Generate the `Segments` list at definition time rather than discovery time, by propagating implicits throughout the tree of nested `mill.Module`s

This currently adds some annoying boilerplate to the definition of cross/abstract modules, which can probably be removed using Macros.

The `Segments` mapping generated by discovery is still present and used in a few places, though it will be removed

9 files changed, 33 insertions, 39 deletions

diff --git a/core/src/test/scala/mill/define/GraphTests.scala b/core/src/test/scala/mill/define/GraphTests.scala
index a850a0d2..718fd673 100644
--- a/core/src/test/scala/mill/define/GraphTests.scala
+++ b/core/src/test/scala/mill/define/GraphTests.scala
@@ -157,7 +157,7 @@ object GraphTests extends TestSuite{
           Graph.transitiveTargets(OSet.from(goals))
         )
         val grouped = Graph.groupAroundImportantTargets(topoSorted) {
-          case t: NamedTask[Any] if mapping.modulesToPaths.contains(t.owner) => t
+          case t: NamedTask[Any] => t
           case t if goals.contains(t) => t
         }
         grouped.keyCount
diff --git a/core/src/test/scala/mill/define/MacroErrorTests.scala b/core/src/test/scala/mill/define/MacroErrorTests.scala
index 90d4e65a..a389feaa 100644
--- a/core/src/test/scala/mill/define/MacroErrorTests.scala
+++ b/core/src/test/scala/mill/define/MacroErrorTests.scala
@@ -30,7 +30,9 @@ object MacroErrorTests extends TestSuite{
             }
           }
         """)
-        assert(e.msg.contains("required: mill.define.Module"))
+        assert(e.msg.contains(
+          "Modules, Targets and Commands can only be defined within a mill Module")
+        )
       }
       'neg - {
 
@@ -72,7 +74,9 @@ object MacroErrorTests extends TestSuite{
             def down = T{ TestUtil.test(left, right) }
           }
         """)
-        assert(borkedCachedDiamond1.msg.contains("required: mill.Module"))
+        assert(borkedCachedDiamond1.msg.contains(
+          "Modules, Targets and Commands can only be defined within a mill Module")
+        )
       }
     }
   }
diff --git a/core/src/test/scala/mill/discover/ConsistencyTests.scala b/core/src/test/scala/mill/discover/ConsistencyTests.scala
index ae66b199..47eb14ce 100644
--- a/core/src/test/scala/mill/discover/ConsistencyTests.scala
+++ b/core/src/test/scala/mill/discover/ConsistencyTests.scala
@@ -1,7 +1,7 @@
 package mill.discover
 
 
-import mill.discover.Mirror.Segment.Label
+import mill.define.Segment.Label
 import mill.util.TestGraphs
 import utest._
 
diff --git a/core/src/test/scala/mill/discover/CrossModuleTests.scala b/core/src/test/scala/mill/discover/CrossModuleTests.scala
index 6ae3d622..7f5cb89c 100644
--- a/core/src/test/scala/mill/discover/CrossModuleTests.scala
+++ b/core/src/test/scala/mill/discover/CrossModuleTests.scala
@@ -2,8 +2,8 @@ package mill.discover
 
 import mill.{Module, T}
 import mill.define.Cross
-import mill.discover.Mirror.Segment
-import mill.discover.Mirror.Segment.Label
+import mill.define.Segment
+import mill.define.Segment.Label
 import mill.util.TestUtil.test
 import utest._
 import mill.util.TestGraphs._
@@ -15,7 +15,7 @@ object CrossModuleTests extends TestSuite{
     'cross - {
       object outer extends TestUtil.BaseModule {
         object crossed extends mill.CrossModule(CrossedModule, "2.10.6", "2.11.8", "2.12.4")
-        case class CrossedModule(n: String) extends Module{
+        case class CrossedModule(n: String, ctx0: Module.Ctx) extends Module()(ctx0){
           def scalaVersion = n
         }
       }
@@ -43,7 +43,7 @@ object CrossModuleTests extends TestSuite{
           if !(platform == "native0.3" && scalaVersion == "2.10.6")
         } yield (platform, scalaVersion)
         object crossed extends mill.CrossModule2(CrossModule, crossMatrix:_*)
-        case class CrossModule(platform: String, scalaVersion: String) extends mill.Module{
+        case class CrossModule(platform: String, scalaVersion: String, ctx0: Module.Ctx) extends mill.Module()(ctx0){
           def suffix = Seq(scalaVersion, platform).filter(_.nonEmpty).map("_"+_).mkString
         }
       }
diff --git a/core/src/test/scala/mill/discover/DiscoveredTests.scala b/core/src/test/scala/mill/discover/DiscoveredTests.scala
index d141352e..83c92adc 100644
--- a/core/src/test/scala/mill/discover/DiscoveredTests.scala
+++ b/core/src/test/scala/mill/discover/DiscoveredTests.scala
@@ -5,7 +5,7 @@ import java.io.InputStreamReader
 import ammonite.main.Router.{ArgSig, EntryPoint}
 import utest._
 import mill.{Module, T}
-import mill.discover.Mirror.Segment.Label
+import mill.define.Segment.Label
 import mill.util.TestGraphs.{TraitWithModuleObject, nestedModule}
 import mill.util.TestUtil
 object DiscoveredTests extends TestSuite{
diff --git a/core/src/test/scala/mill/discover/LabelingTests.scala b/core/src/test/scala/mill/discover/LabelingTests.scala
index 595d3ad9..d1ac0536 100644
--- a/core/src/test/scala/mill/discover/LabelingTests.scala
+++ b/core/src/test/scala/mill/discover/LabelingTests.scala
@@ -1,10 +1,10 @@
 package mill.discover
 
-import mill.define.Task
+import mill.define.{Segment, Task}
 import mill.util.TestGraphs
 import utest._
 import Discovered.mapping
-import mill.discover.Mirror.Segment.Label
+import mill.define.Segment.Label
 object LabelingTests extends TestSuite{
 
   val tests = Tests{
@@ -16,7 +16,7 @@ object LabelingTests extends TestSuite{
       def check(mapping: Discovered.Mapping[_], t: Task[_], relPath: Option[String]) = {
 
 
-        val names: Seq[(Task[_], Seq[Mirror.Segment])] = mapping.targetsToSegments.toSeq
+        val names: Seq[(Task[_], Seq[Segment])] = mapping.targetsToSegments.toSeq
         val nameMap = names.toMap
 
         val targetLabel = nameMap.get(t).map(_.map{case Label(v) => v}.mkString("."))
diff --git a/core/src/test/scala/mill/main/MainTests.scala b/core/src/test/scala/mill/main/MainTests.scala
index 320731fa..013729ff 100644
--- a/core/src/test/scala/mill/main/MainTests.scala
+++ b/core/src/test/scala/mill/main/MainTests.scala
@@ -1,7 +1,7 @@
 package mill.main
 
 import mill.Module
-import mill.define.Task
+import mill.define.{Segment, Task}
 import mill.discover.{Discovered, Mirror}
 import mill.util.TestGraphs._
 import mill.util.TestUtil.test
@@ -14,7 +14,7 @@ object MainTests extends TestSuite{
 
     val resolved = for{
       args <- mill.main.RunScript.parseArgs(selectorString)
-      val crossSelectors = args.map{case Mirror.Segment.Cross(x) => x.toList.map(_.toString) case _ => Nil}
+      val crossSelectors = args.map{case Segment.Cross(x) => x.toList.map(_.toString) case _ => Nil}
       task <- mill.main.Resolve.resolve(args, mapping.mirror, mapping.base, Nil, crossSelectors, Nil)
     } yield task
     assert(resolved == expected)
diff --git a/core/src/test/scala/mill/util/TestGraphs.scala b/core/src/test/scala/mill/util/TestGraphs.scala
index 64fc4737..95ed8bf0 100644
--- a/core/src/test/scala/mill/util/TestGraphs.scala
+++ b/core/src/test/scala/mill/util/TestGraphs.scala
@@ -193,7 +193,7 @@ object TestGraphs{
 
   object singleCross extends TestUtil.BaseModule {
     object cross extends mill.CrossModule(CrossModule, "210", "211", "212")
-    case class CrossModule(scalaVersion: String) extends Module{
+    case class CrossModule(scalaVersion: String, ctx0: Module.Ctx) extends Module()(ctx0){
       def suffix = T{ scalaVersion }
     }
   }
@@ -204,16 +204,16 @@ object TestGraphs{
       if !(platform == "native" && scalaVersion != "212")
     } yield (scalaVersion, platform)
     object cross extends mill.CrossModule2(CrossModule, crossMatrix:_*)
-    case class CrossModule(scalaVersion: String, platform: String) extends Module{
+    case class CrossModule(scalaVersion: String, platform: String, ctx0: Module.Ctx) extends Module()(ctx0){
       def suffix = T{ scalaVersion + "_" + platform }
     }
   }
 
   object indirectNestedCrosses extends TestUtil.BaseModule {
     object cross extends mill.CrossModule(CrossModule, "210", "211", "212")
-    case class CrossModule(scalaVersion: String) extends mill.Module{
+    case class CrossModule(scalaVersion: String, ctx0: Module.Ctx) extends mill.Module()(ctx0){
       object cross2 extends mill.CrossModule(CrossModule, "jvm", "js", "native")
-      case class CrossModule(platform: String) extends mill.Module{
+      case class CrossModule(platform: String, ctx0: Module.Ctx) extends mill.Module{
         def suffix = T{ scalaVersion + "_" + platform }
       }
     }
@@ -221,9 +221,9 @@ object TestGraphs{
 
   object nestedCrosses extends TestUtil.BaseModule {
     object cross extends mill.CrossModule(CrossModule, "210", "211", "212")
-    case class CrossModule(scalaVersion: String) extends mill.Module{
+    case class CrossModule(scalaVersion: String, ctx0: Module.Ctx) extends mill.Module()(ctx0){
       object cross2 extends mill.CrossModule(CrossModule, "jvm", "js", "native")
-      case class CrossModule(platform: String) extends mill.Module{
+      case class CrossModule(platform: String, ctx0: Module.Ctx) extends mill.Module()(ctx0){
         def suffix = T{ scalaVersion + "_" + platform }
       }
     }
diff --git a/core/src/test/scala/mill/util/TestUtil.scala b/core/src/test/scala/mill/util/TestUtil.scala
index 8f5378cb..88d28f8a 100644
--- a/core/src/test/scala/mill/util/TestUtil.scala
+++ b/core/src/test/scala/mill/util/TestUtil.scala
@@ -1,34 +1,32 @@
 package mill.util
 
 import ammonite.main.Router.Overrides
-import ammonite.ops.Path
-import mill.define.Module
-import mill.define.{BasePath, Caller, Target, Task}
+import mill.define._
 import mill.eval.Result
 import utest.assert
-import utest.framework.TestPath
 
 import scala.collection.mutable
 
 object TestUtil {
   class BaseModule(implicit millModuleEnclosing0: sourcecode.Enclosing,
                    millModuleLine0: sourcecode.Line,
-                   millName0: sourcecode.Name)
+                   millName0: sourcecode.Name,
+                   overrides: Overrides)
     extends Module()(
       Module.Ctx.make(
         implicitly,
         implicitly,
         implicitly,
-        BasePath(ammonite.ops.pwd / millModuleEnclosing0.value)
+        BasePath(ammonite.ops.pwd / millModuleEnclosing0.value),
+        Segments(Nil),
+        implicitly
       )
     )
   object test{
 
     def anon(inputs: Task[Int]*) = new Test(inputs)
     def apply(inputs: Task[Int]*)
-            (implicit enclosing0: sourcecode.Enclosing,
-             owner0: Caller[mill.Module],
-             name0: sourcecode.Name)= {
+            (implicit ctx: Module.Ctx)= {
       new TestTarget(inputs, pure = inputs.nonEmpty)
     }
   }
@@ -51,17 +49,9 @@ object TestUtil {
     */
   class TestTarget(inputs: Seq[Task[Int]],
                    val pure: Boolean)
-                  (implicit enclosing0: sourcecode.Enclosing,
-                   lineNum0: sourcecode.Line,
-                   owner0: Caller[mill.Module],
-                   name0: sourcecode.Name,
-                   o: Overrides)
+                  (implicit ctx0: Module.Ctx)
     extends Test(inputs) with Target[Int]{
-    val overrides = o.value
-    val enclosing = enclosing0.value
-    val lineNum = lineNum0.value
-    val owner = owner0.value
-    val name = name0.value
+    val ctx = ctx0.copy(segments0 = Segments(ctx0.segments0.value :+ ctx0.segment))
     val readWrite = upickle.default.IntRW