[2.x] fix: support comma-separated imports in build.sbt (#8829)

Summary
- Fix `SbtParser.importsToLineRanges` to prepend `import` keyword when missing from Dotty's `Import` AST node source spans
- Add unit test for comma-separated import parsing

buildfile/src/main/scala/sbt/internal/parser/SbtParser.scala

@@ -283,6 +283,8 @@ private[sbt] case class SbtParser(path: VirtualFileRef, lines: Seq[String])
     imports.map { tree =>
       val pos = tree.sourcePos
       val content = String(pos.source.content.slice(pos.start, pos.end)).trim
-      (content, tree.sourcePos.line)
+      // Dotty splits `import a, b` into separate Import trees; subsequent ones lack `import`
+      val importStr = if content.startsWith("import ") then content else s"import $content"
+      (importStr, tree.sourcePos.line)
     }
 end SbtParser

buildfile/src/test/scala/sbt/internal/SbtParserTest.scala

@@ -37,6 +37,68 @@ lazy val foo = project
   .settings(x := y)""" -> LineRange(7, 8)))
   }
 
+  test("comma separated imports") {
+    val ref = VirtualFileRef.of("vfile")
+    val code = """import scala.util, util.Random
+
+def f = Random.nextInt()
+"""
+    val p = SbtParser(ref, code.linesIterator.toList)
+    assert(p.imports.size == 2)
+    assert(p.imports(0)._1 == "import scala.util")
+    assert(p.imports(1)._1 == "import util.Random")
+    assert(p.settings.size == 1)
+  }
+
+  test("comma separated imports with three entries") {
+    val ref = VirtualFileRef.of("vfile")
+    val code = """import scala.util, util.Random, util.Properties
+
+val x = 1
+"""
+    val p = SbtParser(ref, code.linesIterator.toList)
+    assert(p.imports.size == 3)
+    assert(p.imports(0)._1 == "import scala.util")
+    assert(p.imports(1)._1 == "import util.Random")
+    assert(p.imports(2)._1 == "import util.Properties")
+  }
+
+  test("comma separated imports with wildcard") {
+    val ref = VirtualFileRef.of("vfile")
+    val code = """import scala.util, util.*
+
+val x = 1
+"""
+    val p = SbtParser(ref, code.linesIterator.toList)
+    assert(p.imports.size == 2)
+    assert(p.imports(0)._1 == "import scala.util")
+    assert(p.imports(1)._1 == "import util.*")
+  }
+
+  test("comma separated imports with rename") {
+    val ref = VirtualFileRef.of("vfile")
+    val code = """import scala.util, util.{Random => Rng}
+
+val x = 1
+"""
+    val p = SbtParser(ref, code.linesIterator.toList)
+    assert(p.imports.size == 2)
+    assert(p.imports(0)._1 == "import scala.util")
+    assert(p.imports(1)._1 == "import util.{Random => Rng}")
+  }
+
+  test("comma separated imports with multiple selectors") {
+    val ref = VirtualFileRef.of("vfile")
+    val code = """import scala.util, util.{Random, Properties}
+
+val x = 1
+"""
+    val p = SbtParser(ref, code.linesIterator.toList)
+    assert(p.imports.size == 2)
+    assert(p.imports(0)._1 == "import scala.util")
+    assert(p.imports(1)._1 == "import util.{Random, Properties}")
+  }
+
   test("isIdentifier") {
     assert(SbtParser.isIdentifier("1a") == false)
   }

sbt-app/src/sbt-test/project/comma-separated-import/build.sbt

@@ -0,0 +1,11 @@
+import scala.util, util.Random
+import scala.collection.mutable, mutable.{ArrayBuffer, ListBuffer}
+import scala.concurrent, concurrent.*
+
+val check = taskKey[Unit]("check comma-separated import works")
+check := {
+  val _ = Random.nextInt()
+  val _ = ArrayBuffer(1, 2, 3)
+  val _ = ListBuffer("a", "b")
+  val _ = Future.successful(1)
+}

sbt-app/src/sbt-test/project/comma-separated-import/test

@@ -0,0 +1,2 @@
+# Verify that comma-separated imports work in build.sbt
+> check