Introduce Common readln() and readlnOrNull() top-level functions #KT-48456

libraries/stdlib/api/js-v1/kotlin.io.kt

@@ -2,4 +2,10 @@ public fun print(message: kotlin.Any?): kotlin.Unit
 
 public fun println(): kotlin.Unit
 
-public fun println(message: kotlin.Any?): kotlin.Unit
+public fun println(message: kotlin.Any?): kotlin.Unit
+
+@kotlin.SinceKotlin(version = "1.6")
+public fun readln(): kotlin.String
+
+@kotlin.SinceKotlin(version = "1.6")
+public fun readlnOrNull(): kotlin.String?

libraries/stdlib/api/js/kotlin.io.kt

@@ -2,4 +2,10 @@ public fun print(message: kotlin.Any?): kotlin.Unit
 
 public fun println(): kotlin.Unit
 
-public fun println(message: kotlin.Any?): kotlin.Unit
+public fun println(message: kotlin.Any?): kotlin.Unit
+
+@kotlin.SinceKotlin(version = "1.6")
+public fun readln(): kotlin.String
+
+@kotlin.SinceKotlin(version = "1.6")
+public fun readlnOrNull(): kotlin.String?

libraries/stdlib/common/src/kotlin/ioH.kt

@@ -15,5 +15,29 @@ public expect fun println(message: Any?)
 /** Prints the given [message] to the standard output stream. */
 public expect fun print(message: Any?)
 
+/**
+ * Reads a line of input from the standard input stream and returns it,
+ * or throws a [RuntimeException] if EOF has already been reached when [readln] is called.
+ *
+ * LF or CRLF is treated as the line terminator. Line terminator is not included in the returned string.
+ *
+ * Currently this function is not supported in Kotlin/JS and throws [UnsupportedOperationException].
+ */
+@SinceKotlin("1.6")
+public expect fun readln(): String
+
+/**
+ * Reads a line of input from the standard input stream and returns it,
+ * or return `null` if EOF has already been reached when [readlnOrNull] is called.
+ *
+ * LF or CRLF is treated as the line terminator. Line terminator is not included in the returned string.
+ *
+ * Currently this function is not supported in Kotlin/JS and throws [UnsupportedOperationException].
+ */
+@SinceKotlin("1.6")
+public expect fun readlnOrNull(): String?
+
+internal class ReadAfterEOFException(message: String?) : RuntimeException(message)
+
 
 internal expect interface Serializable

libraries/stdlib/js/src/kotlin/console.kt

@@ -104,3 +104,9 @@ public actual fun println(message: Any?) {
 public actual fun print(message: Any?) {
     output.print(message)
 }
+
+@SinceKotlin("1.6")
+public actual fun readln(): String = throw UnsupportedOperationException("readln is not supported in Kotlin/JS")
+
+@SinceKotlin("1.6")
+public actual fun readlnOrNull(): String? = throw UnsupportedOperationException("readlnOrNull is not supported in Kotlin/JS")

libraries/stdlib/jvm/src/kotlin/io/Console.kt

@@ -149,7 +149,7 @@ public actual inline fun println() {
  * The input is decoded using the system default Charset. A [CharacterCodingException] is thrown if input is malformed.
  */
 @SinceKotlin("1.6")
-public fun readln(): String = readlnOrNull() ?: throw ReadAfterEOFException("EOF has already been reached")
+public actual fun readln(): String = readlnOrNull() ?: throw ReadAfterEOFException("EOF has already been reached")
 
 /**
  * Reads a line of input from the standard input stream and returns it,
@@ -160,9 +160,7 @@ public fun readln(): String = readlnOrNull() ?: throw ReadAfterEOFException("EOF
  * The input is decoded using the system default Charset. A [CharacterCodingException] is thrown if input is malformed.
  */
 @SinceKotlin("1.6")
-public fun readlnOrNull(): String? = readLine()
-
-private class ReadAfterEOFException(message: String?) : RuntimeException(message)
+public actual fun readlnOrNull(): String? = readLine()
 
 /**
  * Reads a line of input from the standard input stream.

libraries/stdlib/jvm/test/io/Console.kt

@@ -48,6 +48,20 @@ class ConsoleTest {
         testReadLine("first${linuxLineSeparator}second", listOf("first", "second"))
     }
 
+    @Test
+    fun shouldReadMultipleEmptyLines() {
+        testReadLine(
+            "first${linuxLineSeparator}second${linuxLineSeparator}${linuxLineSeparator}${linuxLineSeparator}",
+            listOf("first", "second", "", "")
+        )
+    }
+
+    @Test
+    fun shouldReadAloneCarriageReturn() {
+        val result = readLines("\r", Charsets.UTF_8)
+        assertEquals(listOf("\r"), result)
+    }
+
     @Test
     fun shouldReadConsecutiveEmptyLines() {
         testReadLine("$linuxLineSeparator$linuxLineSeparator", listOf("", ""))

libraries/stdlib/wasm/src/kotlin/io.kt

@@ -23,6 +23,12 @@ public actual fun print(message: Any?) {
     println(message)
 }
 
+@SinceKotlin("1.6")
+public actual fun readln(): String = TODO("Wasm stdlib: IO")
+
+@SinceKotlin("1.6")
+public actual fun readlnOrNull(): String? = TODO("Wasm stdlib: IO")
+
 
 internal actual interface Serializable