Merge pull request #2097 from tgodzik/fallback-semanticdb

improvement: Try and find latest supported semanticdb version

frontend/src/main/scala/bloop/engine/caches/SemanticDBCache.scala

@@ -2,21 +2,30 @@ package bloop.engine.caches
 
 import java.nio.file.Path
 
+import scala.collection.JavaConverters._
+import scala.concurrent.Await
+import scala.concurrent.duration.FiniteDuration
 import scala.util.Failure
 import scala.util.Success
 import scala.util.Try
 
 import bloop.DependencyResolution
 import bloop.SemanticDBCacheLock
+import bloop.engine.ExecutionContext
 import bloop.io.AbsolutePath
 import bloop.io.Paths
 import bloop.logging.Logger
+import bloop.task.Task
 
 import sbt.internal.inc.BloopComponentCompiler
 import sbt.internal.inc.BloopComponentManager
 import sbt.internal.inc.IfMissing
+import java.util.concurrent.ConcurrentHashMap
+import scala.concurrent.Future
 
 object SemanticDBCache {
+  // to avoid resolving the same fallback semanticdb version multiple times
+  private val supportedFallbackSemanticdbVersions = new ConcurrentHashMap[String, String]()
   private def fetchPlugin(
       artifact: DependencyResolution.Artifact,
       logger: Logger
@@ -57,6 +66,41 @@ object SemanticDBCache {
     }
   }
 
+  private def fallbackSemanticdbFetch(
+      scalaVersion: String,
+      artifact: DependencyResolution.Artifact,
+      logger: Logger
+  ): Either[String, AbsolutePath] = {
+    // if scala version is no longer supported find the latest supported semanticdb version
+    def versionFuture =
+      Future {
+        coursierapi.Complete
+          .create()
+          .withScalaVersion(scalaVersion)
+          .withScalaBinaryVersion(scalaVersion.split('.').take(2).mkString("."))
+          .withInput(s"org.scalameta:semanticdb-scalac_$scalaVersion:")
+          .complete()
+          .getCompletions()
+          .asScala
+          .lastOption
+      }(ExecutionContext.ioScheduler)
+
+    def version =
+      try
+        Await.result(versionFuture, FiniteDuration(10, "s"))
+      catch {
+        case _: Throwable => None
+      }
+
+    Option(supportedFallbackSemanticdbVersions.get(scalaVersion)).orElse(version) match {
+      case None =>
+        Left(s"After retry no existing semanticdb version found for scala version $scalaVersion")
+      case Some(semanticdbVersion) =>
+        supportedFallbackSemanticdbVersions.put(scalaVersion, semanticdbVersion)
+        fetchPlugin(artifact.copy(version = semanticdbVersion), logger)
+    }
+  }
+
   @volatile private var latestResolvedScalaSemanticDB: Path = null
   def fetchScalaPlugin(
       scalaVersion: String,
@@ -77,7 +121,16 @@ object SemanticDBCache {
           latestResolvedPlugin
         }
       }
-    } else fetchPlugin(artifact, logger)
+    } else {
+      fetchPlugin(artifact, logger) match {
+        case Right(plugin) => Right(plugin)
+        case Left(error) =>
+          fallbackSemanticdbFetch(scalaVersion, artifact, logger) match {
+            case Left(newError) => Left(error + "\n" + newError)
+            case Right(plugin) => Right(plugin)
+          }
+      }
+    }
   }
 
   @volatile private var latestResolvedJavaSemanticDB: Path = null

frontend/src/test/scala/bloop/bsp/BspMetalsClientSpec.scala

@@ -87,32 +87,6 @@ class BspMetalsClientSpec(
     }
   }
 
-  test("do not initialize metals client and save settings with unsupported scala version") {
-    TestUtil.withinWorkspace { workspace =>
-      val `A` = TestProject(workspace, "A", Nil, scalaVersion = Some("2.12.4"))
-      val projects = List(`A`)
-      val configDir = TestProject.populateWorkspace(workspace, projects)
-      val logger = new RecordingLogger(ansiCodesSupported = false)
-      val extraParams = BloopExtraBuildParams(
-        ownsBuildFiles = None,
-        clientClassesRootDir = None,
-        semanticdbVersion = Some(semanticdbVersion), // Doesn't support 2.12.4
-        supportedScalaVersions = Some(List(testedScalaVersion)),
-        javaSemanticdbVersion = Some(javaSemanticdbVersion)
-      )
-
-      loadBspState(workspace, projects, logger, "Metals", bloopExtraParams = extraParams) { state =>
-        assertNoDiffInSettingsFile(
-          configDir,
-          expectedConfig
-        )
-        // Expect only range positions to be added, semanticdb is not supported
-        assertScalacOptions(state, `A`, "-Yrangepos")
-        assertNoDiff(logger.warnings.mkString(lineSeparator), "")
-      }
-    }
-  }
-
   test("initialize metals client in workspace with already enabled semanticdb") {
     TestUtil.withinWorkspace { workspace =>
       val pluginPath = s"-Xplugin:path-to-plugin/$semanticdbJar"
@@ -333,6 +307,40 @@ class BspMetalsClientSpec(
     }
   }
 
+  test("compile with old semanticDB") {
+    TestUtil.withinWorkspace { workspace =>
+      object JavacOptions {
+        // This will cause to use the forked javac compiler, since addong any `-J` property causes it
+        val A = List("-J-Xms48m")
+      }
+
+      val `A` =
+        TestProject(
+          workspace,
+          "A",
+          dummyFooScalaAndBarJavaSources,
+          javacOptions = JavacOptions.A,
+          // this Scala version is not supported in the newest semanticdb
+          scalaVersion = Some("2.12.8")
+        )
+      val projects = List(`A`)
+      val configDir = TestProject.populateWorkspace(workspace, projects)
+      val logger = new RecordingLogger(ansiCodesSupported = false)
+      WorkspaceSettings.writeToFile(
+        configDir,
+        WorkspaceSettings
+          .fromSemanticdbSettings("0.5.7", semanticdbVersion, List(testedScalaVersion)),
+        logger
+      )
+      loadBspState(workspace, projects, logger) { state =>
+        val compiledState = state.compile(`A`).toTestState
+        assert(compiledState.status == ExitStatus.Ok)
+        assertSemanticdbFileFor("Foo.scala", compiledState)
+        assertSemanticdbFileFor("Bar.java", compiledState)
+      }
+    }
+  }
+
   test("compile with semanticDB using cached plugin") {
     TestUtil.withinWorkspace { workspace =>
       val `A` = TestProject(workspace, "A", dummyFooScalaAndBarJavaSources)