Source file src/net/url/url.go

     1  // Copyright 2009 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  // Package url parses URLs and implements query escaping.
     6  //
     7  // See RFC 3986. This package generally follows RFC 3986, except where
     8  // it deviates for compatibility reasons.
     9  // RFC 6874 followed for IPv6 zone literals.
    10  package url
    11  
    12  // When sending changes, first  search old issues for history on decisions.
    13  // Unit tests should also contain references to issue numbers with details.
    14  
    15  import (
    16  	"errors"
    17  	"fmt"
    18  	"maps"
    19  	"net/netip"
    20  	"path"
    21  	"slices"
    22  	"strconv"
    23  	"strings"
    24  	_ "unsafe" // for linkname
    25  )
    26  
    27  // Error reports an error and the operation and URL that caused it.
    28  type Error struct {
    29  	Op  string
    30  	URL string
    31  	Err error
    32  }
    33  
    34  func (e *Error) Unwrap() error { return e.Err }
    35  func (e *Error) Error() string { return fmt.Sprintf("%s %q: %s", e.Op, e.URL, e.Err) }
    36  
    37  func (e *Error) Timeout() bool {
    38  	t, ok := e.Err.(interface {
    39  		Timeout() bool
    40  	})
    41  	return ok && t.Timeout()
    42  }
    43  
    44  func (e *Error) Temporary() bool {
    45  	t, ok := e.Err.(interface {
    46  		Temporary() bool
    47  	})
    48  	return ok && t.Temporary()
    49  }
    50  
    51  const upperhex = "0123456789ABCDEF"
    52  
    53  func ishex(c byte) bool {
    54  	switch {
    55  	case '0' <= c && c <= '9':
    56  		return true
    57  	case 'a' <= c && c <= 'f':
    58  		return true
    59  	case 'A' <= c && c <= 'F':
    60  		return true
    61  	}
    62  	return false
    63  }
    64  
    65  func unhex(c byte) byte {
    66  	switch {
    67  	case '0' <= c && c <= '9':
    68  		return c - '0'
    69  	case 'a' <= c && c <= 'f':
    70  		return c - 'a' + 10
    71  	case 'A' <= c && c <= 'F':
    72  		return c - 'A' + 10
    73  	default:
    74  		panic("invalid hex character")
    75  	}
    76  }
    77  
    78  type encoding int
    79  
    80  const (
    81  	encodePath encoding = 1 + iota
    82  	encodePathSegment
    83  	encodeHost
    84  	encodeZone
    85  	encodeUserPassword
    86  	encodeQueryComponent
    87  	encodeFragment
    88  )
    89  
    90  type EscapeError string
    91  
    92  func (e EscapeError) Error() string {
    93  	return "invalid URL escape " + strconv.Quote(string(e))
    94  }
    95  
    96  type InvalidHostError string
    97  
    98  func (e InvalidHostError) Error() string {
    99  	return "invalid character " + strconv.Quote(string(e)) + " in host name"
   100  }
   101  
   102  // Return true if the specified character should be escaped when
   103  // appearing in a URL string, according to RFC 3986.
   104  //
   105  // Please be informed that for now shouldEscape does not check all
   106  // reserved characters correctly. See golang.org/issue/5684.
   107  func shouldEscape(c byte, mode encoding) bool {
   108  	// §2.3 Unreserved characters (alphanum)
   109  	if 'a' <= c && c <= 'z' || 'A' <= c && c <= 'Z' || '0' <= c && c <= '9' {
   110  		return false
   111  	}
   112  
   113  	if mode == encodeHost || mode == encodeZone {
   114  		// §3.2.2 Host allows
   115  		//	sub-delims = "!" / "$" / "&" / "'" / "(" / ")" / "*" / "+" / "," / ";" / "="
   116  		// as part of reg-name.
   117  		// We add : because we include :port as part of host.
   118  		// We add [ ] because we include [ipv6]:port as part of host.
   119  		// We add < > because they're the only characters left that
   120  		// we could possibly allow, and Parse will reject them if we
   121  		// escape them (because hosts can't use %-encoding for
   122  		// ASCII bytes).
   123  		switch c {
   124  		case '!', '$', '&', '\'', '(', ')', '*', '+', ',', ';', '=', ':', '[', ']', '<', '>', '"':
   125  			return false
   126  		}
   127  	}
   128  
   129  	switch c {
   130  	case '-', '_', '.', '~': // §2.3 Unreserved characters (mark)
   131  		return false
   132  
   133  	case '$', '&', '+', ',', '/', ':', ';', '=', '?', '@': // §2.2 Reserved characters (reserved)
   134  		// Different sections of the URL allow a few of
   135  		// the reserved characters to appear unescaped.
   136  		switch mode {
   137  		case encodePath: // §3.3
   138  			// The RFC allows : @ & = + $ but saves / ; , for assigning
   139  			// meaning to individual path segments. This package
   140  			// only manipulates the path as a whole, so we allow those
   141  			// last three as well. That leaves only ? to escape.
   142  			return c == '?'
   143  
   144  		case encodePathSegment: // §3.3
   145  			// The RFC allows : @ & = + $ but saves / ; , for assigning
   146  			// meaning to individual path segments.
   147  			return c == '/' || c == ';' || c == ',' || c == '?'
   148  
   149  		case encodeUserPassword: // §3.2.1
   150  			// The RFC allows ';', ':', '&', '=', '+', '$', and ',' in
   151  			// userinfo, so we must escape only '@', '/', and '?'.
   152  			// The parsing of userinfo treats ':' as special so we must escape
   153  			// that too.
   154  			return c == '@' || c == '/' || c == '?' || c == ':'
   155  
   156  		case encodeQueryComponent: // §3.4
   157  			// The RFC reserves (so we must escape) everything.
   158  			return true
   159  
   160  		case encodeFragment: // §4.1
   161  			// The RFC text is silent but the grammar allows
   162  			// everything, so escape nothing.
   163  			return false
   164  		}
   165  	}
   166  
   167  	if mode == encodeFragment {
   168  		// RFC 3986 §2.2 allows not escaping sub-delims. A subset of sub-delims are
   169  		// included in reserved from RFC 2396 §2.2. The remaining sub-delims do not
   170  		// need to be escaped. To minimize potential breakage, we apply two restrictions:
   171  		// (1) we always escape sub-delims outside of the fragment, and (2) we always
   172  		// escape single quote to avoid breaking callers that had previously assumed that
   173  		// single quotes would be escaped. See issue #19917.
   174  		switch c {
   175  		case '!', '(', ')', '*':
   176  			return false
   177  		}
   178  	}
   179  
   180  	// Everything else must be escaped.
   181  	return true
   182  }
   183  
   184  // QueryUnescape does the inverse transformation of [QueryEscape],
   185  // converting each 3-byte encoded substring of the form "%AB" into the
   186  // hex-decoded byte 0xAB.
   187  // It returns an error if any % is not followed by two hexadecimal
   188  // digits.
   189  func QueryUnescape(s string) (string, error) {
   190  	return unescape(s, encodeQueryComponent)
   191  }
   192  
   193  // PathUnescape does the inverse transformation of [PathEscape],
   194  // converting each 3-byte encoded substring of the form "%AB" into the
   195  // hex-decoded byte 0xAB. It returns an error if any % is not followed
   196  // by two hexadecimal digits.
   197  //
   198  // PathUnescape is identical to [QueryUnescape] except that it does not
   199  // unescape '+' to ' ' (space).
   200  func PathUnescape(s string) (string, error) {
   201  	return unescape(s, encodePathSegment)
   202  }
   203  
   204  // unescape unescapes a string; the mode specifies
   205  // which section of the URL string is being unescaped.
   206  func unescape(s string, mode encoding) (string, error) {
   207  	// Count %, check that they're well-formed.
   208  	n := 0
   209  	hasPlus := false
   210  	for i := 0; i < len(s); {
   211  		switch s[i] {
   212  		case '%':
   213  			n++
   214  			if i+2 >= len(s) || !ishex(s[i+1]) || !ishex(s[i+2]) {
   215  				s = s[i:]
   216  				if len(s) > 3 {
   217  					s = s[:3]
   218  				}
   219  				return "", EscapeError(s)
   220  			}
   221  			// Per https://tools.ietf.org/html/rfc3986#page-21
   222  			// in the host component %-encoding can only be used
   223  			// for non-ASCII bytes.
   224  			// But https://tools.ietf.org/html/rfc6874#section-2
   225  			// introduces %25 being allowed to escape a percent sign
   226  			// in IPv6 scoped-address literals. Yay.
   227  			if mode == encodeHost && unhex(s[i+1]) < 8 && s[i:i+3] != "%25" {
   228  				return "", EscapeError(s[i : i+3])
   229  			}
   230  			if mode == encodeZone {
   231  				// RFC 6874 says basically "anything goes" for zone identifiers
   232  				// and that even non-ASCII can be redundantly escaped,
   233  				// but it seems prudent to restrict %-escaped bytes here to those
   234  				// that are valid host name bytes in their unescaped form.
   235  				// That is, you can use escaping in the zone identifier but not
   236  				// to introduce bytes you couldn't just write directly.
   237  				// But Windows puts spaces here! Yay.
   238  				v := unhex(s[i+1])<<4 | unhex(s[i+2])
   239  				if s[i:i+3] != "%25" && v != ' ' && shouldEscape(v, encodeHost) {
   240  					return "", EscapeError(s[i : i+3])
   241  				}
   242  			}
   243  			i += 3
   244  		case '+':
   245  			hasPlus = mode == encodeQueryComponent
   246  			i++
   247  		default:
   248  			if (mode == encodeHost || mode == encodeZone) && s[i] < 0x80 && shouldEscape(s[i], mode) {
   249  				return "", InvalidHostError(s[i : i+1])
   250  			}
   251  			i++
   252  		}
   253  	}
   254  
   255  	if n == 0 && !hasPlus {
   256  		return s, nil
   257  	}
   258  
   259  	var t strings.Builder
   260  	t.Grow(len(s) - 2*n)
   261  	for i := 0; i < len(s); i++ {
   262  		switch s[i] {
   263  		case '%':
   264  			t.WriteByte(unhex(s[i+1])<<4 | unhex(s[i+2]))
   265  			i += 2
   266  		case '+':
   267  			if mode == encodeQueryComponent {
   268  				t.WriteByte(' ')
   269  			} else {
   270  				t.WriteByte('+')
   271  			}
   272  		default:
   273  			t.WriteByte(s[i])
   274  		}
   275  	}
   276  	return t.String(), nil
   277  }
   278  
   279  // QueryEscape escapes the string so it can be safely placed
   280  // inside a [URL] query.
   281  func QueryEscape(s string) string {
   282  	return escape(s, encodeQueryComponent)
   283  }
   284  
   285  // PathEscape escapes the string so it can be safely placed inside a [URL] path segment,
   286  // replacing special characters (including /) with %XX sequences as needed.
   287  func PathEscape(s string) string {
   288  	return escape(s, encodePathSegment)
   289  }
   290  
   291  func escape(s string, mode encoding) string {
   292  	spaceCount, hexCount := 0, 0
   293  	for i := 0; i < len(s); i++ {
   294  		c := s[i]
   295  		if shouldEscape(c, mode) {
   296  			if c == ' ' && mode == encodeQueryComponent {
   297  				spaceCount++
   298  			} else {
   299  				hexCount++
   300  			}
   301  		}
   302  	}
   303  
   304  	if spaceCount == 0 && hexCount == 0 {
   305  		return s
   306  	}
   307  
   308  	var buf [64]byte
   309  	var t []byte
   310  
   311  	required := len(s) + 2*hexCount
   312  	if required <= len(buf) {
   313  		t = buf[:required]
   314  	} else {
   315  		t = make([]byte, required)
   316  	}
   317  
   318  	if hexCount == 0 {
   319  		copy(t, s)
   320  		for i := 0; i < len(s); i++ {
   321  			if s[i] == ' ' {
   322  				t[i] = '+'
   323  			}
   324  		}
   325  		return string(t)
   326  	}
   327  
   328  	j := 0
   329  	for i := 0; i < len(s); i++ {
   330  		switch c := s[i]; {
   331  		case c == ' ' && mode == encodeQueryComponent:
   332  			t[j] = '+'
   333  			j++
   334  		case shouldEscape(c, mode):
   335  			t[j] = '%'
   336  			t[j+1] = upperhex[c>>4]
   337  			t[j+2] = upperhex[c&15]
   338  			j += 3
   339  		default:
   340  			t[j] = s[i]
   341  			j++
   342  		}
   343  	}
   344  	return string(t)
   345  }
   346  
   347  // A URL represents a parsed URL (technically, a URI reference).
   348  //
   349  // The general form represented is:
   350  //
   351  //	[scheme:][//[userinfo@]host][/]path[?query][#fragment]
   352  //
   353  // URLs that do not start with a slash after the scheme are interpreted as:
   354  //
   355  //	scheme:opaque[?query][#fragment]
   356  //
   357  // The Host field contains the host and port subcomponents of the URL.
   358  // When the port is present, it is separated from the host with a colon.
   359  // When the host is an IPv6 address, it must be enclosed in square brackets:
   360  // "[fe80::1]:80". The [net.JoinHostPort] function combines a host and port
   361  // into a string suitable for the Host field, adding square brackets to
   362  // the host when necessary.
   363  //
   364  // Note that the Path field is stored in decoded form: /%47%6f%2f becomes /Go/.
   365  // A consequence is that it is impossible to tell which slashes in the Path were
   366  // slashes in the raw URL and which were %2f. This distinction is rarely important,
   367  // but when it is, the code should use the [URL.EscapedPath] method, which preserves
   368  // the original encoding of Path.
   369  //
   370  // The RawPath field is an optional field which is only set when the default
   371  // encoding of Path is different from the escaped path. See the EscapedPath method
   372  // for more details.
   373  //
   374  // URL's String method uses the EscapedPath method to obtain the path.
   375  type URL struct {
   376  	Scheme      string
   377  	Opaque      string    // encoded opaque data
   378  	User        *Userinfo // username and password information
   379  	Host        string    // host or host:port (see Hostname and Port methods)
   380  	Path        string    // path (relative paths may omit leading slash)
   381  	RawPath     string    // encoded path hint (see EscapedPath method)
   382  	OmitHost    bool      // do not emit empty host (authority)
   383  	ForceQuery  bool      // append a query ('?') even if RawQuery is empty
   384  	RawQuery    string    // encoded query values, without '?'
   385  	Fragment    string    // fragment for references, without '#'
   386  	RawFragment string    // encoded fragment hint (see EscapedFragment method)
   387  }
   388  
   389  // User returns a [Userinfo] containing the provided username
   390  // and no password set.
   391  func User(username string) *Userinfo {
   392  	return &Userinfo{username, "", false}
   393  }
   394  
   395  // UserPassword returns a [Userinfo] containing the provided username
   396  // and password.
   397  //
   398  // This functionality should only be used with legacy web sites.
   399  // RFC 2396 warns that interpreting Userinfo this way
   400  // “is NOT RECOMMENDED, because the passing of authentication
   401  // information in clear text (such as URI) has proven to be a
   402  // security risk in almost every case where it has been used.”
   403  func UserPassword(username, password string) *Userinfo {
   404  	return &Userinfo{username, password, true}
   405  }
   406  
   407  // The Userinfo type is an immutable encapsulation of username and
   408  // password details for a [URL]. An existing Userinfo value is guaranteed
   409  // to have a username set (potentially empty, as allowed by RFC 2396),
   410  // and optionally a password.
   411  type Userinfo struct {
   412  	username    string
   413  	password    string
   414  	passwordSet bool
   415  }
   416  
   417  // Username returns the username.
   418  func (u *Userinfo) Username() string {
   419  	if u == nil {
   420  		return ""
   421  	}
   422  	return u.username
   423  }
   424  
   425  // Password returns the password in case it is set, and whether it is set.
   426  func (u *Userinfo) Password() (string, bool) {
   427  	if u == nil {
   428  		return "", false
   429  	}
   430  	return u.password, u.passwordSet
   431  }
   432  
   433  // String returns the encoded userinfo information in the standard form
   434  // of "username[:password]".
   435  func (u *Userinfo) String() string {
   436  	if u == nil {
   437  		return ""
   438  	}
   439  	s := escape(u.username, encodeUserPassword)
   440  	if u.passwordSet {
   441  		s += ":" + escape(u.password, encodeUserPassword)
   442  	}
   443  	return s
   444  }
   445  
   446  // Maybe rawURL is of the form scheme:path.
   447  // (Scheme must be [a-zA-Z][a-zA-Z0-9+.-]*)
   448  // If so, return scheme, path; else return "", rawURL.
   449  func getScheme(rawURL string) (scheme, path string, err error) {
   450  	for i := 0; i < len(rawURL); i++ {
   451  		c := rawURL[i]
   452  		switch {
   453  		case 'a' <= c && c <= 'z' || 'A' <= c && c <= 'Z':
   454  		// do nothing
   455  		case '0' <= c && c <= '9' || c == '+' || c == '-' || c == '.':
   456  			if i == 0 {
   457  				return "", rawURL, nil
   458  			}
   459  		case c == ':':
   460  			if i == 0 {
   461  				return "", "", errors.New("missing protocol scheme")
   462  			}
   463  			return rawURL[:i], rawURL[i+1:], nil
   464  		default:
   465  			// we have encountered an invalid character,
   466  			// so there is no valid scheme
   467  			return "", rawURL, nil
   468  		}
   469  	}
   470  	return "", rawURL, nil
   471  }
   472  
   473  // Parse parses a raw url into a [URL] structure.
   474  //
   475  // The url may be relative (a path, without a host) or absolute
   476  // (starting with a scheme). Trying to parse a hostname and path
   477  // without a scheme is invalid but may not necessarily return an
   478  // error, due to parsing ambiguities.
   479  func Parse(rawURL string) (*URL, error) {
   480  	// Cut off #frag
   481  	u, frag, _ := strings.Cut(rawURL, "#")
   482  	url, err := parse(u, false)
   483  	if err != nil {
   484  		return nil, &Error{"parse", u, err}
   485  	}
   486  	if frag == "" {
   487  		return url, nil
   488  	}
   489  	if err = url.setFragment(frag); err != nil {
   490  		return nil, &Error{"parse", rawURL, err}
   491  	}
   492  	return url, nil
   493  }
   494  
   495  // ParseRequestURI parses a raw url into a [URL] structure. It assumes that
   496  // url was received in an HTTP request, so the url is interpreted
   497  // only as an absolute URI or an absolute path.
   498  // The string url is assumed not to have a #fragment suffix.
   499  // (Web browsers strip #fragment before sending the URL to a web server.)
   500  func ParseRequestURI(rawURL string) (*URL, error) {
   501  	url, err := parse(rawURL, true)
   502  	if err != nil {
   503  		return nil, &Error{"parse", rawURL, err}
   504  	}
   505  	return url, nil
   506  }
   507  
   508  // parse parses a URL from a string in one of two contexts. If
   509  // viaRequest is true, the URL is assumed to have arrived via an HTTP request,
   510  // in which case only absolute URLs or path-absolute relative URLs are allowed.
   511  // If viaRequest is false, all forms of relative URLs are allowed.
   512  func parse(rawURL string, viaRequest bool) (*URL, error) {
   513  	var rest string
   514  	var err error
   515  
   516  	if stringContainsCTLByte(rawURL) {
   517  		return nil, errors.New("net/url: invalid control character in URL")
   518  	}
   519  
   520  	if rawURL == "" && viaRequest {
   521  		return nil, errors.New("empty url")
   522  	}
   523  	url := new(URL)
   524  
   525  	if rawURL == "*" {
   526  		url.Path = "*"
   527  		return url, nil
   528  	}
   529  
   530  	// Split off possible leading "http:", "mailto:", etc.
   531  	// Cannot contain escaped characters.
   532  	if url.Scheme, rest, err = getScheme(rawURL); err != nil {
   533  		return nil, err
   534  	}
   535  	url.Scheme = strings.ToLower(url.Scheme)
   536  
   537  	if strings.HasSuffix(rest, "?") && strings.Count(rest, "?") == 1 {
   538  		url.ForceQuery = true
   539  		rest = rest[:len(rest)-1]
   540  	} else {
   541  		rest, url.RawQuery, _ = strings.Cut(rest, "?")
   542  	}
   543  
   544  	if !strings.HasPrefix(rest, "/") {
   545  		if url.Scheme != "" {
   546  			// We consider rootless paths per RFC 3986 as opaque.
   547  			url.Opaque = rest
   548  			return url, nil
   549  		}
   550  		if viaRequest {
   551  			return nil, errors.New("invalid URI for request")
   552  		}
   553  
   554  		// Avoid confusion with malformed schemes, like cache_object:foo/bar.
   555  		// See golang.org/issue/16822.
   556  		//
   557  		// RFC 3986, §3.3:
   558  		// In addition, a URI reference (Section 4.1) may be a relative-path reference,
   559  		// in which case the first path segment cannot contain a colon (":") character.
   560  		if segment, _, _ := strings.Cut(rest, "/"); strings.Contains(segment, ":") {
   561  			// First path segment has colon. Not allowed in relative URL.
   562  			return nil, errors.New("first path segment in URL cannot contain colon")
   563  		}
   564  	}
   565  
   566  	if (url.Scheme != "" || !viaRequest && !strings.HasPrefix(rest, "///")) && strings.HasPrefix(rest, "//") {
   567  		var authority string
   568  		authority, rest = rest[2:], ""
   569  		if i := strings.Index(authority, "/"); i >= 0 {
   570  			authority, rest = authority[:i], authority[i:]
   571  		}
   572  		url.User, url.Host, err = parseAuthority(authority)
   573  		if err != nil {
   574  			return nil, err
   575  		}
   576  	} else if url.Scheme != "" && strings.HasPrefix(rest, "/") {
   577  		// OmitHost is set to true when rawURL has an empty host (authority).
   578  		// See golang.org/issue/46059.
   579  		url.OmitHost = true
   580  	}
   581  
   582  	// Set Path and, optionally, RawPath.
   583  	// RawPath is a hint of the encoding of Path. We don't want to set it if
   584  	// the default escaping of Path is equivalent, to help make sure that people
   585  	// don't rely on it in general.
   586  	if err := url.setPath(rest); err != nil {
   587  		return nil, err
   588  	}
   589  	return url, nil
   590  }
   591  
   592  func parseAuthority(authority string) (user *Userinfo, host string, err error) {
   593  	i := strings.LastIndex(authority, "@")
   594  	if i < 0 {
   595  		host, err = parseHost(authority)
   596  	} else {
   597  		host, err = parseHost(authority[i+1:])
   598  	}
   599  	if err != nil {
   600  		return nil, "", err
   601  	}
   602  	if i < 0 {
   603  		return nil, host, nil
   604  	}
   605  	userinfo := authority[:i]
   606  	if !validUserinfo(userinfo) {
   607  		return nil, "", errors.New("net/url: invalid userinfo")
   608  	}
   609  	if !strings.Contains(userinfo, ":") {
   610  		if userinfo, err = unescape(userinfo, encodeUserPassword); err != nil {
   611  			return nil, "", err
   612  		}
   613  		user = User(userinfo)
   614  	} else {
   615  		username, password, _ := strings.Cut(userinfo, ":")
   616  		if username, err = unescape(username, encodeUserPassword); err != nil {
   617  			return nil, "", err
   618  		}
   619  		if password, err = unescape(password, encodeUserPassword); err != nil {
   620  			return nil, "", err
   621  		}
   622  		user = UserPassword(username, password)
   623  	}
   624  	return user, host, nil
   625  }
   626  
   627  // parseHost parses host as an authority without user
   628  // information. That is, as host[:port].
   629  func parseHost(host string) (string, error) {
   630  	if openBracketIdx := strings.LastIndex(host, "["); openBracketIdx != -1 {
   631  		// Parse an IP-Literal in RFC 3986 and RFC 6874.
   632  		// E.g., "[fe80::1]", "[fe80::1%25en0]", "[fe80::1]:80".
   633  		closeBracketIdx := strings.LastIndex(host, "]")
   634  		if closeBracketIdx < 0 {
   635  			return "", errors.New("missing ']' in host")
   636  		}
   637  
   638  		colonPort := host[closeBracketIdx+1:]
   639  		if !validOptionalPort(colonPort) {
   640  			return "", fmt.Errorf("invalid port %q after host", colonPort)
   641  		}
   642  		unescapedColonPort, err := unescape(colonPort, encodeHost)
   643  		if err != nil {
   644  			return "", err
   645  		}
   646  
   647  		hostname := host[openBracketIdx+1 : closeBracketIdx]
   648  		var unescapedHostname string
   649  		// RFC 6874 defines that %25 (%-encoded percent) introduces
   650  		// the zone identifier, and the zone identifier can use basically
   651  		// any %-encoding it likes. That's different from the host, which
   652  		// can only %-encode non-ASCII bytes.
   653  		// We do impose some restrictions on the zone, to avoid stupidity
   654  		// like newlines.
   655  		zoneIdx := strings.Index(hostname, "%25")
   656  		if zoneIdx >= 0 {
   657  			hostPart, err := unescape(hostname[:zoneIdx], encodeHost)
   658  			if err != nil {
   659  				return "", err
   660  			}
   661  			zonePart, err := unescape(hostname[zoneIdx:], encodeZone)
   662  			if err != nil {
   663  				return "", err
   664  			}
   665  			unescapedHostname = hostPart + zonePart
   666  		} else {
   667  			var err error
   668  			unescapedHostname, err = unescape(hostname, encodeHost)
   669  			if err != nil {
   670  				return "", err
   671  			}
   672  		}
   673  
   674  		// Per RFC 3986, only a host identified by a valid
   675  		// IPv6 address can be enclosed by square brackets.
   676  		// This excludes any IPv4, but notably not IPv4-mapped addresses.
   677  		addr, err := netip.ParseAddr(unescapedHostname)
   678  		if err != nil {
   679  			return "", fmt.Errorf("invalid host: %w", err)
   680  		}
   681  		if addr.Is4() {
   682  			return "", errors.New("invalid IP-literal")
   683  		}
   684  		return "[" + unescapedHostname + "]" + unescapedColonPort, nil
   685  	} else if i := strings.LastIndex(host, ":"); i != -1 {
   686  		colonPort := host[i:]
   687  		if !validOptionalPort(colonPort) {
   688  			return "", fmt.Errorf("invalid port %q after host", colonPort)
   689  		}
   690  	}
   691  
   692  	var err error
   693  	if host, err = unescape(host, encodeHost); err != nil {
   694  		return "", err
   695  	}
   696  	return host, nil
   697  }
   698  
   699  // setPath sets the Path and RawPath fields of the URL based on the provided
   700  // escaped path p. It maintains the invariant that RawPath is only specified
   701  // when it differs from the default encoding of the path.
   702  // For example:
   703  // - setPath("/foo/bar")   will set Path="/foo/bar" and RawPath=""
   704  // - setPath("/foo%2fbar") will set Path="/foo/bar" and RawPath="/foo%2fbar"
   705  // setPath will return an error only if the provided path contains an invalid
   706  // escaping.
   707  //
   708  // setPath should be an internal detail,
   709  // but widely used packages access it using linkname.
   710  // Notable members of the hall of shame include:
   711  //   - github.com/sagernet/sing
   712  //
   713  // Do not remove or change the type signature.
   714  // See go.dev/issue/67401.
   715  //
   716  //go:linkname badSetPath net/url.(*URL).setPath
   717  func (u *URL) setPath(p string) error {
   718  	path, err := unescape(p, encodePath)
   719  	if err != nil {
   720  		return err
   721  	}
   722  	u.Path = path
   723  	if escp := escape(path, encodePath); p == escp {
   724  		// Default encoding is fine.
   725  		u.RawPath = ""
   726  	} else {
   727  		u.RawPath = p
   728  	}
   729  	return nil
   730  }
   731  
   732  // for linkname because we cannot linkname methods directly
   733  func badSetPath(*URL, string) error
   734  
   735  // EscapedPath returns the escaped form of u.Path.
   736  // In general there are multiple possible escaped forms of any path.
   737  // EscapedPath returns u.RawPath when it is a valid escaping of u.Path.
   738  // Otherwise EscapedPath ignores u.RawPath and computes an escaped
   739  // form on its own.
   740  // The [URL.String] and [URL.RequestURI] methods use EscapedPath to construct
   741  // their results.
   742  // In general, code should call EscapedPath instead of
   743  // reading u.RawPath directly.
   744  func (u *URL) EscapedPath() string {
   745  	if u.RawPath != "" && validEncoded(u.RawPath, encodePath) {
   746  		p, err := unescape(u.RawPath, encodePath)
   747  		if err == nil && p == u.Path {
   748  			return u.RawPath
   749  		}
   750  	}
   751  	if u.Path == "*" {
   752  		return "*" // don't escape (Issue 11202)
   753  	}
   754  	return escape(u.Path, encodePath)
   755  }
   756  
   757  // validEncoded reports whether s is a valid encoded path or fragment,
   758  // according to mode.
   759  // It must not contain any bytes that require escaping during encoding.
   760  func validEncoded(s string, mode encoding) bool {
   761  	for i := 0; i < len(s); i++ {
   762  		// RFC 3986, Appendix A.
   763  		// pchar = unreserved / pct-encoded / sub-delims / ":" / "@".
   764  		// shouldEscape is not quite compliant with the RFC,
   765  		// so we check the sub-delims ourselves and let
   766  		// shouldEscape handle the others.
   767  		switch s[i] {
   768  		case '!', '$', '&', '\'', '(', ')', '*', '+', ',', ';', '=', ':', '@':
   769  			// ok
   770  		case '[', ']':
   771  			// ok - not specified in RFC 3986 but left alone by modern browsers
   772  		case '%':
   773  			// ok - percent encoded, will decode
   774  		default:
   775  			if shouldEscape(s[i], mode) {
   776  				return false
   777  			}
   778  		}
   779  	}
   780  	return true
   781  }
   782  
   783  // setFragment is like setPath but for Fragment/RawFragment.
   784  func (u *URL) setFragment(f string) error {
   785  	frag, err := unescape(f, encodeFragment)
   786  	if err != nil {
   787  		return err
   788  	}
   789  	u.Fragment = frag
   790  	if escf := escape(frag, encodeFragment); f == escf {
   791  		// Default encoding is fine.
   792  		u.RawFragment = ""
   793  	} else {
   794  		u.RawFragment = f
   795  	}
   796  	return nil
   797  }
   798  
   799  // EscapedFragment returns the escaped form of u.Fragment.
   800  // In general there are multiple possible escaped forms of any fragment.
   801  // EscapedFragment returns u.RawFragment when it is a valid escaping of u.Fragment.
   802  // Otherwise EscapedFragment ignores u.RawFragment and computes an escaped
   803  // form on its own.
   804  // The [URL.String] method uses EscapedFragment to construct its result.
   805  // In general, code should call EscapedFragment instead of
   806  // reading u.RawFragment directly.
   807  func (u *URL) EscapedFragment() string {
   808  	if u.RawFragment != "" && validEncoded(u.RawFragment, encodeFragment) {
   809  		f, err := unescape(u.RawFragment, encodeFragment)
   810  		if err == nil && f == u.Fragment {
   811  			return u.RawFragment
   812  		}
   813  	}
   814  	return escape(u.Fragment, encodeFragment)
   815  }
   816  
   817  // validOptionalPort reports whether port is either an empty string
   818  // or matches /^:\d*$/
   819  func validOptionalPort(port string) bool {
   820  	if port == "" {
   821  		return true
   822  	}
   823  	if port[0] != ':' {
   824  		return false
   825  	}
   826  	for _, b := range port[1:] {
   827  		if b < '0' || b > '9' {
   828  			return false
   829  		}
   830  	}
   831  	return true
   832  }
   833  
   834  // String reassembles the [URL] into a valid URL string.
   835  // The general form of the result is one of:
   836  //
   837  //	scheme:opaque?query#fragment
   838  //	scheme://userinfo@host/path?query#fragment
   839  //
   840  // If u.Opaque is non-empty, String uses the first form;
   841  // otherwise it uses the second form.
   842  // Any non-ASCII characters in host are escaped.
   843  // To obtain the path, String uses u.EscapedPath().
   844  //
   845  // In the second form, the following rules apply:
   846  //   - if u.Scheme is empty, scheme: is omitted.
   847  //   - if u.User is nil, userinfo@ is omitted.
   848  //   - if u.Host is empty, host/ is omitted.
   849  //   - if u.Scheme and u.Host are empty and u.User is nil,
   850  //     the entire scheme://userinfo@host/ is omitted.
   851  //   - if u.Host is non-empty and u.Path begins with a /,
   852  //     the form host/path does not add its own /.
   853  //   - if u.RawQuery is empty, ?query is omitted.
   854  //   - if u.Fragment is empty, #fragment is omitted.
   855  func (u *URL) String() string {
   856  	var buf strings.Builder
   857  
   858  	n := len(u.Scheme)
   859  	if u.Opaque != "" {
   860  		n += len(u.Opaque)
   861  	} else {
   862  		if !u.OmitHost && (u.Scheme != "" || u.Host != "" || u.User != nil) {
   863  			username := u.User.Username()
   864  			password, _ := u.User.Password()
   865  			n += len(username) + len(password) + len(u.Host)
   866  		}
   867  		n += len(u.Path)
   868  	}
   869  	n += len(u.RawQuery) + len(u.RawFragment)
   870  	n += len(":" + "//" + "//" + ":" + "@" + "/" + "./" + "?" + "#")
   871  	buf.Grow(n)
   872  
   873  	if u.Scheme != "" {
   874  		buf.WriteString(u.Scheme)
   875  		buf.WriteByte(':')
   876  	}
   877  	if u.Opaque != "" {
   878  		buf.WriteString(u.Opaque)
   879  	} else {
   880  		if u.Scheme != "" || u.Host != "" || u.User != nil {
   881  			if u.OmitHost && u.Host == "" && u.User == nil {
   882  				// omit empty host
   883  			} else {
   884  				if u.Host != "" || u.Path != "" || u.User != nil {
   885  					buf.WriteString("//")
   886  				}
   887  				if ui := u.User; ui != nil {
   888  					buf.WriteString(ui.String())
   889  					buf.WriteByte('@')
   890  				}
   891  				if h := u.Host; h != "" {
   892  					buf.WriteString(escape(h, encodeHost))
   893  				}
   894  			}
   895  		}
   896  		path := u.EscapedPath()
   897  		if path != "" && path[0] != '/' && u.Host != "" {
   898  			buf.WriteByte('/')
   899  		}
   900  		if buf.Len() == 0 {
   901  			// RFC 3986 §4.2
   902  			// A path segment that contains a colon character (e.g., "this:that")
   903  			// cannot be used as the first segment of a relative-path reference, as
   904  			// it would be mistaken for a scheme name. Such a segment must be
   905  			// preceded by a dot-segment (e.g., "./this:that") to make a relative-
   906  			// path reference.
   907  			if segment, _, _ := strings.Cut(path, "/"); strings.Contains(segment, ":") {
   908  				buf.WriteString("./")
   909  			}
   910  		}
   911  		buf.WriteString(path)
   912  	}
   913  	if u.ForceQuery || u.RawQuery != "" {
   914  		buf.WriteByte('?')
   915  		buf.WriteString(u.RawQuery)
   916  	}
   917  	if u.Fragment != "" {
   918  		buf.WriteByte('#')
   919  		buf.WriteString(u.EscapedFragment())
   920  	}
   921  	return buf.String()
   922  }
   923  
   924  // Redacted is like [URL.String] but replaces any password with "xxxxx".
   925  // Only the password in u.User is redacted.
   926  func (u *URL) Redacted() string {
   927  	if u == nil {
   928  		return ""
   929  	}
   930  
   931  	ru := *u
   932  	if _, has := ru.User.Password(); has {
   933  		ru.User = UserPassword(ru.User.Username(), "xxxxx")
   934  	}
   935  	return ru.String()
   936  }
   937  
   938  // Values maps a string key to a list of values.
   939  // It is typically used for query parameters and form values.
   940  // Unlike in the http.Header map, the keys in a Values map
   941  // are case-sensitive.
   942  type Values map[string][]string
   943  
   944  // Get gets the first value associated with the given key.
   945  // If there are no values associated with the key, Get returns
   946  // the empty string. To access multiple values, use the map
   947  // directly.
   948  func (v Values) Get(key string) string {
   949  	vs := v[key]
   950  	if len(vs) == 0 {
   951  		return ""
   952  	}
   953  	return vs[0]
   954  }
   955  
   956  // Set sets the key to value. It replaces any existing
   957  // values.
   958  func (v Values) Set(key, value string) {
   959  	v[key] = []string{value}
   960  }
   961  
   962  // Add adds the value to key. It appends to any existing
   963  // values associated with key.
   964  func (v Values) Add(key, value string) {
   965  	v[key] = append(v[key], value)
   966  }
   967  
   968  // Del deletes the values associated with key.
   969  func (v Values) Del(key string) {
   970  	delete(v, key)
   971  }
   972  
   973  // Has checks whether a given key is set.
   974  func (v Values) Has(key string) bool {
   975  	_, ok := v[key]
   976  	return ok
   977  }
   978  
   979  // ParseQuery parses the URL-encoded query string and returns
   980  // a map listing the values specified for each key.
   981  // ParseQuery always returns a non-nil map containing all the
   982  // valid query parameters found; err describes the first decoding error
   983  // encountered, if any.
   984  //
   985  // Query is expected to be a list of key=value settings separated by ampersands.
   986  // A setting without an equals sign is interpreted as a key set to an empty
   987  // value.
   988  // Settings containing a non-URL-encoded semicolon are considered invalid.
   989  func ParseQuery(query string) (Values, error) {
   990  	m := make(Values)
   991  	err := parseQuery(m, query)
   992  	return m, err
   993  }
   994  
   995  func parseQuery(m Values, query string) (err error) {
   996  	for query != "" {
   997  		var key string
   998  		key, query, _ = strings.Cut(query, "&")
   999  		if strings.Contains(key, ";") {
  1000  			err = fmt.Errorf("invalid semicolon separator in query")
  1001  			continue
  1002  		}
  1003  		if key == "" {
  1004  			continue
  1005  		}
  1006  		key, value, _ := strings.Cut(key, "=")
  1007  		key, err1 := QueryUnescape(key)
  1008  		if err1 != nil {
  1009  			if err == nil {
  1010  				err = err1
  1011  			}
  1012  			continue
  1013  		}
  1014  		value, err1 = QueryUnescape(value)
  1015  		if err1 != nil {
  1016  			if err == nil {
  1017  				err = err1
  1018  			}
  1019  			continue
  1020  		}
  1021  		m[key] = append(m[key], value)
  1022  	}
  1023  	return err
  1024  }
  1025  
  1026  // Encode encodes the values into “URL encoded” form
  1027  // ("bar=baz&foo=quux") sorted by key.
  1028  func (v Values) Encode() string {
  1029  	if len(v) == 0 {
  1030  		return ""
  1031  	}
  1032  	var buf strings.Builder
  1033  	for _, k := range slices.Sorted(maps.Keys(v)) {
  1034  		vs := v[k]
  1035  		keyEscaped := QueryEscape(k)
  1036  		for _, v := range vs {
  1037  			if buf.Len() > 0 {
  1038  				buf.WriteByte('&')
  1039  			}
  1040  			buf.WriteString(keyEscaped)
  1041  			buf.WriteByte('=')
  1042  			buf.WriteString(QueryEscape(v))
  1043  		}
  1044  	}
  1045  	return buf.String()
  1046  }
  1047  
  1048  // resolvePath applies special path segments from refs and applies
  1049  // them to base, per RFC 3986.
  1050  func resolvePath(base, ref string) string {
  1051  	var full string
  1052  	if ref == "" {
  1053  		full = base
  1054  	} else if ref[0] != '/' {
  1055  		i := strings.LastIndex(base, "/")
  1056  		full = base[:i+1] + ref
  1057  	} else {
  1058  		full = ref
  1059  	}
  1060  	if full == "" {
  1061  		return ""
  1062  	}
  1063  
  1064  	var (
  1065  		elem string
  1066  		dst  strings.Builder
  1067  	)
  1068  	first := true
  1069  	remaining := full
  1070  	// We want to return a leading '/', so write it now.
  1071  	dst.WriteByte('/')
  1072  	found := true
  1073  	for found {
  1074  		elem, remaining, found = strings.Cut(remaining, "/")
  1075  		if elem == "." {
  1076  			first = false
  1077  			// drop
  1078  			continue
  1079  		}
  1080  
  1081  		if elem == ".." {
  1082  			// Ignore the leading '/' we already wrote.
  1083  			str := dst.String()[1:]
  1084  			index := strings.LastIndexByte(str, '/')
  1085  
  1086  			dst.Reset()
  1087  			dst.WriteByte('/')
  1088  			if index == -1 {
  1089  				first = true
  1090  			} else {
  1091  				dst.WriteString(str[:index])
  1092  			}
  1093  		} else {
  1094  			if !first {
  1095  				dst.WriteByte('/')
  1096  			}
  1097  			dst.WriteString(elem)
  1098  			first = false
  1099  		}
  1100  	}
  1101  
  1102  	if elem == "." || elem == ".." {
  1103  		dst.WriteByte('/')
  1104  	}
  1105  
  1106  	// We wrote an initial '/', but we don't want two.
  1107  	r := dst.String()
  1108  	if len(r) > 1 && r[1] == '/' {
  1109  		r = r[1:]
  1110  	}
  1111  	return r
  1112  }
  1113  
  1114  // IsAbs reports whether the [URL] is absolute.
  1115  // Absolute means that it has a non-empty scheme.
  1116  func (u *URL) IsAbs() bool {
  1117  	return u.Scheme != ""
  1118  }
  1119  
  1120  // Parse parses a [URL] in the context of the receiver. The provided URL
  1121  // may be relative or absolute. Parse returns nil, err on parse
  1122  // failure, otherwise its return value is the same as [URL.ResolveReference].
  1123  func (u *URL) Parse(ref string) (*URL, error) {
  1124  	refURL, err := Parse(ref)
  1125  	if err != nil {
  1126  		return nil, err
  1127  	}
  1128  	return u.ResolveReference(refURL), nil
  1129  }
  1130  
  1131  // ResolveReference resolves a URI reference to an absolute URI from
  1132  // an absolute base URI u, per RFC 3986 Section 5.2. The URI reference
  1133  // may be relative or absolute. ResolveReference always returns a new
  1134  // [URL] instance, even if the returned URL is identical to either the
  1135  // base or reference. If ref is an absolute URL, then ResolveReference
  1136  // ignores base and returns a copy of ref.
  1137  func (u *URL) ResolveReference(ref *URL) *URL {
  1138  	url := *ref
  1139  	if ref.Scheme == "" {
  1140  		url.Scheme = u.Scheme
  1141  	}
  1142  	if ref.Scheme != "" || ref.Host != "" || ref.User != nil {
  1143  		// The "absoluteURI" or "net_path" cases.
  1144  		// We can ignore the error from setPath since we know we provided a
  1145  		// validly-escaped path.
  1146  		url.setPath(resolvePath(ref.EscapedPath(), ""))
  1147  		return &url
  1148  	}
  1149  	if ref.Opaque != "" {
  1150  		url.User = nil
  1151  		url.Host = ""
  1152  		url.Path = ""
  1153  		return &url
  1154  	}
  1155  	if ref.Path == "" && !ref.ForceQuery && ref.RawQuery == "" {
  1156  		url.RawQuery = u.RawQuery
  1157  		if ref.Fragment == "" {
  1158  			url.Fragment = u.Fragment
  1159  			url.RawFragment = u.RawFragment
  1160  		}
  1161  	}
  1162  	if ref.Path == "" && u.Opaque != "" {
  1163  		url.Opaque = u.Opaque
  1164  		url.User = nil
  1165  		url.Host = ""
  1166  		url.Path = ""
  1167  		return &url
  1168  	}
  1169  	// The "abs_path" or "rel_path" cases.
  1170  	url.Host = u.Host
  1171  	url.User = u.User
  1172  	url.setPath(resolvePath(u.EscapedPath(), ref.EscapedPath()))
  1173  	return &url
  1174  }
  1175  
  1176  // Query parses RawQuery and returns the corresponding values.
  1177  // It silently discards malformed value pairs.
  1178  // To check errors use [ParseQuery].
  1179  func (u *URL) Query() Values {
  1180  	v, _ := ParseQuery(u.RawQuery)
  1181  	return v
  1182  }
  1183  
  1184  // RequestURI returns the encoded path?query or opaque?query
  1185  // string that would be used in an HTTP request for u.
  1186  func (u *URL) RequestURI() string {
  1187  	result := u.Opaque
  1188  	if result == "" {
  1189  		result = u.EscapedPath()
  1190  		if result == "" {
  1191  			result = "/"
  1192  		}
  1193  	} else {
  1194  		if strings.HasPrefix(result, "//") {
  1195  			result = u.Scheme + ":" + result
  1196  		}
  1197  	}
  1198  	if u.ForceQuery || u.RawQuery != "" {
  1199  		result += "?" + u.RawQuery
  1200  	}
  1201  	return result
  1202  }
  1203  
  1204  // Hostname returns u.Host, stripping any valid port number if present.
  1205  //
  1206  // If the result is enclosed in square brackets, as literal IPv6 addresses are,
  1207  // the square brackets are removed from the result.
  1208  func (u *URL) Hostname() string {
  1209  	host, _ := splitHostPort(u.Host)
  1210  	return host
  1211  }
  1212  
  1213  // Port returns the port part of u.Host, without the leading colon.
  1214  //
  1215  // If u.Host doesn't contain a valid numeric port, Port returns an empty string.
  1216  func (u *URL) Port() string {
  1217  	_, port := splitHostPort(u.Host)
  1218  	return port
  1219  }
  1220  
  1221  // splitHostPort separates host and port. If the port is not valid, it returns
  1222  // the entire input as host, and it doesn't check the validity of the host.
  1223  // Unlike net.SplitHostPort, but per RFC 3986, it requires ports to be numeric.
  1224  func splitHostPort(hostPort string) (host, port string) {
  1225  	host = hostPort
  1226  
  1227  	colon := strings.LastIndexByte(host, ':')
  1228  	if colon != -1 && validOptionalPort(host[colon:]) {
  1229  		host, port = host[:colon], host[colon+1:]
  1230  	}
  1231  
  1232  	if strings.HasPrefix(host, "[") && strings.HasSuffix(host, "]") {
  1233  		host = host[1 : len(host)-1]
  1234  	}
  1235  
  1236  	return
  1237  }
  1238  
  1239  // Marshaling interface implementations.
  1240  // Would like to implement MarshalText/UnmarshalText but that will change the JSON representation of URLs.
  1241  
  1242  func (u *URL) MarshalBinary() (text []byte, err error) {
  1243  	return u.AppendBinary(nil)
  1244  }
  1245  
  1246  func (u *URL) AppendBinary(b []byte) ([]byte, error) {
  1247  	return append(b, u.String()...), nil
  1248  }
  1249  
  1250  func (u *URL) UnmarshalBinary(text []byte) error {
  1251  	u1, err := Parse(string(text))
  1252  	if err != nil {
  1253  		return err
  1254  	}
  1255  	*u = *u1
  1256  	return nil
  1257  }
  1258  
  1259  // JoinPath returns a new [URL] with the provided path elements joined to
  1260  // any existing path and the resulting path cleaned of any ./ or ../ elements.
  1261  // Any sequences of multiple / characters will be reduced to a single /.
  1262  func (u *URL) JoinPath(elem ...string) *URL {
  1263  	elem = append([]string{u.EscapedPath()}, elem...)
  1264  	var p string
  1265  	if !strings.HasPrefix(elem[0], "/") {
  1266  		// Return a relative path if u is relative,
  1267  		// but ensure that it contains no ../ elements.
  1268  		elem[0] = "/" + elem[0]
  1269  		p = path.Join(elem...)[1:]
  1270  	} else {
  1271  		p = path.Join(elem...)
  1272  	}
  1273  	// path.Join will remove any trailing slashes.
  1274  	// Preserve at least one.
  1275  	if strings.HasSuffix(elem[len(elem)-1], "/") && !strings.HasSuffix(p, "/") {
  1276  		p += "/"
  1277  	}
  1278  	url := *u
  1279  	url.setPath(p)
  1280  	return &url
  1281  }
  1282  
  1283  // validUserinfo reports whether s is a valid userinfo string per RFC 3986
  1284  // Section 3.2.1:
  1285  //
  1286  //	userinfo    = *( unreserved / pct-encoded / sub-delims / ":" )
  1287  //	unreserved  = ALPHA / DIGIT / "-" / "." / "_" / "~"
  1288  //	sub-delims  = "!" / "$" / "&" / "'" / "(" / ")"
  1289  //	              / "*" / "+" / "," / ";" / "="
  1290  //
  1291  // It doesn't validate pct-encoded. The caller does that via func unescape.
  1292  func validUserinfo(s string) bool {
  1293  	for _, r := range s {
  1294  		if 'A' <= r && r <= 'Z' {
  1295  			continue
  1296  		}
  1297  		if 'a' <= r && r <= 'z' {
  1298  			continue
  1299  		}
  1300  		if '0' <= r && r <= '9' {
  1301  			continue
  1302  		}
  1303  		switch r {
  1304  		case '-', '.', '_', ':', '~', '!', '$', '&', '\'',
  1305  			'(', ')', '*', '+', ',', ';', '=', '%':
  1306  			continue
  1307  		case '@':
  1308  			// `RFC 3986 section 3.2.1` does not allow '@' in userinfo.
  1309  			// It is a delimiter between userinfo and host.
  1310  			// However, URLs are diverse, and in some cases,
  1311  			// the userinfo may contain an '@' character,
  1312  			// for example, in "http://username:p@ssword@google.com",
  1313  			// the string "username:p@ssword" should be treated as valid userinfo.
  1314  			// Ref:
  1315  			//   https://go.dev/issue/3439
  1316  			//   https://go.dev/issue/22655
  1317  			continue
  1318  		default:
  1319  			return false
  1320  		}
  1321  	}
  1322  	return true
  1323  }
  1324  
  1325  // stringContainsCTLByte reports whether s contains any ASCII control character.
  1326  func stringContainsCTLByte(s string) bool {
  1327  	for i := 0; i < len(s); i++ {
  1328  		b := s[i]
  1329  		if b < ' ' || b == 0x7f {
  1330  			return true
  1331  		}
  1332  	}
  1333  	return false
  1334  }
  1335  
  1336  // JoinPath returns a [URL] string with the provided path elements joined to
  1337  // the existing path of base and the resulting path cleaned of any ./ or ../ elements.
  1338  func JoinPath(base string, elem ...string) (result string, err error) {
  1339  	url, err := Parse(base)
  1340  	if err != nil {
  1341  		return
  1342  	}
  1343  	result = url.JoinPath(elem...).String()
  1344  	return
  1345  }
  1346  

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