Interruptions: A User's Manual

Interruptions are one of the best ways to squander time and money, but the value chain is not always obvious. This handy guide will help you make the case for why you should be interrupting your developers (nay, any employee!) regularly.

Be Transparent

This is something of an open letter to team leads and managers out there: you need to be as transparent with your team as you are legally and contractually allowed to.

Reading Clojure, part 2

Welcome back

Have you gone over the fundamentals on Reading Clojure? Did you shake off that preconception that there’s some magic syntax to declaring and evaluating things beyond the list?

Great! Let’s now go over other things you might encounter when looking at a random source file. I’m first going to give you an overview of types and related things. After it, we’ll then we get into the good stuff like going over a project, and the weird stuff like ->, ->>, #, the quote and other squiggles.

Reading Clojure

Preamble

Back in early December I held a Clojure workshop for the Bucharest Functional Programming meet up. Having to explain the language to developers who were completely new at it was an interesting experience. I decided to start from the ground up: how to even read the blasted thing.

Branching workflow: git-flow and github-flow

Choosing a branching model for macchiato

Lately, I’ve been working on Macchiato to bring web application development libraries for ClojureScript on Node.js. Get a few people of different backgrounds involved on a project, and pretty soon a discussion about methodology will emerge.

Since both Dmitri Sotnikov and myself are working on some libraries at the same time, we had to decide which approach to use.

There are two major alternatives: Git-flow and Github-flow (with Gitlab-flow being a slightly more elaborate version).

Let’s review them.

HTML parsing in Clojure

Once again I’m doing a personal project that requires me to do some HTML parsing. If you have had to look at it, the landscape of Clojure HTML parsing libraries seems to be littered with dead projects.

Let’s look at the options.

Deploying a Clojure application from Gitlab CI to Heroku

Now that we have our Clojure application tested every time we push it to Gitlab, let’s configure another stage to deploy it to Heroku.

This assumes that:

  • Anything you merge to master is ready to deploy,
  • You have your Heroku API key handy, and
  • You already have a Heroku app configured, with all the necessary environment variables.

There’s two ways we can do this.

Using Gitlab CI with a Clojure project

Gitlab allows you not only to have free private repositories, but also to test them using free runners. These can run automatically, on push, for any branch or tag.

I keep a few private repositories with them, for personal projects and small experiments. I decided to give Gitlab CI a shot for a PostgreSQL-backed Clojure project.

There’s a basic example on the Gitlab CI repository. It gets and installs lein, which isn’t necessary. Instead, we’ll build use the clojure:lein Docker image.

Clojure, Cursive and Emacs

J. Pablo Fernández has recently posted a piece with the incendiary title of “Emacs is Hurting Clojure“.

I disagree with the idea behind the title, but then again, he seems to do so himself. He promptly clarifies:

Tip: Uncaught Invariant Violation

Uncaught Invariant Violation: onlyChild must be passed a children with exactly one child.

Are you using Reagent and Bootstrap with ClojureScript, and getting this error?

In my case, the cause was that I had a when inside an OverlayTrigger. Seems like a no-no. Further testing showed you can’t have an if either. Looks like OverlayTrigger can only wrap data, not something that might change.

In my case the solution was simple enough, once I figured out the cause: I just extracted when to wrap the OverlayTrigger, instead of the other way around.