The phrase "convention over configuration" may as well be a buzzword, especially in the recent past. It's typically perpetuated as a myth by its detractors, and as gospel by its dogmatic followers. Most developers and software engineers typically have an affinity to one side or the other. I'm no different.
I like convention.
I believe there is enormous value in conventions. In most contexts, established conventions ease collaboration and ensure that developers are focused on solving the problem at hand. When everyday development trivialities are offloaded from the hands of software teams and handled by the greater community, productivity ensues.
This productivity results from a few characteristics I've observed:
When a developer doesn't have to think about trivial decisions, like where a file should go, what glue code to write, or what database migration tool to use, they can focus on the problem at hand.
If certain aspects of a framework are implicit rather than explicit, glue code and boilerplate are dramatically reduced. Yes, this directly violates the Zen of Python, however, the real problems in your domain become more explicit. When assumptions are made in regards to project structure, variable naming, etc., your business logic floats to the surface.
This means that defaults are sensible, and made for you. If they're the result of the greater community, they're most likely the correct foundation for the majority. If the defaults are not sensible for your situation, you probably already know that. Configure them.
Being opinionated ensure a particular set of conventions, defaults, and requirements. This coincidentally aids in code reuse, because modules can be absorbed into other projects without any additional config. That's a huge win.
This is one of the most productive aspects. When a community has defined an opinionated and established convention, CLI tools and generators can take care of a lot of the associated boilerplate for solving a particular problem. I believe CLI tools, in particular, especially when tied to a framework, are productivity machines.
The command line, just like your text editor, is expressive. A command line tool tied into your development environment can almost read your mind. For example, let's say that I want a component in an Ember app. That means I need a few things:
The Ember CLI generator, as a result of established convention, knows how to do exactly that:
ember g component foo-bar installing create app/components/foo-bar.js create app/templates/components/foo-bar.hbs installing create tests/unit/components/foo-bar-test.js
This allows me to focus on the more important tasks at hand, like naming things. <3.
If there's only one way to do something, everyone will do it that way. This ensures that as a project snowballs into a 1,000+ file monolith, each related problem was solved in the same way. Often times, convention and inflexibility cut down on clever solutions. Your domain logic becomes more explicit because superfluous noise has disappeared (it's all implicit).
If you aren't wasting time rewriting boilerplate over and over, you're less likely to refrain from repeating yourself when you should. Yes, sometimes it is appropriate to repeat yourself. For example, controllers. Please. Repeat. Yourself. If it's not business logic, or easily abstracted into a service, you can do it, I promise.
We all know the secret tool for developers is Google. Conventions make it easier for new members on a project consult with the community (Github, Stackoverflow, Framework documentation) when running into hurdles along the way. I believe it was Yehuda Katz that said (paraphrased):
Frameworks and conventions are for the next developer.
I think there's a lot of truth to that.
After going on and on about convention, I don't believe in convention just for the sake of convention. Convention is a valuable tool, but it's a means to an end. The end is a working, tested piece of software. The end is an ecosystem where developers are productive and happy. It is paramount that established convention can be easily extended when necessary. But, like what DHH wrote in Rails is omakase they should be rare, substitutions that vary on context.
When you need that substitution, you'll know. But, until then, I'd like to focus on writing code rather than configuration.
Just my two cents.