HTML::Element endtag 为 <br> 和 <img>

问题描述 投票：0回答：1

我使用以下 Perl 代码来遍历和格式化一些 HTML：

#!/usr/bin/env perl 
use v5.38;
use HTML::TreeBuilder;
my $indent = 3;
my $content = do {local $/; <DATA>};
my $tree = HTML::TreeBuilder->new();
$tree->parse_content($content);
visit($tree);

sub visit($x) {
    my $depth = $x->depth;
    my $in = ' ' x ($indent * $depth);
    foreach my $e ($x->content_list) {
        # element
        if (ref ($e)) {
            say $in . $e->starttag;
            visit($e);
            say $in . $e->endtag;
        }
        # text
        else {
            say $in . $e;
        }
    }
}
__DATA__
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="utf-8">
</head>
<body>
    <font size=3><strong>
    5/5/61 Bob & Jerry - Arroyo Lounge, Stanford University, Palo Alto, CA
    </strong></font>
    <br>
    <img src="poster.png" alt="poster/ad" title="poster/ad">
    <i>(Robert Hunter and Jerry Garcia; source: McNally, Jackson research)</i>
    <br><br>

    <font size=3><strong>
    5/26/61 Bob & Jerry - Barbara Meier's 16th birthday party, Menlo Park, CA
    </strong></font>
    <br>
    Follow The Drinking Gourd, John Henry, Santy Anno*, Poor Paddy Works On The Railway
    <br>
    <i>(*included on
        <a href="https://www.garciafamilyprovisions.com/product/JY148COMBO/before-the-dead-4cd-set?cp=640_62123_100764" target="_blank">Before The Dead
        </a>;
        <a href="https://gdsets.com/63posters/1961_05_26.jpg" target="_blank">birthday doodle for Barbara by Jerry
        </a>;
        <a href="https://gdsets.com/63posters/1961_05_26a.jpg" target="_blank">the master tape
        </a>
    )
    </i>
    <br><br>

我的问题是每个

<br>
输出为：

<br />
</br>


<br />
和
</br>
都会导致渲染新行。我很惊讶
endtag
在标签
br
（和
img
）的情况下生成了任何东西。

我避免使用 HTML::Tree::traverse 因为文档不鼓励使用它：

[I]如果你想递归访问树中的每个节点，那就差不多了 编写子程序总是比编写子程序更简单 将订购前和/或订购后代码捆绑在回调中 遍历法。

没有给出例子，所以以上是我编造的。

我是否正确使用了 

starttag
和 
endtag
？我是否应该检测何时显示不带结束标记的标记并避免调用结束标记？遍历 HTML 树并美化它的正确/最佳/最简单的方法是什么？

更新：

按照 Stephen Ullrich 的建议，我尝试使用 as_HTML() 进行格式化：

#!/usr/bin/env perl 
use v5.38;
use HTML::TreeBuilder;
say "\%HTML::Element::optionalEndTag= ",
    join ', ', keys %HTML::Element::optionalEndTag;
my $content = do {local $/; <DATA>};
my $tree = HTML::TreeBuilder->new();
$tree->parse_content($content);
# don't encode any entities; indent with three spaces; 
say $tree->as_HTML('', '   ');
__DATA__
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="utf-8">
</head>
<body>
    <font size=3><strong>
    5/5/61 Bob & Jerry - Arroyo Lounge, Stanford University, Palo Alto, CA
    </strong></font>
    <br>
    <img src="poster.png" alt="poster/ad" title="poster/ad">
    <i>(Robert Hunter and Jerry Garcia; source: McNally, Jackson research)</i>
    <br><br>

    <font size=3><strong>
    5/26/61 Bob & Jerry - Barbara Meier's 16th birthday party, Menlo Park, CA
    </strong></font>
    <br>
    Follow The Drinking Gourd, John Henry, Santy Anno*, Poor Paddy Works On The Railway
    <br>
    <i>(*included on
        <a href="https://www.garciafamilyprovisions.com/product/JY148COMBO/before-the-dead-4cd-set?cp=640_62123_100764" target="_blank">Before The Dead
        </a>;
        <a href="https://gdsets.com/63posters/1961_05_26.jpg" target="_blank">birthday doodle for Barbara by Jerry
        </a>;
        <a href="https://gdsets.com/63posters/1961_05_26a.jpg" target="_blank">the master tape
        </a>
    )
    </i>
    <br><br>

输出：

%HTML::Element::optionalEndTag= dt, dd, li, p
<!DOCTYPE html>
<html lang="en">
   <head>
      <meta charset="utf-8" />
   </head>
   <body><font size="3"><strong> 5/5/61 Bob & Jerry - Arroyo Lounge, Stanford University, Palo Alto, CA </strong></font><br /><img alt="poster/ad" src="poster.png" title="poster/ad" /> <i>(Robert Hunter and Jerry Garcia; source: McNally, Jackson research)</i><br />
      <br /><font size="3"><strong> 5/26/61 Bob & Jerry - Barbara Meier's 16th birthday party, Menlo Park, CA </strong></font><br /> Follow The Drinking Gourd, John Henry, Santy Anno*, Poor Paddy Works On The Railway <br /><i>(*included on <a href="https://www.garciafamilyprovisions.com/product/JY148COMBO/before-the-dead-4cd-set?cp=640_62123_100764" target="_blank">Before The Dead </a>; <a href="https://gdsets.com/63posters/1961_05_26.jpg" target="_blank">birthday doodle for Barbara by Jerry </a>; <a href="https://gdsets.com/63posters/1961_05_26a.jpg" target="_blank">the master tape </a> ) </i><br />
      <br />
   </body>
</html>

不幸的是，这还不够“漂亮”。我不明白为什么缩进在前几级之后就消失了。但是，我确实注意到它不会生成

</br>
或
</img>
，尽管事实上
%HTML::Element::optionalEndTag
中没有提到这些标签！

更新2

（尽管它们列在 %HTML::Tagset::emptyElement

 中，由 as_HTML 检查。）

html perl pretty-print html-tree
1个回答
0
投票

<br>

 和
<img>
（等等）是空元素；它们并不打算包围任何东西，因此没有必要使用单独的结束标记。尽管如此，无论 
tag
 是否为空元素，
HTML::Element::endtag 始终生成字符串 </
tag>。

（请注意，starttag 足够智能，可以为 
<
 和 
=... /> 等空标签编写 <img ... />tag
 
attr
<br />
。）


因此，程序员必须明确测试结束标记是否合适。幸运的是，有一个变量 
%HTML::Tagset::emptyElement
，可以将每个空元素映射到 1（真）。


以下代码将以简单的缩进格式打印 OP 中提供的 HTML，每个标签位于单独的行上。


#!/usr/bin/env perl 
use v5.38;
use HTML::TreeBuilder;
my $indent = 3;
my $content = do {local $/; <DATA>};
my $tree = HTML::TreeBuilder->new();
$tree->parse_content($content);
visit($tree);

sub visit($x) {
    use HTML::Tagset;
    my $depth = $x->depth;
    my $in = ' ' x ($indent * $depth);
    for my $e ($x->content_list) {
        if (ref ($e)) {     # element
            say $in . $e->starttag;
            if (! $HTML::Tagset::emptyElement{$e->tag}) {
                visit($e);
                say $e->endtag;
            }
        }
        else {              # text

            # for extra prettiness
            use Text::Wrap;
            $Text::Wrap::columns = 132;
            say wrap($in, $in, $e);
        }
    }
}
__DATA__
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="utf-8">
</head>
<body>
    <font size=3><strong>
    5/5/61 Bob & Jerry - Arroyo Lounge, Stanford University, Palo Alto, CA
    </strong></font>
    <br>
    <img src="poster.png" alt="poster/ad" title="poster/ad">
    <i>(Robert Hunter and Jerry Garcia; source: McNally, Jackson research)</i>
    <br><br>

    <font size=3><strong>
    5/26/61 Bob & Jerry - Barbara Meier's 16th birthday party, Menlo Park, CA
    </strong></font>
    <br>
    Follow The Drinking Gourd, John Henry, Santy Anno*, Poor Paddy Works On The Railway
    <br>
    <i>(*included on
        <a href="https://www.garciafamilyprovisions.com/product/JY148COMBO/before-the-dead-4cd-set?cp=640_62123_100764" target="_blank">Before The Dead
        </a>;
        <a href="https://gdsets.com/63posters/1961_05_26.jpg" target="_blank">birthday doodle for Barbara by Jerry
        </a>;
        <a href="https://gdsets.com/63posters/1961_05_26a.jpg" target="_blank">the master tape
        </a>
    )
    </i>
    <br><br>

输出：


<head>
   <meta charset="utf-8" />
</head>
<body>
   <font size="3">
      <strong>
      5/5/61 Bob & Jerry - Arroyo Lounge, Stanford University, Palo Alto,
     CA
      </strong>
   </font>
   <br />
   <img alt="poster/ad" src="poster.png" title="poster/ad" />

   <i>
      (Robert Hunter and Jerry Garcia; source: McNally, Jackson research)
   </i>
   <br />
   <br />
   <font size="3">
      <strong>
      5/26/61 Bob & Jerry - Barbara Meier's 16th birthday party, Menlo
     Park, CA
      </strong>
   </font>
   <br />
    Follow The Drinking Gourd, John Henry, Santy Anno*, Poor Paddy Works On The
   Railway
   <br />
   <i>
      (*included on
      <a href="https://www.garciafamilyprovisions.com/product/JY148COMBO/before-the-dead-4cd-set?cp=640_62123_100764" target="_blank">
     Before The Dead
      </a>
      ;
      <a href="https://gdsets.com/63posters/1961_05_26.jpg" target="_blank">
     birthday doodle for Barbara by Jerry
      </a>
      ;
      <a href="https://gdsets.com/63posters/1961_05_26a.jpg" target="_blank">
     the master tape
      </a>
       )
   </i>
   <br />
   <br />
</body>

    



      

      
    

  

  

    
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