describe how to use local spinal clone as dependency

Author: NikLeberg

source/SpinalHDL/Developers area/howotuselocalspinalclone.rst

@@ -0,0 +1,117 @@
+How to use a local SpinalHDL clone as project dependency
+========================================================
+
+The default way to use SpinalHDL is by using the released version of it as is
+automatically downloaded by sbt or mill. Living on the cutting edge, you might
+want to use the upstream and non released ``dev`` branch from git directly. Be
+it just because you want to use a new shiny feature or because you want to test
+your own extension to Spinal (please consider upstreaming it by opening a PR)
+within a project.
+
+As an example of where this is used you can also refer to `VexiiRiscv`_.
+
+
+Create local git clone of SpinalHDL
+-----------------------------------
+
+.. code-block:: sh
+
+   cd /somewhere
+   git clone --depth 1 -b dev https://github.com/SpinalHDL/SpinalHDL.git
+
+In the command above you can replace ``dev`` by the name of the branch you want
+to checkout. ``--depth 1`` prevents from downloading the repository history.
+
+
+Configure buildsystem
+---------------------
+
+Depending on which tool you use, instruct either sbt or mill to load the local
+git folder as dependency:
+
+
+Configure sbt (update ``build.sbt``)
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+.. code-block:: scala
+
+   ThisBuild / version := "1.0"              // change as needed
+   ThisBuild / scalaVersion := "2.12.18"     // change as needed
+   ThisBuild / organization := "org.example" // change as needed
+
+   val spinalRoot = file("/somewhere/SpinalHDL")
+   lazy val spinalIdslPlugin = ProjectRef(spinalRoot, "idslplugin")
+   lazy val spinalSim = ProjectRef(spinalRoot, "sim")
+   lazy val spinalCore = ProjectRef(spinalRoot, "core")
+   lazy val spinalLib = ProjectRef(spinalRoot, "lib")
+
+   lazy val projectname = (project in file("."))
+   .settings(
+      Compile / scalaSource := baseDirectory.value / "hw" / "spinal",
+   ).dependsOn(spinalIdslPlugin, spinalSim, spinalCore, spinalLib)
+
+   scalacOptions += (spinalIdslPlugin / Compile / packageBin / artifactPath).map { file =>
+     s"-Xplugin:${file.getAbsolutePath}"
+   }.value
+
+   fork := true
+
+
+Configure mill (update ``build.sc``)
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+.. code-block:: scala
+
+   import mill._, scalalib._
+
+   import $file.^.SpinalHDL.build
+   import ^.SpinalHDL.build.{core => spinalCore}
+   import ^.SpinalHDL.build.{lib => spinalLib}
+   import ^.SpinalHDL.build.{idslplugin => spinalIdslplugin}
+
+   val spinalVers = "1.10.2a"
+   val scalaVers = "2.12.18"
+
+   object projectname extends RootModule with SbtModule {
+      def scalaVersion = scalaVers
+      def sources = T.sources(
+         this.millSourcePath / "hw" / "spinal"
+      )
+
+      def idslplugin = spinalIdslplugin(scalaVers)
+      def moduleDeps = Seq(
+         spinalCore(scalaVers),
+         spinalLib(scalaVers),
+         idslplugin
+      )
+      def scalacOptions = super.scalacOptions() ++ idslplugin.pluginOptions()
+   }
+
+
+Note the line ``import $file.^.SpinalHDL.build``. It is using ammonite REPL
+magic ``$file`` to look up the ``build.sc`` of SpinalHDL. (The ``^`` moves up
+one directory from the current.) This is assuming the following directory
+structure:
+
+.. code-block:: scala
+
+   /somewhere
+   |-SpinalHDL   # <-- cloned spinal git
+   | |-build.sc
+   |-projectname
+   | |-build.sc  # <-- your project, mill is ran from here
+
+
+Done
+----
+
+Note the addition to ``scalacOptions``. Without it, compiling any Spinal project
+might produce countless ``SCOPE VIOLATION`` or ``HIERARCHY VIOLATION`` errors
+because the ``idslplugin`` of spinal is not actually invoked.
+
+After the changes, the next compilation of your project will take a considerable
+amount of time (~2 minutes). This is only for the first compile. After this,
+your project should compile as usual.
+
+
+.. _VexiiRiscv: https://github.com/SpinalHDL/VexiiRiscv/blob/dev/build.sbt