Read args from file, merge args and pass to the cmd.

zio-cli/shared/src/main/scala/zio/cli/CliApp.scala

@@ -8,6 +8,7 @@ import zio.cli.HelpDoc.Span.{code, text}
 import zio.cli.HelpDoc.{h1, p}
 import zio.cli.completion.{Completion, CompletionScript}
 import zio.cli.figlet.FigFont
+import java.nio.file.{Files, Paths}
 
 import scala.annotation.tailrec
 
@@ -56,6 +57,75 @@ object CliApp {
     def printDocs(helpDoc: HelpDoc): UIO[Unit] =
       printLine(helpDoc.toPlaintext(80)).!
 
+    def checkAndGetOptionsFilePaths(topLevelCommand: String): List[String] = {
+      val filename = s".$topLevelCommand"
+
+      val cwd        = java.lang.System.getProperty("user.dir")
+      val homeDirOpt = java.lang.System.getProperty("user.home")
+
+      def parentPaths(path: String): List[String] = {
+        val parts = path.split(java.io.File.separatorChar).filterNot(_.isEmpty)
+
+        (0 to parts.length)
+          .map(i =>
+            s"${java.io.File.separatorChar}${parts
+                .take(i)
+                .mkString(java.io.File.separator)}"
+          )
+          .toList
+      }
+
+      val paths        = parentPaths(cwd)
+      val pathsToCheck = homeDirOpt :: paths
+
+      val existingFiles = pathsToCheck.filter { path =>
+        val filePath = Paths.get(path, filename)
+        Files.exists(filePath)
+      }
+
+      // Print out the paths with existing files
+      existingFiles.foreach(println)
+
+      return existingFiles
+    }
+
+    def loadOptionsFromFile(
+      topLevelCommand: String
+    ): List[String] = {
+      // Get a list of file paths based on the top-level command
+      val filePaths = checkAndGetOptionsFilePaths(topLevelCommand)
+
+      // Read the contents of the files at the given file paths
+      val options: List[String] = filePaths.flatMap { filePath =>
+        val source = scala.io.Source.fromFile(filePath)
+        source.getLines().toList
+      }
+
+      //  Merges a list of options, removing any duplicate keys.
+      //  If there are options with the same keys but different values, it will use the value from the last option in the
+      //  list.
+      def mergeOptionsBasedOnPriority(options: List[String]): List[String] = {
+        val mergedOptions = options.flatMap { opt =>
+          opt.split('=') match {
+            case Array(key)        => Some(key -> None)
+            case Array(key, value) => Some(key -> value)
+            case _ =>
+              None // handles the case when there isn't exactly one '=' in the string
+          }
+        }.toMap.toList.map {
+          case (key, None)  => key
+          case (key, value) => s"$key=$value"
+        }
+
+        mergedOptions
+      }
+
+      // Merge the read options
+      val merged = mergeOptionsBasedOnPriority(options)
+
+      // Return the merged options
+      return merged
+    }
     def run(args: List[String]): ZIO[R, Any, Any] = {
       def executeBuiltIn(builtInOption: BuiltInOption): ZIO[R, Any, Any] =
         builtInOption match {
@@ -115,8 +185,9 @@ object CliApp {
           case Command.Subcommands(parent, _) => prefix(parent)
         }
 
+      val arg_from_config_files = loadOptionsFromFile(self.name)
       self.command
-        .parse(prefix(self.command) ++ args, self.config)
+        .parse(prefix(self.command) ++ arg_from_config_files ++ args, self.config)
         .foldZIO(
           e => printDocs(e.error) *> ZIO.fail(e),
           {