Add scalafmt

.github/workflows/format.yml

@@ -0,0 +1,23 @@
+name: Scalafmt
+
+permissions: {}
+
+on:
+  pull_request:
+    branches: ['**']
+
+jobs:
+  build:
+    name: Code is formatted
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout current branch (full)
+        uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
+          persist-credentials: false
+
+      - name: Check project is formatted
+        uses: jrouly/scalafmt-native-action@v3
+        with:
+          arguments: '--list --mode diff-ref=origin/main'

.scalafmt.conf

@@ -0,0 +1,26 @@
+version = 3.7.17
+runner.dialect = scala212
+maxColumn = 120
+project.git = true
+
+# http://docs.scala-lang.org/style/scaladoc.html recommends the JavaDoc style.
+# scala/scala is written that way too https://github.com/scala/scala/blob/v2.12.2/src/library/scala/Predef.scala
+docstrings.style = Asterisk
+
+# This also seems more idiomatic to include whitespace in import x.{ yyy }
+spaces.inImportCurlyBraces = true
+
+align.tokens."+" = [
+  {
+    code   = "%"
+    owners = [
+      { regex = "Term.ApplyInfix" }
+    ]
+  },
+  {
+    code   = "%%"
+    owners = [
+      { regex = "Term.ApplyInfix" }
+    ]
+  }
+]