Locale-agnostic case conversions by default #KT-43023

libraries/stdlib/samples/test/samples/text/char.kt

@@ -1,8 +1,8 @@
 package samples.text
 
 import samples.*
-import kotlin.test.*
 import java.util.*
+import kotlin.test.*
 
 class Chars {
 
@@ -83,17 +83,41 @@ class Chars {
     }
 
     @Sample
-    fun toUpperCase() {
-        val chars = listOf('a', 'ω', '1', 'A', '+')
-        val upperCases = chars.map { it.toUpperCase() }
-        assertPrints(upperCases, "[A, Ω, 1, A, +]")
+    fun uppercase() {
+        val chars = listOf('a', 'ω', '1', 'ʼn', 'A', '+', 'ß')
+        val uppercaseChar = chars.map { it.uppercaseChar() }
+        val uppercase = chars.map { it.uppercase() }
+        assertPrints(uppercaseChar, "[A, Ω, 1, ʼn, A, +, ß]")
+        assertPrints(uppercase, "[A, Ω, 1, ʼN, A, +, SS]")
     }
 
     @Sample
-    fun toLowerCase() {
-        val chars = listOf('A', 'Ω', '1', 'a', '+')
-        val lowerCases = chars.map { it.toLowerCase() }
-        assertPrints(lowerCases, "[a, ω, 1, a, +]")
+    fun uppercaseLocale() {
+        val chars = listOf('a', '1', 'ʼn', 'A', '+', 'i')
+        val uppercase = chars.map { it.uppercase() }
+        val turkishLocale = Locale.forLanguageTag("tr")
+        val uppercaseTurkish = chars.map { it.uppercase(turkishLocale) }
+        assertPrints(uppercase, "[A, 1, ʼN, A, +, I]")
+        assertPrints(uppercaseTurkish, "[A, 1, ʼN, A, +, İ]")
+    }
+
+    @Sample
+    fun lowercase() {
+        val chars = listOf('A', 'Ω', '1', 'a', '+', 'İ')
+        val lowercaseChar = chars.map { it.lowercaseChar() }
+        val lowercase = chars.map { it.lowercase() }
+        assertPrints(lowercaseChar, "[a, ω, 1, a, +, i]")
+        assertPrints(lowercase, "[a, ω, 1, a, +, \u0069\u0307]")
+    }
+
+    @Sample
+    fun lowercaseLocale() {
+        val chars = listOf('A', 'Ω', '1', 'a', '+', 'İ')
+        val lowercase = chars.map { it.lowercase() }
+        val turkishLocale = Locale.forLanguageTag("tr")
+        val lowercaseTurkish = chars.map { it.lowercase(turkishLocale) }
+        assertPrints(lowercase, "[a, ω, 1, a, +, \u0069\u0307]")
+        assertPrints(lowercaseTurkish, "[a, ω, 1, a, +, i]")
     }
 
     @Sample
@@ -105,10 +129,22 @@ class Chars {
     }
 
     @Sample
-    fun toTitleCase() {
-        val chars = listOf('a', 'Dž', '1', '+')
-        val titleCases = chars.map { it.toTitleCase() }
-        assertPrints(titleCases, "[A, Dž, 1, +]")
+    fun titlecase() {
+        val chars = listOf('a', 'Dž', 'ʼn', '+', 'ß')
+        val titlecaseChar = chars.map { it.titlecaseChar() }
+        val titlecase = chars.map { it.titlecase() }
+        assertPrints(titlecaseChar, "[A, Dž, ʼn, +, ß]")
+        assertPrints(titlecase, "[A, Dž, ʼN, +, Ss]")
+    }
+
+    @Sample
+    fun titlecaseLocale() {
+        val chars = listOf('a', 'Dž', 'ʼn', '+', 'ß', 'i')
+        val titlecase = chars.map { it.titlecase() }
+        val turkishLocale = Locale.forLanguageTag("tr")
+        val titlecaseTurkish = chars.map { it.titlecase(turkishLocale) }
+        assertPrints(titlecase, "[A, Dž, ʼN, +, Ss, I]")
+        assertPrints(titlecaseTurkish, "[A, Dž, ʼN, +, Ss, İ]")
     }
 
     @Sample

libraries/stdlib/samples/test/samples/text/strings.kt

@@ -1,6 +1,7 @@
 package samples.text
 
 import samples.*
+import java.util.Locale
 import kotlin.test.*
 
 class Strings {
@@ -17,6 +18,15 @@ class Strings {
         assertPrints("Abcd".decapitalize(), "abcd")
     }
 
+    @Sample
+    fun replaceFirstChar() {
+        assertPrints("kotlin".replaceFirstChar { it.uppercase() }, "Kotlin")
+
+        val sentence = "Welcome to Kotlin!"
+        val words = sentence.split(' ');
+        assertPrints(words.joinToString(separator = "_") { word -> word.replaceFirstChar { it.lowercase() } }, "welcome_to_kotlin!")
+    }
+
     @Sample
     fun repeat() {
         assertPrints("Word".repeat(4), "WordWordWordWord")
@@ -205,13 +215,27 @@ class Strings {
     }
 
     @Sample
-    fun toLowerCase() {
-        assertPrints("Iced frappé!".toLowerCase(), "iced frappé!")
+    fun lowercase() {
+        assertPrints("Iced frappé!".lowercase(), "iced frappé!")
     }
 
     @Sample
-    fun toUpperCase() {
-        assertPrints("Iced frappé!".toUpperCase(), "ICED FRAPPÉ!")
+    fun lowercaseLocale() {
+        assertPrints("KOTLIN".lowercase(), "kotlin")
+        val turkishLocale = Locale.forLanguageTag("tr")
+        assertPrints("KOTLIN".lowercase(turkishLocale), "kotlın")
+    }
+
+    @Sample
+    fun uppercase() {
+        assertPrints("Iced frappé!".uppercase(), "ICED FRAPPÉ!")
+    }
+
+    @Sample
+    fun uppercaseLocale() {
+        assertPrints("Kotlin".uppercase(), "KOTLIN")
+        val turkishLocale = Locale.forLanguageTag("tr")
+        assertPrints("Kotlin".uppercase(turkishLocale), "KOTLİN")
     }
 
     @Sample