From 6a3c9887c8ea05acea84b1c6285f5920940d0665 Mon Sep 17 00:00:00 2001
From: Eugene Yokota <eed3si9n@gmail.com>
Date: Sat, 11 May 2019 22:19:38 -0400
Subject: [PATCH] Reduce concurrency of scalafmtCheck

Ref https://github.com/scalameta/scalafmt/issues/1399
---
 build.sbt                       |  4 ++--
 project/FixScalafmtPlugin.scala | 23 +++++++++++++++++++++++
 2 files changed, 25 insertions(+), 2 deletions(-)
 create mode 100644 project/FixScalafmtPlugin.scala

diff --git a/build.sbt b/build.sbt
index bb6b63d8d8..5433cb5452 100644
--- a/build.sbt
+++ b/build.sbt
@@ -27,8 +27,8 @@ ThisBuild / version := {
   }
 }
 ThisBuild / licenses := List(("Apache-2.0", url("https://www.apache.org/licenses/LICENSE-2.0")))
-ThisBuild / scalafmtOnCompile := true
-ThisBuild / Test / scalafmtOnCompile := true
+ThisBuild / scalafmtOnCompile := !(Global / insideCI).value
+ThisBuild / Test / scalafmtOnCompile := !(Global / insideCI).value
 
 def buildLevelSettings: Seq[Setting[_]] = Seq(
   // https://github.com/sbt/sbt-git/issues/109
diff --git a/project/FixScalafmtPlugin.scala b/project/FixScalafmtPlugin.scala
new file mode 100644
index 0000000000..35291e473f
--- /dev/null
+++ b/project/FixScalafmtPlugin.scala
@@ -0,0 +1,23 @@
+import sbt._
+import Keys._
+import org.scalafmt.sbt.ScalafmtPlugin
+import ScalafmtPlugin.autoImport._
+
+object FixScalafmtPlugin extends AutoPlugin {
+  override def requires = ScalafmtPlugin
+  override def trigger = allRequirements
+
+  val ScalaFmtTag = ConcurrentRestrictions.Tag("scalafmt")
+
+  override def globalSettings: Seq[Def.Setting[_]] =
+    Seq(
+      concurrentRestrictions += Tags.limit(ScalaFmtTag, 1)
+    )
+
+  override def projectSettings: Seq[Def.Setting[_]] =
+    Seq(
+      scalafmtCheckAll := (scalafmtCheckAll.tag(ScalaFmtTag)).value,
+      Compile / scalafmtCheck := ((Compile / scalafmtCheck).tag(ScalaFmtTag)).value,
+      Test / scalafmtCheck := ((Test / scalafmtCheck).tag(ScalaFmtTag)).value,
+    )
+}