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identifiers: adjust requirements for identifiers

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Based on feedback, a few adjustments have been made to the identifier
requirements. Identifiers that have components that start with a number
are now allowed. This violates RFC 1035 but does not do so for dns names
practically. A total length, of 76 characters is now also enforced. This
decision was completely arbitrary but satifies the requirement for a
maximum length. Often, this is used as the maximum length of a line in
editors, so it should be a good choice.

Signed-off-by: Stephen J Day <stephen.day@docker.com>
This commit is contained in:
Stephen J Day
2017-06-27 17:39:50 -07:00
parent a5fa3bb923
commit 0e34531c58
2 changed files with 20 additions and 5 deletions
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20
identifiers/validate.go
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@@ -6,8 +6,12 @@
// 2.3.1. This will make identifiers safe for use across networks, filesystems
// and other media.
//
// While the character set may expand in the future, we guarantee that the
// identifiers will be safe for use as filesystem path components.
// The identifier specification departs from RFC 1035 in that it allows
// "labels" to start with number and only enforces a total length restriction
// of 76 characters.
//
// While the character set may be expanded in the future, identifiers are
// guaranteed to be safely used as filesystem path components.
package identifiers
import (
@@ -17,7 +21,9 @@ import (
)
const (
label = `[A-Za-z][A-Za-z0-9]+(?:[-]+[A-Za-z0-9]+)*`
maxLength = 76
charclass = `[A-Za-z0-9]+`
label = charclass + `(:?[-]+` + charclass + `)*`
)
var (
@@ -27,7 +33,7 @@ var (
// identifiers.
identifierRe = regexp.MustCompile(reAnchor(label + reGroup("[.]"+reGroup(label)) + "*"))
errIdentifierInvalid = errors.Errorf("invalid, must match %v", identifierRe)
errIdentifierInvalid = errors.New("invalid identifier")
)
// IsInvalid return true if the error was due to an invalid identifer.
@@ -43,8 +49,12 @@ func IsInvalid(err error) bool {
// In general, identifiers that pass this validation, should be safe for use as
// a domain identifier or filesystem path component.
func Validate(s string) error {
if len(s) > maxLength {
return errors.Wrapf(errIdentifierInvalid, "identifier %q greater than maximum length (%d characters)", s, maxLength)
}
if !identifierRe.MatchString(s) {
return errors.Wrapf(errIdentifierInvalid, "identifier %q", s)
return errors.Wrapf(errIdentifierInvalid, "identifier %q must match %v", s, identifierRe)
}
return nil
}