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https://github.com/bazelbuild/rules_scala

Scala rules for Bazel
https://github.com/bazelbuild/rules_scala

bazel bazel-rules scala scalatest

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Scala rules for Bazel

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# Scala Rules for Bazel

[![Build status](https://badge.buildkite.com/90ce5244556df74db805a3c24a703fb87458396f9e1ddd687e.svg?branch=master)](https://buildkite.com/bazel/scala-rules-scala-postsubmit) 



## Where to get help

 - [#scala @ Bazel Slack](https://bazelbuild.slack.com/archives/CDCKJ2KFZ)

 - [Google group](https://groups.google.com/u/1/g/bazel-scala)

 - [Gitter chat](https://gitter.im/bazelbuild_rules_scala/Lobby)



## Overview



[Bazel](https://bazel.build/) is a tool for building and testing software and can handle large,

multi-language projects at scale.



This project defines core build rules for [Scala](https://www.scala-lang.org/) that can be used to build, test, and package Scala projects.



## Rules



* [scala_library](docs/scala_library.md)

* [scala_macro_library](docs/scala_macro_library.md)

* [scala_binary](docs/scala_binary.md)

* [scala_test](docs/scala_test.md)

* [scala_repl](docs/scala_repl.md)

* [scala_library_suite](docs/scala_library_suite.md)

* [scala_test_suite](docs/scala_test_suite.md)

* [thrift_library](docs/thrift_library.md)

* [scala_proto_library](docs/scala_proto_library.md)

* [scala_toolchain](docs/scala_toolchain.md)

* [scala_import](docs/scala_import.md)

* [scala_doc](docs/scala_doc.md)



## Getting started



1. [Install Bazel](https://docs.bazel.build/versions/master/install.html), 

see the [compatibility table](#bazel-compatible-versions).

2. Add the following to your `WORKSPACE` file and update versions with their sha256s if needed:



```starlark

# WORKSPACE

load("@bazel_tools//tools/build_defs/repo:http.bzl", "http_archive")



http_archive(

    name = "bazel_skylib",

    sha256 = "b8a1527901774180afc798aeb28c4634bdccf19c4d98e7bdd1ce79d1fe9aaad7",

    urls = [

        "https://mirror.bazel.build/github.com/bazelbuild/bazel-skylib/releases/download/1.4.1/bazel-skylib-1.4.1.tar.gz",

        "https://github.com/bazelbuild/bazel-skylib/releases/download/1.4.1/bazel-skylib-1.4.1.tar.gz",

    ],

)



# See https://github.com/bazelbuild/rules_scala/releases for up to date version information.

http_archive(

    name = "io_bazel_rules_scala",

    sha256 = "71324bef9bc5a885097e2960d5b8effed63399b55572219919d25f43f468c716",

    strip_prefix = "rules_scala-6.2.1",

    url = "https://github.com/bazelbuild/rules_scala/releases/download/v6.2.1/rules_scala-v6.2.1.tar.gz",

)



load("@io_bazel_rules_scala//:scala_config.bzl", "scala_config")

# Stores Scala version and other configuration

# 2.12 is a default version, other versions can be use by passing them explicitly:

# scala_config(scala_version = "2.11.12")

# Scala 3 requires extras...

#   3.2 should be supported on master. Please note that Scala artifacts for version (3.2.2) are not defined in

#   Rules Scala, they need to be provided by your WORKSPACE. You can use external loader like

#   https://github.com/bazelbuild/rules_jvm_external

scala_config()



load("@io_bazel_rules_scala//scala:scala.bzl", "rules_scala_setup", "rules_scala_toolchain_deps_repositories")



# loads other rules Rules Scala depends on 

rules_scala_setup()



# Loads Maven deps like Scala compiler and standard libs. On production projects you should consider 

# defining a custom deps toolchains to use your project libs instead 

rules_scala_toolchain_deps_repositories(fetch_sources = True)



load("@rules_proto//proto:repositories.bzl", "rules_proto_dependencies", "rules_proto_toolchains")

rules_proto_dependencies()

rules_proto_toolchains()



load("@io_bazel_rules_scala//scala:toolchains.bzl", "scala_register_toolchains")

scala_register_toolchains()



# optional: setup ScalaTest toolchain and dependencies

load("@io_bazel_rules_scala//testing:scalatest.bzl", "scalatest_repositories", "scalatest_toolchain")

scalatest_repositories()

scalatest_toolchain()

```



This will load the `rules_scala` repository at the commit sha

`rules_scala_version` into your Bazel project and register a [scala_toolchain](docs/scala_toolchain.md) at the default Scala version (2.12.20)



Then in your BUILD file just add the following so the rules will be available:

```starlark

load("@io_bazel_rules_scala//scala:scala.bzl", "scala_library", "scala_binary", "scala_test")

```

You may wish to have these rules loaded by default using bazel's prelude. You can add the above to the file `tools/build_rules/prelude_bazel` in your repo (don't forget to have a, possibly empty, BUILD file there) and then it will be automatically prepended to every BUILD file in the workspace.



To run with a persistent worker (much faster), you need to add

```

build --strategy=Scalac=worker

build --worker_sandboxing

```

to your command line, or to enable by default for building/testing add it to your .bazelrc.



## Coverage support



It will produce several .dat files with results for your targets.



You can also add more options to receive a combined coverage report:



```

bazel coverage \

  --combined_report=lcov \

  --coverage_report_generator="@bazel_tools//tools/test/CoverageOutputGenerator/java/com/google/devtools/coverageoutputgenerator:Main" \

  //...

```



This should produce a single `bazel-out/_coverage/_coverage_report.dat` from all coverage files that are generated.



You can extract information from your coverage reports with `lcov`:



```

# For a summary:

lcov --summary your-coverage-report.dat

# For details:

lcov --list your-coverage-report.dat

```



If you prefer an HTML report, then you can use `genhtml` provided also by the `lcov` package.



Coverage support has been only tested with [ScalaTest](http://www.scalatest.org/).



Please check [coverage.md](docs/coverage.md) for more details on coverage support.



## Selecting Scala version



### With toolchains



Rules scala supports the last two released minor versions for each of Scala 2.11, 2.12, 2.13.

Previous minor versions may work but are supported only on a best effort basis.



To configure Scala version you must call `scala_config(scala_version = "2.xx.xx")` and configure 

dependencies by declaring [scala_toolchain](docs/scala_toolchain.md). 

For a quick start you can use `scala_repositories()` and `scala_register_toolchains()`, which have 

dependency providers configured for `2.11.12`, `2.12.20` and `2.13.15` versions.



```starlark

# WORKSPACE

load("@io_bazel_rules_scala//:scala_config.bzl", "scala_config")

scala_config(scala_version = "2.13.15")



load("@rules_proto//proto:repositories.bzl", "rules_proto_dependencies", "rules_proto_toolchains")

rules_proto_dependencies()

rules_proto_toolchains()



load("@io_bazel_rules_scala//scala:toolchains.bzl", "scala_register_toolchains")

scala_register_toolchains()

```



Note: Toolchains are a more flexible way to configure dependencies, so you should prefer that way.

Please also note, that the `overriden_artifacts` parameter is likely to be removed in the future.



### Multiple versions (cross-compilation)



Rules scala supports configuring multiple Scala versions and offers target-level control of which one to use.



Please check [cross-compilation.md](docs/cross-compilation.md) for more details on cross-compilation support.



## Bazel compatible versions



| minimal bazel version | rules_scala gitsha |

|--------|------------------------------------------|

| 5.3.1  | HEAD                                     |

| 4.1.0  | a40063ef97688f056824b22b9e49fae6efd1df0f |

| 3.5.0  | 0f55e9f8cff6494bbff7cd57048d732286a520f5 |

| 2.0.0  | 116709091e5e1aab3346184217b565f4cb7ba4eb |

| 1.1.0  | d681a952da74fc61a49fc3167b03548f42fc5dde |

| 0.28.1 | bd0c388125e12f4f173648fc4474f73160a5c628 |

| 0.23.x | ca655e5a330cbf1d66ce1d9baa63522752ec6011 |

| 0.22.x | f3113fb6e9e35cb8f441d2305542026d98afc0a2 |

| 0.16.x | f3113fb6e9e35cb8f441d2305542026d98afc0a2 |

| 0.15.x | 3b9ab9be31ac217d3337c709cb6bfeb89c8dcbb1 |

| 0.14.x | 3b9ab9be31ac217d3337c709cb6bfeb89c8dcbb1 |

| 0.13.x | 3c987b6ae8a453886759b132f1572c0efca2eca2 |



See [the configuration file](https://github.com/bazelbuild/rules_scala/blob/master/.bazelci/presubmit.yml) for the exact versions verified with the continuous-integration builds.



## Breaking changes



If you're upgrading to a version containing one of these commits, you may encounter a breaking change where there was previously undefined behavior.



- [929b318](https://github.com/bazelbuild/rules_scala/commit/929b3180cc099ba76859f5e88710d2ac087fbfa3) on 2020-01-30: Fixed a bug in the JMH benchmark build that was allowing build failures to creep through. Previously you were able to build a benchmark suite with JMH build errors. Running the benchmark suite would only run the successfully-built benchmarks.



## Usage with [bazel-deps](https://github.com/johnynek/bazel-deps)



Bazel-deps allows you to generate bazel dependencies transitively for maven artifacts. Generally we don't want bazel-deps to fetch

scala artifacts from maven but instead use the ones we get from calling `scala_repositories`. The artifacts can be overridden in the

dependencies file used by bazel-deps:

```yaml

replacements:

  org.scala-lang:

    scala-library:

      lang: scala/unmangled

      target: "@io_bazel_rules_scala_scala_library//:io_bazel_rules_scala_scala_library"

    scala-reflect:

      lang: scala/unmangled

      target: "@io_bazel_rules_scala_scala_reflect//:io_bazel_rules_scala_scala_reflect"

    scala-compiler:

      lang: scala/unmangled

      target: "@io_bazel_rules_scala_scala_compiler//:io_bazel_rules_scala_scala_compiler"



  org.scala-lang.modules:

    scala-parser-combinators:

      lang: scala

      target:

        "@io_bazel_rules_scala_scala_parser_combinators//:io_bazel_rules_scala_scala_parser_combinators"

    scala-xml:

      lang: scala

      target:

        "@io_bazel_rules_scala_scala_xml//:io_bazel_rules_scala_scala_xml"

```



## Publishing to Maven repository

Go [here](docs/publish_to_maven.md)



## Dependency Tracking

Rules Scala supports multiple dependency modes including strict and unused dependency tracking. See

[Dependency Tracking](docs/dependency-tracking.md) for more info.



## Advanced configurable rules

To make the ruleset more flexible and configurable, we introduce a phase architecture. By using a phase architecture, where rule implementations are defined as a list of phases that are executed sequentially, functionality can easily be added (or modified) by adding (or swapping) phases.



Phases provide 3 major benefits:

 - Consumers are able to configure the rules to their specific use cases by defining new phases within their workspace without impacting other consumers.

 - Contributors are able to implement new functionalities by creating additional default phases.

 - Phases give us more clear idea what steps are shared across rules.



See [Customizable Phase](docs/customizable_phase.md) for more info.



### Phase extensions

 - [Scala Format](docs/phase_scalafmt.md)



## Building from source

Setup bazel:

We recommend using [Bazelisk](https://docs.bazel.build/versions/master/install.html) as your default bazel binary



Test & Build:

```

bash test_all.sh

```



You can also use:

```

bazel test //test/...

```

Note `bazel test //...` will not work since we have a sub-folder on the root folder which is meant to be used in a failure scenario in the integration tests.

Similarly to only build you should use `bazel build //src/...` due to that folder.



## Updates

This section contains a list of updates that might require action from the user.



 - [`043ba58`](https://github.com/bazelbuild/rules_scala/commit/043ba58afaf90bf571911123d3353bdf20408a33):

 Updates default scrooge version to `18.6.0`

 - [`76d4ab9`](https://github.com/bazelbuild/rules_scala/commit/76d4ab9f855f78113ee5990a84b0ad55d2417e4a):

 Updates naming for scala artifact replacements in bazel-deps. See [Usage with bazel-deps](#usage-with-bazel-deps)



## Contributing



See [CONTRIBUTING.md](CONTRIBUTING.md) for more info.



## Adopters



Here's a (non-exhaustive) list of companies that use `rules_scala` in production. Don't see yours? [You can add it in a PR](https://github.com/bazelbuild/rules_scala/edit/master/README.md)!



* [Ascend](https://ascend.io/)

* [Canva](https://www.canva.com/)

* [Domino Data Lab](https://www.dominodatalab.com/)

* [Etsy](https://www.etsy.com/)

* [Gemini](https://gemini.com/)

* [Grand Rounds](http://grandrounds.com/)

* [Kitty Hawk](https://kittyhawk.aero/)

* [Meetup](https://meetup.com/)

* [Spotify](https://www.spotify.com/)

* [Stripe](https://stripe.com/)

* [Tally](https://www.meettally.com/)

* [Twitter](https://twitter.com/)

* [VirtusLab](https://virtuslab.com/)

* [VSCO](https://vsco.co)

* [Wix](https://www.wix.com/)