Reimplement check for non-regexp strings using RegexParser

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

@@ -492,11 +492,6 @@ object GpuOverrides extends Logging {
     listeners.clear()
   }
 
-  def canRegexpBeTreatedLikeARegularString(strLit: UTF8String): Boolean = {
-    val s = strLit.toString
-    !regexList.exists(pattern => s.contains(pattern))
-  }
-
   private def convertPartToGpuIfPossible(part: Partitioning, conf: RapidsConf): Partitioning = {
     part match {
       case _: GpuPartitioning => part

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

@@ -404,6 +404,32 @@ class RegexParser(pattern: String) {
 
 }
 
+object RegexParser {
+  private val regexpChars = Seq('\u0000', '\\', '.', '^', '$', '\f')
+  private val regexpEscapedChars = Seq('\\', 'b', 'B', 's', 'S', 'w', 'W', 'd', 'D', 'Q', 'E',
+    'h', 'H', 'v', 'V', 'A', 'a', 'z', 'Z', 'x', 'e', 'c', 'p', 'G', 'R', 'k')
+
+  def isRegExpString(s: String): Boolean = {
+
+    def isRegExpString(ast: RegexAST): Boolean = ast match {
+      case RegexChar(ch) => regexpChars.contains(ch)
+      case RegexEscaped(ch) => regexpEscapedChars.contains(ch)
+      case RegexSequence(parts) => parts.exists(isRegExpString)
+      case _ => true
+    }
+
+    try {
+      val parser = new RegexParser(s)
+      val ast = parser.parse()
+      isRegExpString(ast)
+    } catch {
+      case _: RegexUnsupportedException =>
+        // if we cannot parse it then assume that it might be valid regexp
+        true
+    }
+  }
+}
+
 /**
  * Transpile Java/Spark regular expression to a format that cuDF supports, or throw an exception
  * if this is not possible.

sql-plugin/src/main/scala/org/apache/spark/sql/rapids/stringFunctions.scala

@@ -1296,7 +1296,7 @@ class GpuStringSplitMeta(
     } else {
       val str = regexp.get.value.asInstanceOf[UTF8String]
       if (str != null) {
-        if (!canRegexpBeTreatedLikeARegularString(str)) {
+        if (RegexParser.isRegExpString(str.toString)) {
           willNotWorkOnGpu("regular expressions are not supported yet")
         }
         if (str.numChars() == 0) {

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

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2021, NVIDIA CORPORATION.
+ * Copyright (c) 2021-2022, NVIDIA CORPORATION.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -21,6 +21,24 @@ import org.scalatest.FunSuite
 
 class RegularExpressionParserSuite extends FunSuite {
 
+  test("detect regexp strings") {
+    // Based on https://docs.oracle.com/javase/8/docs/api/java/util/regex/Pattern.html
+    val strings: Seq[String] = Seq("\\", "\u0000", "\\x00",
+      "\f", "\\a", "\\e", "\\cx", "[abc]", "^", "[a-z&&[def]]", ".", "*", "\\d", "\\D",
+      "\\h", "\\H", "\\s", "\\S", "\\v", "\\V", "\\w", "\\w", "\\p", "$", "\\b", "\\B",
+      "\\A", "\\G", "\\Z", "\\z", "\\R", "?", "|", "(abc)", "a{1,}", "\\k", "\\Q", "\\E")
+    for (string <- strings) {
+      assert(RegexParser.isRegExpString(string))
+    }
+  }
+
+  test("detect non-regexp strings") {
+    val strings = Seq("\\.", "A", ",", "\t")
+    for (string <- strings) {
+      assert(!RegexParser.isRegExpString(string))
+    }
+  }
+
   test("empty pattern") {
     assert(parse("") === RegexSequence(ListBuffer()))
   }