String.format does not support no locale #KT-22932

libraries/stdlib/jvm/src/kotlin/text/StringsJVM.kt

@@ -15,6 +15,7 @@ import java.nio.charset.Charset
 import java.nio.charset.CodingErrorAction
 import java.util.Locale
 import java.util.regex.Pattern
+import kotlin.internal.LowPriorityInOverloadResolution
 
 
 /**
@@ -288,17 +289,38 @@ public inline fun String.Companion.format(format: String, vararg args: Any?): St
  * Uses this string as a format string and returns a string obtained by substituting the specified arguments,
  * using the specified locale.
  */
+@LowPriorityInOverloadResolution
 @kotlin.internal.InlineOnly
 public inline fun String.format(locale: Locale, vararg args: Any?): String = java.lang.String.format(locale, this, *args)
 
+/**
+ * Uses this string as a format string and returns a string obtained by substituting the specified arguments,
+ * using the specified locale. If [locale] is `null` then no localization is applied.
+ */
+@SinceKotlin("1.4")
+@JvmName("formatNullable")
+@kotlin.internal.InlineOnly
+public inline fun String.format(locale: Locale?, vararg args: Any?): String = java.lang.String.format(locale, this, *args)
+
 /**
  * Uses the provided [format] as a format string and returns a string obtained by substituting the specified arguments,
  * using the specified locale.
  */
+@LowPriorityInOverloadResolution
 @kotlin.internal.InlineOnly
 public inline fun String.Companion.format(locale: Locale, format: String, vararg args: Any?): String =
     java.lang.String.format(locale, format, *args)
 
+/**
+ * Uses the provided [format] as a format string and returns a string obtained by substituting the specified arguments,
+ * using the specified locale. If [locale] is `null` then no localization is applied.
+ */
+@SinceKotlin("1.4")
+@JvmName("formatNullable")
+@kotlin.internal.InlineOnly
+public inline fun String.Companion.format(locale: Locale?, format: String, vararg args: Any?): String =
+    java.lang.String.format(locale, format, *args)
+
 /**
  * Splits this char sequence around matches of the given regular expression.
 

libraries/stdlib/jvm/test/testUtilsJVM.kt

@@ -5,6 +5,7 @@
 
 package test
 
+import java.util.*
 import kotlin.test.assertEquals
 
 public actual fun assertTypeEquals(expected: Any?, actual: Any?) {
@@ -26,4 +27,7 @@ internal actual inline fun testOnNonJvm6And7(f: () -> Unit) {
     }
 }
 public actual fun testOnJvm(action: () -> Unit) = action()
-public actual fun testOnJs(action: () -> Unit) {}
+public actual fun testOnJs(action: () -> Unit) {}
+
+@Suppress("HasPlatformType", "UNCHECKED_CAST")
+public fun <T> platformNull() = Collections.singletonList(null as T).first()

libraries/stdlib/jvm/test/text/StringJVMTest.kt

@@ -6,6 +6,7 @@
 package test.text
 
 import test.collections.assertArrayNotSameButEquals
+import test.platformNull
 import java.util.*
 import kotlin.test.*
 
@@ -41,9 +42,14 @@ class StringJVMTest {
         assertEquals("1,234,567.890", "%,.3f".format(Locale.ENGLISH, 1234567.890))
         assertEquals("1.234.567,890", "%,.3f".format(Locale.GERMAN,  1234567.890))
         assertEquals("1 234 567,890", "%,.3f".format(Locale("fr"),   1234567.890))
+        assertEquals("1,234,567.890", "%,.3f".format(null,           1234567.890))
+        assertEquals("1,234,567.890", "%,.3f".format(platformNull<Locale>(), 1234567.890))
+
         assertEquals("1,234,567.890", String.format(Locale.ENGLISH, "%,.3f", 1234567.890))
         assertEquals("1.234.567,890", String.format(Locale.GERMAN,  "%,.3f", 1234567.890))
         assertEquals("1 234 567,890", String.format(Locale("fr"),   "%,.3f", 1234567.890))
+        assertEquals("1,234,567.890", String.format(null,           "%,.3f", 1234567.890))
+        assertEquals("1,234,567.890", String.format(platformNull<Locale>(), "%,.3f", 1234567.890))
     }
 
     @Test fun toByteArrayEncodings() {