improve error message if channel build randomly fails

This also improves error message in case input directory does not exist.

Additionally, this prevents an error in case an empty channel is built.

(resolves #6)

CHANGELOG.md

@@ -2,6 +2,9 @@
 
 ## [Unreleased]
 
+### Changed
+- improved error message if channel-build fails randomly in case old files could not be removed
+
 
 ## [0.4.5] - 2024-10-17
 ### Fixed

src/main/scala/sc4pac/ChannelUtil.scala

@@ -180,18 +180,31 @@ object ChannelUtil {
 
       // Finally, we are sure that everything was formatted correctly, so we can
       // move the temp folder to its final destination.
-      os.move.over(tempJsonDir / "metadata", outputDir / "metadata", createFolders = true)
+      try {
+        if (packages.nonEmpty) {  // otherwise metadata folder does not exist (we still want channel contents file though)
+          os.move.over(tempJsonDir / "metadata", outputDir / "metadata", createFolders = true)
+        }
+      } catch {
+        case e: java.nio.file.DirectoryNotEmptyException =>
+          throw new error.FileOpsFailure(
+            s"""Failed to overwrite folder ${outputDir / "metadata"}. If the problem persists, delete it manually and try again.""")
+      }
       os.move.over(tempJsonDir / JsonRepoUtil.channelContentsFilename, outputDir / JsonRepoUtil.channelContentsFilename, createFolders = true)
       System.err.println(s"Successfully wrote channel contents of ${packagesMap.size} packages and assets.")
     }
 
     val packagesTask: Task[Seq[JD.PackageAsset]] =
       ZIO.foreach(inputDirs) { inputDir =>
-        ZIO.foreach(os.walk.stream(inputDir).filter(_.last.endsWith(".yaml")).toSeq) { path =>
-          readAndParsePkgData(path, root = Some(inputDir))
-        }.map(_.flatten)
-      }.map(_.flatten)
-      .mapError(error.YamlFormatIssue(_))
+        ZIO.ifZIO(ZIO.attemptBlockingIO(os.exists(inputDir)))(
+          onFalse = ZIO.fail(new error.FileOpsFailure(s"$inputDir does not exist.")),
+          onTrue = ZIO.foreach(os.walk.stream(inputDir).filter(_.last.endsWith(".yaml")).toSeq) { path =>
+            readAndParsePkgData(path, root = Some(inputDir))
+          }.map(_.flatten)
+        )
+      }.map(_.flatten).mapError {
+        case errStr: String => error.YamlFormatIssue(errStr)
+        case e: java.io.IOException => e
+      }
 
     // result
     ZIO.blocking {

src/main/scala/sc4pac/cli.scala

@@ -53,6 +53,7 @@ object Commands {
         case abort: error.Sc4pacTimeout => { System.err.println(Array("Operation aborted.", abort.getMessage).mkString(" ")); exit(1) }
         case abort: error.Sc4pacNotInteractive => { System.err.println(s"Operation aborted as terminal is non-interactive: ${abort.getMessage}"); exit(1) }
         case abort: error.SymlinkCreationFailed => { System.err.println(s"Operation aborted. ${abort.getMessage}"); exit(1) }  // channel-build command
+        case abort: error.FileOpsFailure => { System.err.println(s"Operation aborted. ${abort.getMessage}"); exit(1) }  // channel-build command
         case abort: error.YamlFormatIssue => { System.err.println(s"Operation aborted. ${abort.getMessage}"); exit(1) }  // channel-build command
         case e => { e.printStackTrace(); exit(2) }
       },

src/main/scala/sc4pac/error.scala

@@ -32,4 +32,6 @@ final class NoChannelsAvailable(val title: String, val detail: String) extends j
 
 final class SymlinkCreationFailed(msg: String) extends java.io.IOException(msg) with Sc4pacErr
 
+final class FileOpsFailure(msg: String) extends java.io.IOException(msg) with Sc4pacErr
+
 final class YamlFormatIssue(msg: String) extends java.io.IOException(msg) with Sc4pacErr