[simoncion]

In my professional experience, types are a godsend for large, and/or long-running projects that have been worked on by many people over the years. They reduce complexity by informing you up-front of the shape of the data and/or objects that a function demands and produces.

If the type-checking system is decent, they also automatically catch a whole class of problems that will only show up at runtime, and may take years to surface. (Ask me about the error-handing code that detonated because it contained a typo in a Ruby class name, which was only discovered three years after it was introduced... when that code was actually exercised during an... exciting outage of a system it depended on.)

[pansa2]

> types are a godsend for large, and/or long-running projects

Agreed. But that doesn't mean that every language needs to be statically-typed, which seems to be where we're heading nowadays.

IMO large and/or long-running projects should be written in languages with sound static type systems, not scripting languages with types tacked on. Conversely, I often work on projects which are neither large nor long-running - for those, a dynamically-typed scripting language works perfectly well.

> a typo in a Ruby class name, which was only discovered three years after it was introduced

So the code containing this typo was never tested? That's asking for trouble even if you have static typing.

[simoncion]

> So the code containing this typo was never tested?

The code absolutely was tested. However, (obviously) not every possible path through the code was tested.

Given a long-enough timeline, you will NEVER remember to test every little thing. Given sufficient code complexity, it can be next to impossible to actually exercise every code path with hand-written tests.

That's one of the troubles with large projects written scripting languages like Ruby... you have to write an assload of tests to replace what you get for free in languages (even "loosely"-typed languages like Erlang) that have pre-runtime type-checking (whether or not it's provided by a compiler).

> Conversely, I often work on projects which are neither large nor long-running - for those, a dynamically-typed scripting language works perfectly well.

Oh yeah, for small things such languages are A-OK. I 1000% agree with that. The big problem (that you may never encounter because I bet that you're smarter than the average unending parade of Project Managers) is how often small projects are forced into becoming big projects, and then huge projects as time goes on.

[ninkendo]

I’d add to this that there’s a good reason the testing culture is so strong in ruby: you absolutely need to write tests for every last little 2-line method to make sure you did it right. With no compilation or type checking step, there’s no other way to know if your code is even valid.

Which means that IME a huge number of tests in my ruby code were doing things that a type checker does automatically: make sure that passing nil makes it return nil, making sure that passing an array does the right thing vs a string, etc etc etc.

I have very vivid memories of working in a large rails code base and having no idea whether my change would work until I actually exercised the code and realized I was completely messing up the contract that some method expected, so I had to slow down and write tests to validate my assumptions.

Fast forward to now, I work in a large Rust code base, and it seems like 99% of the time, if my code compiles, it works flawlessly the first time. So I concentrate on writing integration/functional tests, which give me a lot more bang for my buck than having to write hundreds of little unit tests. (I still write some unit tests, but the need for it is much less… the vast majority of things you’d write tests for in Ruby are things the type and borrow checkers handle for you in Rust.)

[simoncion]

> ...there’s a good reason the testing culture is so strong in ruby:

"Strong" as in "You easily burn 10x more time writing tests as you do code... and not because it's difficult to think through how to write good tests"? If so, yes.

"Good"? Hell, no! That's a bad reason.

> ...a huge number of tests in my ruby code were doing things that a type checker does automatically...

The folks I work with demand that we don't write these tests, so they don't get written. Guess how often code detonates in production because of things a typechecker would have caught... despite the enormous volume of test code.

To be crystal clear, I totally agree with your statements in this comment. I started my "career" with C++ and I'm so damn glad I did. Had I started with Ruby and Rails, I would have come to the conclusion I was far too damn stupid for this field and left to become a lawyer.

[ninkendo]

“Good” in this context didn’t mean “this is a good situation”, but rather “if you’re using ruby, it would be very bad if you didn’t write tests”, and “bad if you don’t” can be roughly reworded as “good if you do”, at least if we’re presupposing that you have to be writing Ruby.