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

1. Add the dependency to your shard.yml:

   dependencies:
     html:
       github: naqvis/crystal-xpath2
   

2. 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

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

Contributors

• Ali Naqvi - creator and maintainer