || name.startsWith("scala-collection-compat_") ||
          name.startsWith("spark-tags_") || name.startsWith("guava-") || name == "unused-1.0.0.jar"
      }
    },

then the assembly jar just includes:

[debug] Including: spark-protobuf_2.12-3.4.0-SNAPSHOT.jar
[debug] Including from cache: protobuf-java-3.21.1.jar

[amaliujia]

just for my own education, is this the same: false -> { }?

looks like a bit magic

[HyukjinKwon]

Yeah, they are same. I believe { } is much more common (googled a bit)

[HyukjinKwon]

Let me get this in first in any event since it works (and the built is technically broken without this change).

[HyukjinKwon]

Merged to master.