introduce BspControlPlugin

Author: satorg

core/src/main/scala/org/typelevel/sbt/BspControlPlugin.scala

@@ -0,0 +1,59 @@
+/*
+ * Copyright 2022 Typelevel
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.typelevel.sbt
+
+import sbt.Keys._
+import sbt._
+import sbtcrossproject.CrossPlugin
+import sbtcrossproject.CrossPlugin.autoImport._
+import sbtcrossproject.Platform
+
+object BspControlPlugin extends AutoPlugin {
+  override def trigger = allRequirements
+  override def requires: Plugins = CrossPlugin
+
+  object autoImport {
+    lazy val tlBspCrossProjectPlatforms: SettingKey[Set[Platform]] =
+      settingKey[Set[Platform]](
+        "set of platforms for which BSP should be enabled (default: not initialized)")
+  }
+
+  import autoImport._
+
+  override def projectSettings: Seq[Setting[?]] = Seq(
+    bspEnabled := {
+      val oldValue = bspEnabled.value
+
+      // We have to check if `crossProjectCrossType` and `crossProjectPlatform`
+      // are initialized. Otherwise, the `sbt-typelevel` won't load itself.
+      (
+        crossProjectCrossType.?.value,
+        crossProjectPlatform.?.value,
+        tlBspCrossProjectPlatforms.?.value
+      ) match {
+        // `tlBspCrossProjectPlatforms` is set by a user explicitly.
+        case (_, Some(projectPlatform), Some(bspPlatforms)) =>
+          bspPlatforms.contains(projectPlatform)
+        // If `CrossType` is `Pure` then enable BSP for the JVM platform only.
+        case (Some(CrossType.Pure), Some(projectPlatform), None) =>
+          projectPlatform == JVMPlatform
+        // Otherwise simply return the old value.
+        case _ => oldValue
+      }
+    }
+  )
+}