Markdown Links in MacVIM
Some text editors have that nice feature that if you want to turn a span of text into a link, you select it, and when you then paste a URL, the editor will create that link in place. My favourite text editor is MacVIM, and I thought it’d be nice to have that feature there as well. Since most of the text I edit in MacVIM is Markdown, selected text needs to be converted into a link following the syntax rules.
Now, MacVIM can be extended (of course). As I didn’t know the language well enough, I thought I’d vibe code it with some help from Claude Sonnet, which I use in my Langdock workspace. (To be clear, I did not use Claude Code, but plain old Claude with a canvas.)
Because I wanted to be able to understand (and assess the quality of) what would come out of this, I started by reading a nice and compact primer on the vim language. That didn’t take long, and after a brief pause to appreciate the quirkiness of the language, I got started.
Phase 1: Building the Thing
The first result looked right. However, it didn’t work at all - hitting Cmd-V on selected text with a URL in the clipboard just pasted the URL instead of the selected text, which was the normal behaviour I had intended to replace.
A few exchanges later, during which Claude gave rather helpful advice
for troubleshooting and debugging, and even added code to produce
debugging output, I realised that I had made a mistake in my first
prompt: I had mentioned I wanted a vim plugin, but had not
mentioned I was using MacVIM. That got me much closer to the goal.
Phase 2: Shrinkwrapping the Thing
I ended up with a version of the plugin that did what I wanted, however it still produced debugging output. So I instructed Claude to take away all the fluff and be minimalistic about the original requirement.
The result fell back to just replacing selected text with the pasted URL. In shrinkwrapping the plugin, Claude had also removed MacVIM specifics that were required to make it work. One instruction later, that was fixed.
However, now it didn’t get the spaces around the freshly created link right. That took one more round, after which pasting of non-URLs was broken. One instruction later, the plugin suddenly contained a syntax error. Once that was addressed, the thing worked as expected (for good).
Phase 3: Understanding the Thing
I don’t think vibe coding should be a discipline where humans delegate everything lazily to an LLM. So I started a new Claude session, fed it the code, and instructed the model to explain it to me. With my entry-level understanding of the vim language, I should be able to appreciate what was going on. That worked well.
Finally, I asked the second Claude session what could be improved about the code. Because LLMs are “eager to please”, I instructed it to avoid digging for “improvements” just for the sake of it, but to apply a fair assessment.
The result was good; there was one actual duplication that made no sense, which hadn’t met my eye and which I subsequently removed. I chose to not adopt another suggestion about removing code duplication for register saving-and-restoring and replacing it with an extra abstraction.
Show me the Code!
All right, all right, here it is. Needless to say, the Markdown source of this post contains several links, all of which were created using the help of this plugin.
Tags: hacking