From 8ff37a341cf66621d9d74609d08335ca52dc7d7d Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Se=CC=81bastien=20Boulet?= <sebastien.boulet@teads.tv>
Date: Thu, 18 Feb 2021 17:16:36 +0100
Subject: [PATCH] Machine-independent args cache

Stamps scalafix arguments using a hash of the files instead of
relying on the lastMofified property in order to produce a
machine-independent "args" cache.
---
 src/main/scala/scalafix/sbt/ScalafixPlugin.scala | 14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)

diff --git a/src/main/scala/scalafix/sbt/ScalafixPlugin.scala b/src/main/scala/scalafix/sbt/ScalafixPlugin.scala
index e5e588dc..46347b10 100644
--- a/src/main/scala/scalafix/sbt/ScalafixPlugin.scala
+++ b/src/main/scala/scalafix/sbt/ScalafixPlugin.scala
@@ -492,7 +492,7 @@ object ScalafixPlugin extends AutoPlugin {
                 case jar =>
                   Seq(jar)
               }
-            write(files.map(FileInfo.lastModified.apply))
+            write(files.map(stampFile))
             write(customDependencies.map(_.toString))
           case Arg.Rules(rules) =>
             rules.foreach {
@@ -509,10 +509,10 @@ object ScalafixPlugin extends AutoPlugin {
           case Arg.Config(maybeFile) =>
             maybeFile match {
               case Some(path) =>
-                write(FileInfo.lastModified(path.toFile))
+                write(stampFile(path.toFile))
               case None =>
                 val defaultConfigFile = file(".scalafix.conf")
-                write(FileInfo.lastModified(defaultConfigFile))
+                write(stampFile(defaultConfigFile))
             }
           case Arg.ParsedArgs(args) =>
             val cacheKeys = args.filter {
@@ -535,6 +535,14 @@ object ScalafixPlugin extends AutoPlugin {
           case Arg.NoCache =>
             throw StampingImpossible
         }
+
+        def stampFile(file: File): Array[Byte] = {
+          // ensure the file exists and is not a directory
+          if (file.isFile)
+            Hash(file)
+          else
+            Array.empty[Byte]
+        }
       }
 
       def diffWithPreviousRuns[T](f: (Boolean, Set[File]) => T): T = {