Find correct next match after matchAt and matchEntire KT-47676

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

@@ -58,6 +58,15 @@ public actual class Regex actual constructor(pattern: String, options: Set<Regex
     private fun initStickyPattern(): RegExp =
         nativeStickyPattern ?: RegExp(pattern, options.toFlags("yu")).also { nativeStickyPattern = it }
 
+    private var nativeMatchesEntirePattern: RegExp? = null
+    private fun initMatchesEntirePattern(): RegExp =
+        nativeMatchesEntirePattern ?: run {
+            if (pattern.startsWith('^') && pattern.endsWith('$'))
+                nativePattern
+            else
+                return RegExp("^${pattern.trimStart('^').trimEnd('$')}$", options.toFlags("gu"))
+        }.also { nativeMatchesEntirePattern = it }
+
 
     /** Indicates whether the regular expression matches the entire [input]. */
     public actual infix fun matches(input: CharSequence): Boolean {
@@ -96,7 +105,7 @@ public actual class Regex actual constructor(pattern: String, options: Set<Regex
         if (startIndex < 0 || startIndex > input.length) {
             throw IndexOutOfBoundsException("Start index out of bounds: $startIndex, input length: ${input.length}")
         }
-        return nativePattern.findNext(input.toString(), startIndex)
+        return nativePattern.findNext(input.toString(), startIndex, nativePattern)
     }
 
     /**
@@ -119,12 +128,8 @@ public actual class Regex actual constructor(pattern: String, options: Set<Regex
      *
      * @return An instance of [MatchResult] if the entire input matches or `null` otherwise.
      */
-    public actual fun matchEntire(input: CharSequence): MatchResult? {
-        if (pattern.startsWith('^') && pattern.endsWith('$'))
-            return find(input)
-        else
-            return Regex("^${pattern.trimStart('^').trimEnd('$')}$", options).find(input)
-    }
+    public actual fun matchEntire(input: CharSequence): MatchResult? =
+        initMatchesEntirePattern().findNext(input.toString(), 0, nativePattern)
 
     @SinceKotlin("1.5")
     @ExperimentalStdlibApi
@@ -132,7 +137,7 @@ public actual class Regex actual constructor(pattern: String, options: Set<Regex
         if (index < 0 || index > input.length) {
             throw IndexOutOfBoundsException("index out of bounds: $index, input length: ${input.length}")
         }
-        return initStickyPattern().findNext(input.toString(), index)
+        return initStickyPattern().findNext(input.toString(), index, nativePattern)
     }
 
 
@@ -247,7 +252,7 @@ public fun Regex_1(pattern: String): Regex = Regex(pattern, emptySet())
 
 
 
-private fun RegExp.findNext(input: String, from: Int): MatchResult? {
+private fun RegExp.findNext(input: String, from: Int, nextPattern: RegExp): MatchResult? {
     this.lastIndex = from
     val match = exec(input)
     if (match == null) return null
@@ -278,6 +283,7 @@ private fun RegExp.findNext(input: String, from: Int): MatchResult? {
                 return groupValues_!!
             }
 
-        override fun next(): MatchResult? = this@findNext.findNext(input, if (range.isEmpty()) range.start + 1 else range.endInclusive + 1)
+        override fun next(): MatchResult? =
+            nextPattern.findNext(input, if (range.isEmpty()) range.start + 1 else range.endInclusive + 1, nextPattern)
     }
 }

libraries/stdlib/test/text/RegexTest.kt

@@ -168,6 +168,7 @@ class RegexTest {
             assertEquals("3c", m.value)
             assertEquals(3, m.groups.size)
             assertEquals(listOf("3c", "3", "c"), m.groups.map { it!!.value })
+            assertNull(m.next())
         }
     }
 
@@ -179,6 +180,17 @@ class RegexTest {
         assertEquals("aaaabbbb", regex.matchEntire(input)!!.value)
     }
 
+    @Test fun matchEntireNext() {
+        val regex = ".*".toRegex()
+        val input = "abc"
+        val match = regex.matchEntire(input)!!
+        assertEquals(input, match.value)
+        val next = assertNotNull(match.next())
+        assertEquals("", next.value)
+        assertEquals(input.length until input.length, next.range)
+        assertNull(next.next())
+    }
+
     @Test fun matchAt() {
         val regex = Regex("[a-z][1-5]", RegexOption.IGNORE_CASE)
         val input = "...a4...B1"
@@ -196,6 +208,11 @@ class RegexTest {
             assertEquals(input.substring(match.range), match.value)
         }
 
+        matches.zipWithNext { (_, m1), (_, m2) ->
+            assertEquals(m2.range, assertNotNull(m1.next()).range)
+        }
+        assertNull(matches.last().second.next())
+
         for (index in listOf(-1, input.length + 1)) {
             assertFailsWith<IndexOutOfBoundsException> { regex.matchAt(input, index) }
             assertFailsWith<IndexOutOfBoundsException> { regex.matchesAt(input, index) }