Parameterize uri resolution and parsing of options, use package:path

lib/options.dart

Index: lib/options.dart
diff --git a/lib/options.dart b/lib/options.dart
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+++ b/lib/options.dart
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+// Copyright (c) 2014, 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.
+
+part of protoc;
+
+/// Helper function implementing a generic option parser that reads
+/// `request.parameters` and treats each token as either a flag ("name") or a
+/// key-value pair ("name=value"). For each option "name", it looks up whether a
+/// [SingleOptionParser] exists in [parsers] and delegates the actual parsing of
+/// the option to it. Returns `true` if no errors were reported.
+bool genericOptionsParser(
+    CodeGeneratorRequest request, CodeGeneratorResponse response,
+    Map<String, SingleOptionParser> parsers) {
+  var parameter = request.parameter != null ? request.parameter : '';
+  var options = parameter.trim().split(',');
+  var map = <String, String>{};
+  var errors = [];
+
+  for (var option in options) {
+    option = option.trim();
+    if (option.isEmpty) continue;
+    var reportError = (details) {
+      errors.add('Error found trying to parse the option: $option.\n$details');
+    };
+
+    var nameValue = option.split('=');
+    if (nameValue.length != 1 && nameValue.length != 2) {
+      reportError('Options should be a single token, or a name=value pair');
+      continue;
+    }
+    var name = nameValue[0].trim();
+    var parser = parsers[name];
+    if (parser == null) {
+      reportError('Unknown option ($name).');
+      continue;
+    }
+
+    var value = nameValue.length > 1 ? nameValue[1].trim() : null;
+    parser.parse(name, value, reportError);
+  }
+
+  if (errors.length == 0) return true;
+
+  response.error = errors.join('\n');
+  return false;
+}
+
+/// Options expected by the protoc code generation compiler.
+class GenerationOptions {
+  /// Maps a fully qualified field name, to the desired name we wish to
+  /// generate. For example `MyMessage.has_field` to `HasFld`.
+  final Map<String, String> fieldNameOverrides;
+
+  GenerationOptions(this.fieldNameOverrides);
+}
+
+/// A parser for a name-value pair option. Options parsed in
+/// [genericOptionsParser] delegate to instances of this class to
+/// parse the value of a specific option.
+abstract class SingleOptionParser {
+
+  /// Parse the [name]=[value] value pair and report any errors to [onError]. If
+  /// the option is a flag, [value] will be null. Note, [name] is commonly
+  /// unused. It is provided because [SingleOptionParser] can be registered for
+  /// multiple option names in [genericOptionsParser].
+  void parse(String name, String value, onError(String details));
+}
+
+/// Parser used by the compiler, which supports the `field_name` option (see
+/// [FieldNameOptionParser]) and any additional option added in [parsers]. If
+/// [parsers] has a key for `field_name`, it will be ignored.
+GenerationOptions parseGenerationOptions(
+    CodeGeneratorRequest request, CodeGeneratorResponse response,
+    [Map<String, SingleOptionParser> parsers]) {
+  var fieldNameOptionParser = new FieldNameOptionParser();
+  var map = {};
+  if (parsers != null) parsers.forEach((k, v) { map[k] = v; });
+  map['field_name'] = fieldNameOptionParser;
+  if (genericOptionsParser(request, response, map)) {
+    return new GenerationOptions(fieldNameOptionParser.mappings);
+  }
+  return null;
+}
+
+/// A [SingleOptionParser] to parse the `field_name` option. This option
+/// overrides the default name given to some fields that would otherwise collide
+/// with existing field names in Dart core objects or in [GeneratedMessage].
+/// (see `README.md` for details).
+class FieldNameOptionParser implements SingleOptionParser {
+  /// Maps a fully qualified field name, to the desired name we wish to
+  /// generate. For example `MyMessage.has_field` to `HasFld`.
+  final Map<String, String> mappings = {};
+
+  void parse(String name, String value, onError(String message)) {
+    if (value == null) {
+      onError('Invalid field_name option, expected a non-emtpy value.');
+      return;
+    }
+
+    List<String> fromTo = value.split('|');
+    if (fromTo.length != 2) {
+      onError('Invalid field_name option, expected a single "|" separator.');
+      return;
+    }
+
+    var fromName = fromTo[0].trim();
+    var toName = fromTo[1].trim();
+    if (fromName.isEmpty || toName.isEmpty) {
+      onError('Invalid field_name option, '
+          '"from" and "to" names should not be empty.');
+      return;
+    }
+
+    mappings['.$fromName'] = toName;
+  }
+}