Function parseURL

data.go:406–435

parseURL parses s as a URL, handling URLs that have been munged by path.Clean or a webserver that collapses multiple slashes. The returned enc bool indicates whether the remote URL was encoded.

(s string, baseURL *url.URL)

// path.Clean or a webserver that collapses multiple slashes.
// The returned enc bool indicates whether the remote URL was encoded.
func parseURL(s string, baseURL *url.URL) (_ *url.URL, enc bool, _ error) {
	// Try to base64 decode the string. If it is not base64 encoded,
	// this will fail quickly on the first invalid character like ":", ".", or "/".
	// Accept the decoded string if it looks like an absolute HTTP URL,
	// or if we have a baseURL and the decoded string did not contain invalid code points.
	// This allows for values like "/path", which do successfully base64 decode,
	// but not to valid code points, to be treated as an unencoded string.
	if b, err := base64.RawURLEncoding.DecodeString(s); err == nil {
		d := string(b)
		if strings.HasPrefix(d, "http://") || strings.HasPrefix(d, "https://") {
			enc = true
			s = d
		} else if baseURL != nil && !strings.ContainsRune(d, unicode.ReplacementChar) {
			enc = true
			s = d
		}
	}

	// If the string looks like a URL encoded absolute HTTP(S) URL, decode it.
	if reIsEncodedURL.MatchString(s) {
		if u, err := url.PathUnescape(s); err == nil {
			enc = true
			s = u
		}
	}

	s = reCleanedURL.ReplaceAllString(s, "$1://$2")
	u, err := url.Parse(s)
	return u, enc, err
}