From d2ccce22ad3cd1bb6befe400dd2d9ad53683b232 Mon Sep 17 00:00:00 2001
From: Jakub Ciesluk <323892@uwr.edu.pl>
Date: Mon, 18 Sep 2023 17:50:26 +0200
Subject: [PATCH] bugfix: Named args completions with default values

---
 .../pc/completions/ArgCompletions.scala       |   7 +-
 .../pc/completions/NamedArgCompletions.scala  |  17 ++-
 .../scala/tests/pc/CompletionArgSuite.scala   | 115 ++++++++++++++++++
 3 files changed, 134 insertions(+), 5 deletions(-)

diff --git a/mtags/src/main/scala-2/scala/meta/internal/pc/completions/ArgCompletions.scala b/mtags/src/main/scala-2/scala/meta/internal/pc/completions/ArgCompletions.scala
index 598b4aa9770..1cfcf6179eb 100644
--- a/mtags/src/main/scala-2/scala/meta/internal/pc/completions/ArgCompletions.scala
+++ b/mtags/src/main/scala-2/scala/meta/internal/pc/completions/ArgCompletions.scala
@@ -19,7 +19,12 @@ trait ArgCompletions { this: MetalsGlobal =>
     val editRange: l.Range =
       pos.withStart(ident.pos.start).withEnd(pos.start).toLsp
     val funPos = apply.fun.pos
-    val method: Tree = typedTreeAt(funPos)
+    val method: Tree = typedTreeAt(funPos) match {
+      case Apply(Block(defParams, app: Apply), _)
+          if defParams.forall(p => p.isInstanceOf[ValDef]) =>
+        app
+      case t => t
+    }
     val methodSym = method.symbol
     lazy val methodsParams: List[MethodParams] = {
       if (methodSym.isModule) getParamsFromObject(methodSym)
diff --git a/mtags/src/main/scala-3/scala/meta/internal/pc/completions/NamedArgCompletions.scala b/mtags/src/main/scala-3/scala/meta/internal/pc/completions/NamedArgCompletions.scala
index 712bc5dac56..a18e7c3ffa1 100644
--- a/mtags/src/main/scala-3/scala/meta/internal/pc/completions/NamedArgCompletions.scala
+++ b/mtags/src/main/scala-3/scala/meta/internal/pc/completions/NamedArgCompletions.scala
@@ -237,15 +237,24 @@ object NamedArgCompletions:
         .getOrElse(baseArgs)
         .filterNot(isUselessLiteral)
 
+      @tailrec
+      def isDefaultArg(t: Tree): Boolean = t match
+        // default args
+        case Ident(name) => name.is(DefaultGetterName)
+        // default args for methods defined in object
+        case Select(_, name) =>
+          name.is(DefaultGetterName)
+        // default args in not-first parameter list
+        // eg. def m(fst: Int)(snd: Int)(arg1: Int, arg2: Int = 123) = ???
+        case Apply(fun, _) => isDefaultArg(fun)
+        case _ => false
+
       val isNamed: Set[Name] = args.iterator
         .zip(baseParams.iterator)
         // filter out synthesized args and default arg getters
         .filterNot {
           case (arg, _) if arg.symbol.denot.is(Flags.Synthetic) => true
-          case (Ident(name), _) => name.is(DefaultGetterName) // default args
-          case (Select(Ident(_), name), _) =>
-            name.is(DefaultGetterName) // default args for apply method
-          case _ => false
+          case (arg, _) => isDefaultArg(arg)
         }
         .map {
           case (NamedArg(name, _), _) => name
diff --git a/tests/cross/src/test/scala/tests/pc/CompletionArgSuite.scala b/tests/cross/src/test/scala/tests/pc/CompletionArgSuite.scala
index 70503cfa302..58c0018f9a1 100644
--- a/tests/cross/src/test/scala/tests/pc/CompletionArgSuite.scala
+++ b/tests/cross/src/test/scala/tests/pc/CompletionArgSuite.scala
@@ -244,6 +244,121 @@ class CompletionArgSuite extends BaseCompletionSuite {
     "",
   )
 
+  check(
+    "default-args",
+    """|object Main {
+       |  def foo() = {
+       |    def deployment(
+       |      fst: String,
+       |      snd: Int = 1,
+       |    ): Option[Int] = ???
+       |    val abc = deployment(@@)
+       |  }
+       |}
+       |""".stripMargin,
+    """|fst = : String
+       |snd = : Int
+       |""".stripMargin,
+    topLines = Some(2),
+  )
+
+  check(
+    "default-args2",
+    """|object Main {
+       |  def deployment(
+       |    fst: String,
+       |    snd: Int = 1,
+       |  ): Option[Int] = ???
+       |  val abc = deployment(@@)
+       |}
+       |""".stripMargin,
+    """|fst = : String
+       |snd = : Int
+       |""".stripMargin,
+    topLines = Some(2),
+  )
+
+  check(
+    "default-args3",
+    """|object Main {
+       |  def deployment(str: String)(
+       |    fst: String,
+       |    snd: Int = 1,
+       |  ): Option[Int] = ???
+       |  val abc = deployment("str")(
+       |    @@
+       |  )
+       |}
+       |""".stripMargin,
+    """|fst = : String
+       |snd = : Int
+       |""".stripMargin,
+    topLines = Some(2),
+  )
+
+  check(
+    "default-args4",
+    """|object Main {
+       |  def deployment(str: String)(opt: Option[Int])(
+       |    fst: String,
+       |    snd: Int = 1,
+       |  ): Option[Int] = ???
+       |  val abc = deployment("str")(None)(
+       |    @@
+       |  )
+       |}
+       |""".stripMargin,
+    """|fst = : String
+       |snd = : Int
+       |""".stripMargin,
+    topLines = Some(2),
+  )
+
+  // NOTE: In Scala 3.3.1 the tree for this test changed, which allowed easy fix
+  // For previous Scala 3 versions it shows wrong completions
+  check(
+    "default-args5",
+    """|object Main {
+       |  def deployment(str: String)(opt: Option[Int] = None)(
+       |    fst: String,
+       |    snd: Int = 1,
+       |  ): Option[Int] = ???
+       |  val abc = deployment("str")(
+       |    @@
+       |  )
+       |}
+       |""".stripMargin,
+    """|abc: (String, Int) => Option[Int]
+       |""".stripMargin,
+    topLines = Some(1),
+    compat = Map(
+      ">=3.3.1" ->
+        """|opt = : Option[Int]
+           |""".stripMargin,
+      "2" ->
+        """|opt = : Option[Int]
+           |""".stripMargin,
+    ),
+  )
+
+  check(
+    "default-args6".tag(IgnoreScala2),
+    """|object Main {
+       |  def deployment(using str: String)(
+       |    fst: String,
+       |    snd: Int = 1,
+       |  ): Option[Int] = ???
+       |  val abc = deployment(using "str")(
+       |    @@
+       |  )
+       |}
+       |""".stripMargin,
+    """|fst = : String
+       |snd = : Int
+       |""".stripMargin,
+    topLines = Some(2),
+  )
+
   checkSnippet( // see: https://github.com/scalameta/metals/issues/2400
     "explicit-dollar",
     """