Josh Goldberg
Larry David in Curb Your Enthusiasm looking consternated

The Cost of a Lint Rule

Apr 17, 202410 minute read

Explaining why deep work can be so difficult in open source.

I put a tricky pull request in review this morning. feat(eslint-plugin): [no-unnecessary-type-parameters] initial implementation: resolving a nearly three-year-old feature request on typescript-eslint to add a lint rule that detects violations of The Golden Rule of Generics.

That PR started off pleasant: a pairing session with Dan Vanderkam and hopes of having it ready in advance of his Effective TypeScript second edition. It ended up being much more complicated than we’d hoped and draining a bunch of both of our time. Such is life in software development.

I think “deep” work like this lint rule is a great showcase of why it can be difficult for projects with limited funding to make progress on larger tasks. So, this blog post is half my bragging (really, venting) about a difficult task I accomplished this week, and half explaining why sponsoring open source projects is so important.

“Joy” Cost

Speaking just for myself, I found this rule incredibly annoying to work on. The rule’s implementation involves recursively traversing through TypeScript types and counting instances of type parameters. That’s just as irritating and mind-melting to debug as it sounds.

Even after we figured out the strategy pivot needed to get it to work reliably, there were a ton of tricky edge cases inherent to figuring out what forms of syntax it should report on. Many of those discovered edge cases turned into “whack-a-mole” development, where resolving one caused others to pop up.

Because I work in the “wild west” of open source, rather than a funded development team, I have far fewer opportunities to pair with others to help get through difficult tasks. Working on this lint rule made me crabby and tired for the days I was working on it. There is a finite number of these tasks that I as an open source maintainer can take on before the joy of coding erodes into the dullness of burnout.

Monetary Cost

Again speaking just for myself, this rule took about two and a half days of work to get into review. For the sake of easy math let’s suppose my compensation should be $100/hour (a reasonable total compensation for senior developers in the US). Calculating roughly six hours of work per day, that’s 2.5 days × 6 hours/day × $100/hour = $1,500.

That’s not factoring in Dan’s time, time it’ll take at least one other project maintainer to review the code, time spent improving the rule based on code review, etc.

The monetary compensation cost of this lint rule rule is easily several thousand dollars.

Opportunity Cost

Most tasks in software development are fairly straightforward if you’ve practiced them a bunch. My normal flow is to take on several “shallow” tasks at a time and context switch during long-running tasks. That’s how I’m able to be effective on multiple open source projects at a time.

But, sometimes you come across a task that involves work you’re not deeply practiced in. For “deep” tasks, you need to put aside other work and focus on slow and steady progress.

I ended up putting aside several other important, time-sensitive commitments to focus on this darn lint rule. Instead of context switching, I would step away from the computer to think deeply or clear my mind.

There’s no good way to estimating what I would have been able to do instead of this lint rule.

Sponsoring Open Source

There are many good reasons to sponsor open source development: to improve software supply chain security, to reward developers for their time, to encourage more people to get into open source, … Letting full-time maintainers like me focus on deep tasks like this is one of them.

I’m only able to spend many hours a day on open source projects such as typescript-eslint because of monetary sponsorships. If I had to go back to consulting or employment to support myself, I would not have the time to regularly tackle deep work like this.

Most open source software projects have teeny development costs compared to the amount of bug reports and feature requests they receive. typescript-eslint’s annual Open Collective budget has never exceeded $50,000.

So, the next time you 👍 a request on an open source project’s GitHub issue tracker, think about how much money that feature request will cost. It might be a lot more than you’d think.


Many thanks to Dan Vanderkam for getting started on no-unnecessary-type-parameters: both the practical rule implementation and helping spread the Golden Rule of Generics. Effective TypeScript is an excellent read, especially the second edition.

Additional thanks to Daniel Afonso for helpful proofreading on this blog post. 💖

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