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perf: compile BCP 47 language tag regex once at package init #341

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perf: compile BCP 47 language tag regex once at package init #341

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52 changes: 27 additions & 25 deletions validators/bcp47.go
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Original file line number Diff line number Diff line change
Expand Up @@ -10,6 +10,33 @@ import (
"golang.org/x/text/language"
)

// languageTagRe is the compiled BCP 47 language tag regex, built once at
// package init to avoid recompiling on every validation call.
var languageTagRe = regexp.MustCompile(strings.Join([]string{
// group 1:
`^(`,
// irregular
`EN-GB-OED|I-AMI|I-BNN|I-DEFAULT|I-ENOCHIAN|I-HAK|I-KLINGON|I-LUX|I-MINGO|I-NAVAJO|I-PWN|I-TAO|I-TAY|I-TSU|`,
`SGN-BE-FR|SGN-BE-NL|SGN-CH-DE|`,
// regular
`ART-LOJBAN|CEL-GAULISH|NO-BOK|NO-NYN|ZH-GUOYU|ZH-HAKKA|ZH-MIN|ZH-MIN-NAN|ZH-XIANG|`,
// privateuse
`X-[A-Z0-9]{1,8}`,
`)$`,

`|`,

// langtag
`^`,
`((?:[A-Z]{2,3}(?:-[A-Z]{3}){0,3})|[A-Z]{4}|[A-Z]{5,8})`, // group 2: language
`(?:-([A-Z]{4}))?`, // group 3: script
`(?:-([A-Z]{2}|[0-9]{3}))?`, // group 4: region
`(?:-((?:[A-Z0-9]{5,8}|[0-9][A-Z0-9]{3})(?:-(?:[A-Z0-9]{5,8}|[0-9][A-Z0-9]{3}))*))?`, // group 5: variant
`(?:-((?:[A-WYZ0-9](?:-[A-Z0-9]{2,8})+)(?:-(?:[A-WYZ0-9](?:-[A-Z0-9]{2,8})+))*))?`, // group 6: extension
`(?:-X(?:-[A-Z0-9]{1,8})+)?`,
`$`,
}, ""))

// isBCP47StrictLanguageTag validates a BCP 47 language tag according to
// https://www.rfc-editor.org/rfc/bcp/bcp47.txt, rejecting POSIX-style tags
// (e.g. en_GB) and Unicode extensions unlike the built-in bcp47_language_tag.
Expand All @@ -27,31 +54,6 @@ func isBCP47StrictLanguageTag(fl validator.FieldLevel) bool {
}

func isValidBCP47StrictLanguageTag(s string) bool {
languageTagRe := regexp.MustCompile(strings.Join([]string{
// group 1:
`^(`,
// irregular
`EN-GB-OED|I-AMI|I-BNN|I-DEFAULT|I-ENOCHIAN|I-HAK|I-KLINGON|I-LUX|I-MINGO|I-NAVAJO|I-PWN|I-TAO|I-TAY|I-TSU|`,
`SGN-BE-FR|SGN-BE-NL|SGN-CH-DE|`,
// regular
`ART-LOJBAN|CEL-GAULISH|NO-BOK|NO-NYN|ZH-GUOYU|ZH-HAKKA|ZH-MIN|ZH-MIN-NAN|ZH-XIANG|`,
// privateuse
`X-[A-Z0-9]{1,8}`,
`)$`,

`|`,

// langtag
`^`,
`((?:[A-Z]{2,3}(?:-[A-Z]{3}){0,3})|[A-Z]{4}|[A-Z]{5,8})`, // group 2: language
`(?:-([A-Z]{4}))?`, // group 3: script
`(?:-([A-Z]{2}|[0-9]{3}))?`, // group 4: region
`(?:-((?:[A-Z0-9]{5,8}|[0-9][A-Z0-9]{3})(?:-(?:[A-Z0-9]{5,8}|[0-9][A-Z0-9]{3}))*))?`, // group 5: variant
`(?:-((?:[A-WYZ0-9](?:-[A-Z0-9]{2,8})+)(?:-(?:[A-WYZ0-9](?:-[A-Z0-9]{2,8})+))*))?`, // group 6: extension
`(?:-X(?:-[A-Z0-9]{1,8})+)?`,
`$`,
}, ""))

languageTag := strings.ToUpper(s)

m := languageTagRe.FindStringSubmatch(languageTag)
Expand Down