align with Spark scalastyle (#1606)

Signed-off-by: Peng Huo <penghuo@gmail.com>

Author: penghuo

.scalafmt.conf

@@ -2,16 +2,15 @@
 
 ## Scala Formatting Guidelines
 
-For Scala code, We use [scalafmt](https://scalameta.org/scalafmt/) to format the code and check the code style. 
 
-To use the plugin, user could check the style
+For Scala code, flint use [spark scalastyle](https://github.com/apache/spark/blob/master/scalastyle-config.xml). Before submitting the PR, 
+make sure to use "scalafmtAll" to format the code. read more in [scalafmt sbt](https://scalameta.org/scalafmt/docs/installation.html#sbt)
 ```
-sbt scalafmtCheck
+sbt scalafmtAll
 ```
-The code can be formatted with
+The code style is automatically checked, but users can also manually check it.
 ```
-sbt scalafmtAll
+sbt sbt scalastyle
 ```
-For more sbt tasks, read more in [scalafmt sbt](https://scalameta.org/scalafmt/docs/installation.html#sbt)
-
-For Intellij user, read more in [scalafmt IntelliJ](https://scalameta.org/scalafmt/docs/installation.html#intellij)
+For IntelliJ user, read more in [scalafmt IntelliJ](https://scalameta.org/scalafmt/docs/installation.html#intellij) to integrate 
+scalafmt with IntelliJ

DEVELOPER_GUIDE.md

@@ -5,33 +5,46 @@
 
 lazy val scala212 = "2.12.14"
 lazy val sparkVersion = "3.3.1"
+lazy val opensearchVersion = "2.6.0"
 
 ThisBuild / version := "0.1.0-SNAPSHOT"
 
 ThisBuild / scalaVersion := scala212
 
+ThisBuild / scalafmtConfig := baseDirectory.value / "dev/.scalafmt.conf"
+
+/**
+ * ScalaStyle configurations
+ */
+ThisBuild / scalastyleConfig := baseDirectory.value / "scalastyle-config.xml"
+
+// Run as part of compile task.
+lazy val compileScalastyle = taskKey[Unit]("compileScalastyle")
+
+// Run as part of test task.
+lazy val testScalastyle = taskKey[Unit]("testScalastyle")
+
+lazy val commonSettings = Seq(
+  // Scalastyle
+  scalastyleConfig := (ThisBuild / scalastyleConfig).value,
+  compileScalastyle := (Compile / scalastyle).toTask("").value,
+  Compile / compile := ((Compile / compile) dependsOn compileScalastyle).value,
+  testScalastyle := (Test / scalastyle).toTask("").value,
+  Test / test := ((Test / test) dependsOn testScalastyle).value)
+
 lazy val root = (project in file("."))
   .aggregate(flintCore, flintSparkIntegration)
-  .settings(
-    name := "flint"
-  )
+  .settings(name := "flint")
 
 lazy val flintCore = (project in file("flint-core"))
-  .settings(
-    name := "flint-core",
-    scalaVersion := scala212
-  )
+  .settings(name := "flint-core", scalaVersion := scala212)
 
 lazy val flintSparkIntegration = (project in file("flint-spark-integration"))
   .dependsOn(flintCore)
   .settings(
+    commonSettings,
     name := "flint-spark-integration",
     scalaVersion := scala212,
-    Compile / compile := (Compile / compile)
-      .dependsOn(Compile / scalafmtCheck)
-      .value,
     libraryDependencies ++= Seq(
       "org.apache.spark" %% "spark-core" % sparkVersion,
-      "org.apache.spark" %% "spark-sql" % sparkVersion
-    )
-  )
+      "org.apache.spark" %% "spark-sql" % sparkVersion))

build.sbt

@@ -0,0 +1,35 @@
+#
+# Copyright OpenSearch Contributors
+# SPDX-License-Identifier: Apache-2.0
+#
+
+version = 3.7.3
+
+# align with spark. https://github.com/apache/spark/blob/master/dev/.scalafmt.conf
+align = none
+align.openParenDefnSite = false
+align.openParenCallSite = false
+align.tokens = []
+importSelectors = "singleLine"
+optIn = {
+  configStyleArguments = false
+}
+danglingParentheses.preset = false
+docstrings.style = Asterisk
+maxColumn = 98
+runner.dialect = scala212
+
+# flint customized rules
+rewrite.rules = [Imports]
+rewrite.imports.sort = scalastyle
+# groups order
+# java
+# scala
+# 3rdParty
+# spark
+rewrite.imports.groups = [
+  ["javax?.*"],
+  ["scala\\..*"],
+  ["(?!org\\.apache\\.spark\\.).*"],
+  ["org\\.apache\\.spark\\..*"]
+]

dev/.scalafmt.conf

@@ -4,3 +4,5 @@
  */
 
 addSbtPlugin("org.scalameta" % "sbt-scalafmt" % "2.4.6")
+addSbtPlugin("org.scalastyle" %% "scalastyle-sbt-plugin" % "1.0.0")
+addSbtPlugin("com.lightbend.sbt" % "sbt-java-formatter" % "0.8.0")