Meeseeks v0.12.0 Meeseeks.XPath View Source

Compile XPath 1.0 selector syntax into Meeseeks.Selectors.

Supported Syntax

Supports almost all XPath 1.0 syntax with a few notable exceptions.

No top-level filter expressions

Due to the way Meeseeks selection works, top-level filter expressions like xpath("(//ol|//ul)[2]"), which would select the second list element in the document, are particularly difficult to implement. An error will be raised if you try to use the above or any other top-level filter expression.

To do the above try something like:

Meeseeks.all(doc, xpath("ol|ul")) |> Enum.at(1)

All other filter expressions, like xpath("//div[2]"), are valid.

No support for variable references

Variable references are not currently supported, meaning expression like xpath("*[position()=$p]") are invalid and will raise an error.

To do the above try something like:

p = 2
xpath("*[position()=" <> Integer.to_string(p) <> "]")

No support for id(), lang(), or translate() functions

These three functions from the core functions library are not currently supported. A runtime error will be raised should they attempt to be used.

Namespace prefixes are not resolved to namespace uris

If you want to find a namespace, search for the namespace prefix of node, not the expanded namespace-uri. xpath("*[namespace-uri()='example']"), not xpath("*[namespace-uri()='https://example.com/ns']")

HTML5 doesn't support processing instructions

Because in HTML5 processing instructions as are parsed as comments, trying to select a processing instruction will not work as expected if you are using meeseeks_html5ever's html parser. To select a processing instruction when parsing with meeseeks_html5ever's html parser, search for comment nodes.

If you've parsed a tuple-tree that had a {:pi, _} or {:pi, _, _} node, selecting processing instructions should work as expected, though if the tuple-tree is the result of parsing with :mochiweb_html, the data might be slightly mangled due to :mochiweb_html's rather suspect decision to parse the data of all processing instructions except <?php .. ?> as attributes.

Examples

iex> import Meeseeks.XPath
iex> xpath("//li[last()]")
%Meeseeks.Selector.Element{
  combinator: %Meeseeks.Selector.Combinator.Children{
    selector: %Meeseeks.Selector.Element{
      combinator: nil,
      filters: [
        %Meeseeks.Selector.XPath.Predicate{e:
          %Meeseeks.Selector.XPath.Expr.Predicate{
            e: %Meeseeks.Selector.XPath.Expr.Function{
              args: [],
              f: :last}}}],
      selectors: [%Meeseeks.Selector.Element.Tag{value: "li"}]}},
  filters: nil,
  selectors: []}
iex> xpath("//ol|//ul")
[%Meeseeks.Selector.Element{
   combinator: %Meeseeks.Selector.Combinator.Children{
     selector: %Meeseeks.Selector.Element{
       combinator: nil,
       filters: nil,
       selectors: [%Meeseeks.Selector.Element.Tag{value: "ol"}]}},
   filters: nil,
   selectors: []},
 %Meeseeks.Selector.Element{
    combinator: %Meeseeks.Selector.Combinator.Children{
      selector: %Meeseeks.Selector.Element{
        combinator: nil,
        filters: nil,
        selectors: [%Meeseeks.Selector.Element.Tag{value: "ul"}]}},
    filters: nil,
    selectors: []}]

Link to this section Summary

Functions

Compiles a string representing XPath selector syntax into one or more Meeseeks.Selectors

Link to this section Functions

Link to this macro

xpath(string_literal) View Source (macro)

Compiles a string representing XPath selector syntax into one or more Meeseeks.Selectors.

When a static string literal is provided this work will be done during compilation, but if a string with interpolated values or a var is provided this work will occur at run time.