Restore binary compatibility checking (#5028)

Author: jackkoenig

.github/workflows/enable-bincompat-checking.yml

@@ -75,7 +75,7 @@ jobs:
         run: |
           VERSION=${{ needs.determine_version.outputs.version }}
           VERSION_NO_V=${VERSION#v}
-          echo $VERSION_NO_V >> project/previous-versions.txt
+          echo $VERSION_NO_V >> etc/previous-versions.txt
       - name: Open PR
         uses: peter-evans/create-pull-request@271a8d0340265f705b14b6d32b9829c1cb33d45e # v7.0.8
         with:

.github/workflows/test.yml

@@ -91,6 +91,23 @@ jobs:
       - name: Test
         run: ./mill -j0 firrtl.cross[].test -oF + svsim.cross[].test -oF + chisel[].test -oF
 
+  mima:
+    name: binary compatibility checking
+    runs-on: ${{ inputs.system }}
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+        with:
+          ref: ${{ inputs.ref }}
+      - name: Setup Java
+        uses: actions/setup-java@v4
+        with:
+          distribution: 'adopt'
+          java-version: ${{ inputs.jvm }}
+      - name: Check Binary Compatibility with MiMa
+        run: ./mill __.mimaReportBinaryIssues
+
   mill:
     name: compile project with mill
     runs-on: ubuntu-24.04

build.mill

@@ -3,6 +3,7 @@
 //| - com.lihaoyi::mill-contrib-jmh:$MILL_VERSION
 //| - com.47deg::github4s:0.33.3
 //| - com.lumidion::sonatype-central-client-requests:0.6.0
+//| - com.github.lolgab::mill-mima::0.2.0
 
 package build
 

etc/previous-versions.txt

@@ -0,0 +1 @@
+7.0.0

release.mill

@@ -7,6 +7,7 @@ import mill.scalalib._
 import mill.scalalib.scalafmt._
 import mill.scalalib.publish._
 import mill.util.Jvm.createJar
+import com.github.lolgab.mill.mima.Mima
 
 //import de.tobiasroeser.mill.vcs.version.VcsVersion
 
@@ -33,7 +34,7 @@ trait ChiselPublishModule extends SonatypeCentralPublishModule {
 
 /** Aggregate project for publishing Chisel as a single artifact
   */
-trait Unipublish extends ScalaModule with ChiselPublishModule {
+trait Unipublish extends ScalaModule with ChiselPublishModule with Mima {
 
   def scalaVersion = v.scalaVersion
 
@@ -43,6 +44,10 @@ trait Unipublish extends ScalaModule with ChiselPublishModule {
   // This is published as chisel
   override def artifactName = "chisel"
 
+  override def mimaPreviousVersions = Task.Input {
+    os.read.lines(BuildCtx.workspaceRoot / "etc" / "previous-versions.txt")
+  }
+
   /** Publish both this project and the plugin (for the default Scala version) */
   override def publishLocal(
     localMvnRepo: String = null,