Fix deleting/renaming resources

Previously this would have no effect on the program. With this commit a
mapping feature was introduced to resources, which remembers from where
a resource file originates.

An integration test for the issue was also added.

Author: jchyb

modules/build/src/main/scala/scala/build/Build.scala

@@ -16,6 +16,7 @@ import scala.build.Ops.*
 import scala.build.compiler.{ScalaCompiler, ScalaCompilerMaker}
 import scala.build.errors.*
 import scala.build.internal.{Constants, CustomCodeWrapper, MainClass, Util}
+import scala.build.internal.resource.ResourceMapper
 import scala.build.options.*
 import scala.build.options.validation.ValidationException
 import scala.build.postprocessing.*
@@ -392,9 +393,9 @@ object Build {
 
     val builds = value(buildScopes())
 
-    copyResourceToClassesDir(builds.main)
+    ResourceMapper.copyResourceToClassesDir(builds.main)
     for (testBuild <- builds.get(Scope.Test))
-      copyResourceToClassesDir(testBuild)
+      ResourceMapper.copyResourceToClassesDir(testBuild)
 
     if (actionableDiagnostics.getOrElse(false)) {
       val projectOptions = builds.get(Scope.Test).getOrElse(builds.main).options
@@ -404,26 +405,6 @@ object Build {
     builds
   }
 
-  private def copyResourceToClassesDir(build: Build): Unit = build match {
-    case b: Build.Successful =>
-      for {
-        resourceDirPath  <- b.sources.resourceDirs.filter(os.exists(_))
-        resourceFilePath <- os.walk(resourceDirPath).filter(os.isFile(_))
-        relativeResourcePath = resourceFilePath.relativeTo(resourceDirPath)
-        // dismiss files generated by scala-cli
-        if !relativeResourcePath.startsWith(os.rel / Constants.workspaceDirName)
-      } {
-        val destPath = b.output / relativeResourcePath
-        os.copy(
-          resourceFilePath,
-          destPath,
-          replaceExisting = true,
-          createFolders = true
-        )
-      }
-    case _ =>
-  }
-
   private def build(
     inputs: Inputs,
     sources: Sources,
@@ -482,6 +463,13 @@ object Build {
   def classesDir(root: os.Path, projectName: String, scope: Scope, suffix: String = ""): os.Path =
     classesRootDir(root, projectName) / s"${scope.name}$suffix"
 
+  def resourcesRegistry(
+    root: os.Path,
+    projectName: String,
+    scope: Scope
+  ): os.Path =
+    root / Constants.workspaceDirName / projectName / s"resources-${scope.name}"
+
   def scalaNativeSupported(
     options: BuildOptions,
     inputs: Inputs

modules/build/src/main/scala/scala/build/internal/resource/ResourceMapper.scala

@@ -0,0 +1,69 @@
+package scala.build.internal.resource
+
+import scala.build.Build
+import scala.build.internal.Constants
+
+object ResourceMapper {
+
+  private def resourceMapping(build: Build.Successful): Map[os.Path, os.RelPath] = {
+    val seq = for {
+      resourceDirPath  <- build.sources.resourceDirs.filter(os.exists(_))
+      resourceFilePath <- os.walk(resourceDirPath).filter(os.isFile(_))
+      relativeResourcePath = resourceFilePath.relativeTo(resourceDirPath)
+      // dismiss files generated by scala-cli
+      if !relativeResourcePath.startsWith(os.rel / Constants.workspaceDirName)
+    } yield (resourceFilePath, relativeResourcePath)
+
+    seq.toMap
+  }
+
+  def copyResourcesToDirWithMapping(
+    output: os.Path,
+    registryFilePath: os.Path,
+    newMapping: Map[os.Path, os.RelPath]
+  ): Unit = {
+
+    val oldRegistry =
+      if (os.exists(registryFilePath))
+        os.read(registryFilePath)
+          .linesIterator
+          .filter(_.nonEmpty)
+          .map(os.RelPath(_))
+          .toSet
+      else
+        Set.empty
+    val removedFiles = oldRegistry -- newMapping.values
+
+    for (f <- removedFiles)
+      os.remove(output / f)
+
+    for ((inputPath, outputPath) <- newMapping)
+      os.copy(
+        inputPath,
+        output / outputPath,
+        replaceExisting = true,
+        createFolders = true
+      )
+
+    if (newMapping.isEmpty)
+      os.remove(registryFilePath)
+    else
+      os.write.over(
+        registryFilePath,
+        newMapping.map(_._2.toString).toVector.sorted.mkString("\n")
+      )
+  }
+
+  /** Copies and maps resources from their original path to the destination path in build output,
+    * also caching output paths in a file.
+    *
+    * Remembering the mapping this way allows for the resource to be removed if the original file is
+    * renamed/deleted.
+    */
+  def copyResourceToClassesDir(build: Build): Unit = build match {
+    case b: Build.Successful =>
+      val fullFilePath = Build.resourcesRegistry(b.inputs.workspace, b.inputs.projectName, b.scope)
+      copyResourcesToDirWithMapping(b.output, fullFilePath, resourceMapping(b))
+    case _ =>
+  }
+}

modules/integration/src/test/scala/scala/cli/integration/RunTestDefinitions.scala

@@ -2096,6 +2096,42 @@ abstract class RunTestDefinitions(val scalaVersionOpt: Option[String])
     }
   }
 
+  test("deleting resources after building") {
+    val projectDir      = "projectDir"
+    val fileName        = "main.scala"
+    val resourceContent = "hello world"
+    val resourcePath    = os.rel / projectDir / "resources" / "test.txt"
+    val inputs = TestInputs(
+      os.rel / projectDir / fileName ->
+        s"""
+           |//> using resourceDir "resources"
+           |
+           |object Main {
+           |  def main(args: Array[String]) = {
+           |    val inputStream = getClass().getResourceAsStream("/test.txt")
+           |    if (inputStream == null) println("null")
+           |    else println("non null")
+           |  }
+           |}
+           |""".stripMargin,
+      resourcePath -> resourceContent
+    )
+
+    inputs.fromRoot { root =>
+      def runCli() =
+        os.proc(TestUtil.cli, extraOptions, projectDir)
+          .call(cwd = root)
+          .out.trim()
+
+      val output1 = runCli()
+      expect(output1 == "non null")
+
+      os.remove(root / resourcePath)
+      val output2 = runCli()
+      expect(output2 == "null")
+    }
+  }
+
   private def maybeScalapyPrefix =
     if (actualScalaVersion.startsWith("2.13.")) ""
     else "import me.shadaj.scalapy.py" + System.lineSeparator()