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Learn how to unleash the full potential of the type system of TypeScript

type-level-typescript.com

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Re: Learn how to unleash the full potential of the type system of TypeScript

#91

Post by somewhereoutth »

> Over the years, the type system of TypeScript has grown from basic type annotations to a large and complex programming language.

Give someone (particularly a developer) the opportunity to build something complicated and undoubtedly they will. So now you have two problems, the complicated program that actually does some hopefully useful work, and another complicated program on top of it that fills your head and slows you down when trying to fix the first complicated program. You may say 'ah yes, but the second complicated program validates the first!'. Not really, it just makes things more complicated. Almost all bugs are logic bugs or inconsistent state bugs (thanks OOP!), almost none are type bugs.

However, static analysis of existing code (in Javascript), without having to write a single extra character, may well have great value in indicating correctness.

Edit:

> TypeScript's type system is a full-fledged programming language in itself!

Run! Run as fast as you can! Note that this 'full-fledged programming language' doesn't actually do anything (to their credit they admit this later on)

Edit2:

> [...] is a type-level unit test. It won't type-check until you find the correct solution.

> I sometimes use @ts-expect-error comments when I want to check that an invalid input is rejected by the type-checker. @ts-expect-error only type-checks if the next line does not!

What new level of hell are we exploring now??

I am genuinely afraid and I'm only halfway through this thing. What's next? A meta type level language to check that our type checking checks??

> 3. Objects & Records

> COMING SOON!

> this chapter hasn't been published yet.

Thank God, I am saved.

Re: Learn how to unleash the full potential of the type system of TypeScript

#92

Post by edgyquant »

somewhereoutth wrote: post #91

> Over the years, the type system of TypeScript has grown from basic type annotations to a large and complex programming language. Give someone (particularly a developer) the opportunity to build something complicated and undoubtedly they will. So now you have two problems, the complicated program that actually does some hopefully useful work, and another complicated program on top of it that fills your head and slow…

Have you worked with typescript? Adding strict types to JavaScript fixes pretty much all the complaints I use to have when working with frontend services/clients.

Typescript isn’t a “now you have two problems” anymore than types in any other language are.

Re: Learn how to unleash the full potential of the type system of TypeScript

#93

Post by bo1024 »

tobyhinloopen wrote: post #64
cogman10 wrote: post #26

A great idea. Now, everyone that learns this stuff, show some restraint! The drawback of a powerful type system is you can very easily get yourself into a type complexity mudhole. Nothing worse than trying to call a method where a simple `Foo` object would do but instead you've defined 60 character definition of `Foo` capabilities in the type system in the method signature. Less is more.

True that. Once types get so complex, I’ve no idea what’s going wrong. Today I had code running fine but throwing errors all over the place because some deeply nested type mismatch between two libraries. I just any’d it… i aint got no time for that shit

But would the code really work without the type checking?

Re: Learn how to unleash the full potential of the type system of TypeScript

#94

Post by kixxauth »

somewhereoutth wrote: post #91

> Over the years, the type system of TypeScript has grown from basic type annotations to a large and complex programming language. Give someone (particularly a developer) the opportunity to build something complicated and undoubtedly they will. So now you have two problems, the complicated program that actually does some hopefully useful work, and another complicated program on top of it that fills your head and slow…

Sooooo agree. Let's layer an abstraction on top of an abstraction to abstract the abstraction.

Re: Learn how to unleash the full potential of the type system of TypeScript

#95

Post by jcparkyn »

zarathustreal wrote: post #83
tunesmith wrote: post #45

Might as well ask here. On our teams, we have the occasional developer that is insistent on using Typescript in an OO fashion. This has always struck me as square peg round hole. Even though I come from an OO background, Typescript strict settings really seem to push me in a direction of using interfaces and types for type signatures, and almost never classes, subclasses, instantiated objects. I don't have a very goo…

>I don't have a very good answer for "yeah, but what about dependency injection"? though. Any thoughts from anyone? There is no "dependency injection" in a functional world, take this opportunity to show your colleague how FP makes their life easier. It's just a function. Instead of a class, implementing an interface, created by a factory, requiring a constructor, all you need is a function. Anything that was previou…

The problem with that is that eventually you want to have the dependencies automatically injected (like how an IoC container would be used in a typical OOP application).

Sure, there's solutions for this in the FP world, but in my experience they tend to have their own drawbacks. Admittedly, I've only ever used TS on the front-end (with no DI), so I've never really looked at what FP-style libraries exist for this.

Re: Learn how to unleash the full potential of the type system of TypeScript

#96

Post by jahewson »

somewhereoutth wrote: post #91

> Over the years, the type system of TypeScript has grown from basic type annotations to a large and complex programming language. Give someone (particularly a developer) the opportunity to build something complicated and undoubtedly they will. So now you have two problems, the complicated program that actually does some hopefully useful work, and another complicated program on top of it that fills your head and slow…

> fills your head and slows you down

What? No it frees-up my mind and speeds me up.

The mental gymnastics I have to engage in to work on large JS projects without TypeScript is unbearable. I have to switch between the two often and it’s night and day.

Re: Learn how to unleash the full potential of the type system of TypeScript

#97

Post by shepherdjerred »

somewhereoutth wrote: post #91

> Over the years, the type system of TypeScript has grown from basic type annotations to a large and complex programming language. Give someone (particularly a developer) the opportunity to build something complicated and undoubtedly they will. So now you have two problems, the complicated program that actually does some hopefully useful work, and another complicated program on top of it that fills your head and slow…

> Almost all bugs are logic bugs or inconsistent state bugs (thanks OOP!), almost none are type bugs.

Many bugs of these classes can be avoided with a sufficiently expressive type system. There’s a reason that Haskell programmers say if it compiles, it probably works correctly.

Re: Learn how to unleash the full potential of the type system of TypeScript

#98

Post by shepherdjerred »

kixxauth wrote: post #94
somewhereoutth wrote: post #91

> Over the years, the type system of TypeScript has grown from basic type annotations to a large and complex programming language. Give someone (particularly a developer) the opportunity to build something complicated and undoubtedly they will. So now you have two problems, the complicated program that actually does some hopefully useful work, and another complicated program on top of it that fills your head and slow…

Sooooo agree. Let's layer an abstraction on top of an abstraction to abstract the abstraction.

That’s the definition of computer science.

Re: Learn how to unleash the full potential of the type system of TypeScript

#99

Post by serverlessmania »

somewhereoutth wrote: post #91

> Over the years, the type system of TypeScript has grown from basic type annotations to a large and complex programming language. Give someone (particularly a developer) the opportunity to build something complicated and undoubtedly they will. So now you have two problems, the complicated program that actually does some hopefully useful work, and another complicated program on top of it that fills your head and slow…

Agree for the OOP part, most devs doing the transition from Java,C# to TypeScript are using the tool to port what they learned and apply it to a JS project and projects like Angular are encouraging this by enabling experimental stuff like decorators, but missing the real point behind TS, the type checking system which is to be fair, really awesome.

Re: Learn how to unleash the full potential of the type system of TypeScript

#100

Post by softfalcon »

johnfn wrote: post #75
cogman10 wrote: post #26

A great idea. Now, everyone that learns this stuff, show some restraint! The drawback of a powerful type system is you can very easily get yourself into a type complexity mudhole. Nothing worse than trying to call a method where a simple `Foo` object would do but instead you've defined 60 character definition of `Foo` capabilities in the type system in the method signature. Less is more.

This is so true. I've been thinking recently that in the same way that "use boring technology" is a pretty well-known concept, so should "use boring types" enter the collective conscious. Type operators are exciting and flashy, but I found that using them too much leads to brittle and confusing types. Saving them for a last resort tends to be the right strategy. Often there's an extremely dumb way to write your types…

Agreed! Boring interface definitions is my rule for typing.

I see way too many folks trying to use Omit(…) and Partial(…) creating absolute typing monstrosities. Feels like typing duct tape and it’s impossible to read the type definition when it’s generated in a tooltip.

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