Need a way to customize fail behavior in menus/param menus

web/webkit/src/main/scala/net/liftweb/sitemap/Loc.scala

@@ -383,14 +383,12 @@ trait Loc[T] {
   }
 
   def doesMatch_?(req: Req): Boolean = {
-    (if (link.isDefinedAt(req)) {
-      link(req) match {
-        case Full(x) if testAllParams(allParams, req) => x
-        case Full(x) => false
-        case x => x.openOr(false)
-      }
-    } else false) && currentValue.isDefined
-    // the loc only matches if we've got a current value
+    link.isDefinedAt(req) &&
+    testAllParams(allParams, req) &&
+    (
+      currentValue.isDefined ||
+      params.contains(Loc.MatchWithoutCurrentValue)
+    )
   }
 
   def breadCrumbs: List[Loc[_]] = _menu.breadCrumbs ::: List(this)
@@ -736,6 +734,27 @@ object Loc {
    */
   case object Hidden extends AnyLocParam
 
+  /**
+   * If this parameter is included, the Loc will continue to execute even if
+   * currentValue is not defined.
+   *
+   * By default, Lift will determine that a Loc does not match a given request
+   * if its currentValue comes up Empty, and as a result will return an HTTP 404.
+   * For situations where this is not the desired, "Not Found" behavior, you can
+   * add the MatchWithoutCurrentValue LocParam to a Loc, then use the IfValue
+   * LocParam to define what should happen when the currentValue is Empty.
+   *
+   * For example, given some class Thing, you could do the following to trigger
+   * a redirect when a Thing with a particular ID isn't found.
+   *
+   * {{{
+   * Menu.param[Thing]("Thing", "Thing", Thing.find(_), _.id) >>
+   *   MatchWithoutCurrentValue >>
+   *   IfValue(_.isDefined, () => RedirectResponse("/page/to/redirect/to"))
+   * }}}
+   */
+  case object MatchWithoutCurrentValue extends AnyLocParam
+
   /**
    * If this is a submenu, use the parent Loc's params
    */

web/webkit/src/test/scala/net/liftweb/sitemap/LocSpec.scala

@@ -18,6 +18,10 @@ package net.liftweb
 package sitemap
 
 import common._
+import mockweb._
+  import MockWeb._
+import mocks._
+
 import org.specs2.mutable.Specification
 
 
@@ -40,6 +44,34 @@ object LocSpec extends Specification  {
       val loc = (Menu.param[Param]("Test", "Test", s => Full(Param(s)), p => p.s) / "foo" / "bar" / *).toLoc
       loc.calcHref(Param("myparam")) mustEqual "/foo/bar/myparam"
     }
+
+    "should not match a Req matching its Link when currentValue is Empty" in {
+      val testMenu = Menu.param[Param]("Test", "Test", s => Empty, p => "bacon") / "foo" / "bar" / *
+      val testSiteMap = SiteMap(testMenu)
+
+      val testLoc = testMenu.toLoc
+      val mockReq = new MockHttpServletRequest("http://test/foo/bar/123")
+
+      testS(mockReq) {
+        testReq(mockReq) { req =>
+          testLoc.doesMatch_?(req) mustEqual false
+        }
+      }
+    }
+
+    "should match a Req matching its Link when currentValue is Empty and MatchWithoutCurrentValue is a param" in {
+      val testMenu = Menu.param[Param]("Test", "Test", s => Empty, p => "bacon") / "foo" / "bar" / * >> Loc.MatchWithoutCurrentValue
+      val testSiteMap = SiteMap(testMenu)
+
+      val testLoc = testMenu.toLoc
+      val mockReq = new MockHttpServletRequest("http://test/foo/bar/123")
+
+      testS(mockReq) {
+        testReq(mockReq) { req =>
+          testLoc.doesMatch_?(req) mustEqual true
+        }
+      }
+    }
   }
 }