Better Building of FIRRTL From Source (#1563)

Using JVM system properties sbt.sourcemode and sbt.workspace, one can now
easily build chisel3 with firrtl from source

Example use:

Assuming firrtl is cloned into the chisel3 root directory:
$ sbt -Dsbt.sourcemode=true -Dsbt.workspace=$PWD

Alternatively, one can set these properties in .sbtopts which can then
be committed, enabling building from source by default

3 files changed, 39 insertions, 21 deletions

diff --git a/README.md b/README.md
index 9ff5f0e3..0dce401c 100644
--- a/README.md
+++ b/README.md
@@ -169,11 +169,11 @@ sbt test
 ### Running Projects Against Local Chisel
 
 To use the development version of Chisel (`master` branch), you will need to build from source and `publishLocal`.
-The repository version can be found in the build.sbt file.
+The repository version can be found in the [build.sbt](build.sbt) file.
 As of the time of writing it was:
 
 ```
-version := "3.2-SNAPSHOT"
+version := "3.4-SNAPSHOT"
 ```
 
 To publish your version of Chisel to the local Ivy (sbt's dependency manager) repository, run:
@@ -188,9 +188,32 @@ If you need to un-publish your local copy of Chisel, remove the directory genera
 In order to have your projects use this version of Chisel, you should update the `libraryDependencies` setting in your project's build.sbt file to:
 
 ```
-libraryDependencies += "edu.berkeley.cs" %% "chisel3" % "3.2-SNAPSHOT"
+libraryDependencies += "edu.berkeley.cs" %% "chisel3" % "3.4-SNAPSHOT"
+```
+
+### Building Chisel with FIRRTL in the same SBT Project
+
+While we recommend using the library dependency approach as described above, it is possible to build Chisel and FIRRTL in a single SBT project.
+
+**Caveats**
+* This only works for the "main" configuration; you cannot build the Chisel tests this way because `treadle` is only supported as a library dependency.
+* Do not `publishLocal` when building this way. The published artifact will be missing the FIRRTL dependency.
+
+This works by using [sbt-sriracha](http://eed3si9n.com/hot-source-dependencies-using-sbt-sriracha), an SBT plugin for toggling between source and library dependencies.
+It provides two JVM system properties that, when set, will tell SBT to include FIRRTL as a source project:
+* `sbt.sourcemode` - when set to true, SBT will look for FIRRTL in the workspace
+* `sbt.workspace` - sets the root directory of the workspace
+
+Example use:
+```bash
+# From root of this repo
+git clone git@github.com:freechipsproject/firrtl.git
+sbt -Dsbt.sourcemode=true -Dsbt.workspace=$PWD
 ```
 
+This is primarily useful for building projects that themselves want to include Chisel as a source dependency.
+As an example, see [Rocket Chip](https://github.com/chipsalliance/rocket-chip)
+
 ### Chisel3 Architecture Overview
 
 The Chisel3 compiler consists of these main parts:
diff --git a/build.sbt b/build.sbt
index 0b0afb4a..8512eb0e 100644
--- a/build.sbt
+++ b/build.sbt
@@ -28,8 +28,9 @@ def javacOptionsVersion(scalaVersion: String): Seq[String] = {
   }
 }
 
-val defaultVersions = Seq(
-  "edu.berkeley.cs" %% "firrtl" % "1.4-SNAPSHOT"
+val defaultVersions = Map(
+  "firrtl" -> "edu.berkeley.cs" %% "firrtl" % "1.4-SNAPSHOT",
+  "treadle" -> "edu.berkeley.cs" %% "treadle" % "1.3-SNAPSHOT"
 )
 
 lazy val commonSettings = Seq (
@@ -45,20 +46,6 @@ lazy val commonSettings = Seq (
   scalacOptions := Seq("-deprecation", "-feature") ++ scalacOptionsVersion(scalaVersion.value),
   libraryDependencies += "org.scala-lang" % "scala-reflect" % scalaVersion.value,
   addCompilerPlugin("org.scalamacros" % "paradise" % "2.1.1" cross CrossVersion.full),
-  // Use the root project's unmanaged base for all sub-projects.
-  unmanagedBase := (unmanagedBase in root).value,
-  // Since we want to examine the classpath to determine if a dependency on firrtl is required,
-  //  this has to be a Task setting.
-  //  Fortunately, allDependencies is a Task Setting, so we can modify that.
-  allDependencies := {
-    allDependencies.value ++ defaultVersions.collect {
-      // If we have an unmanaged jar file on the classpath, assume we're to use that,
-      case m: ModuleID if !(unmanagedClasspath in Compile).value.toString.contains(s"${m.name}.jar") =>
-        //  otherwise let sbt fetch the appropriate artifact, possibly with a specific revision.
-        val mWithRevision = m.withRevision(sys.props.getOrElse(m.name + "Version", m.revision))
-        mWithRevision
-    }
-  }
 )
 
 lazy val publishSettings = Seq (
@@ -109,7 +96,6 @@ lazy val chiselSettings = Seq (
     "junit" % "junit" % "4.13" % "test",
     "org.scalatest" %% "scalatest" % "3.1.2" % "test",
     "org.scalatestplus" %% "scalacheck-1-14" % "3.1.1.1" % "test",
-    "edu.berkeley.cs" %% "treadle" % "1.3-SNAPSHOT" % "test",
     "com.github.scopt" %% "scopt" % "3.7.1"
   ),
   javacOptions ++= javacOptionsVersion(scalaVersion.value)
@@ -179,7 +165,10 @@ lazy val macros = (project in file("macros")).
   settings(commonSettings: _*).
   settings(publishSettings: _*)
 
+lazy val firrtlRef = ProjectRef(workspaceDirectory / "firrtl", "firrtl")
+
 lazy val core = (project in file("core")).
+  sourceDependency(firrtlRef, defaultVersions("firrtl")).
   settings(commonSettings: _*).
   enablePlugins(BuildInfoPlugin).
   settings(
@@ -216,6 +205,7 @@ lazy val chisel = (project in file(".")).
   dependsOn(core).
   aggregate(macros, core, plugin).
   settings(
+    libraryDependencies += defaultVersions("treadle") % "test",
     scalacOptions in Test ++= Seq("-language:reflectiveCalls"),
     scalacOptions in Compile in doc ++= Seq(
       "-diagrams",
diff --git a/project/plugins.sbt b/project/plugins.sbt
index 24ee55eb..867bf6b6 100644
--- a/project/plugins.sbt
+++ b/project/plugins.sbt
@@ -8,7 +8,7 @@ addSbtPlugin("org.scoverage" % "sbt-scoverage" % "1.6.1")
 
 addSbtPlugin("com.typesafe.sbt" % "sbt-site" % "1.4.0")
 
-addSbtPlugin("com.eed3si9n" % "sbt-buildinfo" % "0.9.0")
+addSbtPlugin("com.eed3si9n" % "sbt-buildinfo" % "0.10.0")
 
 addSbtPlugin("com.eed3si9n" % "sbt-unidoc" % "0.4.3")
 
@@ -17,3 +17,8 @@ addSbtPlugin("ch.epfl.scala" % "sbt-scalafix" % "0.9.15")
 addSbtPlugin("com.thoughtworks.sbt-api-mappings" % "sbt-api-mappings" % "3.0.0")
 
 addSbtPlugin("org.scalameta" % "sbt-mdoc" % "2.2.5" )
+
+addSbtPlugin("com.eed3si9n" % "sbt-sriracha" % "0.1.0")
+
+// From FIRRTL for building from source
+addSbtPlugin("ch.epfl.scala" % "sbt-scalafix" % "0.9.19")