Category Archives: Programming

From the depths of time: a 30-year-old bug with a funny explanation

It was 1990 or possibly 1991, and I was working for System Simulation on an Application for Windows 2 – which at that time was a rather exotic extra that a few adventurous people were running on top of their MS-DOS systems. There was no graphical development environment in those days: you’d compile your program using the command-line C compiler cl, and compile your resources (dialogue boxes, menus and suchlike) using the command-line resource compiler, rc.

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Testing with Jest: how to mock an import used by the module you’re testing

I am writing a Jest/RTL test for a React component that invokes another component. I want to mock that second component so I can have it do things like invoking callbacks that the first component passes to it.

But there is nothing specific to React about this requirement: it comes up for non-React modules, too. I have an approach that I have shown to work using trivial modules and I want to document it here for myself and anyone else who finds it useful.

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I miss my Commodore 64

Building modern software is so complicated. So many layers where things can go wrong. Vagrant, VirtualBox, Docker, Maven, JVM, Vert.X, Spring, Node, NPM, Cypress, Chai, SSH, tunnels, git, GitHub, Jenkins, Travis, the list goes on and on.

I understood everything about my Commodore 64. Now I barely understand NPM. I know there are good reasons why things are the way they are. But that doesn’t mean I don’t lament what we’ve lost.

 

Major releases are disasters, and should be avoided whenever possible

If you use semantic versioning in your project — and you should — then you fix bugs in patch releases (e.g. going from v2.4.6 to v2.4.7), and add new features in minor releases (e.g. from v2.4.6 to v2.5.0). These are both unambiguously good things to do: downstream projects that use your project can happily and blindly upgrade to your new versions knowing that everything is compatible and nothing will break.

But when you issue a new major release (e.g. from v2.4.6 to v 3.0.0), that’s because you made an incompatible change. Now the maintainers of downsteam packages have to stop and think and read your release notes before they can be confident whether it’s safe to upgrade, or whether (as with all the various React-related libraries’ major versions) they’re going to have to rewrite their code first. Most often, they won’t have the time or energy to do this for all the many dependencies their project has.

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Passing laws and adding BIB-1 diagnostics

Years ago, I was a member of the Z39.50 Implementers’ Group. We’d gather from all around the world, maybe 30 or 40 of us, and meet for several days to discuss and vote on possible extensions to this venerable (and still important) information retrieval standard.

A common item of business was approving a new diagnostic code. Continue reading

Scottkit is born! Only seven and a half years late!

Those of you who have been reading this blog since 2nd March 2010 — just three days after the blog was born — might remember the fourth post I ever made here: Learning a language vs. learning a culture, on my switching from Perl to Ruby. Way back then, I wrote about “ScottKit — my first non-trivial Ruby program”. Here it is!

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React error-message of the day

This just in:

Failed context type: Invalid context `paneset` of type `Paneset` supplied to `Paneset`, expected instance of `Paneset`.

Oh, the joys of front-end development!

(My best guess: I have two slightly different version of stripes-components library that provides the <Paneset> component in my application, and somehow I’ve got hold of one from the wrong instance.)

“What should I prioritise that ahead of?”

My colleague Jason Skomorowski and I (and many others) work together for Index Data on the FOLIO library services platform. There is a ton of work to do — fascinating work at that, so that I often find myself working on it in the evenings, not because of deadline panic but just because it’s fun to do.

Often when a request for a new feature comes in — whether it’s user-visible functionality, or more exhaustive test coverage, or better continuous integration support, or improvements to documentation — Jason often asks this key question:

“What should I prioritise that ahead of?”

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Rebooting Linux with every new kernel

Back in the early 1990s, when I was working on Sun’s Unix boxes, it was routine for them to be up for multiple years at a time. A reboot was a big event.

Now here we are in 2017, and every single update to the Linux kernel — of which there are several every week — requests a reboot.

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All you need to know about version numbers in one page

A colleague asked me a couple of days ago: “So we roll version numbers forward only with breaking changes, right?”

Well, the best approch for any sane project in 2017 is to follow Semantic Versioning. That is not a long document to read, but here is a summary. In a nutshell, version numbers have three facets, major.minor.patch.

  • If your new release breaks something that used to work, increment major.
  • If your release adds new functionality that clients might want to rely on, increment minor.
  • If your release only fixes a bug, increment patch.

Then dependencies of the form “^3.4.2” (for example, in package.json for a JavaScript project) mean “that version, or anything backwards-compatible with it”. Which means the same major version number (3 in this case) and the same or better minor number (4 or higher); or, if the minor version is the same, then the same or better patch level (2 or higher).

This is an excellent, simple and battle-proven system.

However. Continue reading