Add beforeStart and afterComplete methods on Rule

Rules can then implement initialisation and cleanup behaviours before and after
all semantic documents have been seen.

Author: rorygraves

scalafix-cli/src/main/scala/scalafix/internal/v1/MainOps.scala

@@ -264,6 +264,9 @@ object MainOps {
     val N = files.length
     val width = N.toString.length
     var exit = ExitStatus.Ok
+
+    args.rules.rules.foreach(_.beforeStart())
+
     files.foreach { file =>
       if (args.args.verbose) {
         val message = s"Processing (%${width}s/%s) %s".format(i, N, file)
@@ -273,6 +276,9 @@ object MainOps {
       val next = handleFile(args, file)
       exit = ExitStatus.merge(exit, next)
     }
+
+    args.rules.rules.foreach(_.afterComplete())
+
     adjustExitCode(args, exit, files)
   }
 

scalafix-core/src/main/scala/scalafix/v1/Rule.scala

@@ -34,6 +34,17 @@ abstract class Rule(val name: RuleName) {
    * on the website.
    */
   def isExperimental: Boolean = false
+
+  /**
+   * Called before the rule starts processing documents
+   */
+  def beforeStart(): Unit = {}
+
+  /**
+   * Called after all documents have been processed
+   */
+  def afterComplete(): Unit = {}
+
 }
 
 abstract class SyntacticRule(name: RuleName) extends Rule(name) {

scalafix-testkit/src/main/scala/scalafix/testkit/SemanticRuleSuite.scala

@@ -41,8 +41,9 @@ abstract class SemanticRuleSuite(val props: TestkitProperties)
   def runOn(diffTest: RuleTest): Unit = {
     test(diffTest.path.testName) {
       val (rule, sdoc) = diffTest.run.apply()
+      rule.rules.foreach(_.beforeStart())
       val (fixed, messages) = rule.semanticPatch(sdoc, suppress = false)
-
+      rule.rules.foreach(_.afterComplete())
       val tokens = fixed.tokenize.get
       val obtained = SemanticRuleSuite.stripTestkitComments(tokens)
       val expected = diffTest.path.resolveOutput(props) match {