Parse, Don't Validate (2019)

From the Twitter link:

> IME, people in dynamic languages almost never program this way, though—they prefer to use validation and some form of shotgun parsing. My guess as to why? Writing that kind of code in dynamically-typed languages is often a lot more boilerplate than it is in statically-typed ones!

I feel that once you've got experience working in (usually functional) programming languages with strong static type checking, flakey dynamic code that relies on runtime checks and just being careful to avoid runtime errors makes your skin crawl, and you'll intuitively gravitate towards designs that takes advantage of strong static type checks.

When all you know is dynamic languages, the design guidance you get from strong static type checking is lost so there's more bad design paths you can go down. Patching up flakey code with ad-hoc runtime checks and debugging runtime errors becomes the norm because you just don't know any better and the type system isn't going to teach you.

More general advice would be "prefer strong static type checking over runtime checks" as it makes a lot of design and robustness problems go away.

Even if you can't use e.g. Haskell or OCaml in your daily work, a few weeks or just of few days of trying to learn them will open your eyes and make you a better coder elsewhere. Map/filter/reduce, immutable data structures, non-nullable types etc. have been in other languages for over 30 years before these ideas became more mainstream best practices for example (I'm still waiting for pattern matching + algebraic data types).

It's weird how long it's taking for people to rediscover why strong static types were a good idea.

For what its worth: People don't use dynamic language because they don't know better or never used a static language. To better understand what dynamic languages bring to the table, here are some disadvantages of static types to consider:

Static types are awesome for local reasoning, but they are not that helpful in the context of the larger system (this already starts at the database, see idempotency mismatch).

Code with static types is sometimes larger and more complex than the problem its trying to solve

They tightly couple data to a type system, which (can) introduce incidental complexity >(I'm still waiting for pattern matching + algebraic data types) This is a good example, if you pattern match to a specific structure (e.g. position of fields in your algebraic data type), you tightly coupled your program to this particular structure. If the structure change, you may have to change all the code which pattern matches this structure.

When you said "idempotency mismatch" you were meaning impedance mismatch, right?