TIL on Dev notes

How to run sbt tasks with custom settings

Wed, 01 Oct 2025 00:00:00 +0000

When preparing build configuration in sbt, you might want to write custom sbt task. Task in sbt is like a function that can depend on other tasks and project settings.

Custom sbt tasks

To illustrate it, let’s write a simple task that validates environment, runs tests and builds an app

import sbt.*

lazy val validateAndBuild = taskKey[Unit]("Validates env, runs tests and builds the app")

val root = project.in(file(".")).settings(
  validateAndBuild := {
    validateEnvVars
    test
    assembly
  }
)

Tasks vs immutable settings

This can be handy when the project grows in complexity. One problem with this approach is that we don’t control the inputs to the sub-tasks that we run. In sbt, settings are initialized when the project is loaded and are not mutable.

Understand your build structure and performance

Wed, 29 Jan 2025 00:00:00 +0000

TL;DR: Today I learned that you can trace your build performance with bloop, and it’s especially easy when using Metals. The setup might not be obvious for some.

When working with multi-module projects, build times can sometimes increase unexpectedly. There are a few ways to analyze that statically, but you can always see the live data from your bloop compilation. Let’s explore those options.

Static analysis

When your build.sbt file grows complex it’s easy to lose track of which depends on which. This not only creates confusion and complicates onboarding, but also to slower builds and frustration in consequence.

Your own Bluesky feed

Wed, 27 Nov 2024 00:00:00 +0000

In this post we’ll learn how to build and deploy your own feed on Bluesky. We’ll start with some background info on Bluesky and how feeds work. Then we’ll code and deploy our own feed. Don’t worry about the complexity, it’s mostly filling the gaps in the template.

What’s Bluesky

Bluesky is a decentralized social network. From the end user perspective, it’s very similar to 𝕏 (formerly Twitter). It’s built with AT Protocol which allows programmers to interact with the platform.

Useful commands for inspecting sbt build

Wed, 29 May 2024 00:00:00 +0000

TL;DR Today I learned a few useful commands to help you understand complex sbt builds.

task timing

JAVA_OPTS=-Dsbt.task.timings=true sbt

inspecting task

inspect module/taskName

inspecting task tree

inspect tree module/taskName

Hide irrelevant data in your PRs

Fri, 05 Jan 2024 00:00:00 +0000

TL;DR Today I learned that you can hide irrelevant changes from Github PRs. The syntax for .gitattributes can be tricky though.

In my current project, it’s sometimes necessary to re-generate and commit a bunch of files to the repository. This can happen when you store some IaC or test data in the repository.

Sample repository

To demonstrate the problem, here’s an example repository: https://github.com/majk-p/nice-pr-diffs that features two PRs:

The first one is hard to read https://github.com/majk-p/nice-pr-diffs/pull/1/files because it features a wall of text - new testing data that has been added.

TIL: Debugging Hugo - fixing publish date

Wed, 04 Jan 2023 17:15:00 +0100

TL;DR Today I learned how to fix post visibility by reading the documentation https://gohugo.io/getting-started/usage/#draft-future-and-expired-content

Last night I’ve been finishing my first blog post this year. Upon finishing the text and finding the icon it’s time to fill the metadata. Midnight was minutes away so I set the publish date to 2023-01-04 (next day) and set the draft flag to false.

The problem

Imagine how surprising it was to notice that the article I just wrote doesn’t show up on the main page. Time to debug. First thing is to double check the draft state - all good. Perhaps I’ve made it 2022-01-04 and the post landed a year back? nope, date’s correct.

TIL: Markdown presentations with Marp

Sun, 18 Dec 2022 00:00:00 +0000

Lately I’ve been working on preparing learning materials in Scala. Usually when I work on preparing slides for public speaking I would use https://slides.com/majkp/, but this time I was looking for something self hosted.

In this situation Reveal.js seems like an obvious alternative, but if you want to set up, you either have to download a fixed version which makes the upgrade hard, or build an npm project and add reveal as the dependency.

TIL: Mimic value class in Typescript

Thu, 15 Dec 2022 00:00:00 +0000

TL;DR Today I learned how to mimic Scala-like value class in Typescript

Doing day to day scala I often use value classes to model the data like:

final case class UserId(value: String) extends AnyVal
final case class City(value: String) extends AnyVal

This is especially useful when you want to add some meaning to primitive types. It also makes the compiler help you to avoid passing irrelevant data to downstream methods.

Read more about value classes in the documentation https://docs.scala-lang.org/overviews/core/value-classes.html.