fix: return an error when trying to decode tasty in Scala 2

Since this isn't supported for now we should correctly return an error for this. Right now you can still trigger this in Scala 2 and it just returns an empty string not really giving the user much information about why it didn't work. This way clients can now handle this situation better.
scalameta · Mar 18, 2022 · b47c60d · b47c60d
1 parent c2d8baa
commit b47c60d
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Showing 2 changed files with 38 additions and 4 deletions.
diff --git a/metals/src/main/scala/scala/meta/internal/metals/FileDecoderProvider.scala b/metals/src/main/scala/scala/meta/internal/metals/FileDecoderProvider.scala
@@ -287,14 +287,27 @@ final class FileDecoderProvider(
     else DecoderResponse.failed(path.toURI, "Unsupported extension")
   }
 
+  private def isScala3(path: AbsolutePath): Boolean = {
+    buildTargets
+      .scalaVersion(path)
+      .exists(version => ScalaVersions.isScala3Version(version))
+  }
+
   private def decodeTasty(
       path: AbsolutePath
   ): Future[DecoderResponse] = {
-    if (path.isScala)
+    if (path.isScala && isScala3(path)) {
       selectClassFromScalaFileAndDecode(path.toURI, path, false)(
         decodeFromTastyFile
       )
-    else if (path.isTasty) {
+    } else if (path.isScala) {
+      Future.successful(
+        DecoderResponse.failed(
+          path.toURI,
+          "Decoding tasty is only supported in Scala 3 for now."
+        )
+      )
+    } else if (path.isTasty) {
       findPathInfoForClassesPathFile(path) match {
         case Some(pathInfo) => decodeFromTastyFile(pathInfo)
         case None =>
@@ -305,8 +318,11 @@ final class FileDecoderProvider(
             )
           )
       }
-    } else
-      Future.successful(DecoderResponse.failed(path.toURI, "Invalid extension"))
+    } else {
+      Future.successful(
+        DecoderResponse.failed(path.toURI, "Invalid extension")
+      )
+    }
   }
 
   private def findPathInfoFromJavaSource(

diff --git a/tests/slow/src/test/scala/tests/feature/FileDecoderProviderLspSuite.scala b/tests/slow/src/test/scala/tests/feature/FileDecoderProviderLspSuite.scala
@@ -30,6 +30,24 @@ class FileDecoderProviderLspSuite
     Right(FileDecoderProviderLspSuite.tastySingle)
   )
 
+  check(
+    "tasty-single-not-for-scala2",
+    s"""|/metals.json
+        |{
+        |  "app": {
+        |    "scalaVersion": "${V.scala213}"
+        |  }
+        |}
+        |/app/src/main/scala/Main.scala
+        |package foo.bar.example
+        |object Main
+        |""".stripMargin,
+    "app/src/main/scala/Main.scala",
+    None,
+    "tasty-decoded",
+    Left("Decoding tasty is only supported in Scala 3 for now.")
+  )
+
   check(
     "decode-jar",
     s"""