Allow for missing nesting levels. Fixes #164.

.gitignore

@@ -48,3 +48,4 @@ dependency-reduced-pom.xml
 
 _testOutput
 output
+.attach_pid*

cobol-parser/src/main/scala/za/co/absa/cobrix/cobol/parser/antlr/ParserVisitor.scala

@@ -194,14 +194,20 @@ class ParserVisitor(enc: Encoding,
       levels.pop
     }
 
-    if (levels.top.children.isEmpty) {
-      val newTop = levels.top.copy(children = Some(section))
+    def addLevel(s: Int) = {
+      val newTop = levels.top.copy(children = Some(s))
       levels.pop
       levels.push(newTop)
     }
-    if (!levels.top.children.contains(section))
-      throw new SyntaxErrorException(levels.top.el.children.last.lineNumber, levels.top.el.name,
-        s"The field is a leaf element and cannot contain nested fields.")
+
+    levels.top.children match {
+      case Some(s) if s == section => { }
+      case None => addLevel(section)
+      case Some(s) if s > section => addLevel(section)
+      case _ =>
+        throw new SyntaxErrorException(levels.top.el.children.last.lineNumber, levels.top.el.children.last.name,
+          s"The field is a leaf element and cannot contain nested fields.")
+    }
 
     levels.top.el
   }

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

@@ -19,6 +19,7 @@ package za.co.absa.cobrix.cobol.parser.copybooks
 import org.scalatest.FunSuite
 import org.slf4j.LoggerFactory
 import za.co.absa.cobrix.cobol.parser.CopybookParser
+import za.co.absa.cobrix.cobol.parser.exceptions.SyntaxErrorException
 
 class ParseFieldsNestingSpec extends FunSuite {
 
@@ -53,4 +54,23 @@ class ParseFieldsNestingSpec extends FunSuite {
 
     assert(layout == expectedLayout)
   }
+
+  test("Test copybook parser doesn't allow nesting leaf statements") {
+    val copybookWithCommentLines =
+      """
+      01  ROOT-GROUP.
+          03  NESTED-PRIMITIVE-01  PIC 9(7)    COMP-3.
+          03  NESTED-GRP-01.
+            05  NESTED-NESTED-02   PIC X(7).
+          03  FILL                 PIC X(07).
+        02  FILLER_1               PIC XX.
+          03  NUMERIC-FIELD-01     PIC S9(04)  COMP.
+      """
+
+    val syntaxErrorException = intercept[SyntaxErrorException] {
+      CopybookParser.parseTree(copybookWithCommentLines)
+    }
+    assert(syntaxErrorException.lineNumber == 7)
+    assert(syntaxErrorException.msg.contains("The field is a leaf element and cannot contain nested fields."))
+  }
 }