[SPARK-34981][SQL][TESTS][FOLLOWUP] Fix test failure under Scala 2.13

[sunchao]

What changes were proposed in this pull request?

Fix test failure under Scala 2.13 by making test ScalaFunction StrLenMagic public.

Why are the changes needed?

A few tests are failing when using Scala 2.13 with error message like the following:

[info]   Cause: org.codehaus.commons.compiler.CompileException: File 'generated.java', Line 35, Column 121: failed to compile: org.codehaus.commons.compiler.CompileException: File 'generated.java', Line 35, Column 121: No a
pplicable constructor/method found for actual parameters "org.apache.spark.unsafe.types.UTF8String"; candidates are: "public int org.apache.spark.sql.connector.DataSourceV2FunctionSuite$StrLenMagic$.invoke(org.apache.spark.
unsafe.types.UTF8String)"
[info]   at org.apache.spark.sql.errors.QueryExecutionErrors$.compilerError(QueryExecutionErrors.scala:387)
[info]   at org.apache.spark.sql.catalyst.expressions.codegen.CodeGenerator$.org$apache$spark$sql$catalyst$expressions$codegen$CodeGenerator$$doCompile(CodeGenerator.scala:1415)
[info]   at org.apache.spark.sql.catalyst.expressions.codegen.CodeGenerator$$anon$1.load(CodeGenerator.scala:1501)

This seems to be caused by the fact that the StrLenMagic is using private scope. After removing the private keyword the tests are now passing.

Does this PR introduce any user-facing change?

No

How was this patch tested?

$ dev/change-scala-version.sh 2.13
$ build/sbt "sql/testOnly *.DataSourceV2FunctionSuite" -Pscala-2.13

[SparkQA]

Kubernetes integration test unable to build dist.

exiting with code: 1
URL: https://amplab.cs.berkeley.edu/jenkins/job/SparkPullRequestBuilder-K8s/43165/

[dongjoon-hyun]

Thank you, @sunchao !

[dongjoon-hyun]

I revised the PR description How was this patch tested? section because this recovers Scala 2.13 tests.

[dongjoon-hyun]

+1, LGTM. I manually verified with Scala 2.13. Merged to master.

$ dev/change-scala-version.sh 2.13
$ build/sbt "sql/testOnly *.DataSourceV2FunctionSuite" -Pscala-2.13
...
[info] Run completed in 9 seconds, 581 milliseconds.
[info] Total number of tests run: 29
[info] Suites: completed 1, aborted 0
[info] Tests: succeeded 29, failed 0, canceled 0, ignored 0, pending 0
[info] All tests passed.
[success] Total time: 234 s (03:54), completed May 17, 2021 4:15:35 PM

[sunchao]

Thanks @dongjoon-hyun !

[SparkQA]

Test build #138645 has finished for PR 32575 at commit 4eb00fe.

• This patch passes all tests.
• This patch merges cleanly.
• This patch adds no public classes.