SPARK-38661: [TESTS][FOLLOWUP] Replace Symbol usage with $"" in unit tests

[martin-g]

What changes were proposed in this pull request?

Replace symbols like 'abc and Symbol("abc") (where possible) with the more verbose $"abc" in the test code.

Why are the changes needed?

This is a follow-up of #35560

Building with Scala 2.13 produces a lot of warnings like the following ones:

[warn] /home/runner/work/spark/spark/sql/core/src/test/scala/org/apache/spark/sql/execution/BaseScriptTransformationSuite.scala:562:11: [deprecation @  | origin= | version=2.13.0] symbol literal is deprecated; use Symbol("d") instead
[warn]           'd.cast("string"),
[warn]           ^
[warn] /home/runner/work/spark/spark/sql/core/src/test/scala/org/apache/spark/sql/execution/BaseScriptTransformationSuite.scala:563:11: [deprecation @  | origin= | version=2.13.0] symbol literal is deprecated; use Symbol("e") instead
[warn]           'e.cast("string")).collect())

This should make it easier to upgrade to Scala 3 later.

Does this PR introduce any user-facing change?

No! The PR touches only test classes!

How was this patch tested?

The build at CI must be green!

[srowen]

Thanks @martin-g ! this is larger than the original change, so is it safe to assume that this implements 'foo -> $"foo" basically everywhere in tests?

[AmplabJenkins]

Can one of the admins verify this patch?

[martin-g]

basically everywhere in tests?

This PR also changes Symbol("foo") to `$"foo", where possible.

There are more tests which still use 'foo. Should I add them to this PR or leave them for another follow-up ?

[srowen]

I did skim all of it (wow, big change) and there are maybe a few things we need to fix, but mostly looking good

[martin-g]

@srowen @HeartSaVioR @awdavidson I think the PR is ready for review now!

[srowen]

It's looking OK, let's check tests. I'm slightly uneasy because it's hard to review every line of change, though I think we've skimmed them all. Do you feel pretty good that there aren't other typos?

[awdavidson]

I echo @srowen pretty big change but generally looking ok. Let’s address test failure

Not to increase the scope of this change but a follow up could be to add a scalastyle check warning against the use of ‘foo declaration mainly to avoid it being reintroduced going forward?

[martin-g]

Do you feel pretty good that there aren't other typos?

I've checked all changes and they look OK to me !

The last test failure was because $"foo bar" is not supported. It should stay Symbol("foo bar").

[srowen]

Merged to master

[martin-g]

Thank you for your help, @srowen !