pathtoregexp

Path-to-RegExp

Turn a path string such as /user/:name into a regular expression.

Thanks to path-to-regexp which is the original version written in javascript.

Installation

To install Path-to-RegExp package, you need to install Go and set your Go workspace first.

The first need Go installed (version 1.11+ is required), then you can use the below Go command to install Path-to-RegExp.

$ go get -u github.com/soongo/path-to-regexp

Usage

import pathToRegexp "github.com/soongo/path-to-regexp"

// pathToRegexp.PathToRegexp(path, tokens, options) // tokens and options can be nil
// pathToRegexp.Parse(path, options) // options can be nil
// pathToRegexp.Compile(path, options) // options can be nil
// pathToRegexp.MustCompile(path, options) // like Compile but panics if the error is non-nil
// pathToRegexp.Match(path, options) // options can be nil
// pathToRegexp.MustMatch(path, options) // like Match but panics if the error is non-nil
// pathToRegexp.Must(regexp, err) // wraps a call to a function returning (*regexp2.Regexp, error) and panics if the error is non-nil
// pathToRegexp.EncodeURI(str) // encodes characters in URI except `;/?:@&=+$,#`, like javascript's encodeURI
// pathToRegexp.EncodeURIComponent(str) // encodes characters in URI, like javascript's encodeURIComponent

• path A string, array or slice of strings, or a regular expression with type *github.com/dlclark/regexp2.Regexp.
• tokens An array to populate with tokens found in the path.
  • token
    • Name The name of the token (string for named or number for index)
    • Prefix The prefix character for the segment (e.g. /)
    • Delimiter The delimiter for the segment (same as prefix or default delimiter)
    • Optional Indicates the token is optional (boolean)
    • Repeat Indicates the token is repeated (boolean)
    • Pattern The RegExp used to match this token (string)
• options
  • Sensitive When true the regexp will be case sensitive. (default: false)
  • Strict When true the regexp allows an optional trailing delimiter to match. (default: false)
  • End When true the regexp will match to the end of the string. (default: true)
  • Start When true the regexp will match from the beginning of the string. (default: true)
  • Delimiter The default delimiter for segments. (default: '/')
  • EndsWith Optional character, or list of characters, to treat as "end" characters.
  • Whitelist List of characters to consider delimiters when parsing. (default: nil, any character)
  • Encode How to encode uri. (default: func (uri string, token interface{}) string { return uri })
  • Decode How to decode uri. (default: func (uri string, token interface{}) string { return uri })

var tokens []pathToRegexp.Token
regexp := pathToRegexp.Must(pathToRegexp.PathToRegexp("/foo/:bar", &tokens, nil))
// regexp: ^\/foo\/([^\/]+?)(?:\/)?$
// tokens: [{Name:"bar", Prefix:"/", Delimiter:"/", Optional:false, Repeat:false, Pattern:"[^\\/]+?"}}]

Please note: The Regexp returned by path-to-regexp is intended for ordered data (e.g. pathnames, hostnames). It can not handle arbitrarily ordered data (e.g. query strings, URL fragments, JSON, etc).

Parameters

The path argument is used to define parameters and populate the list of tokens.

Named Parameters

Named parameters are defined by prefixing a colon to the parameter name (:foo). By default, the parameter will match until the next prefix (e.g. [^/]+).

regexp := pathToRegexp.Must(pathToRegexp.PathToRegexp("/:foo/:bar", nil, nil))
// tokens: [
//   {Name:"foo", Prefix:"/", Delimiter:"/", Optional:false, Repeat:false, Pattern:"[^\\/]+?"},
//   {Name:"bar", Prefix:"/", Delimiter:"/", Optional:false, Repeat:false, Pattern:"[^\\/]+?"}
// ]

match, err := regexp.FindStringMatch("/test/route")
for _, g := range match.Groups() {
    fmt.Printf("%q ", g.String())
}
fmt.Printf("%d, %q\n", match.Index, match)
//=> "/test/route" "test" "route" 0, "/test/route"

Please note: Parameter names must use "word characters" ([A-Za-z0-9_]).

Parameter Modifiers

Parameters can be suffixed with a question mark (?) to make the parameter optional.

regexp := pathToRegexp.Must(pathToRegexp.PathToRegexp("/:foo/:bar?", nil, nil))
// tokens: [
//   {Name:"foo", Prefix:"/", Delimiter:"/", Optional:false, Repeat:false, Pattern:"[^\\/]+?"},
//   {Name:"bar", Prefix:"/", Delimiter:"/", Optional:true, Repeat:false, Pattern:"[^\\/]+?"}
// ]

match, err := regexp.FindStringMatch("/test")
for _, g := range match.Groups() {
    fmt.Printf("%q ", g.String())
}
fmt.Printf("%d, %q\n", match.Index, match)
//=> "/test" "test" "" 0, "/test"

match, err = regexp.FindStringMatch("/test/route")
for _, g := range match.Groups() {
    fmt.Printf("%q ", g.String())
}
fmt.Printf("%d, %q\n", match.Index, match)
//=> "/test/route" "test" "route" 0, "/test/route"

Tip: The prefix is also optional, escape the prefix \/ to make it required.

Parameters can be suffixed with an asterisk (*) to denote a zero or more parameter matches. The prefix is used for each match.

regexp := pathToRegexp.Must(pathToRegexp.PathToRegexp("/:foo*", nil, nil))
// tokens: [{Name:"foo", Prefix:"/", Delimiter:"/", Optional:true, Repeat:true, Pattern:"[^\\/]+?"}]

match, err := regexp.FindStringMatch("/")
for _, g := range match.Groups() {
    fmt.Printf("%q ", g.String())
}
fmt.Printf("%d, %q\n", match.Index, match)
//=> "/" "" 0, "/"

match, err = regexp.FindStringMatch("/bar/baz")
for _, g := range match.Groups() {
    fmt.Printf("%q ", g.String())
}
fmt.Printf("%d, %q\n", match.Index, match)
//=> "/bar/baz" "bar/baz" 0, "/bar/baz"

Parameters can be suffixed with a plus sign (+) to denote a one or more parameter matches. The prefix is used for each match.

regexp := pathToRegexp.Must(pathToRegexp.PathToRegexp("/:foo+", nil, nil))
// tokens: [{Name:"foo", Prefix:"/", Delimiter:"/", Optional:false, Repeat:true, Pattern:"[^\\/]+?"}]

match, err := regexp.FindStringMatch("/")
fmt.Println(match)
//=> nil

match, err = regexp.FindStringMatch("/bar/baz")
for _, g := range match.Groups() {
    fmt.Printf("%q ", g.String())
}
fmt.Printf("%d, %q\n", match.Index, match)
//=> "/bar/baz" "bar/baz" 0, "/bar/baz"

Unnamed Parameters

It is possible to write an unnamed parameter that only consists of a matching group. It works the same as a named parameter, except it will be numerically indexed.

regexp := pathToRegexp.Must(pathToRegexp.PathToRegexp("/:foo/(.*)", nil, nil))
// tokens: [
//   {Name:"foo", Prefix:"/", Delimiter:"/", Optional:false, Repeat:false, Pattern:"[^\\/]+?"},
//   {Name:0, Prefix:"/", Delimiter:"/", Optional:false, Repeat:false, Pattern:".*"}
// ]

match, err := regexp.FindStringMatch("/test/route")
for _, g := range match.Groups() {
    fmt.Printf("%q ", g.String())
}
fmt.Printf("%d, %q\n", match.Index, match)
//=> "/test/route" "test" "route" 0, "/test/route"

Custom Matching Parameters

All parameters can have a custom regexp, which overrides the default match ([^/]+). For example, you can match digits or names in a path:

regexpNumbers := pathToRegexp.Must(pathToRegexp.PathToRegexp("/icon-:foo(\\d+).png", nil, nil))
// tokens: {Name:"foo", Prefix:"-", Delimiter:"-", Optional:false, Repeat:false, Pattern:"\\d+"}

match, err := regexpNumbers.FindStringMatch("/icon-123.png")
for _, g := range match.Groups() {
    fmt.Printf("%q ", g.String())
}
//=> "/icon-123.png" "123"

match, err = regexpNumbers.FindStringMatch("/icon-abc.png")
fmt.Println(match)
//=> nil

regexpWord := pathToRegexp.Must(pathToRegexp.PathToRegexp("/(user|u)", nil, nil))
// tokens: {Name:0, Prefix:"/", Delimiter:"/", Optional:false, Repeat:false, Pattern:"user|u"}

match, err = regexpWord.FindStringMatch("/u")
for _, g := range match.Groups() {
    fmt.Printf("%q ", g.String())
}
//=> "/u" "u"

match, err = regexpWord.FindStringMatch("/users")
fmt.Println(match)
//=> nil

Tip: Backslashes need to be escaped with another backslash in Go strings.

Match

The match function will return a function for transforming paths into parameters:

match := pathToRegexp.MustMatch("/user/:id", &pathToRegexp.Options{Decode: func(str string, token interface{}) string {
    return pathToRegexp.DecodeURIComponent(str)
}})

match("/user/123")
//=> &pathtoregexp.MatchResult{Path:"/user/123", Index:0, Params:map[interface {}]interface {}{"id":"123"}}

match("/invalid") //=> nil

match("/user/caf%C3%A9")
//=> &pathtoregexp.MatchResult{Path:"/user/caf%C3%A9", Index:0, Params:map[interface {}]interface {}{"id":"café"}}

Parse

The Parse function will return a list of strings and tokens from a path string:

tokens := pathToRegexp.Parse("/route/:foo/(.*)", nil)

fmt.Printf("%#v\n", tokens[0])
//=> "/route"

fmt.Printf("%#v\n", tokens[1])
//=> pathToRegexp.Token{Name:"foo", Prefix:"/", Delimiter:"/", Optional:false, Repeat:false, Pattern:"[^\\/]+?"}

fmt.Printf("%#v\n", tokens[2])
//=> pathToRegexp.Token{Name:0, Prefix:"/", Delimiter:"/", Optional:false, Repeat:false, Pattern:".*"}

Note: This method only works with strings.

Compile ("Reverse" Path-To-RegExp)

The Compile function will return a function for transforming parameters into a valid path:

toPath := pathToRegexp.MustCompile("/user/:id", &pathToRegexp.Options{Encode: func(str string, token interface{}) string {
    return pathToRegexp.EncodeURIComponent(str)
}})

toPath(map[string]int{"id": 123}) //=> "/user/123"
toPath(map[string]string{"id": "café"}) //=> "/user/caf%C3%A9"
toPath(map[string]string{"id": "/"}) //=> "/user/%2F"

toPath(map[string]string{"id": ":/"}) //=> "/user/%3A%2F"

// Without `encode`, you need to make sure inputs are encoded correctly.
falseValue := false
toPathRaw := pathToRegexp.MustCompile("/user/:id", &pathToRegexp.Options{Validate: &falseValue})
toPathRaw(map[string]string{"id": "%3A%2F"}); //=> "/user/%3A%2F"
toPathRaw(map[string]string{"id": ":/"}); //=> "/user/:/"

toPathRepeated := pathToRegexp.MustCompile("/:segment+", nil)

toPathRepeated(map[string]string{"segment": "foo"}) //=> "/foo"
toPathRepeated(map[string][]string{"segment": {"a", "b", "c"}}) //=> "/a/b/c"

toPathRegexp := pathToRegexp.MustCompile("/user/:id(\\d+)", &pathToRegexp.Options{Validate: &falseValue})

toPathRegexp(map[string]int{"id": 123}) //=> "/user/123"
toPathRegexp(map[string]string{"id": "123"}) //=> "/user/123"
toPathRegexp(map[string]string{"id": "abc"}) //=> "/user/abc"

toPathRegexp = pathToRegexp.MustCompile("/user/:id(\\d+)", nil)
toPathRegexp(map[string]string{"id": "abc"}) //=> panic

Note: The generated function will panic on invalid input. It will do all necessary checks to ensure the generated path is valid. This method only works with strings.