From bcc723490606bcb643ae892ed658cb500cfe9e28 Mon Sep 17 00:00:00 2001
From: Matthew de Detrich <matthew.dedetrich@aiven.io>
Date: Sat, 30 Dec 2023 15:56:42 +1100
Subject: [PATCH] Add PekkoInlinePlugin

---
 .../pekkobuild/PekkoInlinePlugin.scala        | 68 +++++++++++++++++++
 .../pekkobuild/PekkoInlineSettings.scala      | 10 +++
 2 files changed, 78 insertions(+)
 create mode 100644 src/main/scala/com/github/pjfanning/pekkobuild/PekkoInlinePlugin.scala
 create mode 100644 src/main/scala/com/github/pjfanning/pekkobuild/PekkoInlineSettings.scala

diff --git a/src/main/scala/com/github/pjfanning/pekkobuild/PekkoInlinePlugin.scala b/src/main/scala/com/github/pjfanning/pekkobuild/PekkoInlinePlugin.scala
new file mode 100644
index 0000000..5682b66
--- /dev/null
+++ b/src/main/scala/com/github/pjfanning/pekkobuild/PekkoInlinePlugin.scala
@@ -0,0 +1,68 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * license agreements; and to You under the Apache License, version 2.0:
+ *
+ *   https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * This file is part of the Apache Pekko project, derived from Akka.
+ */
+
+package com.github.pjfanning.pekkobuild
+
+import sbt.plugins.JvmPlugin
+import sbt._
+import sbt.Keys._
+
+object PekkoInlinePlugin extends AutoPlugin {
+  override def trigger: PluginTrigger = allRequirements
+
+  override def requires: Plugins = JvmPlugin
+
+  private def flagsForScala2(coreProject: Boolean) = {
+    val baseInlineFlags = Seq(
+      "-opt-inline-from:<sources>",
+      "-opt:l:inline"
+    )
+
+    if (coreProject)
+      baseInlineFlags ++ Seq(
+        // Since the Pekko core project doesn't allow for mixing of different versions,
+        // i.e. you cannot mix pekko-actor 1.0.0 with pekko-streams 1.0.1 at runtime
+        // its safe to do inter sbt project inlining.
+        "-opt-inline-from:org.apache.pekko.**"
+      )
+    else baseInlineFlags ++ Seq(
+      // These are safe to inline even across modules since they are
+      // wrappers for cross compilation that is stable within Pekko.
+      "-opt-inline-from:org.apache.pekko.dispatch.internal.SameThreadExecutionContext**",
+      "-opt-inline-from:org.apache.pekko.util.OptionConverters**",
+      "-opt-inline-from:org.apache.pekko.util.FutureConverters**",
+      "-opt-inline-from:org.apache.pekko.util.FunctionConverters**",
+      "-opt-inline-from:org.apache.pekko.util.PartialFunction**",
+      "-opt-inline-from:org.apache.pekko.util.JavaDurationConverters**"
+    )
+  }
+
+  object autoImport extends PekkoInlineSettings
+
+  import autoImport._
+
+  // Optimizer not yet available for Scala3, see https://docs.scala-lang.org/overviews/compiler-options/optimizer.html
+  private val flagsForScala3 = Seq()
+
+  override lazy val globalSettings = Seq(
+    pekkoInlineEnabled := !sys.props.contains("pekko.no.inline"),
+    pekkoInlineCoreProject := false
+  )
+
+  override lazy val projectSettings = Seq(Compile / scalacOptions ++= {
+    if (pekkoInlineEnabled.value) {
+      CrossVersion.partialVersion(scalaVersion.value) match {
+        case Some((2, n)) if n == 12 | n == 13 =>
+          flagsForScala2(pekkoInlineCoreProject.value)
+        case Some((3, _)) =>
+          flagsForScala3
+      }
+    } else Seq.empty
+  })
+}
diff --git a/src/main/scala/com/github/pjfanning/pekkobuild/PekkoInlineSettings.scala b/src/main/scala/com/github/pjfanning/pekkobuild/PekkoInlineSettings.scala
new file mode 100644
index 0000000..fb74fc4
--- /dev/null
+++ b/src/main/scala/com/github/pjfanning/pekkobuild/PekkoInlineSettings.scala
@@ -0,0 +1,10 @@
+package com.github.pjfanning.pekkobuild
+
+import sbt.{SettingKey, settingKey}
+
+trait PekkoInlineSettings {
+  lazy val pekkoInlineEnabled: SettingKey[Boolean] = settingKey("Whether to enable the Scala 2 inliner for Pekko modules." +
+    "Defaults to pekko.no.inline property")
+  lazy val pekkoInlineCoreProject: SettingKey[Boolean] = settingKey("Whether this is the core Pekko project or a Pekko module " +
+    "since the core Pekko project has different inline settings. Defaults to false")
+}