Update handling of end-of-line single-line comments

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

@@ -90,6 +90,7 @@ object Renderer {
     sb.appendMultiline(string, N)
   }
 
+  // Beneath each binding statement, we insert the evaluated variable, e.g., `x: Int = 1`
   def renderEvaluatedSection(
       doc: EvaluatedDocument,
       section: EvaluatedSection,
@@ -108,15 +109,23 @@ object Renderer {
     section.section.statements.zip(section.source.stats).zipWithIndex.foreach {
       case ((statement, tree), statementIndex) =>
         val pos = tree.pos
-        val leadingStart = stats(statementIndex - 1) match {
+        // for each statement, we need to manage:
+        //   1. the leading trivia: whitespace, newlines
+        //   2. a footer: empty until filled on the last statement in the section
+        //   3. and, internally, the trailing single-line comments of the previous statement
+        val (leading, footer) = stats(statementIndex - 1) match {
           case None =>
-            0
+            (Position.Range(input, 0, pos.start).text, "")
           case Some(previousStatement) =>
-            previousStatement.pos.end
+            val Array(prevTrailingSingleLineComment, leadingTrivia) =
+              section.source.pos.text.substring(previousStatement.pos.end, pos.start).split("\n", 2)
+            val foot =
+              if (statementIndex != (totalStats - 1)) ""
+              else section.source.pos.text.substring(pos.end).split("\n").drop(1).mkString("\n", "\n", "")
+            ("\n" + leadingTrivia, foot)
         }
-        val leadingTrivia = Position.Range(input, leadingStart, pos.start)
         if (!section.mod.isFailOrWarn) {
-          sb.append(leadingTrivia.text)
+          sb.append(leading)
         }
         val endOfLinePosition =
           Position.Range(pos.input, pos.startLine, pos.startColumn, pos.endLine, Int.MaxValue)
@@ -179,6 +188,7 @@ object Renderer {
               sb.append(printer(variable))
           }
         }
+        sb.append(footer)
     }
     baos.toString.trim
   }

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

@@ -210,7 +210,9 @@ class DefaultSuite extends BaseMarkdownSuite {
       |Future.successful(Try(1))
       |val (a, b) = Future.successful(Try(1)) -> 2
       |
-      |Future.successful(Try(1))
+      |Future.successful(Try(1)) // last statement
+      |
+      |// penultimate
       |```
     """.stripMargin,
     """|```scala
@@ -224,8 +226,10 @@ class DefaultSuite extends BaseMarkdownSuite {
        |// a: Future[Try[Int]] = Future(Success(Success(1)))
        |// b: Int = 2
        |
-       |Future.successful(Try(1))
+       |Future.successful(Try(1)) // last statement
        |// res1: Future[Try[Int]] = Future(Success(Success(1)))
+       |
+       |// penultimate
        |```
     """.stripMargin
   )
@@ -271,8 +275,9 @@ class DefaultSuite extends BaseMarkdownSuite {
       |x + y
       |
       |/** Docstring */
-      |class User()
-      |```
+      |class User() // Comment 5
+      |
+      |// ultimate```
     """.stripMargin,
     """|```scala
        |/* Comment 1 */
@@ -289,8 +294,9 @@ class DefaultSuite extends BaseMarkdownSuite {
        |// res0: Int = 4
        |
        |/** Docstring */
-       |class User()
-       |```
+       |class User() // Comment 5
+       |
+       |// ultimate```
     """.stripMargin
   )
 

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

@@ -3,6 +3,44 @@ import mdoc.internal.markdown.ReplVariablePrinter
 
 class VariablePrinterSuite extends BaseMarkdownSuite {
 
+  check(
+    "single-line-comment",
+    """
+      |```scala mdoc
+      |import scala.Int // an import statement
+      |val a: Int = 1 // a variable
+      |val b = 2 // another variable
+      |```
+    """.stripMargin,
+    """|```scala
+       |import scala.Int // an import statement
+       |val a: Int = 1 // a variable
+       |// a: Int = 1
+       |val b = 2 // another variable
+       |// b: Int = 2
+       |```
+    """.stripMargin,
+    baseSettings
+  )
+
+  check(
+    "single-line-comment:compile-only",
+    """|```scala mdoc:compile-only
+       |// a
+       |val a = 10
+       |val b = 20 // b
+       |val c = 30
+       |```""".stripMargin,
+    """|```scala
+       |// a
+       |val a = 10
+       |val b = 20 // b
+       |val c = 30
+       |```
+    """.stripMargin,
+    baseSettings
+  )
+
   val trailingComment = baseSettings.copy(variablePrinter = { variable =>
     variable.runtimeValue match {
       case n: Int if variable.totalVariablesInStatement == 1 => s" // Number($n)"