scala

As of Scala 2.13.0-M5, it's planned that scala.Seq will change from scala.collection.Seq to scala.collection.immutable.Seq. Scala 2.13 collections rework explains a bit about why it's been non-immutable historically. Between the lines, I think it's saying that we should celebrate that scala.Seq will now be immutable out of the box.

Defaulting to immutable sequence would be good for apps and fresh code. The situation is a bit more complicated for library authors.

• If you have a cross-built library, and
• if your users are using your library from multiple Scala versions
• and your users are using Array(...)

this change to immutable Seq could be a breaking change to your API.

This post was coauthored by Eugene Yokota and Yifan Xing.

We need to change the culture around tech conferences to improve the inclusion of women (and people from other backgrounds too!). For that, there needs to be clear signaling and communication about two basic issues:

1. No, it's not ok to hit on women at a conference.
2. Assume technical competence, and treat women as professional peers.

These points should be communicated over and over at each conference before the keynote takes place, and before socializing hours.

Compile, or compile not. There's no warning. Two of my favorite Scala compiler flags lately are "-Xlint" and "-Xfatal-warnings".
Here is an example setting that can be used with subprojects:

ThisBuild / organization := "com.example"
ThisBuild / version      := "0.1.0-SNAPSHOT"
ThisBuild / scalaVersion := "2.12.6"
 
lazy val commonSettings = List(
  scalacOptions ++= Seq(
    "-encoding", "utf8",
    "-deprecation",
    "-unchecked",
    "-Xlint",
    "-feature",
    "-language:existentials",

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).

AdoptOpenJDK 8 and 11

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:

I wanted give Expecty a try, so I forked the repo to eed3si9n/expecty, added sbt build, patched up the code so it works with 2.10, 2.11, 2.12, and 2.13.0-M4, sent a few pull requests upstream, changed the package name, and published my fork to Maven Central:

libraryDependencies += "com.eed3si9n.expecty" %% "expecty" % "0.11.0" % Test

and for Scala.JS and Scala Native:

libraryDependencies += "com.eed3si9n.expecty" %%% "expecty" % "0.11.0" % Test

Here's how we can use this:

scala> import com.eed3si9n.expecty.Expecty.assert
import com.eed3si9n.expecty.Expecty.assert
 
scala> assert(a * b == 7)
java.lang.AssertionError:
 
assert(a * b == 7)
       | | | |
       1 3 3 false
 
  at com.eed3si9n.expecty.Expecty$ExpectyListener.expressionRecorded(Expecty.scala:25)
  at com.eed3si9n.expecty.RecorderRuntime.recordExpression(RecorderRuntime.scala:34)
  ... 38 elide

As you can see, you get a nicer error message automatically.

Yesterday I wrote about cross JVM testing using Travis CI.

testing Scala apps on macOS 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:

Wrote herding cats: day 17 featuring initial and terminal objects, product, duality, and coproduct.

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.

Recently I've been running into interop problems as some platforms are unable to parse file:/foo/bar. But this is not the first time I'm having trouble with file path represented as URI. Considering that the notion of filesystem goes back to 1960s, and URL has been around since 1990s, it's surprising that we haven't come to a concensus on this. But then again, like decimal numbers, once you start digging deeper, or start exchanging data, we find some glitches in the Matrix.

Gigahorse 0.3.0 is now released. See documentation on what it is.

OkHttp support

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._

Wrote herding cats day 16.