Preseve original formatting including trailing statement comments

mdoc/src/main/scala/mdoc/internal/markdown/Renderer.scala

@@ -99,7 +99,10 @@ object Renderer {
         } else {
           sb.append("\n")
         }
-        sb.append(tree.syntax)
+        val pos = tree.pos
+        val endOfLinePosition =
+          Position.Range(pos.input, pos.startLine, pos.startColumn, pos.endLine, Int.MaxValue)
+        sb.append(endOfLinePosition.text)
         if (statement.out.nonEmpty) {
           sb.append("\n")
           appendFreshMultiline(sb, statement.out)

readme.md

@@ -376,7 +376,7 @@ You can choose the Scastie theme when initializing the Scastie modifier:
 ```scala
 import mdoc.modifiers.ScastieModifier
 
-new ScastieModifier(theme = "dark")
+new ScastieModifier(theme = "dark") // default is "light"
 // res0: ScastieModifier = StringModifier(mdoc:scastie)
 ```
 
@@ -521,7 +521,9 @@ After:
 ```scala
 case class User(name: String)
 
-object User { implicit val ordering: Ordering[User] = Ordering.by(_.name) }
+object User {
+  implicit val ordering: Ordering[User] = Ordering.by(_.name)
+}
 
 List(User("John"), User("Susan")).sorted
 // res0: List[User] = List(User("John"), User("Susan"))

runtime/src/main/scala/mdoc/document/Document.scala

@@ -19,7 +19,11 @@ object Document {
 
 final case class Section(statements: List[Statement])
 
-final case class Statement(binders: List[Binder[_]], out: String)
+final case class Statement(
+    binders: List[Binder[_]],
+    out: String,
+    position: RangePosition
+)
 
 final class Binder[T](val value: T, val name: String, val tpe: TPrint[T], pos: RangePosition) {
   override def toString: String = {

runtime/src/main/scala/mdoc/internal/document/DocumentBuilder.scala

@@ -18,6 +18,7 @@ trait DocumentBuilder {
   private val mySections = ArrayBuffer.empty[Section]
   private val myOut = new ByteArrayOutputStream()
   private val myPs = new PrintStream(myOut)
+  private var statementPosition = RangePosition.empty
   private var lastPosition = RangePosition.empty
 
   object $doc {
@@ -37,13 +38,13 @@ trait DocumentBuilder {
     }
 
     def startStatement(startLine: Int, startColumn: Int, endLine: Int, endColumn: Int): Unit = {
-      position(startLine, startColumn, endLine, endColumn)
+      statementPosition = position(startLine, startColumn, endLine, endColumn)
       myBinders.clear()
       myOut.reset()
     }
     def endStatement(): Unit = {
       val out = myOut.toString()
-      myStatements.append(Statement(myBinders.toList, out))
+      myStatements.append(Statement(myBinders.toList, out, statementPosition))
     }
 
     def startSection(): Unit = {

tests/unit/src/test/scala/tests/cli/CliSuite.scala

@@ -5,6 +5,25 @@ import mdoc.internal.BuildInfo
 
 class CliSuite extends BaseCliSuite {
 
+  checkCli(
+    "formatting",
+    """
+      |/index.md
+      |```scala mdoc
+      |List(1,
+      |  2, 3, 4) // comment
+      |```
+    """.stripMargin,
+    """
+      |/index.md
+      |```scala
+      |List(1,
+      |  2, 3, 4) // comment
+      |// res0: List[Int] = List(1, 2, 3, 4)
+      |```
+    """.stripMargin
+  )
+
   checkCli(
     "classpath",
     """

tests/unit/src/test/scala/tests/markdown/MarkdownCompilerSuite.scala

@@ -75,7 +75,7 @@ class MarkdownCompilerSuite extends FunSuite with DiffAssertions {
 
   check(
     "non-val",
-    """println("hello world!") """,
+    """println("hello world!")""",
     """
       |```scala
       |println("hello world!")
@@ -84,4 +84,14 @@ class MarkdownCompilerSuite extends FunSuite with DiffAssertions {
       |""".stripMargin
   )
 
+  check(
+    "comment1",
+    """val x = 2 // comment""",
+    """
+      |```scala
+      |val x = 2 // comment
+      |// x: Int = 2
+      |```
+      |""".stripMargin
+  )
 }

tests/unit/src/test/scala/tests/markdown/VariableRegexSuite.scala

@@ -43,7 +43,7 @@ class VariableRegexSuite extends BaseMarkdownSuite {
       |val x = "1.0"
       |// x: String = "1.0"
       |
-      |x.length
+      |x.length // should match "1.0".length
       |// res0: Int = 3
       |```
     """.stripMargin,