#837 Fix "PIC SVPP9(5) COMP-3" when the scale factor is negative

cobol-parser/src/main/scala/za/co/absa/cobrix/cobol/parser/decoders/BCDNumberDecoders.scala

@@ -92,10 +92,14 @@ object BCDNumberDecoders {
 
     var sign = ""
 
+    // Since when scaleFactor < 0 an additional zero is always added as '0.' we need to scale the original
+    // value left by 1 digit (Fixes: https://github.com/AbsaOSS/cobrix/issues/837)
+    val scaleDotPosition = if (scaleFactor < 0 && scale > 0) scale - 1 else scale
+
     val intendedDecimalPosition = if (mandatorySignNibble)
-      bytes.length * 2 - (scale + 1)
+      bytes.length * 2 - (scaleDotPosition + 1)
     else
-      bytes.length * 2 - scale
+      bytes.length * 2 - scaleDotPosition
 
     val additionalZeros = if (intendedDecimalPosition <= 0) {
       -intendedDecimalPosition + 1

cobol-parser/src/test/scala/za/co/absa/cobrix/cobol/parser/copybooks/ParseCopybookFeaturesSpec.scala

@@ -19,7 +19,8 @@ package za.co.absa.cobrix.cobol.parser.copybooks
 import org.scalatest.funsuite.AnyFunSuite
 import org.slf4j.{Logger, LoggerFactory}
 import za.co.absa.cobrix.cobol.parser.CopybookParser
-import za.co.absa.cobrix.cobol.parser.ast.Group
+import za.co.absa.cobrix.cobol.parser.ast.datatype.Decimal
+import za.co.absa.cobrix.cobol.parser.ast.{Group, Primitive}
 import za.co.absa.cobrix.cobol.parser.exceptions.SyntaxErrorException
 import za.co.absa.cobrix.cobol.parser.policies.FillerNamingPolicy
 import za.co.absa.cobrix.cobol.testutils.SimpleComparisonBase
@@ -312,4 +313,26 @@ class ParseCopybookFeaturesSpec extends AnyFunSuite with SimpleComparisonBase {
 
     assertEqualsMultiline(layout, expectedLayout)
   }
+
+  test("Test parsing copybooks with scaled decimals") {
+    val copybookStr = "      10 N PIC SVPP9(5) COMP-3."
+
+    val copybook = CopybookParser.parseSimple(copybookStr)
+    val layout = copybook.generateRecordLayoutPositions()
+
+    val field = copybook.getFieldByName("N").asInstanceOf[Primitive]
+    val dataType = field.dataType.asInstanceOf[Decimal]
+
+    assert(dataType.scale == 5)
+    assert(dataType.scaleFactor == -2)
+
+    val expectedLayout =
+      """-------- FIELD LEVEL/NAME --------- --ATTRIBS--    FLD  START     END  LENGTH
+        |
+        |10 N                                                  1      1      3      3
+        |"""
+        .stripMargin.replace("\r\n", "\n")
+
+    assertEqualsMultiline(layout, expectedLayout)
+  }
 }

cobol-parser/src/test/scala/za/co/absa/cobrix/cobol/parser/decoders/BinaryDecoderSpec.scala

@@ -226,6 +226,26 @@ class BinaryDecoderSpec extends AnyFunSuite {
     assert (v2.contains("92233720368547757.98"))
   }
 
+  test("Test COMP-3 decimal with scale factor cases") {
+    val v1 = BCDNumberDecoders.decodeBigBCDNumber(Array[Byte](0x06.toByte,0x54.toByte,0x7C.toByte), scale = 0, scaleFactor = 0, mandatorySignNibble = true)
+    assert (v1 == "06547")
+
+    val v2 = BCDNumberDecoders.decodeBigBCDNumber(Array[Byte](0x06.toByte,0x54.toByte,0x7C.toByte), scale = 0, scaleFactor = -1, mandatorySignNibble = true)
+    assert (v2 == "0.006547")
+
+    val v3 = BCDNumberDecoders.decodeBigBCDNumber(Array[Byte](0x06.toByte,0x54.toByte,0x7C.toByte), scale = 0, scaleFactor = -2, mandatorySignNibble = true)
+    assert (v3 == "0.0006547")
+
+    val v4 = BCDNumberDecoders.decodeBigBCDNumber(Array[Byte](0x06.toByte,0x54.toByte,0x7C.toByte), scale = 5, scaleFactor = -1, mandatorySignNibble = true)
+    assert (v4 == "0.006547")
+
+    val v5 = BCDNumberDecoders.decodeBigBCDNumber(Array[Byte](0x06.toByte,0x54.toByte,0x7C.toByte), scale = 5, scaleFactor = -2, mandatorySignNibble = true)
+    assert (v5 == "0.0006547")
+
+    val v6 = BCDNumberDecoders.decodeBigBCDNumber(Array[Byte](0x16.toByte,0x54.toByte,0x7C.toByte), scale = 5, scaleFactor = -2, mandatorySignNibble = true)
+    assert (v6 == "0.0016547")
+  }
+
   test("Test COMP-3U decimal cases") {
     // A simple decimal number
     val v1 = BCDNumberDecoders.decodeBigBCDNumber(Array[Byte](0x15.toByte, 0x88.toByte, 0x40.toByte), scale = 2, scaleFactor = 0, mandatorySignNibble = false)

spark-cobol/src/test/scala/za/co/absa/cobrix/spark/cobol/source/regression/Test17NumericConversions.scala

@@ -281,6 +281,46 @@ class Test17NumericConversions extends AnyWordSpec with SparkTestBase with Binar
         }
       }
     }
+
+    "negative scale factor for DISPLAY AND COMP-3 numbers should be decoded correctly" when {
+      val copybook =
+        """      10 N1 PIC SVPP9(5) COMP-3.
+          |      10 N2 PIC SVPP9(5).
+          |""".stripMargin
+
+      withTempBinFile("scelad_commp3", ".dat", Array(0x06, 0x54, 0x7C, 0xF0, 0xF6, 0xF5, 0xF4, 0xF7).map(_.toByte)) { tmpFileName =>
+        val df = spark
+          .read
+          .format("cobol")
+          .option("copybook_contents", copybook)
+          .option("record_format", "F")
+          .option("pedantic", "true")
+          .load(tmpFileName)
+
+        val actualSchema = df.schema.treeString
+        val row = df.collect().head
+        val actualData1 = row.getDecimal(0).toString
+        val actualData2 = row.getDecimal(1).toString
+
+        "schema should match" in {
+          val expectedSchema =
+            """root
+              | |-- N1: decimal(7,7) (nullable = true)
+              | |-- N2: decimal(7,7) (nullable = true)
+              |""".stripMargin
+
+          assertEqualsMultiline(actualSchema, expectedSchema)
+        }
+
+        "data should match" in {
+          val expectedData = "0.0006547"
+
+          assertEqualsMultiline(actualData1, expectedData)
+          assertEqualsMultiline(actualData2, expectedData)
+        }
+      }
+    }
+
   }
 
 }