Working with GitHub and pull requests a lot, I end up accumulating stale branches that are no longer needed. In this post, we will look at how to clean the stale local branches.
There are mainly two strategies:
Erik Aybar’s Git Tip: Deleting Old Local Branches takes the second approach.
I’ve been thinking about rich console applications, the kind of apps that can display things graphically, not just appending lines at the end. Here are some info, enough parts to be able to write Tetris.
To display some text at an arbitrary location on a termial screen, we first need to understand what a terminal actually is. In the middle of 1960s, companies started selling minicomputers such as PDP-8, and later PDP-11 and VAX-11. These were of a size of a refrigerator, purchased by “computer labs”, and ran operating systems like RT-11 and the original UNIX system that supported up many simultaneous users (12 ~ hundreds?). The users connected to a minicomputer using a physical terminal that looks like a monochrome screen and a keyboard. The classic terminal is VT100 that was introduced in 1978 by DEC.
Whether you want to try using OpenJDK 11-ea, GraalVM, Eclipse OpenJ9, or you are stuck needing to build using OpenJDK 6, jabba has got it all. jabba is a cross-platform Java version manager written by Stanley Shyiko (@shyiko).
Here’s how we can use jabba on Travis CI to cross build using AdoptOpenJDK 8 and 11:
sudo: false
dist: trusty
group: stable
language: scala
scala:
- 2.12.7
env:
global:
- JABBA_HOME=/home/travis/.jabba
matrix:
include:
- env:
- TRAVIS_JDK=adopt@1.8.192-12
- env:
- TRAVIS_JDK=adopt@1.11.0-1
before_install:
- curl -sL https://raw.githubusercontent.com/shyiko/jabba/0.11.0/install.sh | bash && . ~/.jabba/jabba.sh
install:
- $JABBA_HOME/bin/jabba install $TRAVIS_JDK
- unset _JAVA_OPTIONS
- export JAVA_HOME="$JABBA_HOME/jdk/$TRAVIS_JDK" && export PATH="$JAVA_HOME/bin:$PATH" && java -Xmx32m -version
script: sbt -Dfile.encoding=UTF8 -J-XX:ReservedCodeCacheSize=256M ++$TRAVIS_SCALA_VERSION! test
before_cache:
- find $HOME/.ivy2 -name "ivydata-*.properties" -delete
- find $HOME/.sbt -name "*.lock" -delete
cache:
directories:
- $HOME/.ivy2/cache
- $HOME/.sbt/boot
- $HOME/.jabba/jdk
When the job runs you should see something like:
Last week I wrote about using source dependencies with sbt-sriracha for testing purpose. This week we’ll look into using Expecty to do power assert.
Power assert (or power assertion) is a variant of assert(...) function that that prints out detailed error message automatically. It was originally implemented by Peter Niederwieser (@pniederw) for Spock, and in 2009 it was merged into Groovy 1.7. Power assert has spread to Ruby, JavaScript, Rust, etc.
Let’s say you have something like a * b. Using a traditional assert, we would write:
Source dependencies is one of features that existed in sbt since ever, but hasn’t been documented well.
Here’s how to declare source dependency to the latest commit for scopt commandline option parsing library.
lazy val scoptJVMRef = ProjectRef(uri("git://github.com/scopt/scopt.git#c744bc48393e21092795059aa925fe50729fe62b"), "scoptJVM")
ThisBuild / organization := "com.example"
ThisBuild / scalaVersion := "2.12.2"
lazy val root = (project in file("."))
.dependsOn(scoptJVMRef)
.settings(
name := "Hello world"
)
When you start sbt and run compile, sbt will automatically clone scopt/scopt under the staging directory, and link the builds together.
Yesterday I wrote about cross JVM testing using Travis CI.
Here’s how we can test Scala apps on macOS using Travis CI. This is adapted from Lars and Muuki’s method: Testing Scala programs with Travis CI on OS X
dist: trusty
language: scala
matrix:
include:
## build using JDK 8, test using JDK 8
- script:
- sbt universal:packageBin
- cd citest && ./test.sh
jdk: oraclejdk8
## build using JDK 8, test using JDK 8, on macOS
- script:
- sbt universal:packageBin
- cd citest && ./test.sh
## https://github.com/travis-ci/travis-ci/issues/2316
language: java
os: osx
osx_image: xcode9.2
## build using JDK 8, test using JDK 9
- script:
- sbt universal:packageBin
- jdk_switcher use oraclejdk9
- cd citest && ./test.sh
jdk: oraclejdk8
## build using JDK 8, test using JDK 10
- script:
- sbt universal:packageBin
- citest/install-jdk10.sh
- cd citest && ./test.sh
jdk: oraclejdk8
scala:
- 2.10.7
before_install:
# https://github.com/travis-ci/travis-ci/issues/8408
- unset _JAVA_OPTIONS
- if [[ "$TRAVIS_OS_NAME" = "osx" ]]; then
brew update;
brew install sbt;
fi
cache:
directories:
- $HOME/.ivy2/cache
- $HOME/.sbt/boot
before_cache:
- find $HOME/.ivy2 -name "ivydata-*.properties" -delete
- find $HOME/.sbt -name "*.lock" -delete
Normally you’d write jdk: oraclejdk8 at the top level, but since the macOS image does not have the jdk_switcher script travis/travis#2317, we need to add to all entries in the matrix except for the osx one.
Oracle is moving to ship non-LTS JDK every 6 months, and LTS JDK every 3 years. Also it’s converging to OpenJDK. In this scheme, JDK 9 will be EOL in March 2018; JDK 10 will come out in March 2018, and EOL in September 2018; and LTS JDK 11 that replaces JDK 8 in September 2018 will stay with us until 2021.
As we will see quick succession of JDKs in the upcoming months, here’s a how-to on testing your app on JDK 8, JDK 9, and JDK 10 Early Access using Travis CI.
During the SIP-27 trailing commas discussion, one of the thoughts that came to my mind was unifiying some of the commas with semicolons, and take advantage of the semicolon inference.
This doesn’t actually work. @Ichoran kindly pointed out an example:
Seq(
a
b
c
)
This is interpreted to be Seq(a.b(c)) in Scala today.
As tweeted, I made some sbt stickers.
Wrote herding cats: day 17 featuring initial and terminal objects, product, duality, and coproduct.
This holiday break, I somehow got into binge watching Coursera’s Stanford Machine Learning course taught by Andrew Ng. I remember machine learning to be really math heavy, but I found this one more accessible.
Here are some notes for my own use. (I am removing all the fun examples, and making it dry, so if you’re interested in machine learning, you should check out the course or its official notes.)
Machine learning splits into supervised learning and unsupervised learning.
In this post I am going to discuss an old new problem of encoding file path as Uniform Resource Identifier (URI) reference.
As of 2017, the authoritative source of information is RFC 8089 - The “file” URI Scheme written by Matthew Kerwin.
RFC 8089 The "file" URI Scheme https://tools.ietf.org/html/rfc8089 Wow, it actually happened.
— Matthew Kerwin (@phluid61) February 18, 2017
Future readers might also want to search for “file URI scheme RFC”, and find the latest version. If you’re a programmer, read the RFC. This post is to raise the awareness of the some of the issues around file to URI encoding, but it’s not a substitution.
On Tech Hub blog I demonstrated how to use sbt server from VS Code to display compiler errors from a running sbt session. In this post, I’ll show how to do that for Sublime Text 3 in this post.
First, add tomv564/LSP plugin to Sublime Text 3.
cd ~/Library/Application\ Support/Sublime\ Text\ 3/Packagesgit clone https://github.com/tomv564/LSP.gitNext, download sbt-server-stdio.js and save it to ~/bin/ or somewhere you keep scripts. sbt server by default uses Unix domain sockets on POSIX systems and named pipe on Windows, but editors seem to expect stdio. The script is a Node script that’s included as our VS Code extension that discovers the socket, and fronts it with stdio.
Over the weekend I assembled an Ergodox.
It’s been a month since sbt 1.0 shipped, and I can finally sit back and think about sbt server again. Using my weekends time, I started hacking on an implementation of Scala language server on top of sbt server.
A language server is a program that can provide language service to editors like Visual Studio Code, Eclipse Che, and Sublime Text 3 via Language Server Protocol. A typical operation might be textDocument/didOpen, which tells the server that a source file was opened in the editor.
In this post, I’d like to introduce a version scheme that I call Persistent Versioning. Most of the ideas presented in this post are not new or my own. Let me know if there’s already a name for it.
In 2015, Jake Wharton (@JakeWharton) wrote a blog post titled Java Interoperability Policy for Major Version Updates:
A new policy from @jessewilson and I for the libraries we work on to ensure major version updates are interoperable: https://t.co/zKqYRwrXmq
GitHub Pages is a convenient place to host OSS project docs. This post explains how to use Travis CI to deploy your docs automatically on a pull request merge.
Make a directory outside of your project first.
Pick a key name deploy_yourproject_rsa, so you can distinguish it from other keys.
$ mkdir keys
$ cd keys
$ ssh-keygen -t rsa -b 4096 -C "yours@example.com"
Generating public/private rsa key pair.
Enter file in which to save the key (/Users/xxx/.ssh/id_rsa): deploy_website_rsa
Enter passphrase (empty for no passphrase):
Keep the passphrase empty.
In the last post that I wrote about Atreus build, I noted that there’s an issue of keyboard positioning:
Even if I can overcome the layout and memorize the various symbol locations, there’s the issue of the placement. If I place the keyboard in between me and the laptop the screen becomes too far.
I solved this issue by making a tray for Atreus that I can position it on top of the MacBook Pro keyboard.
Last night I finished making my Atreus keyboard from a DYI kit that I got a while back. Here are some of the details:
The kit comes with almost everything you need to assemble the Arteus keyboard. You need lacquer, a soldering iron, solder, and wire cutters.
Gigahorse 0.3.0 is now released. See documentation on what it is.
0.3.0 adds Square OkHttp support. Gigahorse-OkHttp is availble for Scala 2.10, 2.11, and 2.12.
According to the JavaDoc you actually don’t have to close the OkHttpClient instance.
scala> import gigahorse._, support.okhttp.Gigahorse
import gigahorse._
import support.okhttp.Gigahorse
scala> import scala.concurrent._, duration._
import scala.concurrent._
import duration._
scala> val http = Gigahorse.http(Gigahorse.config) // don't have to close
http: gigahorse.HttpClient = gigahorse.support.okhttp.OkhClient@23b48158
I’ve been asked by a few people on downloading JARs, and then running them from an sbt plugin. Most recently, Shane Delmore (@shanedelmore) asked me about this at nescala in Brooklyn.
During an unconference session I hacked together a demo, and I continued some more after I came home.
sbt-sidedish is a toolkit for plugin authors to download and run an app on the side from a plugin. It on its own does not define any plugins.
Wrote herding cats day 16.
Here are a few questions I’ve been thinking about:
The sealed trait and case class is the idiomatic way to represent datatypes in Scala, but it’s impossible to add fields in binary compatible way. Take for example a simple case class Greeting, and see how it would expand into a class and a companion object:
Gigahorse 0.2.0 is now released. The new change is that it abstracts over two backends. @alexdupre contributed migration from AHC 1.9 to AHC 2.0, which is based on Netty 4 in #12.
In addition, there’s now an experimental Akka HTTP support that I added. #15
Please see Gigahorse docs for the details.
gigahorse-github 0.1.0 is released. This is a Gigahorse plugin for Github API v3.
Update: please use Gigahorse 0.1.1
Gigahorse 0.1.0 is now released. It is an HTTP client for Scala with Async Http Client underneath. Please see Gigahorse docs for the details. Here’s an example snippet to get the feel of the library.
scala> import gigahorse._
scala> import scala.concurrent._, duration._
scala> Gigahorse.withHttp(Gigahorse.config) { http =>
val r = Gigahorse.url("http://api.duckduckgo.com").get.
addQueryString(
"q" -> "1 + 1",
"format" -> "json"
)
val f = http.run(r, Gigahorse.asString andThen {_.take(60)})
Await.result(f, 120.seconds)
}
There’s a “pattern” that I’ve been thinking about, which arises in some situation while persisting/serializing objects.
To motivate this, consider the following case class:
scala> case class User(name: String, parents: List[User])
defined class User
scala> val alice = User("Alice", Nil)
alice: User = User(Alice,List())
scala> val bob = User("Bob", alice :: Nil)
bob: User = User(Bob,List(User(Alice,List())))
scala> val charles = User("Charles", bob :: Nil)
charles: User = User(Charles,List(User(Bob,List(User(Alice,List())))))
scala> val users = List(alice, bob, charles)
users: List[User] = List(User(Alice,List()), User(Bob,List(User(Alice,List()))),
User(Charles,List(User(Bob,List(User(Alice,List()))))))
The important part is that it contains parents field, which contains a list of other users.
Now let’s say you want to turn users list of users into JSON.