Create a NullErrorReporter to use when errors don't need to be recorded.

pkg/analyzer/lib/src/generated/error.dart

 // 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.
 
 // This code was auto-generated, is not intended to be edited, and is subject to
 // significant change. Please see the README file for more information.
 
 library engine.error;
 
 import 'dart:collection';
@@ skipping 2102 matching lines @@
 
   static const List<ErrorProperty> values = const [UNIMPLEMENTED_METHODS];
 
   const ErrorProperty(String name, int ordinal) : super(name, ordinal);
 }
 
 /**
  * Instances of the class `ErrorReporter` wrap an error listener with utility methods used to
  * create the errors being reported.
  */
-class ErrorReporter {
+abstract class ErrorReporter {

[Brian Wilkerson, 2014/10/06 14:10:08]

I'm not sure why we needed to make this an abstract class. NullErrorReporter
could have implemented the original definition.

[Paul Berry, 2014/10/06 16:44:39]

Since NullErrorReporter is in the same library as ErrorReporter, it would also
have to have implemented ErrorReporter._hasEqualTypeNames,
ErrorReporter._errorListener, and ErrorReporter._convertTypeNames.  I suppose I
could have just left these methods empty, but that seemed clumsy.

Guess it's a moot point now, though :)

   /**
-   * The error listener to which errors will be reported.
+   * The source used when reporting errors.
    */
-  final AnalysisErrorListener _errorListener;
-
-  /**
-   * The default source to be used when reporting errors.
-   */
-  final Source _defaultSource;
-
-  /**
-   * The source to be used when reporting errors.
-   */
-  Source _source;
-
-  /**
-   * Initialize a newly created error reporter that will report errors to the given listener.
-   *
-   * @param errorListener the error listener to which errors will be reported
-   * @param defaultSource the default source to be used when reporting errors
-   */
-  ErrorReporter(this._errorListener, this._defaultSource) {
-    if (_errorListener == null) {
-      throw new IllegalArgumentException("An error listener must be provided");
-    } else if (_defaultSource == null) {
-      throw new IllegalArgumentException("A default source must be provided");
-    }
-    this._source = _defaultSource;
-  }
-
-  Source get source => _source;
+  Source get source;
 
   /**
    * Creates an error with properties with the given error code and arguments.
    *
    * @param errorCode the error code of the error to be reported
    * @param node the node specifying the location of the error
    * @param arguments the arguments to the error, used to compose the error message
    */
-  AnalysisErrorWithProperties newErrorWithProperties(ErrorCode errorCode, AstNode node, List<Object> arguments) => new AnalysisErrorWithProperties.con2(_source, node.offset, node.length, errorCode, arguments);
+  AnalysisErrorWithProperties newErrorWithProperties(ErrorCode errorCode, AstNode node, List<Object> arguments);
 
   /**
    * Report a passed error.
    *
    * @param error the error to report
    */
-  void reportError(AnalysisError error) {
-    _errorListener.onError(error);
-  }
+  void reportError(AnalysisError error);
 
   /**
    * Report an error with the given error code and arguments.
    *
    * @param errorCode the error code of the error to be reported
    * @param element the element which name should be used as the location of the error
    * @param arguments the arguments to the error, used to compose the error message
    */
-  void reportErrorForElement(ErrorCode errorCode, Element element, List<Object> arguments) {
-    reportErrorForOffset(errorCode, element.nameOffset, element.displayName.length, arguments);
-  }
+  void reportErrorForElement(ErrorCode errorCode, Element element, List<Object> arguments);
 
   /**
    * Report an error with the given error code and arguments.
    *
    * If the arguments contain the names of two or more types, the method
    * [reportTypeErrorForNode] should be used and the types
    * themselves (rather than their names) should be passed as arguments.
    *
    * @param errorCode the error code of the error to be reported
    * @param node the node specifying the location of the error
    * @param arguments the arguments to the error, used to compose the error message
    */
-  void reportErrorForNode(ErrorCode errorCode, AstNode node, List<Object> arguments) {
-    reportErrorForOffset(errorCode, node.offset, node.length, arguments);
-  }
+  void reportErrorForNode(ErrorCode errorCode, AstNode node, List<Object> arguments);
 
   /**
    * Report an error with the given error code and arguments.
    *
    * @param errorCode the error code of the error to be reported
    * @param offset the offset of the location of the error
    * @param length the length of the location of the error
    * @param arguments the arguments to the error, used to compose the error message
    */
-  void reportErrorForOffset(ErrorCode errorCode, int offset, int length, List<Object> arguments) {
-    _errorListener.onError(new AnalysisError.con2(_source, offset, length, errorCode, arguments));
-  }
+  void reportErrorForOffset(ErrorCode errorCode, int offset, int length, List<Object> arguments);
 
   /**
    * Report an error with the given error code and arguments.
    *
    * @param errorCode the error code of the error to be reported
    * @param token the token specifying the location of the error
    * @param arguments the arguments to the error, used to compose the error message
    */
-  void reportErrorForToken(ErrorCode errorCode, Token token, List<Object> arguments) {
-    reportErrorForOffset(errorCode, token.offset, token.length, arguments);
-  }
+  void reportErrorForToken(ErrorCode errorCode, Token token, List<Object> arguments);
 
   /**
    * Report an error with the given error code and arguments. The arguments are expected to contain
    * two or more types. Convert the types into strings by using the display names of the types,
    * unless there are two or more types with the same names, in which case the extended display
    * names of the types will be used in order to clarify the message.
    *
    * If there are not two or more types in the argument list, the method
    * [reportErrorForNode] should be used instead.
    *
    * @param errorCode the error code of the error to be reported
    * @param node the node specifying the location of the error
    * @param arguments the arguments to the error, used to compose the error message
    */
-  void reportTypeErrorForNode(ErrorCode errorCode, AstNode node, List<Object> arguments) {
-    _convertTypeNames(arguments);
-    reportErrorForOffset(errorCode, node.offset, node.length, arguments);
-  }
+  void reportTypeErrorForNode(ErrorCode errorCode, AstNode node, List<Object> arguments);
 
   /**
    * Set the source to be used when reporting errors. Setting the source to `null` will cause
    * the default source to be used.
    *
    * @param source the source to be used when reporting errors
    */
+  void set source(Source source);
+}
+
+class ErrorReporterImpl implements ErrorReporter {
+  /**
+   * The error listener to which errors will be reported.
+   */
+  final AnalysisErrorListener _errorListener;
+
+  /**
+   * The default source to be used when reporting errors.
+   */
+  final Source _defaultSource;
+
+  /**
+   * The source to be used when reporting errors.
+   */
+  Source _source;
+
+  /**
+   * Initialize a newly created error reporter that will report errors to the given listener.
+   *
+   * @param errorListener the error listener to which errors will be reported
+   * @param defaultSource the default source to be used when reporting errors
+   */
+  ErrorReporterImpl(this._errorListener, this._defaultSource) {
+    if (_errorListener == null) {
+      throw new IllegalArgumentException("An error listener must be provided");
+    } else if (_defaultSource == null) {
+      throw new IllegalArgumentException("A default source must be provided");
+    }
+    this._source = _defaultSource;
+  }
+
+  @override
+  Source get source => _source;
+
+  @override
+  AnalysisErrorWithProperties newErrorWithProperties(ErrorCode errorCode, AstNode node, List<Object> arguments) => new AnalysisErrorWithProperties.con2(_source, node.offset, node.length, errorCode, arguments);
+
+  @override
+  void reportError(AnalysisError error) {
+    _errorListener.onError(error);
+  }
+
+  @override
+  void reportErrorForElement(ErrorCode errorCode, Element element, List<Object> arguments) {
+    reportErrorForOffset(errorCode, element.nameOffset, element.displayName.length, arguments);
+  }
+
+  @override
+  void reportErrorForNode(ErrorCode errorCode, AstNode node, List<Object> arguments) {
+    reportErrorForOffset(errorCode, node.offset, node.length, arguments);
+  }
+
+  @override
+  void reportErrorForOffset(ErrorCode errorCode, int offset, int length, List<Object> arguments) {
+    _errorListener.onError(new AnalysisError.con2(_source, offset, length, errorCode, arguments));
+  }
+
+  @override
+  void reportErrorForToken(ErrorCode errorCode, Token token, List<Object> arguments) {
+    reportErrorForOffset(errorCode, token.offset, token.length, arguments);
+  }
+
+  @override
+  void reportTypeErrorForNode(ErrorCode errorCode, AstNode node, List<Object> arguments) {
+    _convertTypeNames(arguments);
+    reportErrorForOffset(errorCode, node.offset, node.length, arguments);
+  }
+
+  @override
   void set source(Source source) {
     this._source = source == null ? _defaultSource : source;
   }
 
   /**
    * Given an array of arguments that is expected to contain two or more types, convert the types
    * into strings by using the display names of the types, unless there are two or more types with
    * the same names, in which case the extended display names of the types will be used in order to
    * clarify the message.
    *
@@ skipping 510 matching lines @@
   @override
   ErrorSeverity get errorSeverity => ErrorSeverity.WARNING;
 
   @override
   ErrorType get type => ErrorType.STATIC_WARNING;
 
   @override
   String get uniqueName => "${runtimeType.toString()}.${name}";
 }
 
+
+/**
+ * The class [NullErrorReporter] presents the same interface as [ErrorReporter]
+ * but discards all error information.
+ */
+class NullErrorReporter implements ErrorReporter {
+  /**
+   * The default source to be used when reporting errors.
+   */
+  final Source _defaultSource;
+
+  /**
+   * The source to be used when reporting errors.
+   */
+  Source _source;
+
+  NullErrorReporter(this._defaultSource) {
+    _source = _defaultSource;
+  }
+
+  @override
+  AnalysisErrorWithProperties newErrorWithProperties(ErrorCode errorCode, AstNode node, List<Object> arguments) {
+    return new AnalysisErrorWithProperties.con2(_source, node.offset, node.length, errorCode, arguments);
+  }
+
+  @override
+  void reportError(AnalysisError error) {
+  }
+
+  @override
+  void reportErrorForElement(ErrorCode errorCode, Element element, List<Object> arguments) {
+  }
+
+  @override
+  void reportErrorForNode(ErrorCode errorCode, AstNode node, List<Object> arguments) {
+  }
+
+  @override
+  void reportErrorForOffset(ErrorCode errorCode, int offset, int length, List<Object> arguments) {
+  }
+
+  @override
+  void reportErrorForToken(ErrorCode errorCode, Token token, List<Object> arguments) {
+  }
+
+  @override
+  void reportTypeErrorForNode(ErrorCode errorCode, AstNode node, List<Object> arguments) {
+  }
+
+  @override
+  void set source(Source source) {
+    this._source = source == null ? _defaultSource : source;
+  }
+
+  @override
+  Source get source => _source;
+}
+
+
 /**
  * The enumeration `PolymerCode` defines Polymer specific problems.
  */
 class PolymerCode extends Enum<PolymerCode> implements ErrorCode {
   static const PolymerCode ATTRIBUTE_FIELD_NOT_PUBLISHED = const PolymerCode('ATTRIBUTE_FIELD_NOT_PUBLISHED', 0, "Field '{0}' in '{1}' must be @published");
 
   static const PolymerCode DUPLICATE_ATTRIBUTE_DEFINITION = const PolymerCode('DUPLICATE_ATTRIBUTE_DEFINITION', 1, "The attribute '{0}' is already defined");
 
   static const PolymerCode EMPTY_ATTRIBUTES = const PolymerCode('EMPTY_ATTRIBUTES', 2, "Empty 'attributes' attribute is useless");
 
@@ skipping 1437 matching lines @@
 
   @override
   String get message => "{0}";
 
   @override
   ErrorType get type => ErrorType.TODO;
 
   @override
   String get uniqueName => "${runtimeType.toString()}.${name}";
 }