sbt 1.0.1 

This is a hotfix release for sbt 1.0.x series.

Bug fixes 


The watch source feature went through a major change from sbt 0.13 to sbt 1.0 using NIO; however, it did not have clear migration path, so we are rectifying that in sbt 1.0.1.

First, sbt.WatchSource is a new alias for Hopefully this is easy enough to remember because the key is named watchSources. Next, def apply(base: File) and def apply(base: File, includeFilter: FileFilter, excludeFilter: FileFilter) constructors were added to the companion object of sbt.WatchSource.

For backward compatiblity, sbt 1.0.1 adds += support (Append instance) from File to Seq[WatchSource].

So, if you have a directory you want to watch:

watchSources += WatchSource(sourceDirectory.value)

If you have a list of files:

watchSources ++= (sourceDirectory.value ** "*.scala").get

#3438 by @Duhemm; #3478 and io#74 by @eed3si9n

sbt 1.0.0 

Features, fixes, changes with compatibility implications 

See Migrating from sbt 0.13.x also.

Dropped dreprecations:





Details of major changes 

Zinc 1: Class-based name hashing 

A major improvement brought into Zinc 1.0 by Grzegorz Kossakowski (commissioned by Lightbend) is class-based name hashing, which will speed up the incremental compilation of Scala in large projects.

Zinc 1.0’s name hashing tracks your code dependendencies at the class level, instead of at the source file level. The GitHub issue sbt/sbt#1104 lists some comparisons of adding a method to an existing class in some projects:

ScalaTest   AndHaveWord class:          Before 49s, After 4s (12x)
Specs2      OptionResultMatcher class:  Before 48s, After 1s (48x)
scala/scala Platform class:             Before 59s, After 15s (3.9x)
scala/scala MatchCodeGen class:         Before 48s, After 17s (2.8x)

This depends on some factors such as how your classes are organized, but you can see 3x ~ 40x improvements. The reason for the speedup is because it compiles fewer source files than before by untangling the classes from source files. In the example adding a method to scala/scala’s Platform class, sbt 0.13’s name hashing used to compile 72 sources, but the new Zinc compiles 6 sources.

Zinc API changes 

sbt server: JSON API for tooling integration 

sbt 1.0 includes server feature, which allows IDEs and other tools to query the build for settings, and invoke commands via a JSON API. Similar to the way that the interactive shell in sbt 0.13 is implemented with shell command, “server” is also just shell command that listens to both human input and network input. As a user, there should be minimal impact because of the server.

In March 2016, we rebooted the “server” feature to make it as small as possible. We worked in collaboration with JetBrains’ @jastice who works on IntelliJ’s sbt interface to narrow down the feature list. sbt 1.0 will not have all the things we originally wanted, but in the long term, we hope to see better integration between IDE and sbt ecosystem using this system. For example, IDEs will be able to issue the compile task and retrieve compiler warning as JSON events:

{"type":"xsbti.Problem","message":{"category":"","severity":"Warn","message":"a pure expression does nothing in statement position; you may be omitting necessary parentheses","position":{"line":2,"lineContent":"  1","offset":29,"pointer":2,"pointerSpace":"  ","sourcePath":"/tmp/hello/Hello.scala","sourceFile":"file:/tmp/hello/Hello.scala"}},"level":"warn"}

Another related feature that was added is the bgRun task which, for example, enables a server process to be run in the background while you run tests against it.

Static validation of build.sbt 

sbt 1.0 prohibits .value calls inside the bodies of if expressions and anonymous functions in a task, @sbtUnchecked annotation can be used to override the check.

The static validation also catches if you forget to call .value in a body of a task.

#3216 and #3225 by @jvican

Eviction warning presentation 

sbt 1.0 improves the eviction warning presetation.


[warn] There may be incompatibilities among your library dependencies.
[warn] Here are some of the libraries that were evicted:
[warn]  * -> 3.0.0
[warn] Run 'evicted' to see detailed eviction warnings


[warn] Found version conflict(s) in library dependencies; some are suspected to be binary incompatible:
[warn]      * com.typesafe.akka:akka-actor_2.12:2.5.0 is selected over 2.4.17
[warn]          +- de.heikoseeberger:akka-log4j_2.12:1.4.0            (depends on 2.5.0)
[warn]          +- com.typesafe.akka:akka-parsing_2.12:10.0.6         (depends on 2.4.17)
[warn]          +- com.typesafe.akka:akka-stream_2.12:2.4.17 ()       (depends on 2.4.17)
[warn] Run 'evicted' to see detailed eviction warnings

#3202 by @eed3si9n


@jrudolph’s sbt-cross-building is a plugin author’s plugin. It adds cross command ^ and sbtVersion switch command ^^, similar to + and ++, but for switching between multiple sbt versions across major versions. sbt 0.13.16 merges these commands into sbt because the feature it provides is useful as we migrate plugins to sbt 1.0.

To switch the sbtVersion in pluginCrossBuild from the shell use:

^^ 1.0.0-M5

Your plugin will now build with sbt 1.0.0-M5 (and its Scala version 2.12.2).

If you need to make changes specific to a sbt version, you can now include them into src/main/scala-sbt-0.13, and src/main/scala-sbt-1.0.0-M5, where the binary sbt version number is used as postfix.

To run a command across multiple sbt versions, set:

crossSbtVersions := Vector("0.13.15", "1.0.0-M5")

Then, run:

^ compile

#3133 by @eed3si9n (forward ported from 0.13.16-M1)


sbt IO 1.0 add variant of IO.copyFile and IO.copyDirectory that accept CopyOptions() is an example of pseudo case class similar to the builder pattern.

import{ IO, CopyOptions }

IO.copyDirectory(source, target)

// The above is same as the following
IO.copyDirectory(source, target, CopyOptions()

io#53 by @dwijnand

Library management API and parallel artifact download 

sbt 1.0 adds Library management API co-authored by Eugene Yokota (@eed3si9n) from Lightbend and Martin Duhem (@Duhemm) from Scala Center. This API aims to abstract Apache Ivy as well as alternative dependency resolution engines Ivy, cached resolution, and Coursier.

Parallel artifact download for Ivy engine was contributed by Jorge (@jvican) from Scala Center. It also introduces Gigahorse OkHttp as the Network API, and it uses Square OkHttp for artifact download as well.

lm#124 by @eed3si9n/@Duhemm, lm#90 by @jvican/@jsuereth and lm#104 by @eed3si9n.

Binary format for Zinc’s internal storage 

Jorge (@jvican) from Scala Center contributed a binary format for Zinc’s internal storage using Google Procol Buffer. The new format provides us with three main advantages:

  1. Backwards and forwards binary compatibility at the analysis format level.
  2. Faster (1.5 ~ 2x) serialization/deserialization of the analysis file.
  3. Provides a better way to make the analysis file machine-independent.

zinc#351 by @jvican

Dependency locking 

Dependency locking feature is still in progress, but Jorge (@jvican) from Scala Center has added a number of related features that would should work together to allow dependency locking.


Too many people to thank here. See Credits


sbt Reference Manual
      1. sbt 1.0.1