Stop using "_" to mean empty version / version to read in BOM

build.mill

@@ -116,7 +116,7 @@ object Deps {
   val asmTree = ivy"org.ow2.asm:asm-tree:9.7.1"
   val bloopConfig = ivy"ch.epfl.scala::bloop-config:1.5.5"
 
-  val coursierVersion = "2.1.20"
+  val coursierVersion = "2.1.21"
   val coursier = ivy"io.get-coursier::coursier:$coursierVersion"
   val coursierInterface = ivy"io.get-coursier:interface:1.0.26"
   val coursierJvm = ivy"io.get-coursier::coursier-jvm:$coursierVersion"

scalalib/src/mill/scalalib/CoursierModule.scala

@@ -235,15 +235,15 @@ object CoursierModule {
     /**
      * Processes dependencies and BOMs with coursier
      *
-     * This makes coursier read and process BOM dependencies, and fill version placeholders
+     * This makes coursier read and process BOM dependencies, and fill empty versions
      * in dependencies with the BOMs.
      *
-     * Note that this doesn't throw when a version placeholder cannot be filled, and just leaves
-     * the placeholder behind.
+     * Note that this doesn't throw when an empty version cannot be filled, and just leaves
+     * the empty version behind.
      *
-     * @param deps dependencies that might have placeholder versions ("_" as version)
+     * @param deps dependencies that might have empty versions
      * @param resolutionParams coursier resolution parameters
-     * @return dependencies with version placeholder filled
+     * @return dependencies with empty version filled
      */
     def processDeps[T: CoursierModule.Resolvable](
         deps: IterableOnce[T],

scalalib/src/mill/scalalib/Dep.scala

@@ -118,8 +118,8 @@ object Dep {
     }
 
     (module.split(':') match {
-      case Array(a, b) => Dep(a, b, "_", cross = empty(platformed = false))
-      case Array(a, "", b) => Dep(a, b, "_", cross = Binary(platformed = false))
+      case Array(a, b) => Dep(a, b, "", cross = empty(platformed = false))
+      case Array(a, "", b) => Dep(a, b, "", cross = Binary(platformed = false))
       case Array(a, b, c) => Dep(a, b, c, cross = empty(platformed = false))
       case Array(a, b, "", c) => Dep(a, b, c, cross = empty(platformed = true))
       case Array(a, "", b, c) => Dep(a, b, c, cross = Binary(platformed = false))

scalalib/src/mill/scalalib/JavaModule.scala

@@ -223,7 +223,8 @@ trait JavaModule
         dep.publication.classifier
       )
       val versionOverrideOpt =
-        if (dep.version == "_") depMgmtMap.get(depMgmtKey).map(_.version).filter(_.nonEmpty)
+        if (dep.version.isEmpty)
+          depMgmtMap.get(depMgmtKey).map(_.version).filter(_.nonEmpty)
         else None
       val extraExclusions = depMgmtMap.get(depMgmtKey).map(_.minimizedExclusions)
       dep
@@ -270,8 +271,7 @@ trait JavaModule
           )
           val values = DependencyManagement.Values(
             Configuration.empty,
-            if (depMgmt.version == "_") "" // shouldn't be needed with future coursier versions
-            else depMgmt.version,
+            depMgmt.version,
             depMgmt.minimizedExclusions,
             depMgmt.optional
           )

scalalib/src/mill/scalalib/PublishModule.scala

@@ -147,7 +147,7 @@ trait PublishModule extends JavaModule { outer =>
   def ivy: T[PathRef] = Task {
     val (rootDepVersions, bomDepMgmt) = bomDetails()
     val publishXmlDeps0 = publishXmlDeps().map { dep =>
-      if (dep.artifact.version == "_")
+      if (dep.artifact.version.isEmpty)
         dep.copy(
           artifact = dep.artifact.copy(
             version = rootDepVersions.getOrElse(
@@ -168,7 +168,7 @@ trait PublishModule extends JavaModule { outer =>
         depManagement().toSeq
           .map(bindDependency())
           .map(_.dep)
-          .filter(depMgmt => depMgmt.version.nonEmpty && depMgmt.version != "_")
+          .filter(_.version.nonEmpty)
       )
       val entries = coursier.core.DependencyManagement.add(
         Map.empty,

scalalib/src/mill/scalalib/publish/Pom.scala

@@ -209,7 +209,7 @@ object Pom {
     val optional = if (d.optional) <optional>true</optional> else NodeSeq.Empty
 
     val version =
-      if (d.artifact.version == "_") NodeSeq.Empty
+      if (d.artifact.version.isEmpty) NodeSeq.Empty
       else <version>{d.artifact.version}</version>
 
     if (d.exclusions.isEmpty)

scalalib/test/src/mill/scalalib/BomTests.scala

@@ -400,7 +400,7 @@ object BomTests extends TestSuite {
           val res = eval(modules.bom.placeholder.check.compileClasspath)
           assert(
             res.left.exists(_.toString.contains(
-              "not found: https://repo1.maven.org/maven2/com/google/protobuf/protobuf-java/_/protobuf-java-_.pom"
+              "not found: https://repo1.maven.org/maven2/com/google/protobuf/protobuf-java//protobuf-java-.pom"
             ))
           )
         }