Adds facilities for extracting Intl.message calls and generating code from translations

pkg/intl/lib/src/intl_message.dart

+// Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
+// 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.
+
+/**
+ * This provides the class IntlMessage to represent an occurence of
+ * [Intl.message] in a program. It is used when parsing sources to extract
+ * messages or to generate code for message substitution.
+ */
+library intl_message;
+
+/**
+ * Represents an occurence of Intl.message in the program's source text. We
+ * assemble it into an object that can be used to write out some translation
+ * format and can also print itself into code.
+ */
+class IntlMessage {
+
+  /**
+   * This holds either Strings or ints representing the message. Literal
+   * parts of the message are stored as strings. Interpolations are represented
+   * by the index of the function parameter that they represent. When writing
+   * out to a translation file format the interpolations must be turned
+   * into the appropriate syntax, and the non-interpolated sections
+   * may be modified. See [fullMessage].
+   */
+  // TODO(alanknight): This will need to be changed for plural support.
+  List messagePieces;
+
+  String description;
+
+  /** The examples from the Intl.message call */
+  String examples;
+
+  /**
+   * The name, which may come from the function name, from the arguments
+   * to Intl.message, or we may just re-use the message.
+   */
+  String _name;
+
+  /** The arguments parameter from the Intl.message call. */
+  List<String> arguments;
+
+  /**
+   * A placeholder for any other identifier that the translation format
+   * may want to use.
+   */
+  String id;
+
+  /**
+   * When generating code, we store translations for each locale
+   * associated with the original message.
+   */
+  Map<String, String> translations = new Map();
+
+  IntlMessage();
+
+  /**
+   * If the message was not given a name, we use the entire message string as
+   * the name.
+   */
+  String get name => _name == null ? computeName() : _name;
+  void set name(x) {_name = x;}
+  String computeName() => name = fullMessage((msg, chunk) => "");
+
+  /**
+   * Return the full message, with any interpolation expressions transformed
+   * by [f] and all the results concatenated. The argument to [f] may be
+   * either a String or an int representing the index of a function parameter
+   * that's being interpolated. See [messagePieces].
+   */
+  String fullMessage([Function f]) {
+    var transform = f == null ? (msg, chunk) => chunk : f;
+    var out = new StringBuffer();
+    messagePieces.map((chunk) => transform(this, chunk)).forEach(out.write);
+    return out.toString();
+  }
+
+  /**
+   * The node will have the attribute names as strings, so we translate
+   * between those and the fields of the class.
+   */
+  void operator []=(attributeName, value) {
+    switch (attributeName) {
+      case "desc" : description = value; return;
+      case "examples" : examples = value; return;
+      case "name" : name = value; return;
+      // We use the actual args from the parser rather than what's given in the
+      // arguments to Intl.message.
+      case "args" : return;
+      default: return;
+    }
+  }
+
+  /**
+   * Record the translation for this message in the given locale, after
+   * suitably escaping it.
+   */
+  String addTranslation(locale, value) =>
+      translations[locale] = escapeAndValidate(locale, value);
+
+  /**
+   * Escape the string and validate that it doesn't contain any interpolations
+   * more complex than including a simple variable value.
+   */
+  String escapeAndValidate(String locale, String s) {
+    const escapes = const {
+      r"\" : r"\\",
+      '"' : r'\"',
+      "\b" : r"\b",
+      "\f" : r"\f",
+      "\n" : r"\n",
+      "\r" : r"\r",
+      "\t" : r"\t",
+      "\v" : r"\v"
+    };
+
+    _escape(String s) => (escapes[s] == null) ? s : escapes[s];
+
+    // We know that we'll be enclosing the string in double-quotes, so we need
+    // to escape those, but not single-quotes. In addition we must escape
+    // backslashes, newlines, and other formatting characters.
+    var escaped = s.splitMapJoin("", onNonMatch: _escape);
+
+    // We don't allow any ${} expressions, only $variable to avoid malicious
+    // code. Disallow any usage of "${". If that makes a false positive
+    // on a translation that legitimate contains "\\${" or other variations,
+    // we'll live with that rather than risk a false negative.
+    var validInterpolations = new RegExp(r"(\$\w+)|(\${\w+})");
+    var validMatches = validInterpolations.allMatches(escaped);
+    escapeInvalidMatches(Match m) {
+      var valid = validMatches.any((x) => x.start == m.start);
+      if (valid) {
+        return m.group(0);
+      } else {
+        return "\\${m.group(0)}";
+      }
+    }
+    return escaped.replaceAllMapped("\$", escapeInvalidMatches);
+  }
+
+  /**
+   * Generate code for this message, expecting it to be part of a map
+   * keyed by name with values the function that calls Intl.message.
+   */
+  String toCode(String locale) {
+    var out = new StringBuffer();
+    // These are statics because we want to closurize them into a map and
+    // that doesn't work for instance methods.
+    out.write('static $name(');
+    out.write(arguments.join(", "));
+    out.write(') => Intl.message("${translations[locale]}");');
+    return out.toString();
+  }
+
+  /**
+   * Escape the string to be used in the name, as a map key. So no double quotes
+   * and no interpolation. Assumes that the string has no existing escaping.
+   */
+  String escapeForName(String s) {
+    var escaped1 = s.replaceAll('"', r'\"');
+    var escaped2 = escaped1.replaceAll('\$', r'\$');
+    return escaped2;
+  }
+
+  String toString() =>
+      "Intl.message(${fullMessage()}, $name, $description, $examples, "
+          "$arguments)";
+}