[stdlib] Improve documentation of Char.isWhitespace and test it behaves the same in different targets

libraries/stdlib/js/src/kotlin/text/charJs.kt

@@ -247,7 +247,12 @@ public actual fun Char.isISOControl(): Boolean {
 }
 
 /**
- * Determines whether a character is whitespace according to the Unicode standard.
+ * Determines whether a character is whitespace.
+ *
+ * A character is considered whitespace if either its Unicode [category][Char.category]
+ * is one of [CharCategory.SPACE_SEPARATOR], [CharCategory.LINE_SEPARATOR], [CharCategory.PARAGRAPH_SEPARATOR],
+ * or it is a [CharCategory.CONTROL] character in range `U+0009..U+000D` or `U+001C..U+001F`.
+ *
  * Returns `true` if the character is whitespace.
  *
  * @sample samples.text.Chars.isWhitespace

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

@@ -90,7 +90,12 @@ public inline fun Char.isJavaIdentifierPart(): Boolean = Character.isJavaIdentif
 public inline fun Char.isJavaIdentifierStart(): Boolean = Character.isJavaIdentifierStart(this)
 
 /**
- * Determines whether a character is whitespace according to the Unicode standard.
+ * Determines whether a character is whitespace.
+ *
+ * A character is considered whitespace if either its Unicode [category][Char.category]
+ * is one of [CharCategory.SPACE_SEPARATOR], [CharCategory.LINE_SEPARATOR], [CharCategory.PARAGRAPH_SEPARATOR],
+ * or it is a [CharCategory.CONTROL] character in range `U+0009..U+000D` or `U+001C..U+001F`.
+ *
  * Returns `true` if the character is whitespace.
  *
  * @sample samples.text.Chars.isWhitespace

libraries/stdlib/native-wasm/src/kotlin/text/Char.kt

@@ -74,7 +74,12 @@ public actual fun Char.isDigit(): Boolean {
 }
 
 /**
- * Determines whether a character is whitespace according to the Unicode standard.
+ * Determines whether a character is whitespace.
+ *
+ * A character is considered whitespace if either its Unicode [category][Char.category]
+ * is one of [CharCategory.SPACE_SEPARATOR], [CharCategory.LINE_SEPARATOR], [CharCategory.PARAGRAPH_SEPARATOR],
+ * or it is a [CharCategory.CONTROL] character in range `U+0009..U+000D` or `U+001C..U+001F`.
+ *
  * Returns `true` if the character is whitespace.
  *
  * @sample samples.text.Chars.isWhitespace

libraries/stdlib/src/kotlin/text/Char.kt

@@ -335,7 +335,12 @@ public expect fun Char.isTitleCase(): Boolean
 public expect fun Char.isISOControl(): Boolean
 
 /**
- * Determines whether a character is whitespace according to the Unicode standard.
+ * Determines whether a character is whitespace.
+ *
+ * A character is considered whitespace if either its Unicode [category][Char.category]
+ * is one of [CharCategory.SPACE_SEPARATOR], [CharCategory.LINE_SEPARATOR], [CharCategory.PARAGRAPH_SEPARATOR],
+ * or it is a [CharCategory.CONTROL] character in range `U+0009..U+000D` or `U+001C..U+001F`.
+ *
  * Returns `true` if the character is whitespace.
  *
  * @sample samples.text.Chars.isWhitespace

libraries/stdlib/src/kotlin/text/Strings.kt

@@ -304,7 +304,7 @@ public inline fun CharSequence.isEmpty(): Boolean = length == 0
 public inline fun CharSequence.isNotEmpty(): Boolean = length > 0
 
 /**
- * Returns `true` if this char sequence is empty or consists solely of whitespace characters.
+ * Returns `true` if this char sequence is empty or consists solely of whitespace characters according to [Char.isWhitespace].
  *
  * @sample samples.text.Strings.stringIsBlank
  */

libraries/stdlib/test/text/CharTest.kt

@@ -17,6 +17,8 @@ class CharTest {
             "Κκϰ", "Ππϖ", "Ρρϱ", "Σςσ", "Φφϕ", "ΩωΩ", "Ṡṡẛ",
             "Θθϑϴ", "Iiİı",
         )
+
+       val allCharsByCategory = (Char.MIN_VALUE..Char.MAX_VALUE).groupBy { it.category }
     }
 
     @Test
@@ -326,6 +328,17 @@ class CharTest {
         assertEquals("Cc", CharCategory.CONTROL.code)
     }
 
+    @Test
+    fun whitespace() {
+        val allWhitespace = (Char.MIN_VALUE..Char.MAX_VALUE).filter { it.isWhitespace() }
+        val expected =
+            listOf(CharCategory.SPACE_SEPARATOR, CharCategory.LINE_SEPARATOR, CharCategory.PARAGRAPH_SEPARATOR)
+                .flatMap { allCharsByCategory[it]!! } +
+                    ('\u0009'..'\u000D') +
+                    ('\u001C'..'\u001F')
+        assertEquals(expected.sorted(), allWhitespace)
+    }
+
     @Test
     fun lowercaseChar() {
         assertEquals('\u0000', '\u0000'.lowercaseChar())