Drop Scala 2.12

- remove 2.12 to 2.13 compatibility classes (RichMap in favor of view.mapValues.toMap, MultiMap in favor of groupBy.view.mapValues.toMap, Stack in favor of mutable.Stack and ArrayBuffer1.reduceToSize1 infavor of ArrayBuffer.dropRightInPlace(length - n)). I thought Stacks were deprecated in 2.13, but mutable.Stacks are available to be used, so I must have made a mistake
- replace Implicits/Misc.using with scala.util.Using.resource
- remove scala collection compat class
- add toOption definition to Maybe* classes
- rename toScalaOption to toOption in Maybe class

DAFFODIL-2987

Author: olabusayoT

.github/workflows/main.yml

@@ -40,7 +40,7 @@ jobs:
       matrix:
         java_distribution: [ temurin ]
         java_version: [ 8, 11, 17, 21 ]
-        scala_version: [ 2.13.16, 2.12.20 ]
+        scala_version: [ 2.13.16 ]
         os: [ ubuntu-22.04, windows-2022, macos-14 ]
         exclude:
           # only run macos on java 17

DEVELOP.md

@@ -281,7 +281,7 @@ Daffodil's Java API from Maven or get Daffodil's Scala API from sbt:
 ```xml
 <dependency>
   <groupId>org.apache.daffodil</groupId>
-  <artifactId>daffodil-japi_2.12</artifactId>
+  <artifactId>daffodil-japi_2.13</artifactId>
   <version>3.4.0</version>
 </dependency>
 ```

build.sbt

@@ -239,7 +239,7 @@ lazy val commonSettings = Seq(
   organization := "org.apache.daffodil",
   version := "4.0.0-SNAPSHOT",
   scalaVersion := "2.13.16",
-  crossScalaVersions := Seq("2.13.16", "2.12.20"),
+  crossScalaVersions := Seq("2.13.16"),
   scalacOptions ++= buildScalacOptions(scalaVersion.value),
   Test / scalacOptions ++= buildTestScalacOptions(scalaVersion.value),
   Compile / compile / javacOptions ++= buildJavacOptions(),
@@ -282,23 +282,11 @@ def buildScalacOptions(scalaVersion: String) = {
   )
 
   val scalaVersionSpecificOptions = CrossVersion.partialVersion(scalaVersion) match {
-    case Some((2, 12)) =>
-      Seq(
-        "-Xfuture",
-        "-Ywarn-infer-any",
-        "-Ywarn-inaccessible"
-        // "-Ywarn-nullary-unit", // we cannot use this. It interferes with the Uniform Access Principle.
-        // See https://stackoverflow.com/questions/7600910/difference-between-function-with-parentheses-and-without.
-      )
     case Some((2, 13)) =>
       Seq(
         "-Xlint:inaccessible",
         "-Xlint:infer-any",
         "-Xlint:nullary-unit",
-        // TODO: scala 2.12 phase out
-        // the import is needed for Scala 2.12 but issues an unused import warning under 2.13, so we add this to
-        // suppresss the warning
-        "-Wconf:origin=scala.collection.compat.*:s",
         // suppress nullary-unit warning in the specific trait
         "-Wconf:cat=lint-nullary-unit:silent,site=org.apache.daffodil.junit.tdml.TdmlTests:silent"
       )

daffodil-cli/bin.NOTICE

@@ -167,19 +167,3 @@ The following NOTICE information applies to binary components distributed with t
   Portions of this code are derived from classes placed in the
   public domain by Arbortext on 10 Apr 2000. See:
   http://www.arbortext.com/customer_support/updates_and_technical_notes/catalogs/docs/README.htm
-
-- org.scala-lang.scala-collection-compat_2.13-<VERSION>.jar
-  scala-collection-compat
-  Copyright (c) 2002-2025 EPFL
-  Copyright (c) 2011-2025 Lightbend, Inc. dba Akka
-
-  Scala includes software developed at
-  LAMP/EPFL (https://lamp.epfl.ch/) and
-  Akka (https://akka.io/).
-
-  Licensed under the Apache License, Version 2.0 (the "License").
-  Unless required by applicable law or agreed to in writing, software
-  distributed under the License is distributed on an "AS IS" BASIS,
-  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-  See the License for the specific language governing permissions and
-  limitations under the License.

daffodil-cli/src/main/scala/org/apache/daffodil/cli/Main.scala

@@ -35,11 +35,12 @@ import javax.xml.parsers.SAXParserFactory
 import javax.xml.transform.TransformerException
 import javax.xml.transform.TransformerFactory
 import javax.xml.transform.stream.StreamResult
-import scala.collection.compat.immutable.ArraySeq
+import scala.collection.immutable.ArraySeq
 import scala.concurrent.Await
 import scala.concurrent.ExecutionContext
 import scala.concurrent.Future
 import scala.concurrent.duration.Duration
+import scala.util.Using
 import scala.util.matching.Regex
 
 import org.apache.daffodil.cli.debugger.CLIDebuggerRunner
@@ -49,7 +50,6 @@ import org.apache.daffodil.core.dsom.ExpressionCompilers
 import org.apache.daffodil.io.DataDumper
 import org.apache.daffodil.io.FormatInfo
 import org.apache.daffodil.io.InputSourceDataInputStream
-import org.apache.daffodil.lib.Implicits.using
 import org.apache.daffodil.lib.api.DaffodilConfig
 import org.apache.daffodil.lib.api.DaffodilConfigException
 import org.apache.daffodil.lib.api.DaffodilTunables
@@ -1240,7 +1240,7 @@ class Main(
                 }
               }
             }
-            using(input) { inStream =>
+            Using.resource(input) { inStream =>
               val output = parseOpts.output.toOption match {
                 case Some("-") | None => STDOUT
                 case Some(file) => new FileOutputStream(file)
@@ -1484,7 +1484,7 @@ class Main(
                       })
                     case Right(bytes) =>
                       Timer.getTimeResult({
-                        using(InputSourceDataInputStream(bytes)) { input =>
+                        Using.resource(InputSourceDataInputStream(bytes)) { input =>
                           val infosetResult =
                             infosetHandler.parse(input, nullOutputStreamForParse)
                           val parseResult = infosetResult.parseResult

daffodil-cli/src/test/scala/org/apache/daffodil/cli/cliTest/Util.scala

@@ -80,7 +80,6 @@ object Util {
       .getOrElse(throw new IllegalStateException("No Scala Version found"))
 
     scalaVersion match {
-      case v if v.startsWith("2.12") => "scala-2.12"
       case v if v.startsWith("2.13") => "scala-2.13"
       case v if v.startsWith("3.") => "scala-" + v
       case _ =>