XPath 2.0+ package for Go, with XPath 3.1 maps and arrays.

License: BSD-3-Clause License

Usage

myfile.xml:

<data>
    <p>hello world!</p>
    <p>hello XML!</p>
</data>

main.go:

package main

import (
	"fmt"
	"log"
	"os"

	"github.com/speedata/goxpath"
)

func dothings() error {
	r, err := os.Open("myfile.xml")
	if err != nil {
		return err
	}
	xp, err := goxpath.NewParser(r)
	if err != nil {
		return err
	}
	seq, err := xp.Evaluate("for $i in /data/p return string($i)")
	if err != nil {
		return err
	}
	for _, itm := range seq {
		fmt.Println(itm)
	}
	return nil
}

func main() {
	if err := dothings(); err != nil {
		log.Fatal(err)
	}
}

When working with namespaces, you need to have them predefined in your query:

myfile.xml:

<a:root xmlns:a="anamespace">
  <a:sub>text</a:sub>
</a:root>

package main

import (
	"fmt"
	"log"
	"os"

	"github.com/speedata/goxpath"
)

func dothings() error {
	r, err := os.Open("myfile.xml")
	if err != nil {
		return err
	}
	xp, err := goxpath.NewParser(r)
	if err != nil {
		return err
	}
	xp.Ctx.Namespaces["a"] = "anamespace"
	seq, err := xp.Evaluate("/a:root/a:sub/text()")
	if err != nil {
		return err
	}
	fmt.Println(seq.Stringvalue())
	return nil
}

func main() {
	if err := dothings(); err != nil {
		log.Fatal(err)
	}
}

Limitations

• No schema types
• No collations
• Not all functions are implemented (see list below)

Implemented functions

This list is copied from XQuery 1.0 and XPath 2.0 Functions and Operators (Second Edition)

Accessors

Function	Accessor	Accepts	Returns
string	string-value	an optional item or no argument	xs:string
data	typed-value	zero or more items	a sequence of atomic values

Functions on Numeric Values

Function	Meaning
abs	Returns the absolute value of the argument.
ceiling	Returns the smallest number with no fractional part that is greater than or equal to the argument.
floor	Returns the largest number with no fractional part that is less than or equal to the argument.
round	Rounds to the nearest number with no fractional part.
round-half-to-even	Takes a number and a precision and returns a number rounded to the given precision. If the fractional part is exactly half, the result is the number whose least significant digit is even.

Functions to Assemble and Disassemble Strings

Function	Meaning
codepoints-to-string	Creates an xs:string from a sequence of Unicode code points.
string-to-codepoints	Returns the sequence of Unicode code points that constitute an xs:string.

Equality and Comparison of Strings

Function	Meaning
compare	Returns -1, 0, or 1, depending on whether the value of the first argument is respectively less than, equal to, or greater than the value of the second argument, according to the rules of the collation that is used.
codepoint-equal	Returns true if the two arguments are equal using the Unicode code point collation.

Functions on String Values

Function	Meaning
concat	Concatenates two or more xs:anyAtomicType arguments cast to xs:string.
string-join	Returns the xs:string produced by concatenating a sequence of xs:strings using an optional separator.
substring	Returns the xs:string located at a specified place within an argument xs:string.
string-length	Returns the length of the argument.
normalize-space	Returns the whitespace-normalized value of the argument.
upper-case	Returns the upper-cased value of the argument.
lower-case	Returns the lower-cased value of the argument.
translate	Returns the first xs:string argument with occurrences of characters contained in the second argument replaced by the character at the corresponding position in the third argument.
normalize-unicode	Returns the normalized value of the first argument in the normalization form specified by the second argument.
encode-for-uri	Returns the xs:string argument with certain characters escaped to enable the resulting string to be used as a path segment in a URI.
iri-to-uri	Returns the xs:string argument with certain characters escaped to enable the resulting string to be used as (part of) a URI.
escape-html-uri	Returns the xs:string argument with certain characters escaped in the manner that html user agents handle attribute values that expect URIs.

Functions Based on Substring Matching

Function	Meaning
contains	Indicates whether one xs:string contains another xs:string. A collation may be specified.
starts-with	Indicates whether the value of one xs:string begins with the collation units of another xs:string. A collation may be specified.
ends-with	Indicates whether the value of one xs:string ends with the collation units of another xs:string. A collation may be specified.
substring-before	Returns the collation units of one xs:string that precede in that xs:string the collation units of another xs:string. A collation may be specified.
substring-after	Returns the collation units of xs:string that follow in that xs:string the collation units of another xs:string. A collation may be specified.

String Functions that Use Pattern Matching

Function	Meaning
matches	Returns an xs:boolean value that indicates whether the value of the first argument is matched by the regular expression that is the value of the second argument.
replace	Returns the value of the first argument with every substring matched by the regular expression that is the value of the second argument replaced by the replacement string that is the value of the third argument.
tokenize	Returns a sequence of one or more xs:strings whose values are substrings of the value of the first argument separated by substrings that match the regular expression that is the value of the second argument.

Additional Boolean Constructor Functions

Function	Meaning
true	Constructs the xs:boolean value 'true'.
false	Constructs the xs:boolean value 'false'.

Functions on Boolean Values

Function	Meaning
not	Inverts the xs:boolean value of the argument.

Component Extraction Functions on Durations, Dates and Times

Function	Meaning
years-from-duration	Returns the year component of an xs:duration value.
months-from-duration	Returns the months component of an xs:duration value.
days-from-duration	Returns the days component of an xs:duration value.
hours-from-duration	Returns the hours component of an xs:duration value.
minutes-from-duration	Returns the minutes component of an xs:duration value.
seconds-from-duration	Returns the seconds component of an xs:duration value.
year-from-dateTime	Returns the year from an xs:dateTime value.
month-from-dateTime	Returns the month from an xs:dateTime value.
day-from-dateTime	Returns the day from an xs:dateTime value.
hours-from-dateTime	Returns the hours from an xs:dateTime value.
minutes-from-dateTime	Returns the minutes from an xs:dateTime value.
seconds-from-dateTime	Returns the seconds from an xs:dateTime value.
timezone-from-dateTime	Returns the timezone from an xs:dateTime value.
year-from-date	Returns the year from an xs:date value.
month-from-date	Returns the month from an xs:date value.
day-from-date	Returns the day from an xs:date value.
timezone-from-date	Returns the timezone from an xs:date value.
hours-from-time	Returns the hours from an xs:time value.
minutes-from-time	Returns the minutes from an xs:time value.
seconds-from-time	Returns the seconds from an xs:time value.
timezone-from-time	Returns the timezone from an xs:time value.

Functions on anyURI

Function	Meaning
resolve-uri	Returns an xs:anyURI representing an absolute xs:anyURI given a base URI and a relative URI.

Timezone Adjustment Functions on Dates and Time Values

Function	Meaning
adjust-dateTime-to-timezone	Adjusts an xs:dateTime value to a specific timezone, or to no timezone at all.
adjust-date-to-timezone	Adjusts an xs:date value to a specific timezone, or to no timezone at all.
adjust-time-to-timezone	Adjusts an xs:time value to a specific timezone, or to no timezone at all.

Functions on Nodes

Function	Meaning
name	Returns the name of the context node or the specified node as an xs:string.
namespace-uri	Returns the namespace URI as an xs:anyURI for the xs:QName of the argument node or the context node if the argument is omitted. This may be the URI corresponding to the zero-length string if the xs:QName is in no namespace.
local-name	Returns the local name of the context node or the specified node as an xs:NCName.
lang	Returns true or false, depending on whether the language of the given node, as defined using the xml:lang attribute, is the same as, or a sublanguage of, the language specified by the argument.
number	Returns the value of the context item after atomization or the specified argument converted to an xs:double.
root	Returns the root of the tree to which the node argument belongs.

Function	Meaning
boolean	Computes the effective boolean value of the argument sequence.
empty	Indicates whether or not the provided sequence is empty.
exists	Indicates whether or not the provided sequence is not empty.
reverse	Reverses the order of items in a sequence.

Aggregate Functions

Function	Meaning
avg	Returns the average of a sequence of values.
count	Returns the number of items in a sequence.
max	Returns the maximum value from a sequence of comparable values.
min	Returns the minimum value from a sequence of comparable values.
sum	Returns the sum of a sequence of values.

Function	Meaning
position	Returns the position of the context item within the sequence of items currently being processed.
last	Returns the number of items in the sequence of items currently being processed.

Context Functions

Function	Meaning
current-dateTime	Returns the current xs:dateTime.
current-date	Returns the current xs:date.
current-time	Returns the current xs:time.

Functions on Sequences

Function	Meaning
distinct-values	Returns a sequence with duplicate values removed.
index-of	Returns the positions of items in a sequence that match a given value.
insert-before	Inserts an item or sequence of items at a specified position in a sequence.
remove	Removes an item from a specified position in a sequence.
unordered	Returns the items in the given sequence in a non-deterministic order.
subsequence	Returns the subsequence of a given sequence, identified by location.

Functions That Test the Cardinality of Sequences

Function	Meaning
zero-or-one	Returns the input sequence if it contains zero or one items. Raises an error otherwise.
one-or-more	Returns the input sequence if it contains one or more items. Raises an error otherwise.
exactly-one	Returns the input sequence if it contains exactly one item. Raises an error otherwise.

Equals, Union, Intersection and Except

Function	Meaning
deep-equal	Returns true if the two arguments have items that compare equal in corresponding positions.

Functions and Operators that Generate Sequences

Function	Meaning
doc	Returns a document node retrieved using the specified URI.
doc-available	Returns true if a document node can be retrieved using the specified URI.

Formatting Functions (XPath 3.0)

Function	Meaning
format-date	Formats an xs:date value using a picture string.
format-number	Formats a number as a string using a picture string.

Sorting (XPath 3.1)

Function	Meaning
sort	Returns a sorted copy of a sequence.

XPath 3.1 Map Functions

Namespace: http://www.w3.org/2005/xpath-functions/map

Function	Meaning
map:get	Returns the value associated with a key in a map.
map:size	Returns the number of entries in a map.
map:keys	Returns the keys of a map as a sequence.
map:contains	Returns true if the map contains an entry with the given key.
map:put	Returns a map with an added or replaced entry.
map:merge	Returns a map that combines the entries from multiple maps.

XPath 3.1 Array Functions

Namespace: http://www.w3.org/2005/xpath-functions/array

Function	Meaning
array:get	Returns the member at a given position in an array.
array:size	Returns the number of members in an array.

Constructor Functions for QNames

Function	Meaning
resolve-QName	Returns an xs:QName with the lexical form given in the first argument. The prefix is resolved using the in-scope namespaces for a given element.
QName	Returns an xs:QName with the namespace URI given in the first argument and the local name and prefix in the second argument.

Functions Related to QNames

Function	Meaning
prefix-from-QName	Returns an xs:NCName representing the prefix of the xs:QName argument.
local-name-from-QName	Returns an xs:NCName representing the local name of the xs:QName argument.
namespace-uri-from-QName	Returns the namespace URI for the xs:QName argument. If the xs:QName is in no namespace, the zero-length string is returned.
namespace-uri-for-prefix	Returns the namespace URI of one of the in-scope namespaces for the given element, identified by its namespace prefix.
in-scope-prefixes	Returns the prefixes of the in-scope namespaces for the given element.

XML Schema Type Constructors

Function	Meaning
xs:integer	Cast to xs:integer.
xs:double	Cast to xs:double.
xs:string	Cast to xs:string.
xs:date	Cast to xs:date.
xs:dateTime	Cast to xs:dateTime.
xs:duration	Cast to xs:duration.
xs:time	Cast to xs:time.

Not yet implemented functions

Accessors

Function	Accessor	Accepts	Returns
node-name	node-name	an optional node	zero or one xs:QName
nilled	nilled	a node	an optional xs:boolean
base-uri	base-uri	an optional node or no argument	zero or one xs:anyURI
document-uri	document-uri	an optional node	zero or one xs:anyURI

Functions and Operators that Generate Sequences

Function	Meaning
id	Returns the sequence of element nodes having an ID value matching the one or more of the supplied IDREF values.
idref	Returns the sequence of element or attribute nodes with an IDREF value matching one or more of the supplied ID values.
collection	Returns a sequence of nodes retrieved using the specified URI or the nodes in the default collection.

Context Functions

Function	Meaning
implicit-timezone	Returns the value of the implicit timezone property from the dynamic context.
default-collation	Returns the value of the default collation property from the static context.
static-base-uri	Returns the value of the Base URI property from the static context.