Mask forward slashes in cross values to fix their cache locations (#2986

)

Fix: #2835

Pull request: #2986

main/eval/src/mill/eval/EvaluatorPaths.scala

@@ -53,6 +53,8 @@ object EvaluatorPaths {
   private val Colon = "[:]".r
   // Dollar sign `$` is our masking-character
   private val Dollar = "[$]".r
+  // Forward-slashed are reserved for directory delimiters
+  private val Slash = "/".r
 
   private val steps: Seq[String => String] = Seq(
     // Step 1: mask all existing dollar signs, so we can use the dollar as masking character
@@ -63,7 +65,9 @@ object EvaluatorPaths {
       case s => s
     },
     // Step 3: Replace colon (:) with $colon
-    s => Colon.replaceAllIn(s, Matcher.quoteReplacement("$colon"))
+    s => Colon.replaceAllIn(s, Matcher.quoteReplacement("$colon")),
+    // Step 4: Replace slash (/) with $slash
+    s => Slash.replaceAllIn(s, Matcher.quoteReplacement("$slash"))
   )
 
   def sanitizePathSegment(segment: String): os.PathChunk = {

main/eval/test/src/mill/eval/EvaluatorPathsTests.scala

@@ -6,7 +6,7 @@ object EvaluatorPathsTests extends TestSuite {
 
   override def tests: Tests = Tests {
     "sanitizedPathSegment" - {
-      "WindowsReservedNames" - {
+      "mask-reserved-chars-and-names" - {
         val replace = Seq(
           // reserved file names under Windows
           "com1.json" -> "com1~.json",
@@ -16,7 +16,9 @@ object EvaluatorPathsTests extends TestSuite {
           // do not collide with the applied `$`-masking character
           "a$colonb" -> "a$$colonb",
           // replace not just the first $
-          "a$$b" -> "a$$$$b"
+          "a$$b" -> "a$$$$b",
+          // replace a forward slash,
+          "a/b" -> "a$slashb"
         )
         val noReplace = Seq(
           "con10.json"