How can I output code that can be loaded as a node module?

[Danny Tuppeny]

Is there any way (today, either using dart2js or dev compiler) to write Dart that would effectively output this?

var vscode = require('vscode');

function activate(context) {
}

function deactivate() {
}

exports.activate = activate;
exports.deactivate = deactivate;

The "vscode" variable can be typed as Dynamic, but I need to get a reference to it and I need to set those two functions against the exports object.

I've been trying for the last few hours without much success (the output of dart2js doesn't make it easier either, and I can't even get the devcompiler to output anything other than a fairly empty stub function).

Here's what I've got so far (I don't know if this is right; like I say, hard to read dart2js output) but I need the output to be loadable as a node js module.

@JS("extension")
library extension;

import "dart:js";
import "package:js/js.dart";

main() {
  context['exports'].activate = activate;
  context['exports'].deactivate = deactivate;
}

activate(dynamic context) {
    print('Congratulations, your extension "dartvs-code" is now active!');
    //var disposable = vscode.commands.registerCommand('extension.sayHello', function () {
    //    vscode.window.showInformationMessage('Hello World!');
    //});
    //context.subscriptions.push(disposable);
}

deactivate() {
}

[Danny Tuppeny]

I managed to get further with this code:

@JS()

library extension;

import "dart:js";
import "package:js/js.dart";

dynamic vscode;

@JS()
external require(String module);

main() {

  vscode = require('vscode');

  print(context);

  context['exports'].activate = activate;
  context['exports'].deactivate = deactivate;
}

activate(dynamic context) {
    print('Congratulations, your extension "dartvs-code" is now active!');

    var disposable = vscode.commands.registerCommand('extension.sayHello', () {
        vscode.window.showInformationMessage('Hello World!');
    });
    context.subscriptions.push(disposable);
}

deactivate() {
}

This gave an error (self is undefined or something)... Managed to get slightly further by pre-pending the contents of the JS file in the node_preamble package to my dart2js output. Now I'm getting this:

Loading development extension at m:/Coding/TestStuff/dartvs-code

Activating extension `DanTup.dartvs-code` failed: Cannot read property 'set$activate' of undefined.

Activating extension `DanTup.dartvs-code` failed: Cannot read property 'set$activate' of undefined

Here is the error stack: TypeError: Cannot read property 'set$activate' of undefined

at dart.main (m:\Coding\TestStuff\dartvs-code\dartvsjs\extension.js:6130:34)

at _IsolateContext.dart._IsolateContext.eval$1 (m:\Coding\TestStuff\dartvs-code\dartvsjs\extension.js:1342:25)

at dart.startRootIsolate (m:\Coding\TestStuff\dartvs-code\dartvsjs\extension.js:1054:23)

at m:\Coding\TestStuff\dartvs-code\dartvsjs\extension.js:6752:11

at m:\Coding\TestStuff\dartvs-code\dartvsjs\extension.js:6753:9

So I'm guessing something is up with context['exports'] though I'm not sure how to fix it. I tried this:

@JS()
external dynamic exports;

However that seems to crash the analyzer (I guess it's a bug to crash in this way, I'll file at GH):

PS M:\Coding\TestStuff\dartvs-code\dartvs> dartanalyzer . --strong
Analyzing [.]...
Unhandled exception:
AnalysisException: Cannot compute DART_ERRORS for M:\Coding\TestStuff\dartvs-code\dartvs\lib\extension.dart
Caused by Unexpected exception while performing VerifyUnitTask for source M:\Coding\TestStuff\dartvs-code\dartvs\lib\extension.dart
#0      AnalysisTask._safelyPerform (package:analyzer/task/model.dart:350)
#1      AnalysisTask.perform (package:analyzer/task/model.dart:238)
#2      AnalysisDriver.performWorkItem (package:analyzer/src/task/driver.dart:284)
#3      AnalysisDriver.computeResult (package:analyzer/src/task/driver.dart:109)
#4      AnalysisContextImpl.computeResult (package:analyzer/src/context/context.dart:703)
#5      AnalysisContextImpl.computeErrors (package:analyzer/src/context/context.dart:651)

[Bob Nystrom]

+jmesserly

I don't know the details very well, but, yes, you can tell dev_compiler to output a node module and then use JS interop to talk to native node libraries. I think the command line flag to pass to dev_compiler is --modules=node.

Cheers!

– bob

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[Samuel Rawlins]

Also see https://github.com/dart-lang/dev_compiler/issues/485 with instructions.

[Danny Tuppeny]

I've actually been trying with the dev compiler for a little while after posting this :)

I hit a differnt issue:

https://github.com/dart-lang/dev_compiler/issues/615

However that's more specific to what I need and John Messerly suggested a small wrapper as a workaround. Giving it a go, though I really have no idea how complete/stable the dev compiler is, so I don't know if going down this route is a good path (I'm going to be relying on calling plain JS objects heavily! ...)

[Danny Tuppeny]

The first line of generated code is:

dart_library.library(...

dart_library is undefined... am I supposed to have a dev_compiler build of the SDK (or the bits I use) in my output? I tried passing --dart-sdk and a path but that didn't change anything (though I suspect it already knew where the SDK was since it's running from it!).

[John Messerly]

Dart SDK is at https://github.com/dart-lang/dev_compiler/blob/master/lib/runtime/dart_sdk.js

dart_library is a little fake module system for the browser (because browsers don't support ES6 module loading yet). You shouldn't need it if you're compiling with ES6 or node modules. But if you did want it, it's in dart_library.js right next to the SDK file I linked above.

[Vijay Menon]

Danny,

If you follow the steps here (3rd comment):

https://github.com/dart-lang/dev_compiler/issues/485

You should not see this.

Vijay

[Danny Tuppeny]

Oops, I had somehow lost "--modules node" from my command when I was looking for options to include the SDK. Adding that in removes dart_library :-)

The instructions you mentioned look like it'll let me build a node version of the SDK (since the version John linked also requires dart_library) but it has a path to a /gen/ folder (a patched SDK?) in the args that I don't see in the repo. Are there any instructions on this; or can I just pass the release 1.18 SDK? (or would it be simpler to just try and use dart_library despite being in node?).

Thanks!

[Vijay Menon]

Ah, you may need to run:

> ./tool/build_sdk.sh

first in a ddc checkout to populate that gen folder. 

[Danny Tuppeny]

Actually, it turned out to be trivial to just tweak dart_sdk (I found the difference here).

Slowly getting there!

[Bob Nystrom]

On Fri, Jul 29, 2016 at 9:21 AM, Danny Tuppeny <da...@tuppeny.com> wrote:

Giving it a go, though I really have no idea how complete/stable the dev compiler is, so I don't know if going down this route is a good path (I'm going to be relying on calling plain JS objects heavily! ...)

It might be a bit of a rocky road today, but I personally think it's a great path to explore and it would be great to get some feedback on it. Running Dart apps on node using dev_compiler and JS interop is a subject close to my heart (but, alas, not close to my schedule...).

– bob

[Danny Tuppeny]

On Friday, 29 July 2016 18:39:11 UTC+1, Bob wrote:

Giving it a go, though I really have no idea how complete/stable the dev compiler is, so I don't know if going down this route is a good path (I'm going to be relying on calling plain JS objects heavily! ...)

It might be a bit of a rocky road today, but I personally think it's a great path to explore and it would be great to get some feedback on it. Running Dart apps on node using dev_compiler and JS interop is a subject close to my heart (but, alas, not close to my schedule...).

Schedules, shmedules!

Do you know of anyone else is trying to do this (that maybe I can "borrow" ideas from if I hit issues)?

[alberto.ags]

now that clearly Dart focuses only to compile to js will be a first class feature add a option to compile for node.js directly.

--

[Bob Nystrom]

On Fri, Jul 29, 2016 at 10:57 AM, Danny Tuppeny <da...@tuppeny.com> wrote:

Do you know of anyone else is trying to do this (that maybe I can "borrow" ideas from if I hit issues)?

I don't offhand, sorry.

– bob

[Thierry Vilmart]

This is old. But if someone has this problem today.

This works to make node modules:

dartdevc bloc_angular/web/main.dart  --modules es6 -o out.js