Question

我正在编写一个用dart和聚合物编写的网站，并遇到一个错误，（见下面的堆栈描述，很长，但不是很有用）。当堆栈跟踪显示时，当聚合物变换器试图从html导入（在MY_APP.html中）内联聚合物元素定义时发生错误。

如果我在MY_APP.html中只有2个自定义元素，我会注释掉其中一个，看看问题是否仍然存在，问题是我有大约20个，一个接一个地尝试它们会很无聊耗费时间，还有什么想法可以确定导致问题的自定义元素？

感谢。

堆栈追踪：

... (OMITTED)
Build error:
Transform polymer (ImportInliner) on MY_PACKAGE_NAME|web/MY_APP.html threw error: The null object does not have a method '[]'.

NoSuchMethodError : method not found: '[]'
Receiver: null
Arguments: [1]
dart:core-patch/object_patch.dart 45                                          Object.noSuchMethod
dart:core/uri.dart 124                                                        Uri.Uri._fromMatch
dart:core/uri.dart 121                                                        Uri.parse
http://127.0.0.1:36562/packages/polymer/src/build/import_inliner.dart 177:24  _UrlNormalizer._newUrl
http://127.0.0.1:36562/packages/polymer/src/build/import_inliner.dart 169:41  _UrlNormalizer.visitElement
http://127.0.0.1:36562/packages/html5lib/dom_parsing.dart 12:50               TreeVisitor.visit
http://127.0.0.1:36562/packages/html5lib/dom_parsing.dart 24:49               TreeVisitor.visitChildren
http://127.0.0.1:36562/packages/html5lib/dom_parsing.dart 30:48               TreeVisitor.visitNodeFallback
http://127.0.0.1:36562/packages/html5lib/dom_parsing.dart 39:50               TreeVisitor.visitElement
http://127.0.0.1:36562/packages/polymer/src/build/import_inliner.dart 173:23  _UrlNormalizer.visitElement
http://127.0.0.1:36562/packages/html5lib/dom_parsing.dart 12:50               TreeVisitor.visit
http://127.0.0.1:36562/packages/html5lib/dom_parsing.dart 24:49               TreeVisitor.visitChildren
http://127.0.0.1:36562/packages/html5lib/dom_parsing.dart 30:48               TreeVisitor.visitNodeFallback
http://127.0.0.1:36562/packages/html5lib/dom_parsing.dart 39:50               TreeVisitor.visitElement
http://127.0.0.1:36562/packages/polymer/src/build/import_inliner.dart 173:23  _UrlNormalizer.visitElement
http://127.0.0.1:36562/packages/html5lib/dom_parsing.dart 12:50               TreeVisitor.visit
http://127.0.0.1:36562/packages/html5lib/dom_parsing.dart 24:49               TreeVisitor.visitChildren
http://127.0.0.1:36562/packages/html5lib/dom_parsing.dart 30:48               TreeVisitor.visitNodeFallback
http://127.0.0.1:36562/packages/html5lib/dom_parsing.dart 39:50               TreeVisitor.visitElement
http://127.0.0.1:36562/packages/polymer/src/build/import_inliner.dart 173:23  _UrlNormalizer.visitElement
http://127.0.0.1:36562/packages/html5lib/dom_parsing.dart 12:50               TreeVisitor.visit
http://127.0.0.1:36562/packages/html5lib/dom_parsing.dart 24:49               TreeVisitor.visitChildren
http://127.0.0.1:36562/packages/html5lib/dom_parsing.dart 30:48               TreeVisitor.visitNodeFallback
http://127.0.0.1:36562/packages/html5lib/dom_parsing.dart 39:50               TreeVisitor.visitElement
http://127.0.0.1:36562/packages/polymer/src/build/import_inliner.dart 173:23  _UrlNormalizer.visitElement
http://127.0.0.1:36562/packages/html5lib/dom_parsing.dart 12:50               TreeVisitor.visit
http://127.0.0.1:36562/packages/html5lib/dom_parsing.dart 24:49               TreeVisitor.visitChildren
http://127.0.0.1:36562/packages/html5lib/dom_parsing.dart 30:48               TreeVisitor.visitNodeFallback
http://127.0.0.1:36562/packages/html5lib/dom_parsing.dart 39:50               TreeVisitor.visitElement
http://127.0.0.1:36562/packages/polymer/src/build/import_inliner.dart 173:23  _UrlNormalizer.visitElement
http://127.0.0.1:36562/packages/html5lib/dom_parsing.dart 12:50               TreeVisitor.visit
http://127.0.0.1:36562/packages/html5lib/dom_parsing.dart 24:49               TreeVisitor.visitChildren
http://127.0.0.1:36562/packages/html5lib/dom_parsing.dart 30:48               TreeVisitor.visitNodeFallback
http://127.0.0.1:36562/packages/html5lib/dom_parsing.dart 39:50               TreeVisitor.visitElement
http://127.0.0.1:36562/packages/polymer/src/build/import_inliner.dart 173:23  _UrlNormalizer.visitElement
http://127.0.0.1:36562/packages/html5lib/dom_parsing.dart 12:50               TreeVisitor.visit
http://127.0.0.1:36562/packages/html5lib/dom_parsing.dart 24:49               TreeVisitor.visitChildren
http://127.0.0.1:36562/packages/html5lib/dom_parsing.dart 30:48               TreeVisitor.visitNodeFallback
http://127.0.0.1:36562/packages/html5lib/dom_parsing.dart 32:52               TreeVisitor.visitDocument
http://127.0.0.1:36562/packages/html5lib/dom_parsing.dart 16:52               TreeVisitor.visit
http://127.0.0.1:36562/packages/polymer/src/build/import_inliner.dart 148:48  ImportInliner._collectImportedDocuments.<fn>.<fn>
dart:async/zone.dart 717                                                      _rootRunUnary
dart:async/zone.dart 854                                                      _RootZone.runUnary
dart:async/future_impl.dart 439                                               _Future._propagateToListeners.handleValueCallback
dart:async/future_impl.dart 522                                               _Future._propagateToListeners
dart:async/future_impl.dart 303                                               _Future._complete
dart:async/future.dart 286                                                    Future.forEach.nextElement
dart:async/zone.dart 717                                                      _rootRunUnary
dart:async/zone.dart 854                                                      _RootZone.runUnary
dart:async/future_impl.dart 439                                               _Future._propagateToListeners.handleValueCallback
dart:async/future_impl.dart 522                                               _Future._propagateToListeners
dart:async/future_impl.dart 303                                               _Future._complete
dart:async/future_impl.dart 354                                               _Future._asyncComplete.<fn>
dart:async/schedule_microtask.dart 23                                         _asyncRunCallbackLoop
dart:async/schedule_microtask.dart 32                                         _asyncRunCallback
dart:isolate-patch/isolate_patch.dart 119                                     _RawReceivePortImpl._handleMessage

../../home/MY_USER_NAME/dart/dart/sdk/lib/_internal/pub/lib/src/barback/load_transformers.dart 560  _call.<fn>
dart:isolate                                                                                 _RawReceivePortImpl._handleMessage
... (OMITTED)

Answer 1

错误来自具有以下内容的自定义元素：

<a href="/blah/{{observableMap['my_key']}}">blah</a>

中，将其更改为：

<a href="{{'/blah/' + observableMap['my_key']}}">blah</a>

编译器很高兴。（这是一个错误吗？）

对于那些有类似问题的人：我能够通过修改common.dart和import_inliner.dart（在包聚合物中）来找到有问题的代码，以添加更多的日志输出。

Answer 2

我最近看到过这样的错误。

我发现的是

相似但不一样......

我在上一个问题中看到你使用了一些不寻常的应用程序布局（在我看来）。文件夹结构很好，但没有使用也没见过元素的HTML和Dart文件位于不同文件夹中的结构。

我用

index.html和index.dart
element1.html和element1.dart（每个聚合物元素一个html和一个dart文件）。
有时当元素更复杂并且在额外元素中分割了一些功能时，我将所有属于一起的文件打包在lib/element1或lib/components/element1

上述链接问题是由元素导入的方式引起的，尤其是当一个元素导入另一个元素时元素导入仍然很不稳定。在Dart / Dartium中，有几个路径会导致一个元素，因为有符号链接，但在构建JavaScript时，只支持一种方式。
见https://code.google.com/p/dart/issues/detail?id=15953
改进这项工作正在进行中（据我所知）。

您组织代码的方式可能有效，但我没有使用它。

编制dart聚合物时找到错误源

2 个答案: