Add dart_messages package.

pkg/dart_messages/lib/parser.js

+// Copyright (c) 2015, the Dart project authors.  Please see the AUTHORS file

[Johnni Winther, 2015/12/11 11:27:29]

Why make a parser in JS? Who will use this?

[floitsch, 2015/12/14 18:56:40]

See https://github.com/floitschG/messages and
http://floitschg.github.io/messages/

The idea is, that the webpage (documenting the messages), extracts as much
information as possible from the messages-file.
This way we don't need to have a build-step to update the dartmsg.org site
(assuming we get a nice domain name).

[Siggi Cherem (dart-lang), 2015/12/14 22:12:07]

I wonder whether people will forget that they are in a restricted Dart and may
have a hard time knowing what's allowed and what not. 

I mentioned this to Florian offline, but just to have it documented here -- An
alternative could be to have a small script that makes a JSON file out of the
shared-messages, and ask developers to follow a small protocol: run the script
every time they update shared_messages.dart and include the JSON file with all
commits. We can include in the test bots a test that ensures that the .json file
is up to date.

If we go down this route, we can accept any Dart within shared_messages.dart.

Because the JSON file will be submitted to the repo, you can fetch it in the
same way you fetched the Dart file below.  

+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+function parseMessages(str) {
+  var result = {};
+  var i;
+
+  function cc() { return str.charCodeAt(i); }
+
+  var SPACE = 32;
+  var NL = 10;
+  var SLASH = 47;
+  var SQUOTE = 39;
+  var DQUOTE = 34;
+  var LBRACE = 123; // {
+  var RBRACE = 125; // }
+  var SEMICOLON = 59;
+  var COMMA = 44;
+  var LBRACKET = 91;
+  var RBRACKET = 93;
+  var BACK_SLASH = 92;
+  var $r = 114;
+
+  // Avoid infinite loops with bad data.
+  var lastNonWhite = -1;
+  var encounteredSameNonWhite = 0;
+
+  // Moves to the next non-white position (skipping over eol-comments).
+  function moveToNextNonWhite() {
+    for (; i < str.length; i++) {
+      var charCode = cc();
+      if (charCode == NL || charCode == SPACE) {
+        // Do nothing.
+      } else if (charCode == SLASH && str.charCodeAt(i + 1) == SLASH) {
+        // Consume until eol.
+        while (cc() != NL) i++;
+      } else {
+        break;
+      }
+    }
+    if (lastNonWhite == i) {
+      if (encounteredSameNonWhite++ == 10)
+      throw "bad input " + i;
+    } else {
+      encounteredSameNonWhite = 0;
+      lastNonWhite = i;
+    }
+  }
+
+  // Automatically concatenates adjacent string literals.
+  function parseString() {
+    var result;
+    // str[i] == '"', str[i] == "'", or str[i] == "r".
+    var allowEscapes = true;
+    var startChar = cc();
+    if (startChar == $r) {
+      i++;
+      startChar = cc();
+      allowEscapes = false;
+    }
+    i++;
+    if (cc() == startChar && str.charCodeAt(i + 1) != startChar) {
+      // Empty string.
+      result = '';
+      i ++;
+    } else {
+      var isMultiline = false;
+      if (cc() == startChar) {
+        isMultiline = true;
+        i += 2;
+        // Multilines ignore the first new line.

[Johnni Winther, 2015/12/11 11:27:29]

Shouldn't you ignore whitespaces until the first new line as well?

[floitsch, 2015/12/14 18:56:40]

We don't need to follow the exact specification (it's a subset), but I added
support for leading spaces.
done.

+        if (cc() == NL) i++;

[Johnni Winther, 2015/12/11 11:27:29]

Remember our source files are converted to platform newlines on checkout so this
won't work on Windows unless we disable the auto-conversion for our messages
files.

[floitsch, 2015/12/14 18:56:40]

I'm now treating "CR" as whitespace. Should make it work.

+      }
+      var startPos = i;
+      for (; i < str.length; i++) {

[Johnni Winther, 2015/12/11 11:27:29]

A file ending with an unterminated string will just silently return `null` as
the result of parseString.

[floitsch, 2015/12/14 18:56:40]

Done.

+        var charCode = cc();
+        if (allowEscapes && charCode == BACK_SLASH) {
+          // Ignore next character.
+          i++;
+          continue;
+        }
+        if (charCode == startChar &&
+            (!isMultiline ||
+             (str.charCodeAt(i + 1) == startChar &&
+              str.charCodeAt(i + 2) == startChar))) {
+          result = str.substring(startPos, i);
+          i += isMultiline ? 3 : 1;
+          break;
+        }
+      }
+    }
+    moveToNextNonWhite();
+    // Another string ?.
+    charCode = cc();
+    if (charCode == SQUOTE || charCode == DQUOTE || charCode == $r) {
+      result += parseString();
+    }
+    return result;
+  }
+
+
+  function parseValue() {
+    var charCode = cc();
+    if (charCode == SQUOTE || charCode == DQUOTE ||
+       (charCode == $r &&
+          (str.charCodeAt(i + 1) == SQUOTE ||
+           str.charCodeAt(i + 1) == DQUOTE))) {
+      return parseString();
+    } else if (charCode == LBRACE) {
+      return parseMap();
+    } else if (charCode == LBRACKET) {
+      return parseList();
+    } else {
+      // Assume it's something we don't support (like DONT_KNOW_HOW_TO_FIX).
+      // Ignore and move to the end of the map.
+      while (true) {
+        var charCode = cc();
+        if (charCode == RBRACE) break;
+        if (charCode == RBRACKET) break;
+        if (charCode == COMMA) break;
+        i++
+      }
+      return null;
+    }
+  }
+
+  function parseList() {
+    var result = [];
+    // str[i] == '['.
+    i++;
+    moveToNextNonWhite();
+    while (cc() != RBRACKET) {
+      result.push(parseValue());
+      moveToNextNonWhite();
+      if (cc() == COMMA) {
+        i++;
+        moveToNextNonWhite();
+      }
+    }
+    i++;
+    return result;
+  }
+
+  // Parse { 'id': ... }
+  function parseMap() {
+    var result = {};
+    // str[i] == '{'.
+    i++;
+    moveToNextNonWhite();
+    while (cc() != RBRACE) {  // "}"
+      var key = parseString();
+      moveToNextNonWhite();
+      i++;  // The ":".

[Johnni Winther, 2015/12/11 11:27:29]

Assert this?

[floitsch, 2015/12/14 18:56:40]

Done.

+      moveToNextNonWhite();
+      result[key] = parseValue();
+      moveToNextNonWhite();
+      if (cc() == COMMA) {
+        i++;
+        moveToNextNonWhite();
+      }
+    }
+    i++;
+    return result;
+  }
+
+  // Skip header.
+  var start = "\nfinal MESSAGES = {";
+  var messagesPos = str.indexOf(start);
+  for (i = messagesPos + start.length; i < str.length; moveToNextNonWhite()) {
+    var charCode = cc();
+    if (charCode == SQUOTE || charCode == DQUOTE) { // '"' or "'"
+      var name = parseString();
+      moveToNextNonWhite();
+      i++; // The ":".
+      moveToNextNonWhite();
+      var data = parseMap();
+      result[name] = data;
+      moveToNextNonWhite();
+      i++; // The trailing "," or the trailing "}".
+    } else if (charCode == RBRACE || charCode == SEMICOLON) { // "}" or ";".
+      break;
+    }
+  }
+  return result;
+}
+
+var messagesUri =
+    'https://raw.githubusercontent.com/dart-lang/sdk/' +
+    'master/pkg/dart_messages/lib/shared_messages.dart';
+
+function loadMessages(callback, onError, uri) {
+  if (!onError) onError = function(e) { throw e; };
+  if (!uri) uri = messagesUri;
+
+  var request = new XMLHttpRequest();
+  request.addEventListener("load", function() {
+    try {
+      callback(parseMessages(this.responseText));
+    } catch (e) {
+      onError(e);
+    }
+  });
+  request.open("GET", uri);
+  request.send();
+}