Add various helpers (#2)

Useful for Almond

Author: alexarchambault

directive-handler/src/main/scala/scala/cli/directivehandler/DirectiveHandler.scala

@@ -51,6 +51,26 @@ trait DirectiveHandler[+T] { self =>
           .map(_.map(f))
     }
 
+  def ignore: DirectiveHandler[IgnoredDirective] =
+    new DirectiveHandler[IgnoredDirective] {
+      def name: String                   = self.name
+      def description: String            = "[ignored]"
+      override def descriptionMd: String = "ignored"
+      def usage: String                  = ""
+      override def usageMd: String       = ""
+      override def examples: Seq[String] = Nil
+      override def tags: Seq[String]     = Nil
+
+      def keys: Seq[String] = self.keys
+
+      private lazy val fieldNames = keys.toSet
+
+      def handleValues(
+        scopedDirective: ScopedDirective
+      ): Either[DirectiveException, ProcessedDirective[IgnoredDirective]] =
+        Right(ProcessedDirective(Some(IgnoredDirective(scopedDirective)), Nil))
+    }
+
 }
 
 object DirectiveHandler extends DirectiveHandlerMacros {

directive-handler/src/main/scala/scala/cli/directivehandler/DirectiveHandlerMacros.scala2.scala

@@ -144,11 +144,7 @@ object DirectiveHandlerMacros {
                 valuesByScope
                   .map {
                     case (scopeOpt, values) =>
-                      parser.value.parse(
-                        scopedDirective.directive.values,
-                        scopedDirective.cwd,
-                        scopedDirective.maybePath
-                      ).map { r =>
+                      parser.value.parse(scopedDirective).map { r =>
                         scopeOpt -> (field[K](r) :: actualDefault(default).tail)
                       }
                   }

directive-handler/src/main/scala/scala/cli/directivehandler/DirectiveHandlerMacros.scala3.scala

@@ -280,11 +280,7 @@ object DirectiveHandlerMacros {
                   valuesByScope
                     .map {
                       case (scopeOpt, values) =>
-                        $parser.parse(
-                          $scopedDirective.directive.values,
-                          $scopedDirective.cwd,
-                          $scopedDirective.maybePath
-                        ).map { r =>
+                        $parser.parse($scopedDirective).map { r =>
                           scopeOpt -> ${
                             genNew(List(newArgs.updated(idx, '{ r }).map(_.asTerm)))
                               .asExprOf[T]

directive-handler/src/main/scala/scala/cli/directivehandler/DirectiveHandlers.scala

@@ -30,4 +30,15 @@ final case class DirectiveHandlers[T](handlers: Seq[DirectiveHandler[T]]) {
       .left.map(CompositeDirectiveException(_))
   }
 
+  def map[U](f: T => U): DirectiveHandlers[U] =
+    copy(handlers = handlers.map(_.map(f)))
+
+  def mapDirectives[U](f: DirectiveHandler[T] => DirectiveHandler[U]): DirectiveHandlers[U] =
+    copy(handlers = handlers.map(f))
+
+  def ++(other: DirectiveHandlers[T]): DirectiveHandlers[T] =
+    if (other.handlers.isEmpty) this
+    else if (handlers.isEmpty) other
+    else DirectiveHandlers(handlers ++ other.handlers)
+
 }

directive-handler/src/main/scala/scala/cli/directivehandler/DirectiveValueParser.scala

@@ -3,6 +3,14 @@ package scala.cli.directivehandler
 import com.virtuslab.using_directives.custom.model.{BooleanValue, EmptyValue, StringValue, Value}
 
 abstract class DirectiveValueParser[+T] {
+
+  def parse(scopedDirective: ScopedDirective): Either[DirectiveException, T] =
+    parse(
+      scopedDirective.directive.values,
+      scopedDirective.cwd,
+      scopedDirective.maybePath
+    )
+
   def parse(
     values: Seq[Value[_]],
     scopePath: ScopePath,
@@ -17,6 +25,8 @@ object DirectiveValueParser {
 
   private final class Mapped[T, +U](underlying: DirectiveValueParser[T], f: T => U)
       extends DirectiveValueParser[U] {
+    override def parse(scopedDirective: ScopedDirective): Either[DirectiveException, U] =
+      underlying.parse(scopedDirective).map(f)
     def parse(
       values: Seq[Value[_]],
       scopePath: ScopePath,

directive-handler/src/main/scala/scala/cli/directivehandler/IgnoredDirective.scala

@@ -0,0 +1,30 @@
+package scala.cli.directivehandler
+
+import com.virtuslab.using_directives.custom.model.Value
+
+final case class IgnoredDirective(directive: ScopedDirective)
+
+object IgnoredDirective {
+
+  implicit val valueParser: DirectiveValueParser[IgnoredDirective] =
+    new DirectiveValueParser[IgnoredDirective] {
+      override def parse(scopedDirective: ScopedDirective)
+        : Either[DirectiveException, IgnoredDirective] =
+        Right(IgnoredDirective(scopedDirective))
+      def parse(
+        values: Seq[Value[_]],
+        scopePath: ScopePath,
+        path: Either[String, os.Path]
+      ): Either[DirectiveException, IgnoredDirective] =
+        Right(
+          IgnoredDirective(
+            ScopedDirective(
+              StrictDirective("", values),
+              path,
+              scopePath
+            )
+          )
+        )
+    }
+
+}