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2 years at Twitter

I was a Staff Engineer at Twitter’s Build/Bazel Migration team. After two incredible years, November 17 was my last day (I took the voluntary separation offer and resigned, not that it matters). Twitter has been a special place to work for, for its culture of excellence, diversity, and outpouring of care for all the people that made Flock the Flock. I am grateful that I got the opportunity to experience that firsthand, and be part of it.

image1

Here’s a quick retrospective on my last two years. Info available here are based on publicly available talks and data. Just from our team 10+ members left Twitter after the buyout, so I’ve sprinkled this post with links to their LinkedIn profiles both current and former.

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sbt 1.8.0

Hi everyone. On behalf of the sbt project, I am happy to announce sbt 1.8.0. This is the eighth feature release of sbt 1.x, a binary compatible release focusing on new features. sbt 1.x is released under Semantic Versioning, and the plugins are expected to work throughout the 1.x series. Please try it out, and report any issues you might come across.

Highlights

  • Updates Coursier to 2.1.0-RC1 to address CVE-2022-37866
  • Updates Ivy fork to 2.3.0-sbt-a8f9eb5bf09d0539ea3658a2c2d4e09755b5133e to address CVE-2022-37866
  • Updates scala-xml to 2.x
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sbt 1.8.0-RC1

Hi everyone. On behalf of the sbt project, I am happy to announce sbt 1.8.0-RC1. This is the eighth feature release of sbt 1.x, a binary compatible release focusing on new features. sbt 1.x is released under Semantic Versioning, and the plugins are expected to work throughout the 1.x series. Please try it out, and report any issues you might come across.

Highlights

sbt 1.8.0 is a small release focused on upgrading scala-xml to 2.x. In theory this breaks the binary compatibility in the plugin ecosystem, but in practice there’s already a mixture of both 1.x and 2.x.

If you encounter a conflict in plugins, try putting the following in project/plugins.sbt:

ThisBuild / libraryDependencySchemes += "org.scala-lang.modules" %% "scala-xml" % VersionScheme.Always
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sbt 1.7.2

I’m happy to announce sbt 1.7.2 patch release is available. Full release note is here - https://github.com/sbt/sbt/releases/tag/v1.7.2

See 1.7.0 release note for the details on 1.7.x features.

Highlights

  • Fixes invalidation of incremental testQuick task #6903 by @gontard
  • Updates sbt new by default to use Giter8 0.15.0
  • Updates launcher to support Scala 3 apps #7035 by @eed3si9n
  • Adds diagnosticCode and diagnosticRelatedInforamation (sic) to InterfaceUtil.problem(...) #7006 by @ckipp01
  • Forwards diagnosticCode to BSP #6998 by @ckipp01
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sbt 1.7.0

Hi everyone. On behalf of the sbt project, I am happy to announce sbt 1.7.0. This is the seventh feature release of sbt 1.x, a binary compatible release focusing on new features. sbt 1.x is released under Semantic Versioning, and the plugins are expected to work throughout the 1.x series. Please try it out, and report any issues you might come across.

How to upgrade

Download the official sbt runner from cs setup, SDKMAN, or download from https://github.com/sbt/sbt/releases/tag/v1.7.0.

The sbt version used for your build is upgraded by putting the following in project/build.properties:

sbt.version=1.7.0

This mechanism allows that sbt 1.7.0 is used only for the builds that you want.

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scopt 4.1.0

scopt 4.1.0 is released. To try new scopt 4.1.0:

libraryDependencies += "com.github.scopt" %% "scopt" % "4.1.0"

scopt 4.1.0 is cross published to the following build matrix:

Scala Version JVM JS (1.x) JS (0.6.x) Native (0.4.x)
3.x ✅ ✅ n/a ✅
2.13.x ✅ ✅ ✅ ✅
2.12.x ✅ ✅ ✅ ✅
2.11.x ✅ ✅ ✅ ✅

scopt is a little command line options parsing library. See https://eed3si9n.com/scopt4 or readme for the details on how to use scopt.

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Eval 0.1.0

I released Eval 0.1.0. Eval evaluates Scala 3 code. It’s a Scala 3 port of Eval class used in sbt.

package example

import com.eed3si9n.eval.Eval
import com.eed3si9n.eval.EvalReporter
import java.nio.file.Paths

@main def main(): Unit =
  val eval = Eval(
    backingDir = Paths.get("/tmp/classes"),
    mkReporter = () => EvalReporter.store
  )
  val result = eval.evalInfer("2")
  println(result.tpe)
  println(result.getValue(this.getClass.getClassLoader))

The above prints:

Int
2
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simplifying sbt with common settings

sbt is simple, in a sense that it has a few concepts like settings and tasks, and it achieves a wide variety of things. An idea popped into my head today that could simplify sbt further. I don’t have an implementation on this yet.

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granularity of testing

In the context of sbt, Bazel, and likely many other build tools, the term test could encompass various levels, and it’s useful to disamgibuate this, especially when we want to configure pre- and post-hooks and parallel execution. In other words, what do we mean when we say “test”?

There are four levels to test:

  1. test command
  2. test modules
  3. test class
  4. test method/expression

test as commandline interface

The top-most level is the test command that the build tools provide to the users.

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sbt 1.6.0

Hi everyone. On behalf of the sbt project, I am happy to announce sbt 1.6.0. This is the sixth feature release of sbt 1.x, a binary compatible release focusing on new features. sbt 1.x is released under Semantic Versioning, and the plugins are expected to work throughout the 1.x series. Please try it out, and report any issues you might come across.

The headline features of sbt 1.6.0 are:

  • Improved JDK 17 support
  • BSP improvements
  • Zinc improvements
  • Remote caching improvements
  • Tab completion of global keys
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sbt 1.6.0-RC2

Hi everyone. On behalf of the sbt project, I am happy to announce sbt 1.6.0-RC2. This is the sixth feature release of sbt 1.x, a binary compatible release focusing on new features. sbt 1.x is released under Semantic Versioning, and the plugins are expected to work throughout the 1.x series. Please try it out, and report any issues you might come across.

  • If no serious issues are found by Saturday, December 25th 2021, 1.6.0-RC2 will become 1.6.0 final.
  • If no serious issues are found by Saturday, December 11th 2021, 1.6.0-RC1 will become 1.6.0 final.

The headline features of sbt 1.6.0 are:

  • Improved JDK 17 support
  • BSP improvements
  • Zinc improvements
  • Remote caching improvements
  • Tab completion of global keys
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sudori part 3

I’m hacking on a small project called sudori, an experimental sbt. The initial goal is to port the macro to Scala 3. It’s an exercise to take the macro apart and see if we can build it from the ground up. This an advanced area of Scala 2 and 3, and I’m finding my way around by trial and error. This is part 3.

It’s been a while since I wrote part 2, but in between I’ve written intro to Scala 3 macros, which is sort of a sudori prequel.

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Starlark 4.2.1

Starlark is a dialect of Python, originally designed as a configuration language for the Bazel build tool. Currently there are implementations in Go, Java, and Rust. As far as I know, the main Java implementation of Starlark has only been available as Bazel’s source repo on GitHub.

Since it would be convenient to have a binary distribution, I’ve forked the repo, and published it as "com.eed3si9n.starlark" % "starlark" % "4.2.1" (com.eed3si9n.starlark:starlark:4.2.1) on Maven Central. The code is the same as Bazel 4.2.1.

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JDK 17 on GitHub Actions

Here’s a quick tutorial of how to test your project on JDK 17 using Ólaf’s olafurpg/setup-scala. As the starting point we’ll use the following setup, which is documented in Setting up GitHub Actions with sbt:

name: CI
on:
  pull_request:
  push:
jobs:
  test:
    strategy:
      fail-fast: false
      matrix:
        include:
          - os: ubuntu-latest
            java: 11
            jobtype: 1
          - os: ubuntu-latest
            java: 11
            jobtype: 2
          - os: ubuntu-latest
            java: 11
            jobtype: 3
    runs-on: ${{ matrix.os }}
    steps:
    - name: Checkout
      uses: actions/checkout@v1
    - name: Setup
      uses: olafurpg/setup-scala@v13
      with:
        java-version: "adopt@1.${{ matrix.java }}"
    - name: Build and test
      run: |
        case ${{ matrix.jobtype }} in
          1)
            sbt -v "mimaReportBinaryIssues; scalafmtCheckAll; +test;"
            ;;
          2)
            sbt -v "scripted actions/*"
            ;;
          3)
            sbt -v "dependency-management/*"
            ;;
          *)
            echo unknown jobtype
            exit 1
        esac
      shell: bash

Let’s say for jobtype 3 we’d like to use JDK 8, and for jobtype 1 and 2 we’d like to test on JDK 17. sbt-ci-release uses jabba to grab the JDKs, and at the moment the openjdk 17.0 distros are not available on jabba yet. However, Eclipse Adoptium fka AdoptOpenJDK does have the binary available, so we can use the custom JDK mode to use it as follows:

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intro to Scala 3 macros

Introduction

Macro is a fun and powerful tool, but overuse of the macro could cause harm as well. Please enjoy macros responsibly.

What is macro? A common explanation given is that a macro is a program that is able to take code as an input and output code. While it’s true, it might not immediately make sense since Scala programmers are often familiar with higher-order functions like (map {...}) and by-name parameter, which on the surface it might seem like it is passing a block of code around.

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Jar Jar Abrams 1.8.0 and sbt-assembly 1.1.0

Jar Jar Abrams 1.8.0 and sbt-assembly 1.1.0 are released.

Jar Jar Abrams is an experimental extension to Jar Jar Links, intended to shade Scala libraries. Thus far we have been using Pants team’s fork of Jar Jar Links, but now that it’s been abandaned, Eric Peters has in-sourced it to jarjar-abrams repo so we can patch it.

Our jarjar fork is released under com.eed3si9n.jarjar organization name and package name.

bug fixes

  • Eric has fixed a bug around ShadeRules.keep.

enhancement

  • ASM was updated to 9.2.

sbt-assembly 1.1.0 upgrades the Jar Jar Abrams dependency to 1.8.0.

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sudori part 2

I’m hacking on a small project called sudori, an experimental sbt. The initial goal is to port the macro to Scala 3. It’s an exercise to take the macro apart and see if we can build it from the ground up. This an advanced area of Scala 2 and 3, and I’m finding my way around by trial and error. This is part 2.

Reference:

Instance

When we think of the build.sbt macro, the first thing that comes to our mind is the Applicative do macro that it implements using .value even though some may not use those terms exactly. The main driver for this imperative-to-functional is in the companion object for an oddly named Instance class:

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sudori part 1

I’m hacking on a small project called sudori, an experimental sbt. The initial goal is to port the macro to Scala 3. It’s an exercise to take the macro apart and see if we can build it from the ground up. This an advanced area of Scala 2 and 3, and I’m finding my way around by trial and error.

Reference:

Convert

I think I’ve identified a basic part called Convert, which doesn’t really depend on anything.

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sbt 1.5.5

I’m happy to announce sbt 1.5.5 patch release is available. Full release note is here - https://github.com/sbt/sbt/releases/tag/v1.5.5

Highlights

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sbt 1.5.4

I’m happy to announce sbt 1.5.4 patch release is available. Full release note is here - https://github.com/sbt/sbt/releases/tag/v1.5.4

How to upgrade

Download the official sbt runner + launcher from SDKMAN or download from https://github.com/sbt/sbt/releases/.

In addition, the sbt version used for your build is upgraded by putting the following in project/build.properties:

sbt.version=1.5.4

This mechanism allows that sbt 1.5.4 is used only for the builds that you want.

Highlights

  • Fixes compiler ClassLoader list to use compilerJars.toList (For Scala 3, this drops support for 3.0.0-M2) #6538 by @adpi2
  • Fixes undercompilation of package object causing “Symbol ’type X’ is missing from the classpath” zinc#983 by @retronym
  • Fixes overcompilation with scalac -release flag zinc#982 by @retronym
  • Fixes BSP on ARM Macs by keeping JNI server socket to keep using JNI ipcsocket#14 by @quelgar

For more details please see https://github.com/sbt/sbt/releases/tag/v1.5.4

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sbt-assembly 1.0.0

In June of 2011, I started working on sbt-assembly for sbt 0.10, based on Coda Hale’s assembly-sbt from sbt 0.7, which in turn was probably inspired by maven-assembly-plugin. After ten years, I’m going to call this one 1.0.0. sbt-assembly 1.0.0 is published to Maven Central.

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sbt 1.5.3

I’m happy to announce sbt 1.5.3 patch release is available. Full release note is here - https://github.com/sbt/sbt/releases/tag/v1.5.3

How to upgrade

Download the official sbt runner + launcher from SDKMAN or download from https://github.com/sbt/sbt/releases/.

In addition, the sbt version used for your build is upgraded by putting the following in project/build.properties:

sbt.version=1.5.3

This mechanism allows that sbt 1.5.3 is used only for the builds that you want.

Highlights

  • Fixes scalacOptions not getting forwarded to ScalaDoc in Scala 3 #6499 by @pikinier20
  • Fixes undercompilation of sealed traits that extends other seal traits zinc#979 by @dwijnand
  • Fixes version parsing not recognizing dots in a prerelease tag lm#377 by @Nirvikalpa108
  • Fixes inputFile resolving to incorrect files when file specific globs are used io#319 by @eatkins
  • Updates to Scala 2.12.14 #6522 by @mkurz

For more details please see https://github.com/sbt/sbt/releases/tag/v1.5.3

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Scala, Python quick reference

syntax Scala Python
immutable variable val x = 1 Starlark:
REV = "1.1.0"
lazy variable lazy val x = 1 n/a
mutable variable var x = 1 in function:
x = 1
if expression if (x > 1) "a" else "b" "a" if x > 1 else "b"
———————- —————————- —————————-
function def add3(x: Int): Int =
x + 3		 def add3(x):
return x + 3
anonymous function _ * 2 not in Starlark:
lambda x: x * 2
———————- —————————- —————————-
List val xs = List(1, 2, 3, 4) xs = [1, 2, 3, 4]
size xs.size len(xs)
empty test xs.isEmpty not xs
head xs.head xs[0]
tail // List(2, 3, 4)
xs.tail		 # [2, 3, 4]
xs[1:]
take // List(1, 2)
xs.take(2)		 # [1, 2]
xs[:2]
drop // List(3, 4)
xs.drop(2)		 # [3, 4]
xs[2:]
drop right // List(1, 2, 3)
xs.dropRight(1)		 # [1, 2, 3]
xs[:-1]
nth element xs(2) xs[2]
map xs.map(_ * 2)

for {
x <- xs
} yield x * 2		 map(lambda x: x * 2, xs)

[x * 2 for x in xs]
filter xs.filter(_ % 2 == 0)

for {
x <- xs if x % 2 == 0
} yield x		 filter(lambda x: not x % 2, xs)

[x for x in xs if not x % 2 ]
fold from left // "a1234"
xs.foldLeft("a") { _ + _ }		 from functools import reduce
# "a1234"
reduce(lambda a,x: a + str(x), xs, "a")
membership xs.contains(3) 3 in xs
———————- —————————- —————————-
String val s = "hello" s = "hello"
variable interpolation val count = 3
s"$count items"		 not in Starlark:
count = 3
f"{count} items"
split // Array(1.2.3, M1)
"1.2.3-M1".split("-")		 # ['1.2.3', 'M1']
"1.2.3-M1".split("-")
substring test s.contains("el") "el" in s
———————- —————————- —————————-
Map val d = Map("a" -> 1,
“b” -> 2)		 d = { "a": 1, "b": 2 }

notes

I’m picking up Python and its Bazel dialect Skylark lately. On the other hand, I’m familiar with Scala and its sbt dialect. Often I know exactly what I want to express, and I am fairly certain Python has the equivalent concept as Scala, but just don’t remember the exact incantation. For people starting Scala, maybe they could use this table in reverse.

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POM consistency for sbt plugins

There’s a long-standing bug that sbt maintainers have known for a while, which is that when sbt plugin is published to a Maven repository, the POM file sbt generates is not valid. From a mailing list thread titled [0.12] plan for instance, Mark McBride reported it in 2012:

On the maven note, the poms generated for plugins aren’t actually valid. Trying to upload them to artifactory without disabling pom consistency checks fails :/

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sbt 1.5.2

I’m happy to announce sbt 1.5.2 patch release is available. Full release note is here - https://github.com/sbt/sbt/releases/tag/v1.5.2

How to upgrade

Download the official sbt runner + launcher from SDKMAN or download from https://github.com/sbt/sbt/releases/.

In addition, the sbt version used for your build is upgraded by putting the following in project/build.properties:

sbt.version=1.5.2

This mechanism allows that sbt 1.5.2 is used only for the builds that you want.

Highlights

For more details please see https://github.com/sbt/sbt/releases/tag/v1.5.2

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Bintray to JFrog Artifactory migration status and sbt 1.5.1

I’m happy to announce sbt 1.5.1 patch release is available. Full release note is here - https://github.com/sbt/sbt/releases/tag/v1.5.1. This post will also report the Bintray to JFrog Artifactory migration.

Bintray to JFrog Artifactory migration status

First and foremost, I would like to thank JFrog for their continued support of sbt project and the Scala ecosystem.

As sbt was taking off in the number of contributors and plugins, we had a Bintray-shaped problem. We wanted individuals to create Ivy-layout repository, publish sbt plugins, but somehow aggregate the resolution to them. Having Github sbt organization allowed fluid ownership of plugin sources, but distributing the binary files were challenge as sbt version was churning. We adopted Bintray in 2014 and it provided the distribution mechanism during our growth years. In addition, we used Bintray to host Debian and RPM installers for sbt, paid for by Lightbend.

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sbt 1.5.0

Hi everyone. On behalf of the sbt project, I am happy to announce sbt 1.5.0. This is the fifth feature release of sbt 1.x, a binary compatible release focusing on new features. sbt 1.x is released under Semantic Versioning, and the plugins are expected to work throughout the 1.x series.

The headline features of sbt 1.5.0 are:

  • Scala 3 support
  • Eviction error
  • Deprecation of sbt 0.13 syntax
  • Coursier-based launcher

How to upgrade

Download the official sbt launcher from SDKMAN or download from https://github.com/sbt/sbt/releases/tag/v1.5.0. This installer includes the new Coursier-based launcher.

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sbt 1.5.0-RC2

Hi everyone. On behalf of the sbt project, I am happy to announce sbt 1.5.0-RC2. This is the fifth feature release of sbt 1.x, a binary compatible release focusing on new features. sbt 1.x is released under Semantic Versioning, and the plugins are expected to work throughout the 1.x series.

  • If no serious issues are found by Saturday, April 3rd 2021, 1.5.0-RC2 will become 1.5.0 final.
  • If no serious issues are found by Saturday, March 27th 2021, 1.5.0-RC1 will become 1.5.0 final.

The headline features of sbt 1.5.0 are:

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sbt 1.4.9

I’m happy to announce sbt 1.4.9 patch release is available. Full release note is here - https://github.com/sbt/sbt/releases/tag/v1.4.9

How to upgrade

Download the official sbt launcher from SDKMAN or download from https://github.com/sbt/sbt/releases/.

In addition, the sbt version used for your build is upgraded by putting the following in project/build.properties:

sbt.version=1.4.9

This mechanism allows that sbt 1.4.9 is used only for the builds that you want.

Highlights

  • sbt 1.4.9 fixes JLine 2 fork + JAnsi version to match that of JLine 3.19.0 to fix line reading, which among other things affected IntelliJ import.
  • sbt 1.4.9 is a maintenance patch. The most notable thing is that this was that it was released without using Bintray, and a few things were dropped. See below for details.

Changes with compatibility implications

sbt 1.4.9 is published to Sonatype OSS without going through Bintray.

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sbt 1.4.8

I’m happy to announce sbt 1.4.8 patch release is available. Full release note is here - https://github.com/sbt/sbt/releases/tag/v1.4.8

How to upgrade

Download the official sbt launcher from SDKMAN or download from https://github.com/sbt/sbt/releases/.

In addition, the sbt version used for your build is upgraded by putting the following in project/build.properties:

sbt.version=1.4.8

This mechanism allows that sbt 1.4.8 is used only for the builds that you want.

Highlights

  • sbt 1.4.8 is a maintenance patch. The most notable thing is that this was the first release that was released without using Bintray, and a few things were dropped. See below for details.

Changes with compatibility implications

sbt 1.4.8 is published to Sonatype OSS without going through Bintray.

Read More…