Ensure compiler options relevant to syntax rewriting don't require being passed after -O:

- `-rewrite`
- `-new-syntax`
- `-old-syntax`
- `-source:<target>`
- `-indent`
- `-no-indent`

Author: Gedochao

modules/cli-options/src/main/scala/scala/cli/commands/ScalacOptions.scala

@@ -33,11 +33,20 @@ object ScalacOptions {
   private val scalacOptionsPurePrefixes =
     Set("-V", "-W", "-X", "-Y")
   private val scalacOptionsPrefixes =
-    Set("-g", "-language", "-opt", "-P", "-target") ++ scalacOptionsPurePrefixes
+    Set("-g", "-language", "-opt", "-P", "-target", "-source") ++ scalacOptionsPurePrefixes
   private val scalacAliasedOptions = // these options don't require being passed after -O and accept an arg
     Set("-encoding", "-release", "-color")
   private val scalacNoArgAliasedOptions = // these options don't require being passed after -O and don't accept an arg
-    Set("-nowarn", "-feature", "-deprecation")
+    Set(
+      "-nowarn",
+      "-feature",
+      "-deprecation",
+      "-rewrite",
+      "-old-syntax",
+      "-new-syntax",
+      "-indent",
+      "-no-indent"
+    )
 
   /** This includes all the scalac options which disregard inputs and print a help and/or context
     * message instead.

modules/integration/src/test/scala/scala/cli/integration/RunTestDefinitions.scala

@@ -2573,4 +2573,53 @@ abstract class RunTestDefinitions(val scalaVersionOpt: Option[String])
           expect(res.out.trim() == "€")
         }
     }
+
+  if (actualScalaVersion.startsWith("3") || actualScalaVersion.startsWith("2.13")) {
+    val fileName       = "Main.scala"
+    val expectedOutput = "Hello"
+    val oldSyntaxCode =
+      s"""object Main extends App {
+         |  if (true) println("$expectedOutput") else println("Error")
+         |}
+         |""".stripMargin
+    val newSyntaxCode =
+      s"""object Main extends App {
+         |  if true then println("$expectedOutput") else println("Error")
+         |}
+         |""".stripMargin
+
+    test("rewrite code to new syntax and then run it correctly (no -O required)") {
+      TestInputs(os.rel / fileName -> oldSyntaxCode)
+        .fromRoot { root =>
+          val res = os.proc(
+            TestUtil.cli,
+            fileName,
+            "-new-syntax",
+            "-rewrite",
+            "-source:3.2-migration"
+          ).call(cwd = root, stderr = os.Pipe)
+          val filePath = root / fileName
+          expect(res.err.trim().contains(s"[patched file $filePath]"))
+          expect(os.read(filePath) == newSyntaxCode)
+          expect(res.out.trim() == expectedOutput)
+        }
+    }
+
+    test("rewrite code to old syntax and then run it correctly (no -O required)") {
+      TestInputs(os.rel / fileName -> newSyntaxCode)
+        .fromRoot { root =>
+          val res = os.proc(
+            TestUtil.cli,
+            fileName,
+            "-old-syntax",
+            "-rewrite",
+            "-source:3.2-migration"
+          ).call(cwd = root, stderr = os.Pipe)
+          val filePath = root / fileName
+          expect(res.err.trim().contains(s"[patched file $filePath]"))
+          expect(os.read(filePath) == oldSyntaxCode)
+          expect(res.out.trim() == expectedOutput)
+        }
+    }
+  }
 }