Patterns such (3?)+ should now fall back to CPU

sql-plugin/src/main/scala/com/nvidia/spark/rapids/RegexParser.scala

@@ -467,6 +467,42 @@ class CudfRegexTranspiler(mode: RegexMode) {
     cudfRegex.toRegexString
   }
 
+  private def isSomeRepetition(f: ListBuffer[RegexAST] => Boolean)(e: RegexAST): Boolean = {
+    e match {
+      case RegexRepetition(_, _) => true
+      case RegexGroup(_, term) => isRepetition(term)
+      case RegexSequence(parts) if f(parts) => isRepetition(parts.last)
+      case _ => false
+    }
+  }
+
+  private def isRepetition = isSomeRepetition(_.nonEmpty)(_)
+  private def isNestedRepetition = isSomeRepetition(_.length == 1)(_)
+
+  private def isSupportedRepetitionBase(e: RegexAST): Boolean = {
+    e match {
+      case RegexEscaped(ch) if ch != 'd' && ch != 'w' => // example: "\B?"
+        false
+
+      case RegexChar(a) if "$^".contains(a) =>
+        // example: "$*"
+        false
+
+      case RegexRepetition(_, _) =>
+        // example: "a*+"
+        false
+
+      case RegexSequence(parts) =>
+        parts.forall(x => isSupportedRepetitionBase(x))
+
+      case RegexGroup(_, term) =>
+        isSupportedRepetitionBase(term)
+
+      case _ => true
+    }
+  }
+
+
   private def rewrite(regex: RegexAST): RegexAST = {
     regex match {
 
@@ -628,20 +664,29 @@ class CudfRegexTranspiler(mode: RegexMode) {
           throw new RegexUnsupportedException(
             "regexp_replace on GPU does not support repetition with ? or *")
 
-        case (RegexEscaped(ch), _) if ch != 'd' && ch != 'w' =>
-          // example: "\B?"
-          throw new RegexUnsupportedException(nothingToRepeat)
+        case (_, QuantifierVariableLength(0,None)) if mode == RegexReplaceMode =>
+          // see https://github.com/NVIDIA/spark-rapids/issues/4468
+          throw new RegexUnsupportedException(
+            "regexp_replace on GPU does not support repetition with {0,}")
 
-        case (RegexChar(a), _) if "$^".contains(a) =>
-          // example: "$*"
-          throw new RegexUnsupportedException(nothingToRepeat)
+        case (_, QuantifierFixedLength(0)) | (_, QuantifierVariableLength(0,Some(0)))
+          if mode != RegexFindMode =>
+          throw new RegexUnsupportedException(
+            "regex_replace and regex_split on GPU do not support repetition with {0} or {0,0}")
 
-        case (RegexRepetition(_, _), _) =>
-          // example: "a*+"
+        case (RegexGroup(_, term), SimpleQuantifier(ch))
+            if "+*".contains(ch) && !isSupportedRepetitionBase(term) =>
           throw new RegexUnsupportedException(nothingToRepeat)
-
-        case _ =>
+        case (RegexGroup(_, term), QuantifierVariableLength(_,None))
+            if !isSupportedRepetitionBase(term) =>
+            // specifically this variable length repetition: \A{2,}
+          throw new RegexUnsupportedException(nothingToRepeat)
+        case (RegexGroup(_, _), SimpleQuantifier(ch)) if ch == '?' =>
           RegexRepetition(rewrite(base), quantifier)
+        case _ if isSupportedRepetitionBase(base) =>
+          RegexRepetition(rewrite(base), quantifier)
+        case _ =>
+          throw new RegexUnsupportedException(nothingToRepeat)
 
       }
 
@@ -650,14 +695,6 @@ class CudfRegexTranspiler(mode: RegexMode) {
         val rr = rewrite(r)
 
         // cuDF does not support repetition on one side of a choice, such as "a*|a"
-        def isRepetition(e: RegexAST): Boolean = {
-          e match {
-            case RegexRepetition(_, _) => true
-            case RegexGroup(_, term) => isRepetition(term)
-            case RegexSequence(parts) if parts.nonEmpty => isRepetition(parts.last)
-            case _ => false
-          }
-        }
         if (isRepetition(ll) || isRepetition(rr)) {
           throw new RegexUnsupportedException(nothingToRepeat)
         }
@@ -667,8 +704,9 @@ class CudfRegexTranspiler(mode: RegexMode) {
         def endsWithLineAnchor(e: RegexAST): Boolean = {
           e match {
             case RegexSequence(parts) if parts.nonEmpty =>
-              isBeginOrEndLineAnchor(parts.last)
-            case _ => false
+              endsWithLineAnchor(parts.last)
+            case RegexEscaped('A') => true
+            case _ => isBeginOrEndLineAnchor(e)
           }
         }
         if (endsWithLineAnchor(ll) || endsWithLineAnchor(rr)) {

tests/src/test/scala/com/nvidia/spark/rapids/RegularExpressionParserSuite.scala

@@ -140,6 +140,21 @@ class RegularExpressionParserSuite extends FunSuite {
       RegexSequence(ListBuffer(RegexOctalChar("047"), RegexChar('7'))))
   }
 
+  test("repetition with group containing simple repetition") {
+    assert(parse("(3?)+") ===
+      RegexSequence(ListBuffer(RegexRepetition(RegexGroup(capture = true, 
+          RegexSequence(ListBuffer(RegexRepetition(RegexChar('3'), 
+          SimpleQuantifier('?'))))),SimpleQuantifier('+')))))
+  }
+
+  test("repetition with group containing escape character") {
+    assert(parse(raw"(\A)+") ===
+      RegexSequence(ListBuffer(RegexRepetition(RegexGroup(capture = true,
+          RegexSequence(ListBuffer(RegexEscaped('A')))),
+          SimpleQuantifier('+'))))
+    )
+  }
+
   test("group containing choice with repetition") {
     assert(parse("(\t+|a)") == RegexSequence(ListBuffer(
       RegexGroup(capture = true, RegexChoice(RegexSequence(ListBuffer(

tests/src/test/scala/com/nvidia/spark/rapids/RegularExpressionTranspilerSuite.scala

@@ -15,6 +15,7 @@
  */
 package com.nvidia.spark.rapids
 
+
 import java.util.regex.Pattern
 
 import scala.collection.mutable.{HashSet, ListBuffer}
@@ -42,7 +43,8 @@ class RegularExpressionTranspilerSuite extends FunSuite with Arm {
       "a^|b",
       "w$|b",
       "\n[^\r\n]x*|^3x",
-      "]*\\wWW$|zb"
+      "]*\\wWW$|zb",
+      "(\\A|\\05)?"
     )
     // data is not relevant because we are checking for compilation errors
     val inputs = Seq("a")
@@ -119,6 +121,13 @@ class RegularExpressionTranspilerSuite extends FunSuite with Arm {
     )
   }
 
+  test("cuDF does not support single repetition both inside and outside of capture groups") {
+    // see https://github.com/NVIDIA/spark-rapids/issues/4487
+    val patterns = Seq("(3?)+", "(3?)*", "(3*)+", "((3?))+")
+    patterns.foreach(pattern => 
+      assertUnsupported(pattern, RegexFindMode, "nothing to repeat"))
+  }
+
   test("cuDF does not support OR at BOL / EOL") {
     val patterns = Seq("$|a", "^|a")
     patterns.foreach(pattern => {
@@ -171,6 +180,13 @@ class RegularExpressionTranspilerSuite extends FunSuite with Arm {
       "\ntest", "test\n", "\ntest\n"))
   }
 
+  test("string anchor \\A will fall back to CPU in some repetitions") {
+    val patterns = Seq(raw"(\A)+", raw"(\A)*", raw"(\A){2,}")
+    patterns.foreach(pattern =>
+      assertUnsupported(pattern, RegexFindMode, "nothing to repeat")
+    )
+  }
+
   test("string anchor \\Z fall back to CPU") {
     for (mode <- Seq(RegexFindMode, RegexReplaceMode)) {
       assertUnsupported("\\Z", mode, "string anchor \\Z is not supported")
@@ -294,6 +310,40 @@ class RegularExpressionTranspilerSuite extends FunSuite with Arm {
     assertCpuGpuMatchesRegexpReplace(patterns, inputs)
   }
 
+  test("regexp_replace - character class repetition - ? and * - fall back to CPU") {
+    val patterns = Seq(raw"[1a-zA-Z]?", raw"[1a-zA-Z]*")
+    patterns.foreach(pattern =>
+      assertUnsupported(pattern, RegexReplaceMode,
+        "regexp_replace on GPU does not support repetition with ? or *"
+      )
+    )
+  }
+
+  test("regexp_replace - character class repetition - {0,} - fall back to CPU") {
+    val patterns = Seq(raw"[1a-zA-Z]{0,}")
+    patterns.foreach(pattern =>
+      assertUnsupported(pattern, RegexReplaceMode,
+        "regexp_replace on GPU does not support repetition with {0,}"
+      )
+    )
+  }
+
+  test("regexp_replace - fall back to CPU for {0} or {0,0}") {
+    val patterns = Seq("a{0}", raw"\02{0}", "a{0,0}", raw"\02{0,0}")
+    patterns.foreach(pattern =>
+      assertUnsupported(pattern, RegexReplaceMode, 
+        "regex_replace and regex_split on GPU do not support repetition with {0} or {0,0}")
+    )
+  }
+
+  test("regexp_split - fall back to CPU for {0} or {0,0}") {
+    val patterns = Seq("a{0}", raw"\02{0}", "a{0,0}", raw"\02{0,0}")
+    patterns.foreach(pattern =>
+      assertUnsupported(pattern, RegexSplitMode,
+        "regex_replace and regex_split on GPU do not support repetition with {0} or {0,0}")
+    )
+  }
+
   test("compare CPU and GPU: regexp find fuzz test with limited chars") {
     // testing with this limited set of characters finds issues much
     // faster than using the full ASCII set