See How Bazel can dramatically improve Scala build times for your growing code base

2. avg build time
(minutes)

4. Infra change

6. Infra change

8. scala_project
├── WORKSPACE
└── src
└── main
└── scala
└── com
├── example
│ ├── A.scala
│ ├── B.scala
│ └── C.scala
└── example2
├── D.scala
├── E.scala
└── F.scala

9. scala_project
├── WORKSPACE
└── src
└── main
└── scala
└── com
├── example
│ ├── A.scala
│ ├── B.scala
│ ├── BUILD
│ └── C.scala
└── example2
├── D.scala
├── E.scala
└── F.scala

10. f(A,B,C)f( )
Source files
env’ variables
dependencies
A
B
C
wix

11. scala_project
├── WORKSPACE
└── src
├── main
│ └── scala
│ └── com
│ └── example
│ ├── A.scala
│ ├── B.scala
│ ├── BUILD FILE
│ ├── C.scala
│ └── Example.scala
└── test
A.scala -> scala_library -> a.jar
scala_library(
name="a",
srcs=[
"A.scala",
],
deps = [":c"])
$ bazel build :a

12. f(A,B,C)f( )
A
B
C

13. A
B
C
f( ) f(A,B,C)

14. f(A,B,C)
f( )
A
B
C
f(A,B,C)
f( )
A
B
C

17. Compilation Test RunPending

18. ✔ ✔ ✔
✔ ✔ ✔
✔ ✔ ✔ ✔

19. ✔ ✔ ✔
✔ ✔ ✔
✔ ✔ ✔ ✔
CI/local tradeoff

25. out of the box

26. scala_project
├── build.sbt / build.gradle / pom.xml
└── src
├── main
├── test

27. scala_project
├── WORKSPACE
└── src
├── main
│ └── scala
│ └── com
│ └── example
│ ├── A.scala
│ ├── B.scala
│ ├── BUILD FILE
│ ├── C.scala
│ └── Example.scala
└── test
scala_project
├── build.sbt / build.gradle / pom.xml
└── src
├── main
├── test

29. scala_project
├── WORKSPACE
└── src
├── main
│ └── scala
│ └── com
│ └── example
│ ├── A.scala
│ ├── B.scala
│ ├── BUILD FILE
│ ├── C.scala
│ └── Example.scala
└── test
A.scala -> scala_library -> a.jar
scala_library(
name="a",
srcs=[
"A.scala",
],
deps = [":c"])
$ bazel build :a

31. scala_project
├── WORKSPACE
└── src
├── main
│ └── scala
│ └── com
│ └── example
│ ├── A.scala
│ ├── B.scala
│ ├── BUILD FILE
│ ├── C.scala
│ └── Example.scala
└── test
B.scala -> scala_binary ->
B.jar + app_runner.sh
scala_binary(
name="b",
srcs=[
"B.scala",
],
main_class="com.example.Foo")
$ bazel run :b

33. ExampleTest.scala -> scala_test ->
example_test.jar + test_runner.sh
scala_test(
name="example_test",
srcs=glob(["*Test.scala"]))
$ bazel test :example_test
scala_project
├── WORKSPACE
└── src
├── main
│ └── scala
│ └── com
│ └── example
│ ├── A.scala
│ ├── B.scala
│ ├── BUILD
│ ├── C.scala
│ └── Example.scala
└── test
└── scala
└── com
└── example
├── BUILD
├── ExampleTest.scala
└── Example2Test.scala

35. f(A,B,C)f( )
A
B
C

37. hash1
hash2

39. scala_toolchain(
name = "my_toolchain_impl",
scalacopts = ["-Ywarn-unused"],
unused_dependency_checker_mode = "off",
visibility = ["//visibility:public"]
)

40. --unused_dependency_checker_mode=WARN|ERROR
...
error:Target '//some_package:unused_dep' is specified as a dependency to //path/to:foo but isn't used, please
remove it from the deps.
buildozer 'remove deps //some_package:unused_dep' //path/to:foo
foo
B unused

41. --strict_java_deps=WARN|ERROR
...
Target '@cats//jar' is used but isn't explicitly declared, please add it to the deps.
buildozer 'add deps @cats//jar' //path/to:foo
foo
specs2
cats

42. --strict_java_deps=WARN|ERROR
...
Target '@cats//jar' is used but isn't explicitly declared, please add it to the deps.
buildozer 'add deps @cats//jar' //path/to:foo
Based on Jason Zaugg’s Classpath Shrinker plugin
foo
specs2
cats

45. scala_toolchain(
name = "wix_plus_one_global_toolchain_impl",
scalacopts = [
"-unchecked",
...
],
plus_one_deps_mode = "on",
scalac_provider_attr = "@core_server_build_tools//toolchains:scalac_default",
visibility = ["//visibility:public"],
)

46. build --strategy=Scalac=worker

48. Scala 2.11.12
scala_repositories(("2.12.6", {
"scala_compiler": "3023b07cc02f2b0217b2c04f8e636b396130b3a8544a8dfad498a19c3e57a863",
"scala_library": "f81d7144f0ce1b8123335b72ba39003c4be2870767aca15dd0888ba3dab65e98",
"scala_reflect": "ffa70d522fc9f9deec14358aa674e6dd75c9dfa39d4668ef15bb52f002ce99fa"
}))