feat: add helm to go mod (#497)

vendor/github.com/prometheus/common/model/metric.go

@@ -14,9 +14,11 @@
 package model
 
 import (
+	"errors"
 	"fmt"
 	"regexp"
 	"sort"
+	"strconv"
 	"strings"
 	"unicode/utf8"
 
@@ -25,14 +27,26 @@ import (
 )
 
 var (
-	// NameValidationScheme determines the method of name validation to be used by
-	// all calls to IsValidMetricName() and LabelName IsValid(). Setting UTF-8 mode
-	// in isolation from other components that don't support UTF-8 may result in
-	// bugs or other undefined behavior. This value is intended to be set by
-	// UTF-8-aware binaries as part of their startup. To avoid need for locking,
-	// this value should be set once, ideally in an init(), before multiple
-	// goroutines are started.
-	NameValidationScheme = LegacyValidation
+	// NameValidationScheme determines the global default method of the name
+	// validation to be used by all calls to IsValidMetricName() and LabelName
+	// IsValid().
+	//
+	// Deprecated: This variable should not be used and might be removed in the
+	// far future. If you wish to stick to the legacy name validation use
+	// `IsValidLegacyMetricName()` and `LabelName.IsValidLegacy()` methods
+	// instead. This variable is here as an escape hatch for emergency cases,
+	// given the recent change from `LegacyValidation` to `UTF8Validation`, e.g.,
+	// to delay UTF-8 migrations in time or aid in debugging unforeseen results of
+	// the change. In such a case, a temporary assignment to `LegacyValidation`
+	// value in the `init()` function in your main.go or so, could be considered.
+	//
+	// Historically we opted for a global variable for feature gating different
+	// validation schemes in operations that were not otherwise easily adjustable
+	// (e.g. Labels yaml unmarshaling). That could have been a mistake, a separate
+	// Labels structure or package might have been a better choice. Given the
+	// change was made and many upgraded the common already, we live this as-is
+	// with this warning and learning for the future.
+	NameValidationScheme = UTF8Validation
 
 	// NameEscapingScheme defines the default way that names will be escaped when
 	// presented to systems that do not support UTF-8 names. If the Content-Type
@@ -48,7 +62,7 @@ var (
 type ValidationScheme int
 
 const (
-	// LegacyValidation is a setting that requirets that metric and label names
+	// LegacyValidation is a setting that requires that all metric and label names
 	// conform to the original Prometheus character requirements described by
 	// MetricNameRE and LabelNameRE.
 	LegacyValidation ValidationScheme = iota
@@ -269,10 +283,6 @@ func metricNeedsEscaping(m *dto.Metric) bool {
 	return false
 }
 
-const (
-	lowerhex = "0123456789abcdef"
-)
-
 // EscapeName escapes the incoming name according to the provided escaping
 // scheme. Depending on the rules of escaping, this may cause no change in the
 // string that is returned. (Especially NoEscaping, which by definition is a
@@ -307,7 +317,7 @@ func EscapeName(name string, scheme EscapingScheme) string {
 			} else if isValidLegacyRune(b, i) {
 				escaped.WriteRune(b)
 			} else {
-				escaped.WriteRune('_')
+				escaped.WriteString("__")
 			}
 		}
 		return escaped.String()
@@ -317,21 +327,15 @@ func EscapeName(name string, scheme EscapingScheme) string {
 		}
 		escaped.WriteString("U__")
 		for i, b := range name {
-			if isValidLegacyRune(b, i) {
+			if b == '_' {
+				escaped.WriteString("__")
+			} else if isValidLegacyRune(b, i) {
 				escaped.WriteRune(b)
 			} else if !utf8.ValidRune(b) {
 				escaped.WriteString("_FFFD_")
-			} else if b < 0x100 {
+			} else {
 				escaped.WriteRune('_')
-				for s := 4; s >= 0; s -= 4 {
-					escaped.WriteByte(lowerhex[b>>uint(s)&0xF])
-				}
-				escaped.WriteRune('_')
-			} else if b < 0x10000 {
-				escaped.WriteRune('_')
-				for s := 12; s >= 0; s -= 4 {
-					escaped.WriteByte(lowerhex[b>>uint(s)&0xF])
-				}
+				escaped.WriteString(strconv.FormatInt(int64(b), 16))
 				escaped.WriteRune('_')
 			}
 		}
@@ -389,8 +393,9 @@ func UnescapeName(name string, scheme EscapingScheme) string {
 			// We think we are in a UTF-8 code, process it.
 			var utf8Val uint
 			for j := 0; i < len(escapedName); j++ {
-				// This is too many characters for a utf8 value.
-				if j > 4 {
+				// This is too many characters for a utf8 value based on the MaxRune
+				// value of '\U0010FFFF'.
+				if j >= 6 {
 					return name
 				}
 				// Found a closing underscore, convert to a rune, check validity, and append.
@@ -443,7 +448,7 @@ func (e EscapingScheme) String() string {
 
 func ToEscapingScheme(s string) (EscapingScheme, error) {
 	if s == "" {
-		return NoEscaping, fmt.Errorf("got empty string instead of escaping scheme")
+		return NoEscaping, errors.New("got empty string instead of escaping scheme")
 	}
 	switch s {
 	case AllowUTF8: