Track dependencies using OriginalTreeAttachments

internal/compiler-bridge/src/main/scala-2.11/xsbt/Compat.scala

@@ -13,9 +13,15 @@ package xsbt
 
 import java.io.PrintWriter
 import xsbti.compile.Output
+import scala.tools.nsc.Global
 import scala.tools.nsc.Settings
 
-abstract class Compat
+abstract class Compat {
+  val global: Global
+  import global._
+
+  protected def processOriginalTreeAttachment(in: Tree)(func: Tree => Unit): Unit = ()
+}
 object Compat {
   // IR is renamed to Results
   val Results = scala.tools.nsc.interpreter.IR

internal/compiler-bridge/src/main/scala-2.12/xsbt/Compat.scala

@@ -13,9 +13,21 @@ package xsbt
 
 import java.io.PrintWriter
 import xsbti.compile.Output
+import scala.tools.nsc.Global
 import scala.tools.nsc.Settings
 
-abstract class Compat
+abstract class Compat {
+  val global: Global
+  import global._
+
+  /** If given tree contains object tree attachment calls func on tree from attachment. */
+  protected def processOriginalTreeAttachment(in: Tree)(func: Tree => Unit): Unit = {
+    import analyzer._
+    in.attachments.get[OriginalTreeAttachment].foreach { a =>
+      func(a.original)
+    }
+  }
+}
 object Compat {
   // IR is renamed to Results
   val Results = scala.tools.nsc.interpreter.IR

internal/compiler-bridge/src/main/scala/xsbt/Dependency.scala

@@ -455,9 +455,15 @@ final class Dependency(val global: CallbackGlobal) extends LocateClassFile with
           inspectedOriginalTrees.add(original)
         }
         addTypeDependencies(typeTree.tpe)
+
       case m @ MacroExpansionOf(original) if inspectedOriginalTrees.add(original) =>
         traverse(original)
         super.traverse(m)
+
+      case l: Literal =>
+        processOriginalTreeAttachment(l)(traverse)
+        super.traverse(l)
+
       case _: ClassDef | _: ModuleDef if !ignoredSymbol(tree.symbol) =>
         // make sure we cache lookups for all classes declared in the compilation unit; the recorded information
         // will be used in Analyzer phase

internal/compiler-bridge/src/main/scala/xsbt/ExtractUsedNames.scala

@@ -290,6 +290,8 @@ class ExtractUsedNames[GlobalType <: CallbackGlobal](val global: GlobalType)
           TypeDependencyTraverser.setCacheAndOwner(cache, _currentOwner)
           TypeDependencyTraverser.traverse(tpe)
         }
+      case l: Literal =>
+        processOriginalTreeAttachment(l)(traverse)
       case _ =>
     }
 

internal/compiler-bridge/src/main/scala_2.10/xsbt/Compat.scala

@@ -144,6 +144,8 @@ abstract class Compat {
     // `original` has been renamed to `expandee` in 2.11.x
     @inline final def expandee: Tree = self.original
   }
+
+  protected def processOriginalTreeAttachment(in: Tree)(func: Tree => Unit): Unit = ()
 }
 
 /** Defines compatibility utils for [[ZincCompiler]]. */

internal/compiler-bridge/src/main/scala_2.13/xsbt/Compat.scala

@@ -13,10 +13,22 @@ package xsbt
 
 import java.io.PrintWriter
 import xsbti.compile.Output
+import scala.tools.nsc.Global
 import scala.tools.nsc.Settings
 import scala.tools.nsc.interpreter.shell.ReplReporterImpl
 
-abstract class Compat
+abstract class Compat {
+  val global: Global
+  import global._
+
+  /** If given tree contains object tree attachment calls func on tree from attachment. */
+  protected def processOriginalTreeAttachment(in: Tree)(func: Tree => Unit): Unit = {
+    import analyzer._
+    in.attachments.get[OriginalTreeAttachment].foreach { a =>
+      func(a.original)
+    }
+  }
+}
 object Compat {
   // IR is renamed to Results
   val Results = scala.tools.nsc.interpreter.Results

zinc/src/sbt-test/source-dependencies/constants/test

@@ -0,0 +1,6 @@
+$ copy-file changes/B.scala B.scala
+
+$ copy-file changes/A1.scala A.scala
+> run 1
+$ copy-file changes/A2.scala A.scala
+> run 2

zinc/src/test/scala/sbt/inc/IncrementalCompilerSpec.scala

@@ -147,7 +147,7 @@ class IncrementalCompilerSpec extends BaseCompilerSpec {
       }
   }
 
-  it should "track dependencies for nested inner Java classes" in withTmpDir { tmp =>
+  it should "track dependencies from nested inner Java classes" in withTmpDir { tmp =>
     val project = VirtualSubproject(tmp.toPath / "p1")
     val comp = project.setup.createCompiler()
     try {
@@ -189,4 +189,26 @@ class IncrementalCompilerSpec extends BaseCompilerSpec {
       comp.close()
     }
   }
+
+  it should "track dependencies on constants" in withTmpDir { tmp =>
+    val project = VirtualSubproject(tmp.toPath / "p1")
+    val comp = project.setup.createCompiler()
+    try {
+      val s1 = "object A { final val i = 1 }"
+      val s1b = "object A { final val i = 2 }"
+      val s2 = "class B { def i = A.i }"
+      val s3 = "class C { def i = 3 }"
+
+      val f1 = StringVirtualFile("A.scala", s1)
+      val f1b = StringVirtualFile("A.scala", s1b)
+      val f2 = StringVirtualFile("B.scala", s2)
+      val f3 = StringVirtualFile("C.scala", s3)
+
+      val res1 = comp.compile(f1, f2, f3)
+      val res2 = comp.compile(f1b, f2, f3)
+      assert(recompiled(res1, res2) == Set("A", "B"))
+    } finally {
+      comp.close()
+    }
+  }
 }