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Provide a method for explicitly checking label names for legacy valid…
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…ity. (#682)

This is needed in Prometheus for modes when legacy validation has been explicitly requested but UTF-8 is otherwise enabled.

Signed-off-by: Owen Williams <[email protected]>
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ywwg authored Aug 26, 2024
1 parent 19d0796 commit 6623230
Showing 1 changed file with 18 additions and 9 deletions.
27 changes: 18 additions & 9 deletions model/labels.go
Original file line number Diff line number Diff line change
Expand Up @@ -97,26 +97,35 @@ var LabelNameRE = regexp.MustCompile("^[a-zA-Z_][a-zA-Z0-9_]*$")
// therewith.
type LabelName string

// IsValid returns true iff name matches the pattern of LabelNameRE for legacy
// names, and iff it's valid UTF-8 if NameValidationScheme is set to
// UTF8Validation. For the legacy matching, it does not use LabelNameRE for the
// check but a much faster hardcoded implementation.
// IsValid returns true iff the name matches the pattern of LabelNameRE when
// NameValidationScheme is set to LegacyValidation, or valid UTF-8 if
// NameValidationScheme is set to UTF8Validation.
func (ln LabelName) IsValid() bool {
if len(ln) == 0 {
return false
}
switch NameValidationScheme {
case LegacyValidation:
for i, b := range ln {
if !((b >= 'a' && b <= 'z') || (b >= 'A' && b <= 'Z') || b == '_' || (b >= '0' && b <= '9' && i > 0)) {
return false
}
}
return ln.IsValidLegacy()
case UTF8Validation:
return utf8.ValidString(string(ln))
default:
panic(fmt.Sprintf("Invalid name validation scheme requested: %d", NameValidationScheme))
}
}

// IsValidLegacy returns true iff name matches the pattern of LabelNameRE for
// legacy names. It does not use LabelNameRE for the check but a much faster
// hardcoded implementation.
func (ln LabelName) IsValidLegacy() bool {
if len(ln) == 0 {
return false
}
for i, b := range ln {
if !((b >= 'a' && b <= 'z') || (b >= 'A' && b <= 'Z') || b == '_' || (b >= '0' && b <= '9' && i > 0)) {
return false
}
}
return true
}

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