Extract mima as a separate build step

Author: adamw

.github/workflows/ci.yml

@@ -31,8 +31,6 @@ jobs:
       run: sudo apt-get install libidn11-dev
     - name: Compile
       run: sbt -v compile
-    - name: Check MiMa # disable for major releases
-      run: sbt -v mimaReportBinaryIssues
     - name: Test
       run: sbt -v test
     - name: Cleanup
@@ -43,6 +41,37 @@ jobs:
         find $HOME/.cache/coursier/v1                -name "ivydata-*.properties" -delete || true
         find $HOME/.sbt                              -name "*.lock"               -delete || true
 
+  mima:
+    # run on external PRs, but not on internal PRs since those will be run by push to branch
+    if: github.event_name == 'push' || github.event.pull_request.head.repo.full_name != github.repository
+    runs-on: ubuntu-20.04
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v2
+        with:
+          fetch-depth: 0 # checkout tags so that dynver works properly (we need the version for MiMa)
+      - name: Set up JDK 11
+        uses: actions/setup-java@v1
+        with:
+          java-version: 11
+      - name: Cache sbt
+        uses: actions/cache@v2
+        with:
+          path: |
+            ~/.sbt
+            ~/.ivy2/cache
+            ~/.coursier
+          key: sbt-cache-${{ runner.os }}-JVM-${{ hashFiles('project/build.properties') }}
+      - name: Check MiMa # disable for major releases
+        run: sbt -v mimaReportBinaryIssues
+      - name: Cleanup
+        run: |
+          rm -rf "$HOME/.ivy2/local" || true
+          find $HOME/.ivy2/cache                       -name "ivydata-*.properties" -delete || true
+          find $HOME/.ivy2/cache                       -name "*-LM-SNAPSHOT*"       -delete || true
+          find $HOME/.cache/coursier/v1                -name "ivydata-*.properties" -delete || true
+          find $HOME/.sbt                              -name "*.lock"               -delete || true
+
   publish:
     name: Publish release
     needs: [ci]

build.sbt

@@ -29,14 +29,15 @@ val commonSettings = commonSmlBuildSettings ++ ossPublishSettings ++ Seq(
   libraryDependencies ++= Seq(
     "org.scalatest" %% "scalatest" % scalaTestVersion % Test
   ),
-  mimaPreviousArtifacts := previousStableVersion.value.map(organization.value %% moduleName.value % _).toSet,
-  mimaReportBinaryIssues := { if ((publish / skip).value) {} else mimaReportBinaryIssues.value },
+  mimaPreviousArtifacts := Set.empty,
   versionScheme := Some("semver-spec")
 )
 
 val commonJvmSettings = commonSettings ++ Seq(
   scalacOptions ++= Seq("-target:jvm-1.8"),
-  ideSkipProject := (scalaVersion.value != scala2_13)
+  ideSkipProject := (scalaVersion.value != scala2_13),
+  mimaPreviousArtifacts := previousStableVersion.value.map(organization.value %% moduleName.value % _).toSet,
+  mimaReportBinaryIssues := { if ((publish / skip).value) {} else mimaReportBinaryIssues.value }
 )
 
 val commonJsSettings = commonSettings ++ Seq(