Integrate flat classpath with the compiler

This commit integrates with the compiler the whole flat classpath
representation build next to the recursive one as an alternative.

From now flat classpath really works and can be turned on. There's
added flag -YclasspathImpl with two options: recursive (the default
one) and flat.

It was needed to make the dynamic dispatch to the particular
classpath representation according to the chosen type of a classpath
representation.

There's added PathResolverFactory which is used instead of a concrete
implementation of a path resolver. It turned out that only a small
subset of path resolvers methods is used outside this class in Scala
sources. Therefore, PathResolverFactory returns an instance of a base
interface PathResolverResult providing only these used methods.

PathResolverFactory in combination with matches in some other places
ensures that in all places using classpath we create/get the proper
representation.

Also the classPath method in Global is modified to use the dynamic
dispatch. This is very important change as a return type changed to
the base ClassFileLookup providing subset of old ClassPath public
methods. It can be problematic if someone was using in his project
the explicit ClassPath type or public methods which are not provided
via ClassFileLookup. I tested flat classpath with sbt and Scala IDE
and there were no problems. Also was looking at sources of some other
projects like e.g. Scala plugin for IntelliJ and there shouldn't be
problems, I think, but it would be better to check these changes
using the community build.

Scalap's Main.scala is changed to be able to use both implementations
and also to use flags related to the classpath implementation.

The classpath invalidation is modified to work properly with the old
(recursive) classpath representation after changes made in a Global.
In the case of the attempt to use the invalidation for the flat cp it
just throws exception with a message that the flat one currently
doesn't support the invalidation. And also that's why the partest's
test for the invalidation has been changed to use (always) the old
implementation. There's added an adequate comment with TODO to this
file.

There's added partest test generating various dependencies
(directories, zips and jars with sources and class files) and testing
whether the compilation and further running an application works
correctly, when there are these various types of entries specified as
-classpath and -sourcepath. It should be a good approximation of real
use cases.

1 files changed, 26 insertions, 3 deletions

diff --git a/test/junit/scala/tools/nsc/symtab/SymbolTableForUnitTesting.scala b/test/junit/scala/tools/nsc/symtab/SymbolTableForUnitTesting.scala
index e4be42ac96..d61c62784c 100644
--- a/test/junit/scala/tools/nsc/symtab/SymbolTableForUnitTesting.scala
+++ b/test/junit/scala/tools/nsc/symtab/SymbolTableForUnitTesting.scala
@@ -3,6 +3,9 @@ package symtab
 
 import scala.reflect.ClassTag
 import scala.reflect.internal.{Phase, NoPhase, SomePhase}
+import scala.tools.nsc.classpath.FlatClassPath
+import scala.tools.nsc.settings.ClassPathRepresentationType
+import scala.tools.util.FlatClassPathResolver
 import scala.tools.util.PathResolver
 import util.ClassPath
 import io.AbstractFile
@@ -26,13 +29,28 @@ class SymbolTableForUnitTesting extends SymbolTable {
   class LazyTreeCopier extends super.LazyTreeCopier with TreeCopier
 
   override def isCompilerUniverse: Boolean = true
-  def classPath = new PathResolver(settings).result
+
+  def classPath = platform.classPath
+  def flatClassPath: FlatClassPath = platform.flatClassPath
 
   object platform extends backend.Platform {
     val symbolTable: SymbolTableForUnitTesting.this.type = SymbolTableForUnitTesting.this
     lazy val loaders: SymbolTableForUnitTesting.this.loaders.type = SymbolTableForUnitTesting.this.loaders
+
     def platformPhases: List[SubComponent] = Nil
-    val classPath: ClassPath[AbstractFile] = new PathResolver(settings).result
+
+    lazy val classPath: ClassPath[AbstractFile] = {
+      assert(settings.YclasspathImpl.value == ClassPathRepresentationType.Recursive,
+        "It's not possible to use the recursive classpath representation, when it's not the chosen classpath scanning method")
+      new PathResolver(settings).result
+    }
+
+    private[nsc] lazy val flatClassPath: FlatClassPath = {
+      assert(settings.YclasspathImpl.value == ClassPathRepresentationType.Flat,
+        "It's not possible to use the flat classpath representation, when it's not the chosen classpath scanning method")
+      new FlatClassPathResolver(settings).result
+    }
+
     def isMaybeBoxed(sym: Symbol): Boolean = ???
     def needCompile(bin: AbstractFile, src: AbstractFile): Boolean = ???
     def externalEquals: Symbol = ???
@@ -50,7 +68,12 @@ class SymbolTableForUnitTesting extends SymbolTable {
 
   class GlobalMirror extends Roots(NoSymbol) {
     val universe: SymbolTableForUnitTesting.this.type = SymbolTableForUnitTesting.this
-    def rootLoader: LazyType = new loaders.PackageLoader(classPath)
+
+    def rootLoader: LazyType = settings.YclasspathImpl.value match {
+      case ClassPathRepresentationType.Flat => new loaders.PackageLoaderUsingFlatClassPath(FlatClassPath.RootPackage, flatClassPath)
+      case ClassPathRepresentationType.Recursive => new loaders.PackageLoader(classPath)
+    }
+
     override def toString = "compiler mirror"
   }