Upgrade to Scala 3.8.0 and refactor for improved null safety

.github/workflows/ci.yml

@@ -22,7 +22,7 @@ jobs:
     strategy:
       matrix:
         os: [ubuntu-latest]
-        scala: [2.13.18]
+        scala: [3.8.0-RC5]
         java: [temurin@21]
     runs-on: ${{ matrix.os }}
     steps:
@@ -64,7 +64,7 @@ jobs:
     strategy:
       matrix:
         os: [ubuntu-latest]
-        scala: [2.13.18]
+        scala: [3.8.0-RC5]
         java: [temurin@21]
     runs-on: ${{ matrix.os }}
     steps:
@@ -84,12 +84,12 @@ jobs:
       - name: Setup sbt
         uses: sbt/setup-sbt@v1
 
-      - name: Download target directories (2.13.18)
+      - name: Download target directories (3.8.0-RC5)
         uses: actions/download-artifact@v6
         with:
-          name: target-${{ matrix.os }}-2.13.18-${{ matrix.java }}
+          name: target-${{ matrix.os }}-3.8.0-RC5-${{ matrix.java }}
 
-      - name: Inflate target directories (2.13.18)
+      - name: Inflate target directories (3.8.0-RC5)
         run: |
           tar xf targets.tar
           rm targets.tar

.scalafmt.conf

@@ -1,6 +1,6 @@
 //description of properties: https://scalameta.org/scalafmt/docs/configuration.html
 version = "3.10.3"
-runner.dialect = scala213source3
+runner.dialect = scala3
 maxColumn = 120
 
 continuationIndent {
@@ -81,13 +81,6 @@ rewrite.neverInfix.excludeFilters = [
   theSameElementsAs
   //below extends default
   theSameElementsInOrderAs
-  like
-  zip
-  orElse
-  getOrElse
-  matchOpt
-  map
-  flatMap
 ]
 
 xmlLiterals.assumeFormatted = true

build.sbt

@@ -1,6 +1,6 @@
 import org.jetbrains.sbtidea.Keys._
 
-ThisBuild / scalaVersion := "2.13.18"
+ThisBuild / scalaVersion := "3.8.0-RC5"
 ThisBuild / intellijPluginName := "intellij-hocon"
 ThisBuild / intellijBuild := "253.29346.138"
 ThisBuild / githubWorkflowJavaVersions := Seq(JavaSpec.temurin("21"))
@@ -11,30 +11,48 @@ val junitVersion = "4.13.2"
 val commonsTextVersion = "1.15.0"
 val opentest4jVersion = "1.3.0"
 
-lazy val hocon = project.in(file(".")).enablePlugins(SbtIdeaPlugin).settings(
-  version := "2026.1.2-SNAPSHOT",
-  Compile / scalaSource := baseDirectory.value / "src",
-  Test / scalaSource := baseDirectory.value / "test",
-  Compile / resourceDirectory := baseDirectory.value / "resources",
-  Global / javacOptions ++= Seq("--release", "21"),
-  Global / scalacOptions ++= Seq(
-    "-deprecation",
-    "-feature",
-    "-unchecked",
-    "-Xfatal-warnings",
-    "-Xsource:3"
-  ),
-  ideBasePackages := Seq("org.jetbrains.plugins.hocon"),
-  intellijPlugins := Seq("com.intellij.java-i18n", "com.intellij.modules.json").map(_.toPlugin),
-  intellijExtraRuntimePluginsInTests := Seq("org.jetbrains.kotlin").map(_.toPlugin),
-  libraryDependencies ++= Seq(
-    "org.apache.commons" % "commons-text" % commonsTextVersion,
-    "com.github.sbt" % "junit-interface" % junitInterfaceVersion % Test,
-    "junit" % "junit" % junitVersion % Test,
-    "org.opentest4j" % "opentest4j" % opentest4jVersion % Test,
-  ),
-  packageLibraryMappings := Seq.empty, // allow scala-library
-  patchPluginXml := pluginXmlOptions { xml =>
-    xml.version = version.value
-  }
-)
+lazy val hocon = project
+  .in(file("."))
+  .enablePlugins(SbtIdeaPlugin)
+  .settings(
+    version := "2026.1.2-SNAPSHOT",
+    Compile / scalaSource := baseDirectory.value / "src",
+    Test / scalaSource := baseDirectory.value / "test",
+    Compile / resourceDirectory := baseDirectory.value / "resources",
+    Global / javacOptions ++= Seq("--release", "21"),
+    Global / scalacOptions ++= Seq(
+      "-deprecation",
+      "-feature",
+      "-unchecked",
+      "-deprecation",
+      "-explain",
+      "-old-syntax",
+      "-unchecked",
+      "-language:noAutoTupling",
+      "-Vprofile",
+      "-Ycheck:all",
+      "-Ycheck:macros",
+      "-Ydebug-missing-refs",
+      "-Yexplain-lowlevel",
+      "-Yexplicit-nulls",
+      "-Wsafe-init",
+      "-Yshow-suppressed-errors",
+      "-Yshow-var-bounds",
+      "-Werror",
+      "-Wunused:all",
+      "-preview",
+    ),
+    ideBasePackages := Seq("org.jetbrains.plugins.hocon"),
+    intellijPlugins := Seq("com.intellij.java-i18n", "com.intellij.modules.json").map(_.toPlugin),
+    intellijExtraRuntimePluginsInTests := Seq("org.jetbrains.kotlin").map(_.toPlugin),
+    libraryDependencies ++= Seq(
+      "org.apache.commons" % "commons-text" % commonsTextVersion,
+      "com.github.sbt" % "junit-interface" % junitInterfaceVersion % Test,
+      "junit" % "junit" % junitVersion % Test,
+      "org.opentest4j" % "opentest4j" % opentest4jVersion % Test,
+    ),
+    packageLibraryMappings := Seq.empty, // allow scala-library
+    patchPluginXml := pluginXmlOptions { xml =>
+      xml.version = version.value
+    },
+  )

resources/META-INF/plugin.xml

@@ -76,11 +76,11 @@
                              displayName="HOCON"/>
 
         <localInspection language="HOCON"
-                         implementationClass="org.jetbrains.plugins.hocon.ref.HoconIncludeResolutionInspection"
+                         implementationClass="org.jetbrains.plugins.hocon.ref.AbstractHoconIncludeResolutionInspection.HoconIncludeResolutionInspection$"
                          displayName="Include resolution" groupName="HOCON" enabledByDefault="true"
                          level="WARNING"/>
         <localInspection language="HOCON"
-                         implementationClass="org.jetbrains.plugins.hocon.ref.HoconRequiredIncludeResolutionInspection"
+                         implementationClass="org.jetbrains.plugins.hocon.ref.AbstractHoconIncludeResolutionInspection.HoconRequiredIncludeResolutionInspection$"
                          displayName="Required include resolution" groupName="HOCON" enabledByDefault="true"
                          level="ERROR"/>
 
@@ -108,11 +108,11 @@
     </extensions>
 
     <actions>
-        <action class="org.jetbrains.plugins.hocon.navigation.HoconGotoNextAction" id="HoconGotoNext"
+        <action class="org.jetbrains.plugins.hocon.navigation.HoconGotoPrevNextAction$HoconGotoNextAction" id="HoconGotoNext"
                 text="HOCON: Go to Next Definition"
                 description="Navigates to the next definition of a property in a HOCON file"
                 use-shortcut-of="GotoImplementation"/>
-        <action class="org.jetbrains.plugins.hocon.navigation.HoconGotoPrevAction" id="HoconGotoPrev"
+        <action class="org.jetbrains.plugins.hocon.navigation.HoconGotoPrevNextAction$HoconGotoPrevAction" id="HoconGotoPrev"
                 text="HOCON: Go to Previous Definition"
                 description="Navigates to the previous definition of a property in a HOCON file"
                 use-shortcut-of="GotoSuperMethod"/>

src/org/jetbrains/plugins/hocon/codestyle/HoconLanguageCodeStyleSettingsProvider.scala

@@ -20,8 +20,8 @@ class HoconLanguageCodeStyleSettingsProvider extends LanguageCodeStyleSettingsPr
   private val ObjectFieldsWithAssignmentWrap = "Object fields with '=' or '+='"
 
   override def customizeSettings(consumer: CodeStyleSettingsCustomizable, settingsType: SettingsType): Unit = {
-    def showCustomOption(name: String, title: String, group: String, options: AnyRef*): Unit =
-      consumer.showCustomOption(classOf[HoconCustomCodeStyleSettings], name, title, group, options: _*)
+    def showCustomOption(name: String, title: String, group: String | Null, options: AnyRef*): Unit =
+      consumer.showCustomOption(classOf[HoconCustomCodeStyleSettings], name, title, group, options*)
 
     import CodeStyleSettingsCustomizable.{WRAP_VALUES, WRAP_VALUES_FOR_SINGLETON}
     import com.intellij.psi.codeStyle.LanguageCodeStyleSettingsProvider.SettingsType.*
@@ -37,7 +37,7 @@ class HoconLanguageCodeStyleSettingsProvider extends LanguageCodeStyleSettingsPr
             SpacingOption.SPACE_WITHIN_METHOD_CALL_PARENTHESES,
             SpacingOption.SPACE_BEFORE_COMMA,
             SpacingOption.SPACE_AFTER_COMMA,
-          ).map(_.name): _*
+          ).map(_.name)*
         )
 
         consumer.renameStandardOption(SpacingOption.SPACE_WITHIN_BRACES.name, "Object braces")

src/org/jetbrains/plugins/hocon/editor/HoconCommenter.scala

@@ -11,23 +11,23 @@ class HoconCommenter extends CodeDocumentationAwareCommenter {
 
   def getLineCommentTokenType: IElementType = HoconTokenType.DoubleSlashComment
 
-  def getBlockCommentSuffix: String = null
+  def getBlockCommentSuffix: String | Null = null
 
-  def getBlockCommentPrefix: String = null
+  def getBlockCommentPrefix: String | Null = null
 
-  def getCommentedBlockCommentPrefix: String = null
+  def getCommentedBlockCommentPrefix: String | Null = null
 
-  def getCommentedBlockCommentSuffix: String = null
+  def getCommentedBlockCommentSuffix: String | Null = null
 
-  def getDocumentationCommentLinePrefix: String = null
+  def getDocumentationCommentLinePrefix: String | Null = null
 
-  def getBlockCommentTokenType: IElementType = null
+  def getBlockCommentTokenType: IElementType | Null = null
 
-  def getDocumentationCommentTokenType: IElementType = null
+  def getDocumentationCommentTokenType: IElementType | Null = null
 
   def isDocumentationComment(element: PsiComment): Boolean = false
 
-  def getDocumentationCommentSuffix: String = null
+  def getDocumentationCommentSuffix: String | Null = null
 
-  def getDocumentationCommentPrefix: String = null
+  def getDocumentationCommentPrefix: String | Null = null
 }

src/org/jetbrains/plugins/hocon/editor/HoconObjectEntryMover.scala

@@ -7,7 +7,7 @@ import com.intellij.openapi.editor.Editor
 import com.intellij.openapi.util.Key
 import com.intellij.psi.{PsiElement, PsiFile}
 import org.jetbrains.plugins.hocon.editor.HoconObjectEntryMover.{PrefixModKey, PrefixModification}
-import org.jetbrains.plugins.hocon.psi.*
+import org.jetbrains.plugins.hocon.psi.{HObjectField, *}
 
 import scala.annotation.tailrec
 
@@ -133,18 +133,21 @@ class HoconObjectEntryMover extends LineMover {
     def canInsertInto(field: HObjectField) =
       !inSingleLine(field) && {
         val lineToInsertAfter = if (down) firstNonCommentLine(field) else endLine(field) - 1
-        file.elementsAt(document.getLineEndOffset(lineToInsertAfter)).collectFirst {
-          case entries: HObjectEntries => entries.prefixingField.map(_.enclosingObjectField).contains(field)
-          case _: HKeyedField => false
-        } getOrElse false
+        file
+          .elementsAt(document.getLineEndOffset(lineToInsertAfter))
+          .collectFirst {
+            case entries: HObjectEntries => entries.prefixingField.map(_.enclosingObjectField).contains(field)
+            case _: HKeyedField => false
+          }
+          .getOrElse(false)
       }
 
     def adjacentEntry(entry: HObjectEntry) =
       if (down) entry.nextEntry else entry.prevEntry
 
     def fieldToDescendInto(field: HObjectField): Option[(HObjectField, List[String])] =
       for {
-        adjacentField <- adjacentEntry(field).collect { case f: HObjectField => f }.filter(canInsertInto)
+        adjacentField <- adjacentEntry(field).collectOnly[HObjectField].filter(canInsertInto)
         prefixToRemove <- {
           val prefix = adjacentField.keyedField.fieldsInPathForward.map(keyString).toList
           val removablePrefix = field.keyedField.fieldsInPathForward
@@ -161,43 +164,47 @@ class HoconObjectEntryMover extends LineMover {
     def trySpecializedFieldMove(objField: HObjectField) = {
       val sourceRange = lineRange(objField)
 
-      fieldToAscendOutOf(objField).map { case (enclosingField, prefixToAdd) =>
-        val targetRange =
-          if (down) new LineRange(sourceRange.endLine, endLine(enclosingField) + 1)
-          else new LineRange(startLine(enclosingField), sourceRange.startLine)
-        val mod = PrefixModification(objField.getTextOffset, 0, prefixToAdd.mkString("", ".", "."))
-        (sourceRange, targetRange, Some(mod))
-
-      } orElse fieldToDescendInto(objField).map { case (adjacentField, prefixToRemove) =>
-        val targetRange =
-          if (down) new LineRange(sourceRange.endLine, firstNonCommentLine(adjacentField) + 1)
-          else new LineRange(endLine(adjacentField), sourceRange.startLine)
-        val prefixStr = prefixToRemove.mkString("", ".", ".")
-        val needsGuard = document.getCharsSequence.charAt(objField.getTextOffset + prefixStr.length).isWhitespace
-        val mod = PrefixModification(objField.getTextOffset, prefixStr.length, if (needsGuard) "\"\"" else "")
-        (sourceRange, targetRange, Some(mod))
-      }
+      fieldToAscendOutOf(objField)
+        .map { case (enclosingField, prefixToAdd) =>
+          val targetRange =
+            if (down) new LineRange(sourceRange.endLine, endLine(enclosingField) + 1)
+            else new LineRange(startLine(enclosingField), sourceRange.startLine)
+          val mod = (objField.getTextOffset, 0, prefixToAdd.mkString("", ".", "."))
+          (sourceRange, targetRange, Some(mod))
+
+        }
+        .orElse(fieldToDescendInto(objField).map { case (adjacentField, prefixToRemove) =>
+          val targetRange =
+            if (down) new LineRange(sourceRange.endLine, firstNonCommentLine(adjacentField) + 1)
+            else new LineRange(endLine(adjacentField), sourceRange.startLine)
+          val prefixStr = prefixToRemove.mkString("", ".", ".")
+          val needsGuard = document.getCharsSequence.charAt(objField.getTextOffset + prefixStr.length).isWhitespace
+          val mod = (objField.getTextOffset, prefixStr.length, if (needsGuard) "\"\"" else "")
+          (sourceRange, targetRange, Some(mod))
+        })
     }
 
     def tryEntryMove(entry: HObjectEntry) = {
       val sourceRange = lineRange(entry)
-      adjacentMovableEntry(entry).map { adjacentEntry =>
-        (sourceRange, lineRange(adjacentEntry), None)
-      } orElse {
-        val maxLinePos = editor.offsetToLogicalPosition(document.getTextLength)
-        val maxLine = if (maxLinePos.column == 0) maxLinePos.line else maxLinePos.line + 1
-        val nearLine = if (down) sourceRange.endLine else sourceRange.startLine - 1
-
-        if (nearLine >= 0 && nearLine < maxLine)
-          Some((sourceRange, singleLineRange(nearLine), None))
-        else None
-      }
+      adjacentMovableEntry(entry)
+        .map { adjacentEntry =>
+          (sourceRange, lineRange(adjacentEntry), None)
+        }
+        .orElse {
+          val maxLinePos = editor.offsetToLogicalPosition(document.getTextLength)
+          val maxLine = if (maxLinePos.column == 0) maxLinePos.line else maxLinePos.line + 1
+          val nearLine = if (down) sourceRange.endLine else sourceRange.startLine - 1
+
+          if (nearLine >= 0 && nearLine < maxLine)
+            Some((sourceRange, singleLineRange(nearLine), None))
+          else None
+        }
     }
 
     val rangesOpt: Option[(LineRange, LineRange, Option[PrefixModification])] =
       enclosingAnchoredEntry(element).flatMap {
         case objField: HObjectField =>
-          trySpecializedFieldMove(objField) orElse tryEntryMove(objField)
+          trySpecializedFieldMove(objField).orElse(tryEntryMove(objField))
         case include: HInclude =>
           tryEntryMove(include)
       }
@@ -211,7 +218,7 @@ class HoconObjectEntryMover extends LineMover {
   }
 
   override def beforeMove(editor: Editor, info: MoveInfo, down: Boolean): Unit =
-    info.getUserData(PrefixModKey).foreach { case PrefixModification(offset, length, replacement) =>
+    info.getUserData(PrefixModKey).foreach { case (offset, length, replacement) =>
       // we need to move caret manually when adding prefix exactly at caret position
       val caretModel = editor.getCaretModel
       val shouldMoveCaret = length == 0 && caretModel.getOffset == offset
@@ -224,7 +231,7 @@ class HoconObjectEntryMover extends LineMover {
 
 object HoconObjectEntryMover {
 
-  case class PrefixModification(offset: Int, length: Int, replacement: String)
+  type PrefixModification = (offset: Int, length: Int, replacement: String)
 
   val PrefixModKey = new Key[Option[PrefixModification]]("PrefixMod")
 }

src/org/jetbrains/plugins/hocon/editor/HoconQuoteHandler.scala

@@ -14,7 +14,7 @@ class HoconQuoteHandler extends SimpleTokenSetQuoteHandler(HoconTokenType.Quoted
 
   def getConcatenatableStringTokenTypes: TokenSet = TokenSet.EMPTY
 
-  def getStringConcatenationOperatorRepresentation: String = null
+  def getStringConcatenationOperatorRepresentation: String | Null = null
 
   def getStringTokenTypes: TokenSet = myLiteralTokenSet