New C# to Javascript compiler released

http://www.erik-kallen.se/blog/saltarelle-open-source-c-to-javascript-compiler

by erik-kallen • 14 years ago

109 79 14 years ago

bdfh424• 14 years ago

The very best of luck when it comes to debugging the code when it is running in the browser.

Maybe your experiences are different to mine but I avoid such abstractions wherever possible.

It has become fashionable to say things like "JavaScript ... is not well suited for developing large systems" - indeed so much so it often passes without comment but when it is JavaScript that will be run by the browser then JavaScript is what you should be writing.

erik-kallen12• 14 years ago

Actually, debugging is quite simple. The generated script (unless minified) is very similar to the input code. Are you also against other options such as CoffeeScript? And do you think it is very hard to debug higher-level languages such as C, C# or Java because "if you are writing code to run on a processor, it is assembly you should be writing"?

jrajav• 14 years ago

Well, he actually said "debugging code when it is running," which a lot of people find valuable. Of course you can debug anything in the looser sense of the term, but tools like debuggers make the process more productive.

And yes, many people are against Coffeescript too for precisely this reason.

prasincs2• 14 years ago

The question is how similar? Coffeescript has come a long way in keeping symbols similar enough to be debuggable and not polluting the javascript namespace. Once the code grows to a certain size, tracing from line number in error to a line of code in your source becomes non-trivial.

Also, since this has been a constant pain for me when using Google Closure compiler, how do you anticipate this tool working with existing javascript libraries? Hypothetically, can I port a C# application ( a reasonable/simple one, not with crazy winforms and stuff)? Is there a spec you're adhering to?

prasincs2• 14 years ago

I agree. Having had used GWT and other similar cross compiling to javascript type tools, it's often a huge problem in debugging than if you just write a short javascript code. No offense to the author but projects like these that try to fit a static language like Java/C# that run in their own managed environments into dynamic world of Javascript fail miserably.

I fear projects like these tend to attract programmers who know C#, Java but don't quite want to learn javascript and they don't even try to do it once they run out of runway in this tool. And, the code becomes undebuggable, bloated on the browser.

Nothing against other languages, they're amazing at what they do. But, javascript is, for better or worse, the language of browsers. And it's really powerful with established best practices to organize, debug code + great tools (thanks to Chrome Team @ Google and Mozilla).

From a programming languages/compilers standpoint, it definitely tickles my fancy :)

giulianob3• 14 years ago

I program both C# and JS on an almost daily basis and am pretty well versed in both. I have to say that JS is great for adding scripting to pages but for large apps it's a nightmare (especially when coupled w/ the dom).

raverbashing• 14 years ago

Really, really

GWT is not the answer, Dart is not the answer, not writing JS is not the answer (maybe CoffeeScript but I'm skeptical)

JS may have its warts, but in the end that's what browsers understand. That's what you'll have to know to debug things.

And the browser doesn't have to execute 2x, 3x the code, and use more memory as well

If you want something to help my perception is that it should be a thin shin (like CS) rather than "full bells and whistles" on top like GWT or Dart

marcelvr2• 14 years ago

"... but when it is JavaScript that will be run by the browser then JavaScript is what you should be writing."

So by that logic, one shouldn't be writing C# that targets the CLR either, but should rather be coding in MSIL directly. Mmm, no thanks!

weego• 14 years ago

Come on, we all know that isn't a logical equality.

bdfh424• 14 years ago

But JavaScript is not (another daft meme) "the assembler of the web" as it is itself interpreted (or what have you) into byte code for execution.

The point is that one should limit the level of abstraction to one which sits in that comfort zone between code that is sensible to humans and code that is sensible to the machine running it and (perhaps more importantly) the available dev/debug tools.

mistercow• 14 years ago

>when it is JavaScript that will be run by the browser then JavaScript is what you should be writing.

Of course, source maps will soon make this point largely moot.

batista• 14 years ago

Haven't happened for the last 2 years we've been waiting for them.

Kototama• 14 years ago

Maybe that's where source maps come handy?

http://www.html5rocks.com/en/tutorials/developertools/source...

eckyptang5• 14 years ago

This sounds like a solution to a problem that probably shouldn't exist because there is a solution that shouldn't exist to start with which has caused a problem that doesn't need to occur.

The slightly overbearing complexity of the solution matches the linguistic complexity of the statement above :)

dmethvin• 14 years ago

They do come in handy, if only they were supported everywhere. Right now it's just Chrome and a small number of tools.

WayneDB2• 14 years ago

I don't see the problem.

- If I had written Javascript, I would have to debug the Javascript that is running in the browser.

- If a tool writes Javascript for me, I have to debug Javascript running in the browser.

A better wish would be: I hope that your tool outputs nicely formatted and easy to debug Javascript.

bdfh424• 14 years ago

But it will not write JavaScript the way you would write it - and (avoiding arguments about personality in code) that JavaScript will be way harder to follow and debug.

dotborg• 14 years ago

You should run and debug the C# code, before you compile it to JS, that's how I understand the idea behind this project.

hhudolet• 14 years ago

Looks cool, but need more docs and samples (for each feature)!

jaz• 14 years ago

I came across a similar project on /r/csharp last week. The project's called Blade, and is available here - https://github.com/vannatech/blade

erik-kallen12• 14 years ago

Saltarelle is way more complete, though.

WayneDB2• 14 years ago

Thanks Erik! I haven't touched Script# due to the fact that development stalled and it (was) closed source.

Looking forward to seeing how this performs.

josephcooney• 14 years ago

Script# is alive and well AFAIK. It is hosted on github, with about 9 commits from the primary author in the last week.

https://github.com/nikhilk/scriptsharp/commits/master

erik-kallen12• 14 years ago

But all those commits are, unfortunately, tiny. Also the compiler is not open-source only the runtime library (which Saltarelle uses a modified copy of).

scorcher• 14 years ago

I don't really get this. Surely JavaScript and C# are so hugely different that any converted code would be horrific? Wouldn't it be simpler to just write JavaScript in JavaScript?

jeswin• 14 years ago

- Translating a statically-typed Object Oriented language to JS wouldn't produce hugely different (/horrific) code. From inheritance to lambdas, there are comparable features available in JS. Going from JS to C# might be harder though.

- It might be simpler to write JS, but I can imagine people wanting to see if type-safety has benefits.

erik-kallen12• 14 years ago

That's right, it doesn't get horrific until you use goto or yield (which don't exist in Javascript so they have to be emulated).

0ptr2• 14 years ago

I totally agree that JavaScript can easily end up being a huge mess especially when project grows. Using more strict language like C# can help on that. I have to try this, good job!

ecocentrik• 14 years ago

There are frameworks and best practices for organizing JavaScript heavy projects. I'm all for solutions to unify front and backend web application development so cheers to Erik for developing this, I've just never been a fan of cross language compilation.

eckyptang5• 14 years ago

Flash, silverlight, Java, native apps...

acron0• 14 years ago

Not entirely the same, but for those of us on Window, I prefer the look of http://jsil.org.

erik-kallen12• 14 years ago

JSIL is also great, but its philosophy is that yo write .net code and run it in the browser, whereas Saltarelle's (and Script#'s) is that you write Javascript but with better tools. Also, the script that JSIL generates is very far from what you would write by hand, whereas that generated by Saltarelle/Script# can be distinguished from hand-written script primarily because the indentation is always correct and there is never an accidental loose comparison operator.

azakai2• 14 years ago

Could you not somehow reuse the JSIL code generator, and add things for the approach you took in Saltarelle (good integration with JQuery etc.)?

Another question, did you do any performance comparisons of Saltarelle? (to normal C# builds, to JSIL, or anything else?)

OllieJones• 14 years ago

Wow! A great hack on hacker news! Thanks Erik. Don't let the griping grind you down.

TazeTSchnitzel3• 14 years ago

Wow, very cool. I like C#, and the DOM is actually specified with types, so statically-typed web dev with this would be awesome.

Hovertruck• 14 years ago

You can get the majority of this functionality with Closure Compiler though, without needing to abstract the entire language away.

TazeTSchnitzel3• 14 years ago

That's true, but I don't really like the closure compiler's syntax.

Fizzer2• 14 years ago

Looks impressive!

I'm curious how you're doing the parsing. I see that you reference both NRefactory (which reads C#) and Cecil (which reads IL) -- can you talk about how are each of these used and how you combine them?

Also, did you consider using Roslyn (Microsoft's official C# parser)? Obviously it's still beta, but once it's complete would it remove the need for Cecil and NRefactory completely?

erik-kallen12• 14 years ago

Why would I want to use the proprietary Roslyn when I have a working solution with the open-source NRefactory and Cecil?

Fizzer2• 14 years ago

I can think of a dozen reasons off the top of my head. But if you prefer to avoid proprietary utilities that's understandable.

hpguy• 14 years ago

NRefactory itself depends on Cecil, so his translator might not use Cecil at all.

DougWebb3• 14 years ago

I don't see how you can really use this without already being very familiar with Javascript. While you're writing your code you'd need to be constantly aware of how the code will be translated to js (so you can use the correct attributes and define datatypes correctly), and you'd also need to be aware of avoiding. NET library classes that can't be used by the translated js. It seems easier to just learn to manage large js projects.

michaelwww4• 14 years ago

I think what you're saying is a given...

DougWebb3• 14 years ago

The author might assume it, but I think it needs to be explicitly stated. Tools like this are often sold as "You don't need to know X because you can now code in Y and translate automatically to X!" That never works out though because there are always leaky abstractions. (For this project, just take a look at the Attributes docs to see how leaky the abstractions are.)

I've had to work with a bunch of C, C++, Java, Perl, and C# developers who were good at backend stuff and just started to learn HTML, CSS, and Javascript, and they're mostly pretty awful at it until they give in and dedicate themselves to the frontend web developer platform and environment. Prior to that they'd grasp at tools like this one that seem to offer hope that they won't have to learn that nasty javascript.

eranation3• 14 years ago

The reason I'm looking for either C# / Scala JS compiler is that I'm a static typing fan, I am an old school developer who likes IDEs and like discovering API by pressing ctrl+space, instead of mentally knowing it or constantly checking the API docs, I know it's against the trend, and not considered cool, but this gets me working software out the door. I'm much more productive and have much less bugs while writing old school, unpopular Java, and using the IDE's (eclipse) sugar features. Scala is now my favorite language (I really hope it was a little more new dev friendly, it can become very syntax overwhelming sometimes) as I can many of the functional features in Ruby / Python / JavaScript / Clojure, but still stay in Static Java land.

Another thing static typing gives me that I really wish I had in JavaScript, is (almost) worry free refactoring.

In Java, I can extract methods, constants, delegates, change method signatures, rename members, fix typos in code, and never to worry I copy pasted something wrong.

I have yet to find such a way to do it safely in JavaScript / CoffeScript or any other dynamically typed language. (feel free to point if I'm missing something, I said I'm not that a great of a developer)

So maybe I'm just not good enough as a developer, but I like IDEs to protect me, perhaps I'm not smart enough to use VIM / Emacs / TextMate, and I can't memorize APIs. Static typing + functional features make me the most productive. So C# / Scala / Java 8 javascript compilers are on the top of my wish list.

DougWebb3• 14 years ago

I hear you, but I can't agree. Maybe it's my background. For 13 years as a professional developer my primary languages were Perl and Javascript, using Vim and the Unix command-line as my IDE. For the past 1.5 years I've swapped C# for Perl and Visual Studio for my IDE (still have a vi emulator though.) Intellisense is definitely useful, but I find it gets in the way a lot... both literally by overlapping the code around the code I'm typing, and figuratively by trying to insert text while I type which causes me to double-type characters and backspace a lot. It does help with remembering (not learning) APIs, but that's one of my concerns about translating to js: Intellisense won't know which APIs are usable and which ones are not. If you're a C# developer who's dependent on Intellisense, it's going to mislead you here.

Regarding refactoring, it's hardly worry free for me. I always have to double check what VS is going to do when I use its refactoring tools, because sometimes it makes a significant mistake. Now, that's often caused by the way I wrote some code and I have to fix it up as part of my refactoring, but I would have discovered that while refactoring manually too, and if I trusted VS I wouldn't have discovered it at all. So VS helps a bit with the typing, but it's not much faster than I'd be without it. A lot of that is probably because I learned to refactor using vim, grep, sed, and other Unix command-line tools, so I have no problem doing large-scale refactoring changes touching thousands of lines over a 100k+ line codebase. Extracting a method is childs play in comparison, and I don't mind the extra few seconds it takes to do it manually exactly the way I want it.

There is definitely a need for better javascript editing tools. VS, with the right plugins, wouldn't be bad, but I'm not sure Intellisense can really cut it. When I'm putting some code into an MVC template or js file and I want to refer to a jQuery plugin I know is loaded by my layout template, there is no way for Intellisense to know about that plugin or its API, so it can't help me. In contrast if I load my app in Firefox and use Firebug's console and debugger, I can type in some code and it's able to show me the API in real-time because it's reflecting the live javascript objects as I type. That's the kind of intellisense I want.

goggles992• 14 years ago

How does this compare to http://sharpkit.net (free for small and open source projects) Feature wise? SharpKit seems more complete (language support and has source map debugging support on Chrome). Also support for all popular JS libraries.

erik-kallen12• 14 years ago

SharpKit is only free as long as you want to use it for projects that don't need it (the limit is like 2k lines or something). When I last tried it I was not very happy with the code it generated. Additionally, it uses the standard mscorlib so it is not unlikely that you will end up calling methods that are not implemented (which is the very problem the tool is designed to avoid). If it were open source, I would have contributed to SharpKit instead of rolling my own, but it is not.

When it comes to the language support, I think Saltarelle is slightly ahead, as it supports goto and yield (I don't count SharpKit's implementation of yield which translate 'yield return "x"' to '$yield.push("x")' and then returns the $yield array).

goggles992• 14 years ago

Thanks for the reply, This seems to be a very nice tool. I will definitely try it out. Though I don't think that I will switch unless debugging is implemented (via source maps) like SharpKit has. This is invaluable to me at times.

consultutah• 14 years ago

We use an older version of Script# for a very large site at work. This looks like it might be worth trying to upgrade to.

But what I really want is a way to convert Silverlight to JS. I don't care whether it is source or binary level conversion, but it would be awesome to take projects we've written in silverlight and run them on any browser without a plugin.

skrebbel• 14 years ago

As I see the author reads these comments, I'd just like to add that this makes me very excited. C# is my favourite language by far, combining some of the most powerful (mainstream) language features with some of the most powerful dev tools out there.

Having the ability to run the same code in the browser and on the server, in C#, is really a big thing for me.

I think the debugging problem stated in many comments here is overrated: If you're writing an app the size that seriously benefits from the modularity, the tool support and the type checking of a language like C#, you will have a relatively small amount of code directly touching the DOM. All of that other code can be simply unit tested in C#-o-world, straight from the dev environment. If you're writing C#, don't test and debug like it's JS!

Surely such an approach won't catch all bugs and the occasional leaky abstraction (or compiler bug), but it should get one pretty far. Some in-browser unit testing lib together with the fact that the generated JS is quite readable indeed, should help me get the rest of the way.

Can't wait to dive in!

michaelwww4• 14 years ago

After the initial curve of getting VC10 configured right, I did an inheritance test. It worked (copied base class prototype, called base constructor with this.) Minutes later I was happily converting C# code to nicely formatted JavaScript. Having spent the last two weeks converting JS to Dart (basically a one way process because you don't want to look at Dart->JS), I'd say this project is a winner and immediately usable. I'm positive there are C# features and libraries that don't convert well, or at all, but I'm not interested in those in the browser any way.

randomfool3• 14 years ago

My largest criticism for projects like this is that I absolutely abhor running into compiler errors. When you don't fully trust the compiler, it suddenly becomes a suspect when code isn't working like you think it should.

Given decent source maps to allow debugging through the original code, I don't think solutions like this are terribly different than native Javascript. The primary difference though is that I trust the browser JS interpreters and VMs more than I trust many X->JS compilers.

NonEUCitizen• 14 years ago

Does this include a library for accessing Canvas ? Thanks.

prpatel• 14 years ago

good grief... just learn some fscking JavaScript already! It's not _that_ hard!

New C# to Javascript compiler released

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