Reproducible builds, composing different CBT version and various improvements

One large commit, because it is was hard to do these things in isolation or to separate them now.

CBT now knows how to load other versions of itself
 - Support for reproducible builds (!), by providing a CBT git URL and hash to tie build to
 - Support for composing builds using different CBT versions (!)
 - introduce (in compatibility/) Java interfaces all CBT versions need  to stay compatible with, so they can talk to each other. And put extension methods to these interfaces in cbt package object

Class loading
 - add some sanity checks for class loading
 - improve class loader invalidation to fix bugs
 - implement caching in Java land class loaders. In particular to prevent the system class loader to repeatedly generate ClassNotFound exceptions in each sink of the class loader DAG for non JDK classes (meaning major speed up for projects with many classes).
 - getting rid of transient class loader cache unifying into "persistent" one instead (which is still wrong as invalidation eventually needs to invalidate entire sub graphs of the class loading DAG, not single class loaders. Seems like we'll have to abandon the hashmap based approach and tie caching to dependency objects)

Other Caching
 - cache dependencies extracted from xml files, which was one major time killer, but invalidate cache when cbt changed (maven dependency user facing api needs simplification now!)
 - memorize last successful compile time in the file system rather than memory, to guard against unnecessary recompiling even across launches (or when using cbt direct)

Structural improvements
 - Factor out ClassLoaderCache on Java land into its own class.
 - Port MultiClassLoader to Java land, to better compose classloaders in NailgunLauncher.
 - Remove many global constants and variables (in object paths and in NailgunLauncher) and pass them through instead. Needed for composing of builds.
 - move more code from resolver into Lib for less entanglement with classes (needed to compatibility interfaces) and better re-usability
 - remove canBeCached. Everything can be cached now, but we need to be careful about correct invalidation.
 - remove build announcing produced jars. We can add if ever needed.
 - change callNullary to return exit code instead of Unit as preparation for next commit introducing "recursive"

ScalaTest
 - Makes ScalaTest support work (still a bit too inflexible, but mostly works well)

1 files changed, 105 insertions, 62 deletions

diff --git a/nailgun_launcher/EarlyDependencies.java b/nailgun_launcher/EarlyDependencies.java
index f4d446c..7a8d033 100644
--- a/nailgun_launcher/EarlyDependencies.java
+++ b/nailgun_launcher/EarlyDependencies.java
@@ -10,90 +10,133 @@ import static cbt.NailgunLauncher.*;
 class EarlyDependencies{
 
   /** ClassLoader for stage1 */
-  ClassLoader stage1;
+  ClassLoader classLoader;
+  String[] classpathArray;
   /** ClassLoader for zinc */
   ClassLoader zinc;
 
-  String scalaReflect_2_11_8_File = MAVEN_CACHE + "/org/scala-lang/scala-reflect/2.11.8/scala-reflect-2.11.8.jar";
-  String scalaCompiler_2_11_8_File = MAVEN_CACHE + "/org/scala-lang/scala-compiler/2.11.8/scala-compiler-2.11.8.jar";
-  String scalaXml_1_0_5_File = MAVEN_CACHE + "/org/scala-lang/modules/scala-xml_2.11/1.0.5/scala-xml_2.11-1.0.5.jar";
-  String scalaLibrary_2_11_8_File = MAVEN_CACHE + "/org/scala-lang/scala-library/2.11.8/scala-library-2.11.8.jar";
-  String zinc_0_3_9_File = MAVEN_CACHE + "/com/typesafe/zinc/zinc/0.3.9/zinc-0.3.9.jar";
-  String incrementalCompiler_0_13_9_File = MAVEN_CACHE + "/com/typesafe/sbt/incremental-compiler/0.13.9/incremental-compiler-0.13.9.jar";
-  String compilerInterface_0_13_9_File = MAVEN_CACHE + "/com/typesafe/sbt/compiler-interface/0.13.9/compiler-interface-0.13.9-sources.jar";
-  String scalaCompiler_2_10_5_File = MAVEN_CACHE + "/org/scala-lang/scala-compiler/2.10.5/scala-compiler-2.10.5.jar";
-  String sbtInterface_0_13_9_File = MAVEN_CACHE + "/com/typesafe/sbt/sbt-interface/0.13.9/sbt-interface-0.13.9.jar";
-  String scalaReflect_2_10_5_File = MAVEN_CACHE + "/org/scala-lang/scala-reflect/2.10.5/scala-reflect-2.10.5.jar";
-  String scalaLibrary_2_10_5_File = MAVEN_CACHE + "/org/scala-lang/scala-library/2.10.5/scala-library-2.10.5.jar";
-
-  public EarlyDependencies() throws MalformedURLException, IOException, NoSuchAlgorithmException{
-    download(new URL(MAVEN_URL + "/org/scala-lang/scala-reflect/2.11.8/scala-reflect-2.11.8.jar"), Paths.get(scalaReflect_2_11_8_File), "b74530deeba742ab4f3134de0c2da0edc49ca361");
-    download(new URL(MAVEN_URL + "/org/scala-lang/scala-compiler/2.11.8/scala-compiler-2.11.8.jar"), Paths.get(scalaCompiler_2_11_8_File), "fe1285c9f7b58954c5ef6d80b59063569c065e9a");
+  String scalaReflect_2_11_8_File;
+  String scalaCompiler_2_11_8_File;
+  String scalaXml_1_0_5_File;
+  String scalaLibrary_2_11_8_File;
+  String zinc_0_3_9_File;
+  String incrementalCompiler_0_13_9_File;
+  String compilerInterface_0_13_9_File;
+  String scalaCompiler_2_10_5_File;
+  String sbtInterface_0_13_9_File;
+  String scalaReflect_2_10_5_File;
+  String scalaLibrary_2_10_5_File;
+
+  public EarlyDependencies(
+    String mavenCache, String mavenUrl, ClassLoaderCache2<ClassLoader> classLoaderCache, ClassLoader rootClassLoader
+  ) throws Exception {
+    scalaReflect_2_11_8_File = mavenCache + "/org/scala-lang/scala-reflect/2.11.8/scala-reflect-2.11.8.jar";
+    scalaCompiler_2_11_8_File = mavenCache + "/org/scala-lang/scala-compiler/2.11.8/scala-compiler-2.11.8.jar";
+    scalaXml_1_0_5_File = mavenCache + "/org/scala-lang/modules/scala-xml_2.11/1.0.5/scala-xml_2.11-1.0.5.jar";
+    scalaLibrary_2_11_8_File = mavenCache + "/org/scala-lang/scala-library/2.11.8/scala-library-2.11.8.jar";
+    zinc_0_3_9_File = mavenCache + "/com/typesafe/zinc/zinc/0.3.9/zinc-0.3.9.jar";
+    incrementalCompiler_0_13_9_File = mavenCache + "/com/typesafe/sbt/incremental-compiler/0.13.9/incremental-compiler-0.13.9.jar";
+    compilerInterface_0_13_9_File = mavenCache + "/com/typesafe/sbt/compiler-interface/0.13.9/compiler-interface-0.13.9-sources.jar";
+    scalaCompiler_2_10_5_File = mavenCache + "/org/scala-lang/scala-compiler/2.10.5/scala-compiler-2.10.5.jar";
+    sbtInterface_0_13_9_File = mavenCache + "/com/typesafe/sbt/sbt-interface/0.13.9/sbt-interface-0.13.9.jar";
+    scalaReflect_2_10_5_File = mavenCache + "/org/scala-lang/scala-reflect/2.10.5/scala-reflect-2.10.5.jar";
+    scalaLibrary_2_10_5_File = mavenCache + "/org/scala-lang/scala-library/2.10.5/scala-library-2.10.5.jar";
+
+    download(new URL(mavenUrl + "/org/scala-lang/scala-reflect/2.11.8/scala-reflect-2.11.8.jar"), Paths.get(scalaReflect_2_11_8_File), "b74530deeba742ab4f3134de0c2da0edc49ca361");
+    download(new URL(mavenUrl + "/org/scala-lang/scala-compiler/2.11.8/scala-compiler-2.11.8.jar"), Paths.get(scalaCompiler_2_11_8_File), "fe1285c9f7b58954c5ef6d80b59063569c065e9a");
 
     // org.scala-lang:scala-library:2.10.5
-    download(new URL(MAVEN_URL + "/org/scala-lang/scala-library/2.10.5/scala-library-2.10.5.jar"), Paths.get(scalaLibrary_2_10_5_File), "57ac67a6cf6fd591e235c62f8893438e8d10431d");
-    ClassLoader scalaLibrary_2_10_5_ = cachePut(
-      classLoader( scalaLibrary_2_10_5_File ),
-      scalaLibrary_2_10_5_File
-    );
+    download(new URL(mavenUrl + "/org/scala-lang/scala-library/2.10.5/scala-library-2.10.5.jar"), Paths.get(scalaLibrary_2_10_5_File), "57ac67a6cf6fd591e235c62f8893438e8d10431d");
+
+    String[] scalaLibrary_2_10_5_ClasspathArray = new String[]{scalaLibrary_2_10_5_File};
+    String scalaLibrary_2_10_5_Classpath = classpath( scalaLibrary_2_10_5_ClasspathArray );
+    ClassLoader scalaLibrary_2_10_5_ =
+      classLoaderCache.contains( scalaLibrary_2_10_5_Classpath )
+      ? classLoaderCache.get( scalaLibrary_2_10_5_Classpath )
+      : classLoaderCache.put( classLoader( scalaLibrary_2_10_5_File, rootClassLoader ), scalaLibrary_2_10_5_Classpath );
 
     // org.scala-lang:scala-reflect:2.10.5
-    download(new URL(MAVEN_URL + "/org/scala-lang/scala-reflect/2.10.5/scala-reflect-2.10.5.jar"), Paths.get(scalaReflect_2_10_5_File), "7392facb48876c67a89fcb086112b195f5f6bbc3");
-    ClassLoader scalaReflect_2_10_5_ = cachePut(
-      classLoader( scalaReflect_2_10_5_File, scalaLibrary_2_10_5_ ),
-      scalaLibrary_2_10_5_File, scalaReflect_2_10_5_File
-    );
+    download(new URL(mavenUrl + "/org/scala-lang/scala-reflect/2.10.5/scala-reflect-2.10.5.jar"), Paths.get(scalaReflect_2_10_5_File), "7392facb48876c67a89fcb086112b195f5f6bbc3");
+
+    String[] scalaReflect_2_10_5_ClasspathArray = new String[]{scalaLibrary_2_10_5_File, scalaReflect_2_10_5_File};
+    String scalaReflect_2_10_5_Classpath = classpath( scalaReflect_2_10_5_ClasspathArray );
+    ClassLoader scalaReflect_2_10_5_ =
+      classLoaderCache.contains( scalaReflect_2_10_5_Classpath )
+      ? classLoaderCache.get( scalaReflect_2_10_5_Classpath )
+      : classLoaderCache.put( classLoader( scalaReflect_2_10_5_File, scalaLibrary_2_10_5_ ), scalaReflect_2_10_5_Classpath );
 
     // com.typesafe.sbt:sbt-interface:0.13.9
-    download(new URL(MAVEN_URL + "/com/typesafe/sbt/sbt-interface/0.13.9/sbt-interface-0.13.9.jar"), Paths.get(sbtInterface_0_13_9_File), "29848631415402c81b732e919be88f268df37250");
-    ClassLoader sbtInterface_0_13_9_ = cachePut(
-      classLoader( sbtInterface_0_13_9_File, scalaReflect_2_10_5_ ),
-      sbtInterface_0_13_9_File, scalaLibrary_2_10_5_File, scalaReflect_2_10_5_File
-    );
+    download(new URL(mavenUrl + "/com/typesafe/sbt/sbt-interface/0.13.9/sbt-interface-0.13.9.jar"), Paths.get(sbtInterface_0_13_9_File), "29848631415402c81b732e919be88f268df37250");
+
+    String[] sbtInterface_0_13_9_ClasspathArray = new String[]{sbtInterface_0_13_9_File, scalaLibrary_2_10_5_File, scalaReflect_2_10_5_File};
+    String sbtInterface_0_13_9_Classpath = classpath( sbtInterface_0_13_9_ClasspathArray );
+    ClassLoader sbtInterface_0_13_9_ =
+      classLoaderCache.contains( sbtInterface_0_13_9_Classpath )
+      ? classLoaderCache.get( sbtInterface_0_13_9_Classpath )
+      : classLoaderCache.put( classLoader( sbtInterface_0_13_9_File, scalaReflect_2_10_5_ ), sbtInterface_0_13_9_Classpath );
 
     // org.scala-lang:scala-compiler:2.10.5
-    download(new URL(MAVEN_URL + "/org/scala-lang/scala-compiler/2.10.5/scala-compiler-2.10.5.jar"), Paths.get(scalaCompiler_2_10_5_File), "f0f5bb444ca26a6e489af3dd35e24f7e2d2d118e");
-    ClassLoader scalaCompiler_2_10_5_ = cachePut(
-      classLoader( scalaCompiler_2_10_5_File, sbtInterface_0_13_9_ ),
-      sbtInterface_0_13_9_File, scalaCompiler_2_10_5_File, scalaLibrary_2_10_5_File, scalaReflect_2_10_5_File
-    );
+    download(new URL(mavenUrl + "/org/scala-lang/scala-compiler/2.10.5/scala-compiler-2.10.5.jar"), Paths.get(scalaCompiler_2_10_5_File), "f0f5bb444ca26a6e489af3dd35e24f7e2d2d118e");
+
+    String[] scalaCompiler_2_10_5_ClasspathArray = new String[]{sbtInterface_0_13_9_File, scalaCompiler_2_10_5_File, scalaLibrary_2_10_5_File, scalaReflect_2_10_5_File};
+    String scalaCompiler_2_10_5_Classpath = classpath( scalaCompiler_2_10_5_ClasspathArray );
+    ClassLoader scalaCompiler_2_10_5_ =
+      classLoaderCache.contains( scalaCompiler_2_10_5_Classpath )
+      ? classLoaderCache.get( scalaCompiler_2_10_5_Classpath )
+      : classLoaderCache.put( classLoader( scalaCompiler_2_10_5_File, sbtInterface_0_13_9_ ), scalaCompiler_2_10_5_Classpath );
 
     // com.typesafe.sbt:compiler-interface:0.13.9
-    download(new URL(MAVEN_URL + "/com/typesafe/sbt/compiler-interface/0.13.9/compiler-interface-0.13.9-sources.jar"), Paths.get(compilerInterface_0_13_9_File), "2311addbed1182916ad00f83c57c0eeca1af382b");
-    ClassLoader compilerInterface_0_13_9_ = cachePut(
-      classLoader( compilerInterface_0_13_9_File, scalaCompiler_2_10_5_ ),
-      compilerInterface_0_13_9_File, sbtInterface_0_13_9_File, scalaCompiler_2_10_5_File, scalaLibrary_2_10_5_File, scalaReflect_2_10_5_File
-    );
+    download(new URL(mavenUrl + "/com/typesafe/sbt/compiler-interface/0.13.9/compiler-interface-0.13.9-sources.jar"), Paths.get(compilerInterface_0_13_9_File), "2311addbed1182916ad00f83c57c0eeca1af382b");
+
+    String[] compilerInterface_0_13_9_ClasspathArray = new String[]{compilerInterface_0_13_9_File, sbtInterface_0_13_9_File, scalaCompiler_2_10_5_File, scalaLibrary_2_10_5_File, scalaReflect_2_10_5_File};
+    String compilerInterface_0_13_9_Classpath = classpath( compilerInterface_0_13_9_ClasspathArray );
+    ClassLoader compilerInterface_0_13_9_ =
+      classLoaderCache.contains( compilerInterface_0_13_9_Classpath )
+      ? classLoaderCache.get( compilerInterface_0_13_9_Classpath )
+      : classLoaderCache.put( classLoader( compilerInterface_0_13_9_File, scalaCompiler_2_10_5_ ), compilerInterface_0_13_9_Classpath );
 
     // com.typesafe.sbt:incremental-compiler:0.13.9
-    download(new URL(MAVEN_URL + "/com/typesafe/sbt/incremental-compiler/0.13.9/incremental-compiler-0.13.9.jar"), Paths.get(incrementalCompiler_0_13_9_File), "fbbf1cadbed058aa226643e83543c35de43b13f0");
-    ClassLoader incrementalCompiler_0_13_9_ = cachePut(
-      classLoader( incrementalCompiler_0_13_9_File, compilerInterface_0_13_9_ ),
-      compilerInterface_0_13_9_File, incrementalCompiler_0_13_9_File, sbtInterface_0_13_9_File, scalaCompiler_2_10_5_File, scalaLibrary_2_10_5_File, scalaReflect_2_10_5_File
-    );
+    download(new URL(mavenUrl + "/com/typesafe/sbt/incremental-compiler/0.13.9/incremental-compiler-0.13.9.jar"), Paths.get(incrementalCompiler_0_13_9_File), "fbbf1cadbed058aa226643e83543c35de43b13f0");
+
+    String[] incrementalCompiler_0_13_9_ClasspathArray = new String[]{compilerInterface_0_13_9_File, incrementalCompiler_0_13_9_File, sbtInterface_0_13_9_File, scalaCompiler_2_10_5_File, scalaLibrary_2_10_5_File, scalaReflect_2_10_5_File};
+    String incrementalCompiler_0_13_9_Classpath = classpath( incrementalCompiler_0_13_9_ClasspathArray );
+    ClassLoader incrementalCompiler_0_13_9_ =
+      classLoaderCache.contains( incrementalCompiler_0_13_9_Classpath )
+      ? classLoaderCache.get( incrementalCompiler_0_13_9_Classpath )
+      : classLoaderCache.put( classLoader( incrementalCompiler_0_13_9_File, compilerInterface_0_13_9_ ), incrementalCompiler_0_13_9_Classpath );
 
     // com.typesafe.zinc:zinc:0.3.9
-    download(new URL(MAVEN_URL + "/com/typesafe/zinc/zinc/0.3.9/zinc-0.3.9.jar"), Paths.get(zinc_0_3_9_File), "46a4556d1f36739879f4b2cc19a73d12b3036e9a");
-    ClassLoader zinc_0_3_9_ = cachePut(
-      classLoader( zinc_0_3_9_File, incrementalCompiler_0_13_9_ ),
-      compilerInterface_0_13_9_File, incrementalCompiler_0_13_9_File, sbtInterface_0_13_9_File, zinc_0_3_9_File, scalaCompiler_2_10_5_File, scalaLibrary_2_10_5_File, scalaReflect_2_10_5_File
-    );
+    download(new URL(mavenUrl + "/com/typesafe/zinc/zinc/0.3.9/zinc-0.3.9.jar"), Paths.get(zinc_0_3_9_File), "46a4556d1f36739879f4b2cc19a73d12b3036e9a");
+
+    String[] zinc_0_3_9_ClasspathArray = new String[]{compilerInterface_0_13_9_File, incrementalCompiler_0_13_9_File, sbtInterface_0_13_9_File, zinc_0_3_9_File, scalaCompiler_2_10_5_File, scalaLibrary_2_10_5_File, scalaReflect_2_10_5_File};
+    String zinc_0_3_9_Classpath = classpath( zinc_0_3_9_ClasspathArray );
+    ClassLoader zinc_0_3_9_ =
+      classLoaderCache.contains( zinc_0_3_9_Classpath )
+      ? classLoaderCache.get( zinc_0_3_9_Classpath )
+      : classLoaderCache.put( classLoader( zinc_0_3_9_File, incrementalCompiler_0_13_9_ ), zinc_0_3_9_Classpath );
 
     // org.scala-lang:scala-library:2.11.8
-    download(new URL(MAVEN_URL + "/org/scala-lang/scala-library/2.11.8/scala-library-2.11.8.jar"), Paths.get(scalaLibrary_2_11_8_File), "ddd5a8bced249bedd86fb4578a39b9fb71480573");
-    ClassLoader scalaLibrary_2_11_8_ = cachePut(
-      classLoader( scalaLibrary_2_11_8_File ),
-      scalaLibrary_2_11_8_File
-    );
+    download(new URL(mavenUrl + "/org/scala-lang/scala-library/2.11.8/scala-library-2.11.8.jar"), Paths.get(scalaLibrary_2_11_8_File), "ddd5a8bced249bedd86fb4578a39b9fb71480573");
+
+    String[] scalaLibrary_2_11_8_ClasspathArray = new String[]{scalaLibrary_2_11_8_File};
+    String scalaLibrary_2_11_8_Classpath = classpath( scalaLibrary_2_11_8_ClasspathArray );
+    ClassLoader scalaLibrary_2_11_8_ =
+      classLoaderCache.contains( scalaLibrary_2_11_8_Classpath )
+      ? classLoaderCache.get( scalaLibrary_2_11_8_Classpath )
+      : classLoaderCache.put( classLoader( scalaLibrary_2_11_8_File, rootClassLoader ), scalaLibrary_2_11_8_Classpath );
 
     // org.scala-lang.modules:scala-xml_2.11:1.0.5
-    download(new URL(MAVEN_URL + "/org/scala-lang/modules/scala-xml_2.11/1.0.5/scala-xml_2.11-1.0.5.jar"), Paths.get(scalaXml_1_0_5_File), "77ac9be4033768cf03cc04fbd1fc5e5711de2459");
-    ClassLoader scalaXml_1_0_5_ = cachePut(
-      classLoader( scalaXml_1_0_5_File, scalaLibrary_2_11_8_ ),
-      scalaXml_1_0_5_File, scalaLibrary_2_11_8_File
-    );
+    download(new URL(mavenUrl + "/org/scala-lang/modules/scala-xml_2.11/1.0.5/scala-xml_2.11-1.0.5.jar"), Paths.get(scalaXml_1_0_5_File), "77ac9be4033768cf03cc04fbd1fc5e5711de2459");
+
+    String[] scalaXml_1_0_5_ClasspathArray = new String[]{scalaXml_1_0_5_File, scalaLibrary_2_11_8_File};
+    String scalaXml_1_0_5_Classpath = classpath( scalaXml_1_0_5_ClasspathArray );
+    ClassLoader scalaXml_1_0_5_ =
+      classLoaderCache.contains( scalaXml_1_0_5_Classpath )
+      ? classLoaderCache.get( scalaXml_1_0_5_Classpath )
+      : classLoaderCache.put( classLoader( scalaXml_1_0_5_File, scalaLibrary_2_11_8_ ), scalaXml_1_0_5_Classpath );
   
-    stage1 = scalaXml_1_0_5_;
+    classLoader = scalaXml_1_0_5_;
+    classpathArray = scalaXml_1_0_5_ClasspathArray;
 
     zinc = zinc_0_3_9_;
   }