HXT：在纯代码中读取和写入HTML到字符串时出现令人惊讶的行为 [英] HXT: Surprising behavior when reading and writing HTML to String in pure code
问题描述
我想从String中读取HTML，处理它并使用HXT以String形式返回已更改的文档。由于此操作不需要IO，我宁愿使用 runLA 而不是 runX 执行Arrow。
代码如下所示（为简单起见，省略了处理）：
$ $ $ $ $ $ $ $ runLA hread>>> writeDocumentToString [withOutputHTML，withIndent yes]）html
然而，结果中缺少code> html 标签：
[\\\
< ; head> \\\
< title> \\ n伪造< /标题> \\\
< / head> \\\
< body> \\\
一些微不足道的文本。\\\
< / body> \\\
，]
当我使用runX代替这个时：
runX（readString [] html>>> writeDocumentToString [withOutputHTML，withIndent yes]）
我得到预期的结果：
[< html> \\\
< head> \\\
< title>虚假< / title> \\ n< / head> \\\
< body> \\\
一些微不足道的文本。\\\
< / body> \\\
< / html> \ n]
为什么会这样，我该如何解决它？
如果您查看两者的 XmlTree s，您会看到 readString 增加了顶级/元素。对于非 IO runLA 版本：
> putStr。 formatTree显示。 head $ runLA xread html
--- XTaghtml[]
|
+ --- XText\\\
|
+ --- XTaghead[]
...
并使用 runX ：
> putStr。 formatTree显示。 head =<< runX（readString [] html）
--- XTag/[NTree（XAttrtransfer-Status）[NTree（XText200）...
|
+ --- XTaghtml[]
|
+ --- XText\\\
|
+ --- XTaghead[]
...
writeDocumentToString 使用 getChildren 来剥离此根元素。
一个简单的方法是使用类似于 selem 的东西来将 xread 的输出封装到一个类似的根元素中，为了使它看起来像输入的类型 writeDocumentToString 期望：
> runLA（selem/[xread]>>> writeDocumentToString [withOutputHTML，withIndent yes]）html
[< html> \\\
< head> \\\
< title> Bogus< / title> \\\
< / head> \\\
< body> \\\
一些琐碎的文本。\\\
< / body> \\\
< / html> \\\
]
这会产生所需的输出。
I want to read HTML from a String, process it and return the changed document as a String using HXT. As this operation does not require IO, I would rather execute the Arrow with runLA than with runX.
The code look like this (omitting the processing for simplicity):
runLA (hread >>> writeDocumentToString [withOutputHTML, withIndent yes]) html
However, the surrounding html tag is missing in the result:
["\n <head>\n <title>Bogus</title>\n </head>\n <body>\n Some trivial bogus text.\n </body>\n",""]
When I use runX instead like this:
runX (readString [] html >>> writeDocumentToString [withOutputHTML, withIndent yes])
I get the expected result:
["<html>\n <head>\n <title>Bogus</title>\n </head>\n <body>\n Some trivial bogus text.\n </body>\n</html>\n"]
Why is that, and how can I fix it?
If you look at the XmlTrees for both, you'll see that readString adds a top-level "/" element. For the non-IO runLA version:
> putStr . formatTree show . head $ runLA xread html
---XTag "html" []
|
+---XText "\n "
|
+---XTag "head" []
...
And with runX:
> putStr . formatTree show . head =<< runX (readString [] html)
---XTag "/" [NTree (XAttr "transfer-Status") [NTree (XText "200")...
|
+---XTag "html" []
|
+---XText "\n "
|
+---XTag "head" []
...
writeDocumentToString uses getChildren to strip off this root element.
One easy way around this is to use something like selem to wrap the output of xread in a similar root element, in order to make it look like the kind of input writeDocumentToString expects:
> runLA (selem "/" [xread] >>> writeDocumentToString [withOutputHTML, withIndent yes]) html
["<html>\n <head>\n <title>Bogus</title>\n </head>\n <body>\n Some trivial bogus text.\n </body>\n</html>\n"]
This produces the desired output.
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