The headline features of sbt 1.5.0 are:
- Scala 3 support
- Eviction error
- Deprecation of sbt 0.13 syntax
- Coursier-based launcher
Scala 3 support
sbt 1.5.0 adds built-in Scala 3 support, contributed by Scala Center. Main implementation was done by Adrien Piquerez (@adpi2) based on EPFL/LAMP's sbt-dotty. You can now use Scala 3.0.0-RC2 like any other Scala version.
ThisBuild / scalaVersion := "3.0.0-RC2"This will compile the following Hello.scala:
package example
@main def hello(arg: String*): Unit =
if arg.isEmpty then println("hello")
else println(s"hi ${arg.head}")Note: To support cross testing of various Scala 3.x releases, crossTarget directory will contain the full Scala version. #6415
Scala 2.13-3.x sandwich
Scala 3.0.x shares the standard library with Scala 2.13, and since Scala 2.13.4, they can mutually consume the output of each other as external library. This allows you to create Scala 2.13-3.x sandwich, a layering of dependencies coming from different Scala versions.
Warning: Library authors should generally treat Scala 3.0 as any other major version, and prefer to cross publish _3 variant to avoid the conflict. Some libraries may encode a particular notion in different ways for Scala 2.13 and 3.0. For example, arity abstraction may use Shapeless HList in Scala 2.13, but built-in Tuple types in Scala 3.0. Thus it's generally not safe to have _2.13 and _3 versions of the same library in the classpath, even transitively. Application developers should be free to use .cross(CrossVersion.for3Use2_13) as long as the transitive dependency graph will not introduce _2.13 variant of a library you already have in _3 variant.
sbt 1.5.0 introduces new cross building operand to use _3 variant when scalaVersion is 2.13.x, and vice versa:
("a" % "b" % "1.0").cross(CrossVersion.for3Use2_13)
("a" % "b" % "1.0").cross(CrossVersion.for2_13Use3)Deprecation of sbt 0.13 syntax
sbt 1.5.0 deprecates both the sbt 0.13 style shell syntax proj/config:intask::key and sbt 0.13 style build.sbt DSL key in (Compile, intask) in favor of the unified slash syntax.
There's a syntactic Scalafix rule for unified slash syntax
to semi-automatically rewrite existing sbt 0.13 syntax to the slash syntax. Currently it requires the use of scalafix CLI
and it's not very precise (because it's a syntactic rule that only looks at the shape of the code) but it gets most of the job done.
$ scalafix --rules=https://gist.githubusercontent.com/eed3si9n/57e83f5330592d968ce49f0d5030d4d5/raw/7f576f16a90e432baa49911c9a66204c354947bb/Sbt0_13BuildSyntax.scala *.sbt project/*.scala
See https://www.scala-sbt.org/1.x/docs/Migrating-from-sbt-013x.html#slash for details.
Eviction error
sbt 1.5.0 removes eviction warning, and replaces it with stricter eviction error. Unlike the eviction warning that was based on speculation, eviction error only uses the ThisBuild / versionScheme information supplied by the library authors.
For example:
lazy val use = project
.settings(
name := "use",
libraryDependencies ++= Seq(
"org.http4s" %% "http4s-blaze-server" % "0.21.11",
// https://repo1.maven.org/maven2/org/typelevel/cats-effect_2.13/3.0.0-M4/cats-effect_2.13-3.0.0-M4.pom
// is published with early-semver
"org.typelevel" %% "cats-effect" % "3.0.0-M4",
),
)The above build will fail to build use/compile with the following error:
[error] stack trace is suppressed; run last use / update for the full output
[error] (use / update) found version conflict(s) in library dependencies; some are suspected to be binary incompatible:
[error]
[error] * org.typelevel:cats-effect_2.12:3.0.0-M4 (early-semver) is selected over {2.2.0, 2.0.0, 2.0.0, 2.2.0}
[error] +- use:use_2.12:0.1.0-SNAPSHOT (depends on 3.0.0-M4)
[error] +- org.http4s:http4s-core_2.12:0.21.11 (depends on 2.2.0)
[error] +- io.chrisdavenport:vault_2.12:2.0.0 (depends on 2.0.0)
[error] +- io.chrisdavenport:unique_2.12:2.0.0 (depends on 2.0.0)
[error] +- co.fs2:fs2-core_2.12:2.4.5 (depends on 2.2.0)
[error]
[error]
[error] this can be overridden using libraryDependencySchemes or evictionErrorLevelThis is because Cats Effect 2.x and 3.x are found in the classpath, and Cats Effect has declared that it uses early-semver. If the user wants to opt-out of this, the user can do so per module:
ThisBuild / libraryDependencySchemes += "org.typelevel" %% "cats-effect" % VersionScheme.Alwaysor globally as:
ThisBuild / evictionErrorLevel := Level.InfoOn the other hand, if you want to bring back the guessing feature in eviction warning, you can do using the following settings:
ThisBuild / assumedVersionScheme := VersionScheme.PVP
ThisBuild / assumedVersionSchemeJava := VersionScheme.EarlySemVer
ThisBuild / assumedEvictionErrorLevel := Level.Warn@eed3si9n implemented this in #6221, inspired in part by Scala Center's sbt-eviction-rules, which was implemented by Alexandre Archambault (@alxarchambault) and Julien Richard-Foy (@julienrf).
ThisBuild / packageTimestamp setting
In sbt 1.4.0 we started wiping out the timestamps in JAR to make the builds more repeatable. This had an unintended consequence of breaking Play's last-modified response header.
To opt out of this default, the user can use:
ThisBuild / packageTimestamp := Package.keepTimestamps
// or
ThisBuild / packageTimestamp := Package.gitCommitDateTimestampCoursier-based launcher
sbt launcher shipped in the official installer of sbt is a generic launcher that is able to launch all versions of sbt. For the sbt launcher shipped with sbt 1.5.0 installer, its internal dependency resolver used to resolve sbt itself was updated from Apache Ivy to Coursier (Dependency resolver for the built has been updated to Coursier in sbt 1.3.0).
You can use -Dsbt.launcher.coursier=false to opt out of using Coursier and used Apache Ivy instead. launcher#86 by @eed3si9n
Other updates
- Fixes
SemanticdbPlugincreating duplicatescalacOptionsor dropping-Yrangepos#6296/#6316 by @bjaglin and @eed3si9n - Fixes tab completion of dependency configurations
Compile,Test, etc #6283 by @eed3si9n - Fixes exit code calculation in
StashOnFailure#6266 by @melezov - Fixes concurrency issues with
testQuick#6326 by @RafalSumislawski - Updates to Scala 2.12.13.
- Updates to Coursier 2.0.15, includes
reloadmemory fix by @jtjeferreira and behind-the-proxy IntelliJ import fix added by @eed3si9n - Warns when
ThisBuild / versionSchemeis missing while publishing #6310 by @eed3si9n - Use 2010-01-01 for the repeatable build timestamp wipe-out to avoid negative date #6254 by @takezoe (There's an active discussion to use commit date instead)
- Adds FileInput/FileOutput that avoids intermediate String parsing #5515 by @jtjeferreira
- Support credential file without realm lm#367 by @MasseGuillaume
- Support MUnit out of box #6335 by @julienrf
- Automatically publishLocal plugin dependency subprojects before
scripted#6351 by @steinybot