[SPARK-14426][SQL] Merge PerserUtils and ParseUtils

## What changes were proposed in this pull request?

We have ParserUtils and ParseUtils which are both utility collections for use during the parsing process.
Those names and what they are used for is very similar so I think we can merge them.

Also, the original unescapeSQLString method may have a fault. When "\u0061" style character literals are passed to the method, it's not unescaped successfully.
This patch fix the bug.

## How was this patch tested?

Added a new test case.

Author: Kousuke Saruta <sarutak@oss.nttdata.co.jp>

Closes apache#12199 from sarutak/merge-ParseUtils-and-ParserUtils.

scalastyle-config.xml

@@ -116,7 +116,7 @@ This file is divided into 3 sections:
 
   <check level="error" class="org.scalastyle.file.NewLineAtEofChecker" enabled="true"></check>
 
-  <check level="error" class="org.scalastyle.scalariform.NonASCIICharacterChecker" enabled="true"></check>
+  <check customId="nonascii" level="error" class="org.scalastyle.scalariform.NonASCIICharacterChecker" enabled="true"></check>
 
   <check level="error" class="org.scalastyle.scalariform.SpaceAfterCommentStartChecker" enabled="true"></check>
 

sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/parser/ParserUtils.scala

@@ -16,11 +16,12 @@
  */
 package org.apache.spark.sql.catalyst.parser
 
+import scala.collection.mutable.StringBuilder
+
 import org.antlr.v4.runtime.{CharStream, ParserRuleContext, Token}
 import org.antlr.v4.runtime.misc.Interval
 import org.antlr.v4.runtime.tree.TerminalNode
 
-import org.apache.spark.sql.catalyst.parser.ParseUtils.unescapeSQLString
 import org.apache.spark.sql.catalyst.plans.logical.LogicalPlan
 import org.apache.spark.sql.catalyst.trees.{CurrentOrigin, Origin}
 
@@ -87,6 +88,81 @@ object ParserUtils {
     }
   }
 
+  /** Unescape baskslash-escaped string enclosed by quotes. */
+  def unescapeSQLString(b: String): String = {
+    var enclosure: Character = null
+    val sb = new StringBuilder(b.length())
+
+    def appendEscapedChar(n: Char) {
+      n match {
+        case '0' => sb.append('\u0000')
+        case '\'' => sb.append('\'')
+        case '"' => sb.append('\"')
+        case 'b' => sb.append('\b')
+        case 'n' => sb.append('\n')
+        case 'r' => sb.append('\r')
+        case 't' => sb.append('\t')
+        case 'Z' => sb.append('\u001A')
+        case '\\' => sb.append('\\')
+        // The following 2 lines are exactly what MySQL does TODO: why do we do this?
+        case '%' => sb.append("\\%")
+        case '_' => sb.append("\\_")
+        case _ => sb.append(n)
+      }
+    }
+
+    var i = 0
+    val strLength = b.length
+    while (i < strLength) {
+      val currentChar = b.charAt(i)
+      if (enclosure == null) {
+        if (currentChar == '\'' || currentChar == '\"') {
+          enclosure = currentChar
+        }
+      } else if (enclosure == currentChar) {
+        enclosure = null
+      } else if (currentChar == '\\') {
+
+        if ((i + 6 < strLength) && b.charAt(i + 1) == 'u') {
+          // \u0000 style character literals.
+
+          val base = i + 2
+          val code = (0 until 4).foldLeft(0) { (mid, j) =>
+            val digit = Character.digit(b.charAt(j + base), 16)
+            (mid << 4) + digit
+          }
+          sb.append(code.asInstanceOf[Char])
+          i += 5
+        } else if (i + 4 < strLength) {
+          // \000 style character literals.
+
+          val i1 = b.charAt(i + 1)
+          val i2 = b.charAt(i + 2)
+          val i3 = b.charAt(i + 3)
+
+          if ((i1 >= '0' && i1 <= '1') && (i2 >= '0' && i2 <= '7') && (i3 >= '0' && i3 <= '7')) {
+            val tmp = ((i3 - '0') + ((i2 - '0') << 3) + ((i1 - '0') << 6)).asInstanceOf[Char]
+            sb.append(tmp)
+            i += 3
+          } else {
+            appendEscapedChar(i1)
+            i += 1
+          }
+        } else if (i + 2 < strLength) {
+          // escaped character literals.
+          val n = b.charAt(i + 1)
+          appendEscapedChar(n)
+          i += 1
+        }
+      } else {
+        // non-escaped character literals.
+        sb.append(currentChar)
+      }
+      i += 1
+    }
+    sb.toString()
+  }
+
   /** Some syntactic sugar which makes it easier to work with optional clauses for LogicalPlans. */
   implicit class EnhancedLogicalPlan(val plan: LogicalPlan) extends AnyVal {
     /**

sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/parser/ExpressionParserSuite.scala

@@ -415,7 +415,7 @@ class ExpressionParserSuite extends PlanTest {
     assertEqual("'\\110\\145\\154\\154\\157\\041'", "Hello!")
 
     // Unicode
-    assertEqual("'\\u0087\\u0111\\u0114\\u0108\\u0100\\u0032\\u0058\\u0041'", "World :)")
+    assertEqual("'\\u0057\\u006F\\u0072\\u006C\\u0064\\u0020\\u003A\\u0029'", "World :)")
   }
 
   test("intervals") {

sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/parser/ParserUtilsSuite.scala

@@ -0,0 +1,65 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.spark.sql.catalyst.parser
+
+import org.apache.spark.SparkFunSuite
+
+class ParserUtilsSuite extends SparkFunSuite {
+
+  import ParserUtils._
+
+  test("unescapeSQLString") {
+    // scalastyle:off nonascii
+
+    // String not including escaped characters and enclosed by double quotes.
+    assert(unescapeSQLString(""""abcdefg"""") == "abcdefg")
+
+    // String enclosed by single quotes.
+    assert(unescapeSQLString("""'C0FFEE'""") == "C0FFEE")
+
+    // Strings including single escaped characters.
+    assert(unescapeSQLString("""'\0'""") == "\u0000")
+    assert(unescapeSQLString(""""\'"""") == "\'")
+    assert(unescapeSQLString("""'\"'""") == "\"")
+    assert(unescapeSQLString(""""\b"""") == "\b")
+    assert(unescapeSQLString("""'\n'""") == "\n")
+    assert(unescapeSQLString(""""\r"""") == "\r")
+    assert(unescapeSQLString("""'\t'""") == "\t")
+    assert(unescapeSQLString(""""\Z"""") == "\u001A")
+    assert(unescapeSQLString("""'\\'""") == "\\")
+    assert(unescapeSQLString(""""\%"""") == "\\%")
+    assert(unescapeSQLString("""'\_'""") == "\\_")
+
+    // String including '\000' style literal characters.
+    assert(unescapeSQLString("""'3 + 5 = \070'""") == "3 + 5 = \u0038")
+    assert(unescapeSQLString(""""\000"""") == "\u0000")
+
+    // String including invalid '\000' style literal characters.
+    assert(unescapeSQLString(""""\256"""") == "256")
+
+    // String including a '\u0000' style literal characters (\u732B is a cat in Kanji).
+    assert(unescapeSQLString(""""How cute \u732B are"""")  == "How cute \u732B are")
+
+    // String including a surrogate pair character
+    // (\uD867\uDE3D is Okhotsk atka mackerel in Kanji).
+    assert(unescapeSQLString(""""\uD867\uDE3D is a fish"""") == "\uD867\uDE3D is a fish")
+
+    // scalastyle:on nonascii
+  }
+
+  // TODO: Add test cases for other methods in ParserUtils
+}