bugfix: Completions for named args in wrong order (#18702)

connected to scalameta/metals#5728

Author: jkciesluk

presentation-compiler/src/main/dotty/tools/pc/completions/Completions.scala

@@ -56,8 +56,8 @@ class Completions(
 
   val coursierComplete = new CoursierComplete(BuildInfo.scalaVersion)
 
+  private lazy val adjustedPath = Completion.resolveTypedOrUntypedPath(path, pos)
   private lazy val completionMode =
-    val adjustedPath = Completion.resolveTypedOrUntypedPath(path, pos)
     val mode = Completion.completionMode(adjustedPath, pos)
     path match
       case Literal(Constant(_: String)) :: _ => Mode.Term // literal completions
@@ -451,6 +451,7 @@ class Completions(
         val args = NamedArgCompletions.contribute(
           pos,
           path,
+          adjustedPath,
           indexedContext,
           config.isCompletionSnippetsEnabled()
         )

presentation-compiler/src/main/dotty/tools/pc/completions/NamedArgCompletions.scala

@@ -2,8 +2,10 @@ package dotty.tools.pc.completions
 
 import scala.util.Try
 
+import dotty.tools.dotc.ast.NavigateAST
 import dotty.tools.dotc.ast.Trees.ValDef
 import dotty.tools.dotc.ast.tpd.*
+import dotty.tools.dotc.ast.untpd
 import dotty.tools.dotc.core.Constants.Constant
 import dotty.tools.dotc.core.ContextOps.localContext
 import dotty.tools.dotc.core.Contexts.Context
@@ -12,7 +14,10 @@ import dotty.tools.dotc.core.Flags
 import dotty.tools.dotc.core.Flags.Method
 import dotty.tools.dotc.core.NameKinds.DefaultGetterName
 import dotty.tools.dotc.core.Names.Name
+import dotty.tools.dotc.core.StdNames.*
+import dotty.tools.dotc.core.SymDenotations.NoDenotation
 import dotty.tools.dotc.core.Symbols
+import dotty.tools.dotc.core.Symbols.NoSymbol
 import dotty.tools.dotc.core.Symbols.Symbol
 import dotty.tools.dotc.core.Types.AndType
 import dotty.tools.dotc.core.Types.AppliedType
@@ -33,8 +38,9 @@ object NamedArgCompletions:
   def contribute(
       pos: SourcePosition,
       path: List[Tree],
+      untypedPath: => List[untpd.Tree],
       indexedContext: IndexedContext,
-      clientSupportsSnippets: Boolean
+      clientSupportsSnippets: Boolean,
   )(using ctx: Context): List[CompletionValue] =
     path match
       case (ident: Ident) :: ValDef(_, _, _) :: Block(_, app: Apply) :: _
@@ -43,7 +49,7 @@ object NamedArgCompletions:
           Some(ident),
           app,
           indexedContext,
-          clientSupportsSnippets
+          clientSupportsSnippets,
         )
       case (ident: Ident) :: rest =>
         def getApplyForContextFunctionParam(path: List[Tree]): Option[Apply] =
@@ -63,9 +69,29 @@ object NamedArgCompletions:
             Some(ident),
             app,
             indexedContext,
-            clientSupportsSnippets
+            clientSupportsSnippets,
           )
         contribution.getOrElse(Nil)
+      case (app: Apply) :: _ =>
+        /**
+         * def foo(aaa: Int, bbb: Int, ccc: Int) = ???
+         * val x = foo(
+         *  bbb = 123,
+         *  ccc = 123,
+         *  @@
+         * )
+         * In this case, typed path doesn't contain already provided arguments
+         */
+        untypedPath match
+          case (ident: Ident) :: (app: Apply) :: _ =>
+            contribute(
+              Some(ident),
+              app,
+              indexedContext,
+              clientSupportsSnippets,
+            )
+          case _ =>
+            Nil
       case _ =>
         Nil
     end match
@@ -87,7 +113,7 @@ object NamedArgCompletions:
       ident: Option[Ident],
       apply: Apply,
       indexedContext: IndexedContext,
-      clientSupportsSnippets: Boolean
+      clientSupportsSnippets: Boolean,
   )(using context: Context): List[CompletionValue] =
     def isUselessLiteral(arg: Tree): Boolean =
       arg match
@@ -117,6 +143,11 @@ object NamedArgCompletions:
 
     val argss = collectArgss(apply)
 
+    def fallbackFindApply(sym: Symbol) =
+      sym.info.member(nme.apply) match
+        case NoDenotation => Nil
+        case den => List(den.symbol)
+
     // fallback for when multiple overloaded methods match the supplied args
     def fallbackFindMatchingMethods() =
       def maybeNameAndIndexedContext(
@@ -182,7 +213,9 @@ object NamedArgCompletions:
           if foundPotential.contains(method.symbol) then foundPotential
           else method.symbol :: foundPotential
         else List(method.symbol)
-      else fallbackFindMatchingMethods()
+      else if method.symbol.is(Method) || method.symbol == NoSymbol then
+        fallbackFindMatchingMethods()
+      else fallbackFindApply(method.symbol)
       end if
     end matchingMethods
 
@@ -227,8 +260,13 @@ object NamedArgCompletions:
         def refineParams(method: Tree, level: Int): List[ParamSymbol] =
           method match
             case Select(Apply(f, _), _) => refineParams(f, level + 1)
-            case Select(h, v) => getRefinedParams(h.symbol.info, level)
-            case _ => defaultBaseParams
+            case Select(h, name) =>
+              // for Select(foo, name = apply) we want `foo.symbol`
+              if name == nme.apply then getRefinedParams(h.symbol.info, level)
+              else getRefinedParams(method.symbol.info, level)
+            case Apply(f, _) =>
+              refineParams(f, level + 1)
+            case _ => getRefinedParams(method.symbol.info, level)
         refineParams(method, 0)
       end baseParams
 
@@ -330,15 +368,15 @@ object NamedArgCompletions:
             param.nameBackticked + " = " + memberName + " "
           CompletionValue.namedArg(
             label = editText,
-            param
+            param,
           )
         }
       }
 
     params.map(p =>
       CompletionValue.namedArg(
         s"${p.nameBackticked} = ",
-        p
+        p,
       )
     ) ::: findPossibleDefaults() ::: fillAllFields()
   end contribute
@@ -411,4 +449,4 @@ case class JustSymbol(symbol: Symbol)(using Context) extends ParamSymbol:
   def info: Type = symbol.info
 
 case class RefinedSymbol(symbol: Symbol, name: Name, info: Type)
-    extends ParamSymbol
+    extends ParamSymbol

presentation-compiler/test/dotty/tools/pc/tests/completion/CompletionArgSuite.scala

@@ -1038,3 +1038,71 @@ class CompletionArgSuite extends BaseCompletionSuite:
          |""".stripMargin,
       topLines = Some(1),
     )
+
+  @Test def `second-first` =
+    check(
+      """|object Main {
+         |  def foo(aaa: Int, bbb: Int, ccc: Int) = aaa + bbb + ccc
+         |  val k = foo (
+         |    bbb = 123,
+         |    aa@@
+         |  )
+         |} 
+         |""".stripMargin,
+      """|aaa = : Int
+         |""".stripMargin,
+      topLines = Some(1),
+    )
+
+  @Test def `second-first2` =
+    check(
+      """|object Main {
+         |  def foo(aaa: Int, bbb: Int, ccc: Int) = aaa + bbb + ccc
+         |  val k = foo (
+         |    bbb = 123,
+         |    ccc = 123,
+         |    aa@@
+         |  )
+         |} 
+         |""".stripMargin,
+      """|aaa = : Int
+         |""".stripMargin,
+      topLines = Some(1),
+    )
+
+  @Test def `second-first3` =
+    check(
+      """|object Main {
+         |  def foo(ddd: Int)(aaa: Int, bbb: Int, ccc: Int) = aaa + bbb + ccc
+         |  val k = foo(123)(
+         |    bbb = 123,
+         |    ccc = 123,
+         |    aa@@
+         |  )
+         |} 
+         |""".stripMargin,
+      """|aaa = : Int
+         |""".stripMargin,
+      topLines = Some(1),
+    )
+
+  @Test def `second-first4` =
+    check(
+      """|object O:
+         |  val hello: (x: Int, y: Int) => Unit = (x, _) => println(x)
+         |val k = O.hello(y = 1, @@)
+         |""".stripMargin,
+      """|x = : Int
+         |""".stripMargin,
+      topLines = Some(1),
+    )
+
+  @Test def `second-first5` =
+    check(
+      """|val hello: (x: Int) => Int => (str: String, ccc: String) => Unit = x => j => (str, _) => println(str)
+         |val k = hello(x = 1)(2)(ccc = "abc", @@)
+         |""".stripMargin,
+      """|str = : String
+         | """.stripMargin,
+      topLines = Some(1),
+    )