Saturday 8 September 2018


One Tool To Rule Them All

A recent twitter thread reminded me of a trope that I see frequently as a library author (and just as a general observer) - let’s call it “monotoolism”.

Examples of this might be examples like:

  • “wait, you’re still using ‘LINQ to SQL’? I thought you were using ‘Dapper’?”
  • “Google’s protobuf impementation provides opinionated JSON parsing, but my JSON doesn’t fit that layout - how do I get the library to parse my layout?”
  • “how do I parse HTML with a regular expression?”
  • etc

The common theme here being the expectation that once you have one tool in a codebase that fits a particular category: that’s it - there is one and only one tool against each category; one “data access tool”, one “string parsing tool”, etc.

This has always irked me. I understand where people are coming from - they don’t want an explosion of different tools to have to worry about:

  • they don’t want an overly complex dependency tree
  • they don’t want to have to check licensing / compliance etc against a huge number of libraries
  • they don’t want to have to train everyone to use a plethora of tools
  • etc

It absolutely makes sense to minimize the dependency count, and to remove unnecessary library overlap. But the key word in that sentence: “unnecessary” - and I mean that in a fairly loose sense: you can use the handle of a screwdriver to drive in a nail if you try hard enough, but it is much easier (and you get a better outcome) if you use a hammer. I think I’d include a hammer as a “necessary” tool alongside a set of screwdrivers if you’re doing any form of construction (but is that a metric or imperial hammer?).

I often see people either expressing frustration that their chosen “one tool to rule them all” can’t do tangentially-related-feature-X, or bending their code massively out of shape to try to make it do it; sometimes they even succeed, which is even scarier as a library author - because now there’s some completely undesigned-for, unspecified, undocumented and just unknown usage in the wild (quite possibly abusing reflection to push buttons that aren’t exposed) that the library author is going to get yelled at when it breaks.

XKCD: Workflow

It is OK to use more than one tool!

Yes, it is desirable to minimize the number of unnecessary tools. But: it is OK to use more than one tool. Expected, even. You absolutely should be wary of uncontrolled tool propogation, but I strongly advocate against being too aggressive with rebukes along the lines of:

We already have a tool that does something kinda like that; can you just torture the tool and the domain model a bit and see if it works well enough to just about work?

Remember, the options here are:

  1. two (or more) different tools, each used in their intended way, closely following their respective documented examples in ways that are “obviously right” and which it is easy to ask questions of the library authors or the community
  2. one single tool, tortured and warped beyond recognition, looking nothing like… anything, where even the tool’s authors can’t understand what you’re doing (let alone why, and they’re probably too afraid to ask), where you’re the only usage like that, ever, and where your “elegant hack” might stop working in the next minor revision, because it wasn’t a tested scenario

I prefer “1”. It’ll keep your model cleaner. It’ll keep you relationship with the tool more successful. Yes, it will mean that you occasionally need more than one tool listed in a particular box. Deal with it! If the tool really is complex enough that this is problematic, just move the ugly complexity behind some abstraction, then only a limited number of people need to worry about how it works.

Always use the right tool for the job.