模式编译在 LibXML.pm 失败

Question

我正在使用 XML::LibXML 读取大型 HTML 文件。构建这样的模式时：

XML::LibXML::Pattern->new('//span[@class="entry"]');

它给出了以下错误：

Compilation of pattern failed at /Users/chris/perl5/perlbrew/perls/perl-5.31.3/lib/site_perl/5.31.3/darwin-2level/XML/LibXML.pm line 2138.

但是这个工作正常：

XML::LibXML::Pattern->new('//span');

我不确定 [@class="entry"] 部分是否不受 XML::LibXML::Pattern 支持，或者我只是做错了。

如有任何信息，我们将不胜感激。提前致谢。

Answer 1

虽然是有效的 XPath，但它不是有效的 Pattern。

Patterns are a small subset of XPath language, which is limited to (disjunctions of) location paths involving the child and descendant axes in abbreviated form as described by the extended BNF given below:
Selector ::=     Path ( '|' Path )*
Path     ::=     ('.//' | '//' | '/' )? Step ( '/' Step )*
Step     ::=     '.' | NameTest
NameTest ::=     QName | '*' | NCName ':' '*'
For readability, whitespace may be used in selector XPath expressions even though not explicitly allowed by the grammar: whitespace may be freely added within patterns before or after any token, where
token     ::=     '.' | '/' | '//' | '|' | NameTest
Note that no predicates or attribute tests are allowed.

（强调我的。）

模式编译在 LibXML.pm 失败

Compilation of pattern failed at LibXML.pm

perl

html-parsing

libxml2