pkg/dev_compiler/tool/input_sdk/private/ddc_runtime/errors.dart

// Copyright (c) 2015, 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 dart._runtime;

// We need to set these properties while the sdk is only partially initialized
// so we cannot use regular Dart fields.
// The default values for these properties are set when the global_ final field
// in runtime.dart is initialized.

// Override, e.g., for testing
void trapRuntimeErrors(bool flag) {
  JS('', 'dart.__trapRuntimeErrors = #', flag);
}

void ignoreWhitelistedErrors(bool flag) {
  JS('', 'dart.__ignoreWhitelistedErrors = #', flag);
}

// TODO(jmesserly): remove this?
void ignoreAllErrors(bool flag) {
  JS('', 'dart.__ignoreAllErrors = #', flag);
}

argumentError(value) {
  if (JS('!', 'dart.__trapRuntimeErrors')) JS('', 'debugger');
  throw ArgumentError.value(value);
}

throwUnimplementedError(String message) {
  if (JS('!', 'dart.__trapRuntimeErrors')) JS('', 'debugger');
  throw UnimplementedError(message);
}

assertFailed(message) {
  if (JS('!', 'dart.__trapRuntimeErrors')) JS('', 'debugger');
  throw AssertionErrorImpl(message);
}

throwCyclicInitializationError([Object field]) {
  if (JS('!', 'dart.__trapRuntimeErrors')) JS('', 'debugger');
  throw CyclicInitializationError(field);
}

throwNullValueError() {
  // TODO(vsm): Per spec, we should throw an NSM here.  Technically, we ought
  // to thread through method info, but that uglifies the code and can't
  // actually be queried ... it only affects how the error is printed.
  if (JS('!', 'dart.__trapRuntimeErrors')) JS('', 'debugger');
  throw NoSuchMethodError(
      null, Symbol('<Unexpected Null Value>'), null, null, null);
}

castError(obj, expectedType, [@notNull bool isImplicit = false]) {
  var actualType = getReifiedType(obj);
  var message = _castErrorMessage(actualType, expectedType);
  if (JS('!', 'dart.__ignoreAllErrors')) {
    JS('', 'console.error(#)', message);
    return obj;
  }
  if (JS('!', 'dart.__trapRuntimeErrors')) JS('', 'debugger');
  var error = isImplicit ? TypeErrorImpl(message) : CastErrorImpl(message);
  throw error;
}

String _castErrorMessage(from, to) {
  // If both types are generic classes, see if we can infer generic type
  // arguments for `from` that would allow the subtype relation to work.
  var fromClass = getGenericClass(from);
  if (fromClass != null) {
    var fromTypeFormals = getGenericTypeFormals(fromClass);
    var fromType = instantiateClass(fromClass, fromTypeFormals);
    var inferrer = _TypeInferrer(fromTypeFormals);
    if (inferrer.trySubtypeMatch(fromType, to)) {
      var inferredTypes = inferrer.getInferredTypes();
      if (inferredTypes != null) {
        var inferred = instantiateClass(fromClass, inferredTypes);
        return "Type '${typeName(from)}' should be '${typeName(inferred)}' "
            "to implement expected type '${typeName(to)}'.";
      }
    }
  }
  return "Type '${typeName(from)}' is not a subtype of "
      "expected type '${typeName(to)}'.";
}

/// The symbol that references the thrown Dart Object (typically but not
/// necessarily an [Error] or [Exception]), used by the [exception] function.
final Object _thrownValue = JS('', 'Symbol("_thrownValue")');

/// For a Dart [Error], this provides access to the JS Error object that
/// contains the stack trace if the error was thrown.
final Object _jsError = JS('', 'Symbol("_jsError")');

/// Gets the thrown Dart Object from an [error] caught by a JS catch.
///
/// If the throw originated in Dart, the result will typically be an [Error]
/// or [Exception], but it could be any Dart object.
///
/// If the throw originated in JavaScript, then there is not a corresponding
/// Dart value, so we just return the error object.
Object getThrown(Object error) {
  if (error != null) {
    // Get the Dart thrown value, if any.
    var value = JS('', '#[#]', error, _thrownValue);
    if (value != null) return value;
  }
  // Otherwise return the original object.
  return error;
}

final _stackTrace = JS('', 'Symbol("_stackTrace")');

/// Returns the stack trace from an [error] caught by a JS catch.
///
/// If the throw originated in Dart, we should always have JS Error
/// (see [throw_]) so we can create a Dart [StackTrace] from that (or return a
/// previously created instance).
///
/// If the throw originated in JavaScript and was an `Error`, then we can get
/// the corresponding stack trace the same way we do for Dart throws. If the
/// throw object was not an Error, then we don't have a JS trace, so we create
/// one here.
StackTrace stackTrace(Object error) {
  if (JS<bool>('!', '!(# instanceof Error)', error)) {
    // We caught something that isn't a JS Error.
    //
    // We should only hit this path when a non-Error was thrown from JS. In
    // case, there is no stack trace available, so create one here.
    return _StackTrace.missing(error);
  }

  // If we've already created the Dart stack trace object, return it.
  StackTrace trace = JS('', '#[#]', error, _stackTrace);
  if (trace != null) return trace;

  // Otherwise create the Dart stack trace (by parsing the JS stack), and
  // cache it so we don't repeat the parsing/allocation.
  return JS('', '#[#] = #', error, _stackTrace, _StackTrace(error));
}

StackTrace stackTraceForError(Error error) {
  return stackTrace(JS('', '#[#]', error, _jsError));
}

/// Implements `rethrow` of [error], allowing rethrow in an expression context.
///
/// Note: [error] must be the raw JS error caught in the JS catch, not the
/// unwrapped value returned by [getThrown].
@JSExportName('rethrow')
void rethrow_(Object error) {
  JS('', 'throw #', error);
}

/// Subclass of JS `Error` that wraps a thrown Dart object, and evaluates the
/// message lazily by calling `toString()` on the wrapped Dart object.
///
/// Also creates a pointer from the Dart [Error] to the JS Error
/// (via [_jsError]). This is used to implement [Error.stackTrace].
///
/// TODO(jmesserly): Dart Errors should simply be JS Errors.
final Object DartError = JS(
    '!',
    '''class DartError extends Error {
      constructor(error) {
        super();
        this[#] = error;
        if (error instanceof # && error[#] == null) error[#] = this;
      }
      get message() {
        return #(this[#]);
      }
    }''',
    _thrownValue,
    Error,
    _jsError,
    _jsError,
    _toString,
    _thrownValue);

/// Subclass of [DartError] for cases where we're rethrowing with a different,
/// original Dart StackTrace object.
///
/// This includes the original stack trace in the JS Error message so it doesn't
/// get lost if the exception reaches JS.
final Object RethrownDartError = JS(
    '!',
    '''class RethrownDartError extends # {
      constructor(error, stackTrace) {
        super(error);
        this[#] = stackTrace;
      }
      get message() {
        return super.message + "\\n    " + #(this[#]) + "\\n";
      }
    }''',
    DartError,
    _stackTrace,
    _toString,
    _stackTrace);

/// Implements `throw` of [exception], allowing for throw in an expression
/// context, and capturing the current stack trace.
@JSExportName('throw')
void throw_(Object exception) {
  /// Wrap the object so we capture a new stack trace, and so it will print
  /// nicely from JS, as if it were a normal JS error.
  JS('', 'throw new #(#)', DartError, exception);
}

/// Returns a JS error for throwing the Dart [exception] Object and using the
/// provided stack [trace].
///
/// This is used by dart:async to rethrow unhandled errors in [Zone]s, and by
/// `async`/`async*` to rethrow errors from Futures/Streams into the generator
/// (so a try/catch in there can catch it).
///
/// If the exception and trace originated from the same Dart throw, then we can
/// simply return the original JS Error. Otherwise, we have to create a new JS
/// Error. The new error will have the correct Dart trace, but it will not have
/// the correct JS stack trace (visible if JavaScript ends up handling it). To
/// fix that, we use [RethrownDartError] to preserve the Dart trace and make
/// sure it gets displayed in the JS error message.
Object createErrorWithStack(Object exception, StackTrace trace) {
  if (trace is _StackTrace) {
    /// Optimization: if this stack trace and exception already have a matching
    /// Error, we can just rethrow it.
    var originalError = trace._jsError;
    if (identical(exception, getThrown(originalError))) {
      return originalError;
    }
  }
  var error = JS('', 'new #(#)', RethrownDartError, exception);
  JS('', '#[#] = #', error, _stackTrace, trace);
  return error;
}

// This is a utility function: it is only intended to be called from dev
// tools.
void stackPrint(Object error) {
  JS('', 'console.log(#.stack ? #.stack : "No stack trace for: " + #)', error,
      error, error);
}

class _StackTrace implements StackTrace {
  final Object _jsError;
  final Object _jsObjectMissingTrace;
  String _trace;

  _StackTrace(this._jsError) : _jsObjectMissingTrace = null;

  _StackTrace.missing(Object caughtObj)
      : _jsObjectMissingTrace = caughtObj != null ? caughtObj : 'null',
        _jsError = JS('', 'Error()');

  String toString() {
    if (_trace != null) return _trace;

    var e = _jsError;
    String trace = '';
    if (e != null && JS('bool', 'typeof # === "object"', e)) {
      trace = e is NativeError ? e.dartStack() : JS<String>('', '#.stack', e);
      if (trace != null && stackTraceMapper != null) {
        trace = stackTraceMapper(trace);
      }
    }
    if (trace.isEmpty || _jsObjectMissingTrace != null) {
      String jsToString;
      try {
        jsToString = JS('', '"" + #', _jsObjectMissingTrace);
      } catch (_) {
        jsToString = '<error converting JS object to string>';
      }
      trace = 'Non-error `$jsToString` thrown by JS does not have stack trace.'
          '\nCaught in Dart at:\n\n$trace';
    }
    return _trace = trace;
  }
}