New method to format date-time in locale and LC_TIME sensitive way

pkg/humanize/humanize.go

@@ -9,10 +9,13 @@ import (
 	"time"
 
 	"github.com/goodsign/monday"
+	"github.com/jeandeaual/go-locale"
 	"golang.org/x/text/language"
 	"golang.org/x/text/message"
 )
 
+var cachedSystemLocale = ""
+
 // Numericf produces a string from of the given number with give fixed precision
 // in base 10 with thousands separators after every three orders of magnitude
 // using thousands and decimal separator according to LC_NUMERIC; defaulting "en".
@@ -31,58 +34,59 @@ func Monetaryf(value float64, precision int) string {
 	return f(value, precision, "LC_MONETARY", false)
 }
 
-// Attempt to determine the locale from the current environment. If usage is provided, treat it as the name of a LC_xxx environment variable.
-// LANGUAGE
-// LC_ALL       Will override the setting of all other LC_* variables.
-// LC_MONETARY  Sets the locale for the LC_MONETARY category.
-// LC_NUMERIC   Sets the locale for the LC_NUMERIC category.
-// LC_TIME      Sets the locale for the LC_TIME category.
-// LANG         Used as a substitute for any unset LC_* variable.  If LANG is unset, it will act as if set to "C"
-// Local is language[_territory][.codeset] [@modifier]
-func DetectLocale(usage string) string {
-	if lc, ok := os.LookupEnv("LANGUAGE"); ok {
-		return lc
-	}
-	if lc, ok := os.LookupEnv("LC_ALL"); ok {
-		return lc
-	}
-	if usage != "" {
-		if lc, ok := os.LookupEnv(strings.ToUpper(usage)); ok {
-			return lc
-		}
+// borrowed from go-locale/util.go
+func splitLocale(locale string) (string, string) {
+	// Remove the encoding, if present
+	formattedLocale := strings.Split(locale, ".")[0]
+	// Normalize by replacing the hyphens with underscores
+	formattedLocale = strings.Replace(formattedLocale, "-", "_", -1)
+
+	// Split at the underscore
+	split := strings.Split(formattedLocale, "_")
+	language := split[0]
+	territory := ""
+	if len(split) > 1 {
+		territory = split[1]
 	}
-	if lc, ok := os.LookupEnv("LANG"); ok {
-		return lc
-	}
-	return "C"
-}
 
-// func DetectLanguage(usage string) language.Tag {
-// 	lc := DetectLocale(usage)
-// 	if lc == "C" {
-// 		lc = "en"
-// 	}
-// 	return language.Make(lc)
-// }
+	return language, territory
+}
 
-// Locale is language[_territory][.codeset] [@modifier]
-func FormatTime(time time.Time, layout string) string {
-	// Attempt to use the environment to determine monday.Locale
-	xxx := strings.Split(DetectLocale("LC_TIME"), ".")[0]
-	bits := strings.Split(xxx, "_")
-
-	// Look for a supported Locale with default to en_US
-	var locale monday.Locale = monday.LocaleEnUS // default
-	if len(bits) == 2 {
-		lookFor := monday.Locale(strings.ToLower(bits[0]) + "_" + strings.ToUpper(bits[1]))
-		for _, v := range monday.ListLocales() {
-			if v == lookFor {
-				locale = v
+// GetLocale returns the current locale as defined in IETF BCP 47 (e.g. "en-US").
+// The envvar is provided this is checked first, before the platform-specific defaults.
+func getLocale(envvar string) string {
+	userLocale := "en-US" // default language-REGION
+	// First try looking up envar directly
+	envlang, ok := os.LookupEnv(envvar)
+	if ok {
+		language, region := splitLocale(envlang)
+		userLocale = language
+		if len(region) > 0 {
+			userLocale = strings.Join([]string{language, region}, "-")
+		}
+	} else {
+		// Then use (cached) system-specific locale
+		if cachedSystemLocale == "" {
+			if loc, err := locale.GetLocale(); err == nil {
+				userLocale = loc
+				cachedSystemLocale = loc
 			}
+		} else {
+			userLocale = cachedSystemLocale
 		}
 	}
+	return userLocale
+}
+
+// formatTimeExplicit formats the given time using the prescribed layout with the provided userLocale
+func formatTimeExplicit(time time.Time, layout string, userLocale string) string {
+	mondayLocale := monday.Locale(strings.Replace(userLocale, "-", "_", 1))
+	return monday.Format(time, layout, mondayLocale)
+}
 
-	return monday.Format(time, layout, locale)
+// FormatTime is a dropin replacement time.Format(layout) that uses system locale + LC_TIME
+func FormatTime(time time.Time, layout string) string {
+	return formatTimeExplicit(time, layout, getLocale("LC_TIME"))
 }
 
 // f formats given value, with precision decimal places using thousands and decimal

pkg/humanize/humanize_test.go

@@ -54,9 +54,41 @@ func TestScaleNumeric(t *testing.T) {
 }
 
 func TestFormatTime(t *testing.T) {
-	s := FormatTime(time.Now(), "Jan 2006")
-	t.Logf("First: %s", s)
-	if Monetaryf(834142.3256, 2) != "834,142.3256" {
-		t.FailNow()
+	testData := map[string]map[string]string{
+		"en_GB": {
+			"Monday 2 January 2006": "Wednesday 12 March 2014",
+			"Jan 2006":              "Mar 2014",
+			"02 Jan 2006":           "12 Mar 2014",
+			"02/01/2006":            "12/03/2014",
+		},
+		"en_US": {
+			"Monday 2 January 2006": "Wednesday 12 March 2014",
+			"Jan 2006":              "Mar 2014",
+			"02 Jan 2006":           "12 Mar 2014",
+			"02/01/2006":            "12/03/2014", // ??
+		},
+		"fr_FR": {
+			"Monday 2 January 2006": "mercredi 12 mars 2014",
+			"Jan 2006":              "mars 2014",
+			"02 Jan 2006":           "12 mars 2014",
+			"02/01/2006":            "12/03/2014",
+		},
+		"de_DE": {
+			"Monday 2 January 2006": "Mittwoch 12 März 2014",
+			"Jan 2006":              "Mär 2014",
+			"02 Jan 2006":           "12 Mär 2014",
+			"02/01/2006":            "12/03/2014",
+		},
+	}
+
+	testTime := time.Date(2014, 3, 12, 0, 0, 0, 0, time.Local)
+	for locale, tests := range testData {
+		for layout, result := range tests {
+			s := formatTimeExplicit(testTime, layout, locale)
+			if s != result {
+				t.Fatalf("Expected layout '%s' in locale %s to render '%s' but got '%s'", layout, locale, result, s)
+			}
+
+		}
 	}
 }