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The long awaited 0.8.0 release from Reason React is out of beta! This includes a lot of the niceties of writing React but in a very fast, type safe language. I

The long awaited 0.8.0 release from Reason React is out of beta! This includes a lot of the niceties of writing React but in a very fast, type safe language. If this is your first time hearing about Reason, watch a video from its creator (Jordan Walke, creator of React) to learn more: https://www.youtube.com/watch?v=5fG_lyNuEAw&t=11s https://www.youtube.com/watch?v=5fG_lyNuEAw&t=11s Fun facts about Reason: - exports TypeScript! If you have a TS project and looking for some extra speed & stability, you don't have to sacrifice type safety interop - It powers all of Messenger.com. The team put out a case study where they went from ~10 bugs a week to less than 10 a quarter by switching to Reason - It uses the npm / yarn ecosystem so you can use your favorite / current packages without looking for something new.

parhamn 6y ago
Awesome! Question, say you use TypeScript already, what are the biggest tangible gains in terms of safety (measured by fewer bugs in production) you think can be achieved by using Reason?
- bgorman 6y ago
  With ReasonML and other ML languages the type system is advanced enough to make many error conditions unrepresentable in the type system, and therefore the bugs move from runtime to compile time. Typescript has slowly been making its type system more powerful and exhaustive, but ultimately the fact that it is a superset of javascript will always keep it from having the compile time safety you can get in other languages. ReasonML (OCaml) natively supports pattern matching, variants (Sum types), polymorphic variants, smart constructors, abstract data types, recursive types, and modules. When you know how to use all of these features, you can prevent a remarkably large surface of bugs from ever compiling. As a new user, the first feature that will probably bring a smile to your face is pattern matching with variants. If you are interested I highly recommend the book "Learn Type-Driven Development"
  - _bxg1 6y ago
    What's the editor support like? TypeScript has industry-leading editor integration with insanely fast response times. I'm always wary of new languages for this reason; I've been burned before by Facebook's own Flow type system.
    - dmit 6y ago
      Reason support in VSCode is very solid.
      - davesnx 6y ago
        That's not even true. It's still very early days for Reason VSCode tooling, since you might find a few extensions that support most of the cases but lacks a few key features that you might be used to while writing JS/TS.
    - bgorman 6y ago
      As far as editor support, I have used reason-language-server (https://github.com/jaredly/reason-language-server https://github.com/jaredly/reason-language-server) with Emacs (current), Vim and VSCode (provided through reason-vscode plugin). I used to use IntelliJ, and there was a solid plugin for that as well. ReasonML's compiler is way faster than Typescript's.
      - _bxg1 6y ago
        There's a difference between "the compiler is faster when run at the CLI" and "the language server is faster". A good language server remains responsive by doing quick, partial compilations on just the section that changed. A bad language server just wraps the standard compiler and re-runs the whole thing when a file is saved. The latter will eat up CPU/RAM and make for a frustrating dev experience, no matter how relatively-fast the base compilation time is.
        yawaramin 6y ago
- deleted 6y ago
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- yawaramin 6y ago
  - Full-fledged support for pattern-matching exhaustiveness check, not something you have to bake together using a 'tag' field. This means if you match on i.e. integers, the compiler will warn you if you don't include a catch-all default case. - Simple module system where you don't need to deal with named vs default imports and all the weird bugs getting them mixed up can bring - TypeScript's inherent JS-like nature can pop up subtle bugs like forgetting to type a pair of parentheses: function isSupported(): boolean { return false; } function test() { console.log(true && isSupported); // true } Or doing object/array indexing and forgetting to handle the case of 'undefined' because TypeScript doesn't enforce that. Or how any typings from before version 2 are suspect because they were written with the assumption that every type can be implicitly nullable. There are lots of these little footguns all over the place. - Higher-quality bindings: more stuff captured at the type level, you're not left to deal with bindings full of 'any', 'object', and 'function' It's not even just about safety though. One of the biggest productivity drivers in Reason is its iteration speed–the compiler is so fast that you can try out changes basically as fast as you can save the file. And there are other things, like how all modules are implicitly available in scope, so you don't need to manage a 'wall of imports' at the top of every file before you can actually get to the code itself.
  - Kaze404 6y ago
    > TypeScript's inherent JS-like nature can pop up subtle bugs like forgetting to type a pair of parentheses FWIW this was just fixed in TypeScript 3.9.
    - yawaramin 6y ago
      Interesting, can you link me? EDIT: I just tried in the TypeScript Playground (v3.9.2), it's actually rather worse than I thought, it prints not 'false' but the actual function itself as a value...
      - jordwalke 6y ago
        - It's Just JavaScript With Types - It's Usable - It Has Full Type Safety Pick two. I think the TypeScript is aware of the tradeoffs, have chosen the first two, and the result is a great developer/IDE experience for JavaScript programs (props!). Reason chooses the last two and creates a great experience for writing very safe web apps.
- thegreatpeter 6y ago
  1. Pattern Matching Pattern matching has been by far my most favorite feature as someone coming from TypeScript: https://gist.github.com/peterpme/10840585ddced15a7f4ecd05394e6091 https://gist.github.com/peterpme/10840585ddced15a7f4ecd05394... The ability to use "constants" that are inherently typed mean less mistakes and a better path forward for handling your application state. Refactoring with this in mind, becomes a lot safer. For example, if I had a reducer that needed a new action, I would add that action to the `type`. The compiler would then tell me every place I needed to handle that case. 2."Implicit" Types (types that don't get in the way) I don't need to type everything like I would in TypeScript. ReasonML already figures all of that out for me. I _can_ add the type if I want (for readability purposes). There is no such thing a `any` or any type of escape hatch for that (this can be frustrating at first) but once you get it, you write code more confidently. 3. React & Refactoring Say I've got a bunch of React components I need to refactor. Reason types both the prop key and value. If I remove a prop or change that prop's data structure, I'll immediately know all the places I need to make that change. I know some folks may roll their eyes when they read this, but after using both Reason and TypeScript at Draftbit, I strongly believe it's a competitive advantage. The stuff we ship in Reason just doesn't break.
  - machiaweliczny 6y ago
    Is it possible to compile in presence of errors? I love TS that it's gradual and for prototyping I can use "transpileOnly" and after I'm done I can verify everything. I have bad memories from typing json interfeces for Elm while prototyping (maybe could be disabled).
    - pkilgore 6y ago
      No, but you can slowly Reason-ify a javascript (or typescript!) app at the interfaces using gentype[1], which emits javascript/typescript/flow interfaces for the reason side. It works perfectly well to ship a slowly-becoming-reason frontend app. But you do have to have the compiler give the thumbs up before it will compile the reason side of the project. You can also checkout the tutorial for slowly converting a single file here, although I find myself doing this sort of thing very rarely: https://reasonml.github.io/docs/en/converting-from-js https://reasonml.github.io/docs/en/converting-from-js [1] https://github.com/cristianoc/genType https://github.com/cristianoc/genType
- davesnx 6y ago
  There are a few differences between both, a lot of people mention the fast compilation and the type inference. I would add that the types from Reason are much "smaller" and concise, Option type or Result type and the immutability of Records/Objects creates an environment of safety that I don't have it in TypeScript.
- cies 6y ago
  All good arguments in this thread. One I miss: TS fixes some of JSs issues, but many it cannot fix by still being a super set of JS. Reason is similar (enough) to JS syntax-wise, while not having to deal with it's quirks. This is huge for me.
Matthias247 6y ago
> - It powers all of Messenger.com. The team put out a case study where they went from ~10 bugs a week to less than 10 a quarter by switching to Reason Did they move from Typescript or Javascript?
- yawaramin 6y ago
  More details here: https://reasonml.org/blog/messenger-50-reason https://reasonml.org/blog/messenger-50-reason
dmit 6y ago
Congratulations on the release! I have a couple questions for you (and any other contributors!) about the project, but I don't know how to phrase them without coming off as combative. Please accept the following as genuine curiosity rather than malice. 1) You called the 0.8 release "huge" in the release notes, even though it adds 11 new functions, removes 2, and updates 2 compared to 0.7, released a year prior. Is there something else about 0.8 that makes it larger than the sum of the API changes? 2) BuckleScript has seemingly been a one-man show for ~3 years. It is lagging noticeably behind the progress of the main OCaml project (including jsoo). ReasonML has a couple prominent contributors, but the overall (public) activity is dwarfed by Hongbo Zhang's work on BS. Is this because the ReasonML project is considered to be in a stable state, sufficient for production work?
- yawaramin 6y ago
  1) You can see a complete list of changes here https://github.com/reasonml/reason-react/blob/a70d9e6b51ed0ab27a895fa13807436d20db5620/HISTORY.md#080-042020 https://github.com/reasonml/reason-react/blob/a70d9e6b51ed0a... . We consider it a huge release partly because it adds some long-awaited bindings, partly because of the documentation improvements, and partly because of how community-driven the release was. 2) BuckleScript's creator works for Facebook and has both a specific focus and a long-term vision for the project, more details here: https://www.youtube.com/watch?v=iWEQjvGGiTA https://www.youtube.com/watch?v=iWEQjvGGiTA . He also regularly blogs about ongoing improvements: https://reasonml.org/blog https://reasonml.org/blog . Facebook Web Messenger and other products are heavily reliant on BuckleScript. I would consider that to be production-ready.
  - dmit 6y ago
    To clarify, the link in 1) is where I took the number of changes from. And Re: 2) I have no doubt that Mr. Zhang knows what he's doing. I was just noting how even after the prodigious amount of work he has put into BS over the years, it is still falling behind JSOO which has the benefit of being more tightly bound to the parent OCaml project. I know about the different tradeoffs JSOO and BS have made. All I meant to say is that one super-productive person is apparently (and understandably) not able to keep up with upstream (i.e. Inria + Jane Street + many others) in this case. And then we have the ReasonML project that has seen even less activity recently. If ReasonML in its current state is considered a finished product that requires minimal maintenance, I couldn't think of a better endorsement, to be honest.
dmitriid 6y ago
> It powers all of Messenger.com. The team put out a case study where they went from ~10 bugs a week to less than 10 a quarter by switching to Reason When they did that, I was running into numerous behaviour bugs on Messenger.com. Anything from weird image uploads to link previews not showing up in one chat but working in another etc. Reduction in pure code bugs is nice and all, but a very synthetic and useless metric overall IMO.
Scarbutt 6y ago
If the language has proved to be worthy, why messenger.com only though?
- fulafel 6y ago
  This meritocratic model is unfortunately not really how language popularity plays out in the real world. At least not on career-length timescales.
  - Scarbutt 6y ago
    Was referring to Facebook usage only, like in, why isn't it used more at FB?
    - jordwalke 6y ago
      It is.
    - vosper 6y ago
      I asked a similar question recently, one of the maintainers was nice enough to reply with some info. Perhaps this sheds some light: https://news.ycombinator.com/item?id=23116754 https://news.ycombinator.com/item?id=23116754
    - fulafel 6y ago
      I think the point stands doubly strong in case of Facebook. They're a PHP shop after all.
      - Scarbutt 6y ago
        PHP doesn't run in the browser...
        fulafel 6y ago
        Sure, but using it in the backend tells us that there is no language meritocracy at FB.
namelosw 6y ago
Congratulations! I hope Reason and Reason React could get more tractions. I'm wondering, will there be more marketing for Reason or Reason React after it reaching 1.0? I found when introducing this kind of technology for day jobs, people either get confused or concerned usually, even though it really looks like React now. It seems to be very hard to have programming languages taking off without marketing nowadays because the adoption usually comes from other people's adoption. It's the "threshold of immortality" of programming languages according to Simon Peyton Jones.

parhamn 6y ago

Awesome! Question, say you use TypeScript already, what are the biggest tangible gains in terms of safety (measured by fewer bugs in production) you think can be achieved by using Reason?

bgorman 6y ago
With ReasonML and other ML languages the type system is advanced enough to make many error conditions unrepresentable in the type system, and therefore the bugs move from runtime to compile time. Typescript has slowly been making its type system more powerful and exhaustive, but ultimately the fact that it is a superset of javascript will always keep it from having the compile time safety you can get in other languages. ReasonML (OCaml) natively supports pattern matching, variants (Sum types), polymorphic variants, smart constructors, abstract data types, recursive types, and modules. When you know how to use all of these features, you can prevent a remarkably large surface of bugs from ever compiling. As a new user, the first feature that will probably bring a smile to your face is pattern matching with variants. If you are interested I highly recommend the book "Learn Type-Driven Development"
- _bxg1 6y ago
  What's the editor support like? TypeScript has industry-leading editor integration with insanely fast response times. I'm always wary of new languages for this reason; I've been burned before by Facebook's own Flow type system.
  - dmit 6y ago
    Reason support in VSCode is very solid.
    - davesnx 6y ago
      That's not even true. It's still very early days for Reason VSCode tooling, since you might find a few extensions that support most of the cases but lacks a few key features that you might be used to while writing JS/TS.
  - bgorman 6y ago
    As far as editor support, I have used reason-language-server (https://github.com/jaredly/reason-language-server https://github.com/jaredly/reason-language-server) with Emacs (current), Vim and VSCode (provided through reason-vscode plugin). I used to use IntelliJ, and there was a solid plugin for that as well. ReasonML's compiler is way faster than Typescript's.
    - _bxg1 6y ago
      There's a difference between "the compiler is faster when run at the CLI" and "the language server is faster". A good language server remains responsive by doing quick, partial compilations on just the section that changed. A bad language server just wraps the standard compiler and re-runs the whole thing when a file is saved. The latter will eat up CPU/RAM and make for a frustrating dev experience, no matter how relatively-fast the base compilation time is.
      - yawaramin 6y ago
deleted 6y ago
[deleted]
yawaramin 6y ago
- Full-fledged support for pattern-matching exhaustiveness check, not something you have to bake together using a 'tag' field. This means if you match on i.e. integers, the compiler will warn you if you don't include a catch-all default case. - Simple module system where you don't need to deal with named vs default imports and all the weird bugs getting them mixed up can bring - TypeScript's inherent JS-like nature can pop up subtle bugs like forgetting to type a pair of parentheses: function isSupported(): boolean { return false; } function test() { console.log(true && isSupported); // true } Or doing object/array indexing and forgetting to handle the case of 'undefined' because TypeScript doesn't enforce that. Or how any typings from before version 2 are suspect because they were written with the assumption that every type can be implicitly nullable. There are lots of these little footguns all over the place. - Higher-quality bindings: more stuff captured at the type level, you're not left to deal with bindings full of 'any', 'object', and 'function' It's not even just about safety though. One of the biggest productivity drivers in Reason is its iteration speed–the compiler is so fast that you can try out changes basically as fast as you can save the file. And there are other things, like how all modules are implicitly available in scope, so you don't need to manage a 'wall of imports' at the top of every file before you can actually get to the code itself.
- Kaze404 6y ago
  > TypeScript's inherent JS-like nature can pop up subtle bugs like forgetting to type a pair of parentheses FWIW this was just fixed in TypeScript 3.9.
  - yawaramin 6y ago
    Interesting, can you link me? EDIT: I just tried in the TypeScript Playground (v3.9.2), it's actually rather worse than I thought, it prints not 'false' but the actual function itself as a value...
    - jordwalke 6y ago
      - It's Just JavaScript With Types - It's Usable - It Has Full Type Safety Pick two. I think the TypeScript is aware of the tradeoffs, have chosen the first two, and the result is a great developer/IDE experience for JavaScript programs (props!). Reason chooses the last two and creates a great experience for writing very safe web apps.
thegreatpeter 6y ago
1. Pattern Matching Pattern matching has been by far my most favorite feature as someone coming from TypeScript: https://gist.github.com/peterpme/10840585ddced15a7f4ecd05394e6091 https://gist.github.com/peterpme/10840585ddced15a7f4ecd05394... The ability to use "constants" that are inherently typed mean less mistakes and a better path forward for handling your application state. Refactoring with this in mind, becomes a lot safer. For example, if I had a reducer that needed a new action, I would add that action to the `type`. The compiler would then tell me every place I needed to handle that case. 2."Implicit" Types (types that don't get in the way) I don't need to type everything like I would in TypeScript. ReasonML already figures all of that out for me. I _can_ add the type if I want (for readability purposes). There is no such thing a `any` or any type of escape hatch for that (this can be frustrating at first) but once you get it, you write code more confidently. 3. React & Refactoring Say I've got a bunch of React components I need to refactor. Reason types both the prop key and value. If I remove a prop or change that prop's data structure, I'll immediately know all the places I need to make that change. I know some folks may roll their eyes when they read this, but after using both Reason and TypeScript at Draftbit, I strongly believe it's a competitive advantage. The stuff we ship in Reason just doesn't break.
- machiaweliczny 6y ago
  Is it possible to compile in presence of errors? I love TS that it's gradual and for prototyping I can use "transpileOnly" and after I'm done I can verify everything. I have bad memories from typing json interfeces for Elm while prototyping (maybe could be disabled).
  - pkilgore 6y ago
    No, but you can slowly Reason-ify a javascript (or typescript!) app at the interfaces using gentype[1], which emits javascript/typescript/flow interfaces for the reason side. It works perfectly well to ship a slowly-becoming-reason frontend app. But you do have to have the compiler give the thumbs up before it will compile the reason side of the project. You can also checkout the tutorial for slowly converting a single file here, although I find myself doing this sort of thing very rarely: https://reasonml.github.io/docs/en/converting-from-js https://reasonml.github.io/docs/en/converting-from-js [1] https://github.com/cristianoc/genType https://github.com/cristianoc/genType
davesnx 6y ago
There are a few differences between both, a lot of people mention the fast compilation and the type inference. I would add that the types from Reason are much "smaller" and concise, Option type or Result type and the immutability of Records/Objects creates an environment of safety that I don't have it in TypeScript.
cies 6y ago
All good arguments in this thread. One I miss: TS fixes some of JSs issues, but many it cannot fix by still being a super set of JS. Reason is similar (enough) to JS syntax-wise, while not having to deal with it's quirks. This is huge for me.

Matthias247 6y ago

> - It powers all of Messenger.com. The team put out a case study where they went from ~10 bugs a week to less than 10 a quarter by switching to Reason Did they move from Typescript or Javascript?

yawaramin 6y ago
More details here: https://reasonml.org/blog/messenger-50-reason https://reasonml.org/blog/messenger-50-reason

dmit 6y ago

Congratulations on the release! I have a couple questions for you (and any other contributors!) about the project, but I don't know how to phrase them without coming off as combative. Please accept the following as genuine curiosity rather than malice. 1) You called the 0.8 release "huge" in the release notes, even though it adds 11 new functions, removes 2, and updates 2 compared to 0.7, released a year prior. Is there something else about 0.8 that makes it larger than the sum of the API changes? 2) BuckleScript has seemingly been a one-man show for ~3 years. It is lagging noticeably behind the progress of the main OCaml project (including jsoo). ReasonML has a couple prominent contributors, but the overall (public) activity is dwarfed by Hongbo Zhang's work on BS. Is this because the ReasonML project is considered to be in a stable state, sufficient for production work?

yawaramin 6y ago
1) You can see a complete list of changes here https://github.com/reasonml/reason-react/blob/a70d9e6b51ed0ab27a895fa13807436d20db5620/HISTORY.md#080-042020 https://github.com/reasonml/reason-react/blob/a70d9e6b51ed0a... . We consider it a huge release partly because it adds some long-awaited bindings, partly because of the documentation improvements, and partly because of how community-driven the release was. 2) BuckleScript's creator works for Facebook and has both a specific focus and a long-term vision for the project, more details here: https://www.youtube.com/watch?v=iWEQjvGGiTA https://www.youtube.com/watch?v=iWEQjvGGiTA . He also regularly blogs about ongoing improvements: https://reasonml.org/blog https://reasonml.org/blog . Facebook Web Messenger and other products are heavily reliant on BuckleScript. I would consider that to be production-ready.
- dmit 6y ago
  To clarify, the link in 1) is where I took the number of changes from. And Re: 2) I have no doubt that Mr. Zhang knows what he's doing. I was just noting how even after the prodigious amount of work he has put into BS over the years, it is still falling behind JSOO which has the benefit of being more tightly bound to the parent OCaml project. I know about the different tradeoffs JSOO and BS have made. All I meant to say is that one super-productive person is apparently (and understandably) not able to keep up with upstream (i.e. Inria + Jane Street + many others) in this case. And then we have the ReasonML project that has seen even less activity recently. If ReasonML in its current state is considered a finished product that requires minimal maintenance, I couldn't think of a better endorsement, to be honest.

dmitriid 6y ago

> It powers all of Messenger.com. The team put out a case study where they went from ~10 bugs a week to less than 10 a quarter by switching to Reason When they did that, I was running into numerous behaviour bugs on Messenger.com. Anything from weird image uploads to link previews not showing up in one chat but working in another etc. Reduction in pure code bugs is nice and all, but a very synthetic and useless metric overall IMO.

Scarbutt 6y ago

If the language has proved to be worthy, why messenger.com only though?

fulafel 6y ago
This meritocratic model is unfortunately not really how language popularity plays out in the real world. At least not on career-length timescales.
- Scarbutt 6y ago
  Was referring to Facebook usage only, like in, why isn't it used more at FB?
  - jordwalke 6y ago
    It is.
  - vosper 6y ago
    I asked a similar question recently, one of the maintainers was nice enough to reply with some info. Perhaps this sheds some light: https://news.ycombinator.com/item?id=23116754 https://news.ycombinator.com/item?id=23116754
  - fulafel 6y ago
    I think the point stands doubly strong in case of Facebook. They're a PHP shop after all.
    - Scarbutt 6y ago
      PHP doesn't run in the browser...
      - fulafel 6y ago
        Sure, but using it in the backend tells us that there is no language meritocracy at FB.

namelosw 6y ago

Congratulations! I hope Reason and Reason React could get more tractions. I'm wondering, will there be more marketing for Reason or Reason React after it reaching 1.0? I found when introducing this kind of technology for day jobs, people either get confused or concerned usually, even though it really looks like React now. It seems to be very hard to have programming languages taking off without marketing nowadays because the adoption usually comes from other people's adoption. It's the "threshold of immortality" of programming languages according to Simon Peyton Jones.