improvement: Add flags to release for JDK 8

build.sbt

@@ -95,7 +95,12 @@ lazy val interfaces = crossProject(JVMPlatform, NativePlatform)
       IO.write(props, "scalafmt properties", out)
       List(out)
     },
-  ).jvmSettings(crossVersion := CrossVersion.disabled, autoScalaLibrary := false)
+  ).jvmSettings(
+    javacOptions ++= Seq("-source", "8", "-target", "8"),
+    Compile / doc / javacOptions := Seq(),
+    crossVersion := CrossVersion.disabled,
+    autoScalaLibrary := false,
+  )
 
 lazy val sysops = crossProject(JVMPlatform, NativePlatform)
   .withoutSuffixFor(JVMPlatform).in(file("scalafmt-sysops")).settings(
@@ -175,7 +180,7 @@ val scalacJvmOptions = Def.setting {
   val unused = Seq("imports", "privates", "locals", "patvars", "implicits")
     .map(x => s"-Ywarn-unused:$x")
 
-  cross ++ unused
+  cross ++ unused ++ Seq("-target:8", "-release:8")
 }
 
 lazy val cli = crossProject(JVMPlatform, NativePlatform)

scalafmt-tests-community/common/src/main/scala/org/scalafmt/community/common/TestHelpers.scala

@@ -58,9 +58,9 @@ object TestHelpers {
         val out1 = x1.formattedCode
         val lines2 = x1.formattedCode.count(_ == '\n')
         val (duration2, result2) = formatCode(out1)
-        def saveFormatted(): Unit = Files.writeString(
+        def saveFormatted(): Unit = Files.write(
           Paths.get(absPathString + s".formatted.$styleName"),
-          out1,
+          out1.getBytes(),
           StandardOpenOption.CREATE,
           StandardOpenOption.TRUNCATE_EXISTING,
         )

scalafmt-tests/shared/src/test/scala/org/scalafmt/util/FormatAssertions.scala

@@ -90,7 +90,7 @@ trait FormatAssertions {
       " " * e.pos.startColumn + "^", // arrow
       linesAfterCaret.mkString("\n"),
       "====== full result: ======",
-      obtained.stripTrailing(),
+      obtained.trim(),
     ).filter(_.nonEmpty).mkString("", "\n", "\n")
   }
 }