Add transitiveClosure() to DynamicGraph.

modules/kobalt-plugin-api/src/main/kotlin/com/beust/kobalt/internal/DynamicGraph.kt

@@ -30,6 +30,28 @@ class DynamicGraph<T> {
     private val dependedUpon = HashMultimap.create<Node<T>, Node<T>>()
     private val dependingOn = HashMultimap.create<Node<T>, Node<T>>()
 
+    fun transitiveClosure(root: T): Set<T> {
+        val result = hashSetOf<T>()
+        val seen = hashSetOf<T>()
+        val toProcess = arrayListOf<T>().apply {
+            add(root)
+        }
+        while (toProcess.any()) {
+            val newToProcess = arrayListOf<T>()
+            toProcess.forEach {
+                if (! seen.contains(it)) {
+                    result.add(it)
+                    newToProcess.addAll(dependedUpon[Node(it)].map { it.value })
+                    seen.add(it)
+                }
+            }
+            toProcess.clear()
+            toProcess.addAll(newToProcess)
+        }
+
+        return result
+    }
+
     fun addNode(t: T) = synchronized(nodes) {
         nodes.add(Node(t))
     }

src/test/kotlin/com/beust/kobalt/internal/DynamicGraphTest.kt

@@ -2,6 +2,7 @@ package com.beust.kobalt.internal
 
 import com.beust.kobalt.misc.Topological
 import com.beust.kobalt.misc.log
+import org.assertj.core.api.Assertions.assertThat
 import org.testng.Assert
 import org.testng.annotations.Test
 import java.util.*
@@ -48,6 +49,21 @@ class DynamicGraphTest {
         }
     }
 
+    @Test
+    fun transitive() {
+        DynamicGraph<Int>().apply {
+            addEdge(1, 2)
+            addEdge(1, 3)
+            addEdge(2, 4)
+            addEdge(6, 7)
+            assertThat(transitiveClosure(1)).isEqualTo(setOf(1, 2, 3, 4))
+            assertThat(transitiveClosure(2)).isEqualTo(setOf(2, 4))
+            assertThat(transitiveClosure(3)).isEqualTo(setOf(3))
+            assertThat(transitiveClosure(6)).isEqualTo(setOf(6, 7))
+            assertThat(transitiveClosure(7)).isEqualTo(setOf(7))
+            println("done")
+        }
+    }
 
     @Test
     private fun testExecutorWithSkip() {