Crystal XPath2

Crystal XPath2 Shard provide XPath implementation in Pure Crystal. Performs the compilation of XPath expression and provides mechanism to select/evaluate nodes from HTML or other documents using XPath expression

Supported Features

The basic XPath patterns.

The basic XPath patterns cover 90% of the cases that most stylesheets will need.

node : Selects all child elements with node Name of node.
* : Selects all child elements.
@attr : Selects the attribute attr.
@* : Selects all attributes.
node() : Matches an org.w3c.dom.Node.
text() : Matches a org.w3c.dom.Text node.
comment() : Matches a comment.
. : Selects the current node.
.. : Selects the parent of current node.
/ : Selects the document node.
a[expr] : Select only those nodes matching a which also satisfy the expression expr.
a[n] : Selects the nth matching node matching a When a filter's expression is a number, XPath selects based on position.
a/b : For each node matching a, add the nodes matching b to the result.
a//b : For each node matching a, add the descendant nodes matching b to the result.
//b : Returns elements in the entire document matching b.
a|b : All nodes matching a or b, union operation(not boolean or).
(a, b, c) : Evaluates each of its operands and concatenates the resulting sequences, in order, into a single result sequence

Node Axes

child::* : The child axis selects children of the current node.
descendant::* : The descendant axis selects descendants of the current node. It is equivalent to "//".
descendant-or-self::* : Selects descendants including the current node.
attribute::* : Selects attributes of the current element. It is equivalent to @*
following-sibling::* : Selects nodes after the current node.
preceding-sibling::* : Selects nodes before the current node.
following::* : Selects the first matching node following in document order, excluding descendants.
preceding::* : Selects the first matching node preceding in document order, excluding ancestors.
parent::* : Selects the parent if it matches. The ".." pattern from the core is equivalent to 'parent::node()'.
ancestor::* : Selects matching ancestors.
ancestor-or-self::* : Selects ancestors including the current node.
self::* : Selects the current node. '.' is equivalent to "self::node()".

Expressions

Shard supports three types: number, boolean, string.

path : Selects nodes based on the path.
a = b : Standard comparisons.
- a = b true if a equals b.
- a != b true if a is not equal to b.
- a < b true if a is less than b.
- a <= b true if a is less than or equal to b.
- a > b true if a is greater than b.
- a >= b true if a is greater than or equal to b.
a + b : Arithmetic expressions.
- - a Unary minus
- a + b Add
- a - b Substract
- a * b Multiply
- a div b Divide
- a mod b Floating point mod, like Java.
a or b : Boolean or operation.
a and b : Boolean and operation.
(expr) : Parenthesized expressions.
fun(arg1, ..., argn) : Function calls:

Function	Supported
`boolean()`	✓
`ceiling()`	✓
`choose()`	✗
`concat()`	✓
`contains()`	✓
`count()`	✓
`current()`	✗
`document()`	✗
`element-available()`	✗
`ends-with()`	✓
`false()`	✓
`floor()`	✓
`format-number()`	✗
`function-available()`	✗
`generate-id()`	✗
`id()`	✗
`key()`	✗
`lang()`	✗
`last()`	✓
`local-name()`	✓
`name()`	✓
`namespace-uri()`	✓
`normalize-space()`	✓
`not()`	✓
`number()`	✓
`position()`	✓
`replace()`	✓
`reverse()`	✓
`round()`	✓
`starts-with()`	✓
`string()`	✓
`string-length()`	✓
`substring()`	✓
`substring-after()`	✓
`substring-before()`	✓
`sum()`	✓
`system-property()`	✗
`translate()`	✓
`true()`	✓
`unparsed-entity-url()`	✗

Installation

Add the dependency to your shard.yml:

dependencies:
  xpath2:
    github: naqvis/crystal-xpath2

Run shards install

Usage

refer to spec for usage examples or refer to Crystal HTML5 and JSON XPath for implementation details.

Development

To run all tests:

crystal spec

Contributing

Fork it (https://github.com/naqvis/crystal-xpath2/fork)
Create your feature branch (git checkout -b my-new-feature)
Commit your changes (git commit -am 'Add some feature')
Push to the branch (git push origin my-new-feature)
Create a new Pull Request

Contributors

Ali Naqvi - creator and maintainer