What is the /packages/$sdk/ folder inside a Google Dart build for?

Question

After building a Google Dart web app in Dart Editor (the Pub Build (Generates JS) option) the folder layout is like this. My app imports both dart:html and dart:async but It seems I can upload everything but the $sdk folder to my server and the app will run fine in both Dartium and in other browsers. Is there some reason I need to upload the $sdk folder, and what is it for? Tried googling but I see no answer, thanks in advance!

Edit: Here's a working example of my project from DartEditor 1.5.8 and below is the code for it.

hexclock.dart:

import 'dart:html';
import 'dart:async';
DateTime theTime;
String theHour, theMinute, theSecond;
Timer theTimer;
void main() {
  theTimer = new Timer.periodic(new Duration(seconds: 1), getTime);
}

void updateColours(){
  String bgcol = "#" + theHour + theMinute + theSecond;
  querySelector("body").style.backgroundColor = bgcol;
}

void printTime() {
  querySelector("#hour").text = theHour;
  querySelector("#minute").text = theMinute;
  querySelector("#second").text = theSecond;
}

void getTimeInit(){
  theTime = new DateTime.now();
  theHour = "${checkZero(theTime.hour)}";
  theMinute = "${checkZero(theTime.minute)}";
  theSecond = "${checkZero(theTime.second)}";
  printTime();
  updateColours();
}

void getTime(Timer t){
  theTime = new DateTime.now();
  theHour = "${checkZero(theTime.hour)}";
  theMinute = "${checkZero(theTime.minute)}";
  theSecond = "${checkZero(theTime.second)}";
  querySelector("#title").style.opacity = "0";
  querySelector("#clock").style.opacity = "1";
  printTime();
  updateColours();
}

String checkZero(int anInt){
  if (anInt < 10)
    return "0${anInt}";
  else
    return "${anInt}";
}

hexclock.html:

<!DOCTYPE html>
<html>
  <head>
    <meta charset="utf-8">
    <meta name="viewport" content="width=device-width, initial-scale=1">
    <title>HexClock</title>
    <script async type="application/dart" src="hexclock.dart"></script>
    <script async src="packages/browser/dart.js"></script>
    <link href='http://fonts.googleapis.com/css?family=Droid+Sans+Mono' rel='stylesheet' type='text/css'>
    <link rel="stylesheet" href="hexclock.css">
  </head>
  <body> 
    <div id="title" class="centre">hexclock</div>
    <div id="clock" class="centre">#<span id="hour">&nbsp;&nbsp;</span><span id="minute">&nbsp;&nbsp;</span><span id="second">&nbsp;&nbsp;</span></div>
  </body>
</html>

pubspec.yaml:

name: HexClock
description: A sample web application
dependencies:
  browser: any

Danny Tuppeny Danny Tuppeny · Accepted Answer · 2014-09-13T12:17:41

In the pub source code I found this:

  // "$sdk" is a pseudo-package that allows the dart2js transformer to find
  // the Dart core libraries without hitting the file system directly. This
  // ensures they work with source maps.
  var libPath = path.join(sdk.rootDirectory, "lib");
  var sdkSources = listDir(libPath, recursive: true)
      .where((file) => path.extension(file) == ".dart")
      .map((file) {
    var idPath = path.join("lib",
        path.relative(file, from: sdk.rootDirectory));
    return new AssetId('\$sdk', path.toUri(idPath).toString());
  });

I don't know if this matches exactly what you're seeing, but my guess is that it's related. This would in theory allow client-side debugging even through SDK functions, which could be very useful.

What is the /packages/$sdk/ folder inside a Google Dart build for?

2 Answers