After writing a lot of metrics for a project in a previous life, not adding any support for Prometheus makes me feel nervous of deploying my code in production.
2. Tests are good, integration tests are gooder.
I'm currently writing tests for a single module only (e.g., only tests for the "view" layer). It gives me some idea of what is right and what is wrong, but in no way I feel those tests say my code is doing what it should do.
3. Tests make better APIs
We build stuff in layers. Tests allow use to see how the API of a layer behaves and we can make better APIs by just checking our struggles writing tests.
4. Future thinking is future trashing
Solve the problem at hand. Don't think "We can do this in a more general way and, in the future, it will be easier to add more". Adding more will never come and you'll have to deal with a pile of trash.
Solve one problem, then solve the next. A patter of problem will emerge -- or not.
5. Code reviews are for architecture, not style
Do not complain about a misplaced semi-colon or a "missing space before parenthesis" in a code review. That's not the forum for this -- unless you found an architectural problem, then you can point both.
5 1/2. Code formatting tools are ok, but are no silver bullet
Computers are very flexible into reading code, but humans are not.
(I may even say that, if the tool is moving a lot of your code, there may be a real architecture problem with your code.)
6. Documentation is a love letter to your future self
Yeah, it's tiring to write the damn documentation on every freaking function, but your future self will thank you for letting the code explained on what it's doing.
6 1/3 The documentation of a function is its contract
The documentation should reflect the code; if it doesn't, you have a problem with your code, not your documentation.
6 2/3. Documentation with an "and" means you're doing it wrong
A function should do one thing and one thing only. If you have to add an "and" to its description, it probably means the function is doing two things and you should break it apart.
6 3/3. Good languages come with integrated documentation
If the language comes with its own way of documenting functions/classes/modules/whatever and it comes with even the simplest doc generator, you can be sure all the language things and libraries will have a good documentation.
But languages with no integrated documentation will most of the time have bad documentation.
7. When it is time to stop, it is time to stop
Learn when you can't code anymore. Learn when you can't process things anymore. Don't push beyond it, it will just make things worse in the future.
8. A language is much more than a language
A programming language is that thing that you write and make things "go". But it has much more beyond special words: It has a build system, it has a dependency control system, it has a way of making tools/libraries/frameworks interact, it has a community, it has a way of dealing with people.
Don't pick languages just 'cause they easier to use.
9. Code of conduct protect _you_, not _them_
When you're beginning with any language/library/framework, check their CoC; they will protect _you_ from being harassed for not immediately getting what is going on instead of blocking you from telling them what you think.
(Addendum: Most of the time, people against CoCs are the ones that want to break it in the first place.)
10. Learn to say no
Sometimes, you'll have to say no: No, I can't do it; no, it can't be made in this time; no, I don't feel capable of doing this; no, I don't feel comfortable writing this.
11. You're responsible for the use of your code
This is hard. Very very hard. It's the difference between "freedom" and "responsibility".
There is nothing wrong in writing, for example, a software to capture people's faces and detect their ethnicity, but you have to think about what that will be used on.
12. Understand and stay way of cargo cult
"Cargo cult" is the idea that, if someone else did, so can we. Most of the time, cargo cult is simply an "easy way out" of a problem: Why would we think about how to properly store our users if X did that?
"If BigCompany stores data like this, so can we".
"If BigCompany is behind this, this is good."
13. Companies look for specialists but keep generalists longer
If you know a lot about one single language, it may make it easier to get a job, but in the long run, language usage dies and you'll need to find something else. Knowing a bit about a lot of other languages helps in the long run, not to mention that may help you think of better solutions.
"A language that doesn't affect the way you think about programming, is not worth knowing." -- Alan Perlis
14. Data flows beat patterns
(This is personal opinion) When you understand how the data must flow in your code, you'll end up with better code than if you applied a bunch of design patterns.
14 1/2. Design patterns are used to describe solutions, not to find them
(Again, personal opinion) Most of the time I saw design patterns being applied, they were applied as a way to find a solution, so you end up twisting a solution -- and, sometimes, the problem it self -- to fit the pattern.
First, solve your problem; find a good solution; then you can check the patterns to know how you name that solution.
15. Think of the users
Think how the data you're collecting from your users will be used -- this is more prevalent on these days, where "privacy" is a premium.
If you capture any used data, remember to protect it against unauthorized use.
15 1/2. The best secure way to deal with user data is not to capture it
You can be sure that, at some point, the data will leak, either by some security flaw or human interference.
If you don't capture any user data -- or store it in anonymized way -- you won't have any problems.
16. Types say what you data means
Memory is just a sequence of bytes; bytes are just numbers from 0 to 255; what those numbers mean is described on the language type system.
For example, in C, a `char` type of value 65 is most probably the letter "A", which an `int` of value is 65 is the number 65.
Remember this when dealing with your data.
17. Cognitive Dissonance is the readability killer
"Cognitive dissonance" is a fancy way of saying "I need to remember two (or more) different things at the same time to understand this."
For example, adding booleans to count the number of True values is a mild cognitive dissonance 'cause one can think "What do you mean True plus True equals 2?"
17 1/2. The Magical Number Seven, Plus or Minus Two
"The magical number" is a psychology article about the number of things one can keep in their mind at the same time.
If you have a function, that calls a function, that calls a function, that calls a function, that calls a function, that calls function, you may be sure it will be a hell to read later.
Think more about: I'll get the result of this function, then pass it to the second function, get its result, pass to the third an so on.
18. Shortcuts are nice, but only in the short run
A lot of languages/libraries/frameworks add a way to make things shorter, reducing the number of things you need to type.
But, later, that will bite you and you'll have to remove the shortcut and do the long things.
So learn what the shortcut does before using it.
(Addendum to "Spec first": The times I stood longer looking at my own code wondering what to do next were when we didn't have the next step defined. It is a good sign that it's time to stop and discuss it with your coworkers -- or maybe rethink the solution.)
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