Fix links to parent packages

Author: romanowski

scala3doc/src/dotty/dokka/site/StaticSiteLocationProvider.scala

@@ -112,15 +112,10 @@ class StaticSiteLocationProvider(pageNode: RootPageNode)(using ctx: DokkaContext
     override def pathTo(node: PageNode, context: PageNode): String =
       if node == context then ""
       else
-        val nodePaths = getPathsIndex.get(node).asScala
-        val contextPaths = Option(context).fold(Nil)(getPathsIndex.get(_).asScala.dropRight(1))
-        val commonPaths = nodePaths.zip(contextPaths).takeWhile{ case (a, b) => a == b }.size
+        val nodePaths = getPathsIndex.get(node).asScala.toList
+        val contextPaths = Option(context).fold(Nil)(getPathsIndex.get(_).asScala).toList
+        relativePath(contextPaths, nodePaths)
 
-        val contextPath = contextPaths.drop(commonPaths).map(_ => "..")
-        val nodePath = nodePaths.drop(commonPaths) match
-            case l if l.isEmpty => Seq("index")
-            case l => l
-        (contextPath ++ nodePath).mkString("/")
 
     val externalLocationProviders: List[(List[Regex], ExternalLocationProvider)] =
       val sourceSet = ctx.getConfiguration.getSourceSets.asScala(0)
@@ -155,4 +150,15 @@ class StaticSiteLocationProvider(pageNode: RootPageNode)(using ctx: DokkaContext
           regexes.exists(r => r.matches(path))
         }.fold(null)(_(1).resolve(dri.withNoOrigin))
         case None => null
-      }
+      }
+
+def relativePath(fullFrom: Seq[String], to: Seq[String]): String =
+  val from = fullFrom.dropRight(1)
+  val commonPaths = to.zip(from).takeWhile{ case (a, b) => a == b }.size
+
+  val contextPath = from.drop(commonPaths).map(_ => "..")
+  val nodePath = to.drop(commonPaths) match
+      case Nil if contextPath.isEmpty && to.nonEmpty=> Seq("..", to.last)
+      case Nil => Seq("index")
+      case l => l
+  (contextPath ++ nodePath).mkString("/")

scala3doc/test/dotty/dokka/site/RelativeLinksTests.scala

@@ -0,0 +1,24 @@
+package dotty.dokka.site
+
+import org.junit.Test
+import org.junit.Assert._
+
+class RelativePathsLink:
+
+  @Test
+  def testLinks() =
+    def path(from: String, to: String) =
+      relativePath(from.split('/').toList, to.split('/').toList)
+
+    assertEquals(relativePath(Nil, Seq("a", "b")), "a/b")
+
+    assertEquals(
+      path("api/dotty/dokka/tasty/comments/wiki", "api/dotty/dokka/tasty/comments"),
+      "../comments"
+    )
+
+    assertEquals(
+      path("api/dotty/dokka/tasty/comments/wiki", "api/index"),
+      "../../../../index"
+    )
+