Data sources: Don't fail if URL doesn't specify protocol (#24497)

pkg/api/datasource/validation.go

@@ -0,0 +1,50 @@
+package datasource
+
+import (
+	"fmt"
+	"net/url"
+	"regexp"
+
+	"github.com/grafana/grafana/pkg/infra/log"
+)
+
+var logger = log.New("datasource")
+
+// URLValidationError represents an error from validating a data source URL.
+type URLValidationError struct {
+	error
+
+	url string
+}
+
+// Error returns the error message.
+func (e URLValidationError) Error() string {
+	return fmt.Sprintf("Validation of data source URL %q failed: %s", e.url, e.error.Error())
+}
+
+// Unwrap returns the wrapped error.
+func (e URLValidationError) Unwrap() error {
+	return e.error
+}
+
+// reURL is a regexp to detect if a URL specifies the protocol. We match also strings where the actual protocol is
+// missing (i.e., "://"), in order to catch these as invalid when parsing.
+var reURL = regexp.MustCompile("^[^:]*://")
+
+// ValidateURL validates a data source URL.
+//
+// If successful, the valid URL object is returned, otherwise an error is returned.
+func ValidateURL(urlStr string) (*url.URL, error) {
+	// Make sure the URL starts with a protocol specifier, so parsing is unambiguous
+	if !reURL.MatchString(urlStr) {
+		logger.Debug(
+			"Data source URL doesn't specify protocol, so prepending it with http:// in order to make it unambiguous")
+		urlStr = fmt.Sprintf("http://%s", urlStr)
+	}
+	u, err := url.Parse(urlStr)
+	if err != nil {
+		return nil, URLValidationError{error: err, url: urlStr}
+	}
+
+	return u, nil
+}