add transitive ordering constraint example

Author: liufengyun

compiler/src/dotty/tools/dotc/plugins/Plugins.scala

@@ -194,7 +194,7 @@ object Plugins {
        """.stripMargin
     )
 
-    // propagate transitive constraints from related phases to current phase: transitivity
+    // propagate constraints from related phases to current phase: transitivity
     def propagate(phase: Phase): OrderingReq = {
       def propagateRunsBefore(beforePhase: Class[_]): Set[Class[_]] =
         if (beforePhase == phase.getClass)
@@ -221,8 +221,6 @@ object Plugins {
       runsAfter  = runsAfter.flatMap(propagateRunsAfter)
       runsBefore = runsBefore.flatMap(propagateRunsBefore)
 
-      // orderRequirements.update(phase.getClass, (runsBefore, runsAfter) )
-
       (runsAfter, runsBefore)
     }
 

compiler/test/dotty/tools/dotc/plugins/PluginsTest.scala

@@ -5,6 +5,7 @@ import org.junit.Test
 import dotty.tools.dotc._
 import plugins._
 import transform.MegaPhase.MiniPhase
+import core.Phases.Phase
 
 class PluginsTest {
   class TestPhase extends PluginPhase { def phaseName = this.getClass.getName }
@@ -38,6 +39,10 @@ class PluginsTest {
 
   def classOfPhase(p: PluginPhase): Class[_ <: PluginPhase] = p.getClass.asInstanceOf[Class[_ <: PluginPhase]]
 
+  def debugPlan(plan: List[List[Phase]]): Unit = {
+    println(plan.mkString("plan:\n- ", "\n- ", ""))
+  }
+
   @Test
   def insertAfter = {
     object M1 extends TestPhase {
@@ -172,6 +177,34 @@ class PluginsTest {
     assert(updatedPlan2(5)(0) eq M2)
   }
 
+  @Test
+  def orderingTransitive = {
+    object M1 extends TestPhase {
+      override val runsAfter = Set(classOf[P3d])
+      override val runsBefore = Set(classOfPhase(M2), classOf[P7])
+    }
+    object M2 extends TestPhase {
+      override val runsAfter = Set(classOf[P3d])
+      override val runsBefore = Set(classOf[P5], classOf[P8])
+    }
+    object M3 extends TestPhase {
+      override val runsAfter = Set(classOfPhase(M2), classOf[P2])
+      override val runsBefore = Set(classOf[P4], classOf[P8])
+    }
+
+    // M1 inserted to plan first
+    val updatedPlan1 = Plugins.schedule(basicPlan, M1 :: M2 :: M3 :: Nil)
+    assert(updatedPlan1(3)(0) eq M1)
+    assert(updatedPlan1(4)(0) eq M2)
+    assert(updatedPlan1(5)(0) eq M3)
+
+    // M2 inserted to plan first
+    val updatedPlan2 = Plugins.schedule(basicPlan, M2 :: M1 :: M3 :: Nil)
+    assert(updatedPlan1(3)(0) eq M1)
+    assert(updatedPlan1(4)(0) eq M2)
+    assert(updatedPlan1(5)(0) eq M3)
+  }
+
 
   @Test
   def deterministic = {