pkg/compiler/lib/src/diagnostics/invariant.dart

// Copyright (c) 2012, 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.

library dart2js.diagnostics.invariant;

import 'spannable.dart';

/// Flag that can be used in assertions to assert that a code path is only
/// executed as part of development.
///
/// This flag is automatically set to true if helper methods like, [debugPrint],
/// [debugWrapPrint], [trace], and [reportHere] are called.
bool DEBUG_MODE = false;

/// Assert that [DEBUG_MODE] is `true` and provide [message] as part of the
/// error message.
assertDebugMode(String message) {
  assert(DEBUG_MODE,
      failedAt(NO_LOCATION_SPANNABLE, 'Debug mode is not enabled: $message'));
}

/// Throws a [SpannableAssertionFailure].
///
/// Use this method to provide better information for assertion by calling
/// [failedAt] as the second argument to an `assert` statement:
///
///     assert(condition, failedAt(position, message));
///
/// [spannable] must be non-null and will be used to provide positional
/// information in the generated error message.
///
/// This method can also be used to throw a [SpannableAssertionFailure] outside
/// an assert:
///
///     failedAt(position, message);
///
/// or, if the enclosing function requires a result or control flow:
///
///     throw failedAt(position, message);
///
bool failedAt(Spannable spannable, [String message]) {
  // TODO(johnniwinther): Use [spannable] and [message] to provide better
  // information on assertion errors.
  if (spannable == null) {
    throw new SpannableAssertionFailure(CURRENT_ELEMENT_SPANNABLE,
        'Spannable was null for failedAt. Use CURRENT_ELEMENT_SPANNABLE.');
  }
  throw new SpannableAssertionFailure(spannable, message);
}