+++
title = "Things I Learnt The Hard Way - Documentation Is a Love Letter To Your Future Self"
date = 2019-06-21

[taxonomies]
tags = ["en-au", "books", "things i learnt", "documentation"]
+++

We all know writing the damn docs for functions and classes and modules is a
pain in the backside. But realizing what you were thinking when you wrote the
function will save your butt in the future.

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When I say that it will save your butt, I don't mean the documentation will
tell you something like "Here are the lotto numbers in 2027"[^1] or "If John
complains about your future code review, here is some shit he did in the
past".

I mean, it will explain how the _flow_ of your code is expected to do. Imaging
this: pick your code and replace every function call to its documentation. Can
you understand what it is expected by reading that? If you can,
congratulations, you won't have a problem in the future; if you can't... well,
I have some bad news for you...

One point that may come here is "Code is its own documentation" or
"self-documenting code". I do understand, and yes, simpler functions may make
the documentation redundant (for example, if you notice that you need a
function that multiplies two numbers -- and only do that -- giving it a
description of "Multiples two numbers" may look redundant), but you have to
ask yourself _why_ you needed such simple function. _Why_ it exists? _Where_
it sits in the general data flow?

Another thing you can document: rarely used functions. One example is Java
Collectors: In Java, you can create a stream of data, which you can apply
transformations and such and, in the end, you may put the resulting collection
of data into another structure -- a list, for example. The thing is,
collecting to a list is pretty common, but collecting into a map, with a
function as key and another value as value, splitting the result into two
different data blocks, is not that common. Because it is uncommon to see such
collector, it is a good idea to add tips on what each option is.

That's the things you need to document.

[^1]: Please, don't make me revise this in 2027... :(

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