Add removePrefix, removeSuffix, removeEnclosing methods.

Deprecate trimLeading/trimTrailing/trim(String) methods in favor of new ones.

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

@@ -1,10 +1,12 @@
 package kotlin
 
 /** Returns the string with leading and trailing text matching the given string removed */
-public fun String.trim(text: String): String = trimLeading(text).trimTrailing(text)
+deprecated("Use removeEnclosing(text, text) or removePrefix(text).removeSuffix(text)")
+public fun String.trim(text: String): String = removePrefix(text).removeSuffix(text)
 
 /** Returns the string with the prefix and postfix text trimmed */
-public fun String.trim(prefix: String, postfix: String): String = trimLeading(prefix).trimTrailing(postfix)
+deprecated("Use removeEnclosing(prefix, suffix) or removePrefix(prefix).removeSuffix(suffix)")
+public fun String.trim(prefix: String, postfix: String): String = removePrefix(prefix).removeSuffix(postfix)
 
 /**
  * Returns the string with leading and trailing characters matching the [predicate] trimmed.
@@ -72,29 +74,11 @@ public fun String.trimLeading(vararg chars: Char): String = trimLeading { it in
  */
 public fun String.trimTrailing(vararg chars: Char): String = trimTrailing { it in chars }
 
-/**
+deprecated("Use removePrefix() instead")
- * If this string starts with the given [prefix], returns a copy of this string
+public fun String.trimLeading(prefix: String): String = removePrefix(prefix)
- * with the prefix removed. Otherwise, returns this string.
- */
-public fun String.trimLeading(prefix: String): String {
-    var answer = this
-    if (answer.startsWith(prefix)) {
-        answer = answer.substring(prefix.length())
-    }
-    return answer
-}
 
-/**
+deprecated("Use removeSuffix() instead")
- * If this string ends with the given [postfix], returns a copy of this string
+public fun String.trimTrailing(postfix: String): String = removeSuffix(postfix)
- * with the postfix removed. Otherwise, returns this string.
- */
-public fun String.trimTrailing(postfix: String): String {
-    var answer = this
-    if (answer.endsWith(postfix)) {
-        answer = answer.substring(0, length() - postfix.length())
-    }
-    return answer
-}
 
 /**
  * Returns a string with leading and trailing whitespace trimmed.
@@ -356,6 +340,47 @@ public fun String.removeRange(firstIndex: Int, lastIndex: Int): String {
  */
 public fun String.removeRange(range: IntRange): String = removeRange(range.start, range.end + 1)
 
+/**
+ * If this string starts with the given [prefix], returns a copy of this string
+ * with the prefix removed. Otherwise, returns this string.
+ */
+public fun String.removePrefix(prefix: String): String {
+    if (startsWith(prefix)) {
+        return substring(prefix.length())
+    }
+    return this
+}
+
+/**
+ * If this string ends with the given [suffix], returns a copy of this string
+ * with the suffix removed. Otherwise, returns this string.
+ */
+public fun String.removeSuffix(suffix: String): String {
+    if (endsWith(suffix)) {
+        return substring(0, length() - suffix.length())
+    }
+    return this
+}
+
+/**
+ * Removes from a string both the given [prefix] and [suffix] if and only if
+ * it starts with the [prefix] and ends with the [suffix].
+ * Otherwise returns this string unchanged.
+ */
+public fun String.removeEnclosing(prefix: String, suffix: String): String {
+    if (startsWith(prefix) && endsWith(suffix)) {
+        return substring(prefix.length(), length() - suffix.length())
+    }
+    return this
+}
+
+/**
+ * Removes the given [enclosing] string both from the start and the end of this string
+ * if and only if it starts with and ends with the [enclosing].
+ * Otherwise returns this string unchanged.
+ */
+public fun String.removeEnclosing(enclosing: String): String = removeEnclosing(enclosing, enclosing)
+
 /**
  * Replace part of string before the first occurrence of given delimiter with the [replacement] string.
  * If the string does not contain the delimiter, returns [missingDelimiterValue] which defaults to the original string.

libraries/stdlib/test/text/StringTest.kt

@@ -242,4 +242,26 @@ class StringTest {
         }
     }
 
+    test fun removePrefix() {
+        assertEquals("fix", "prefix".removePrefix("pre"), "Removes prefix")
+        assertEquals("prefix", "preprefix".removePrefix("pre"), "Removes prefix once")
+        assertEquals("sample", "sample".removePrefix("value"))
+        assertEquals("sample", "sample".removePrefix(""))
+    }
+
+    test fun removeSuffix() {
+        assertEquals("suf", "suffix".removeSuffix("fix"), "Removes suffix")
+        assertEquals("suffix", "suffixfix".removeSuffix("fix"), "Removes suffix once")
+        assertEquals("sample", "sample".removeSuffix("value"))
+        assertEquals("sample", "sample".removeSuffix(""))
+    }
+
+    test fun removeEnclosing() {
+        assertEquals("value", "<value>".removeEnclosing("<", ">"))
+        assertEquals("<value>", "<<value>>".removeEnclosing("<", ">"), "Removes enclosing once")
+        assertEquals("<value", "<value".removeEnclosing("<", ">"), "Only removes enclosing when both prefix and suffix present")
+        assertEquals("value>", "value>".removeEnclosing("<", ">"), "Only removes enclosing when both prefix and suffix present")
+        assertEquals("value", "value".removeEnclosing("<", ">"))
+    }
+
 }