[ruby] Fixed anltr warnings on possible empty string matches (#4921)

joern-cli/frontends/rubysrc2cpg/src/main/antlr4/io/joern/rubysrc2cpg/parser/RubyParser.g4

@@ -187,7 +187,7 @@ indexingArgumentList
  # commandIndexingArgumentList
  | operatorExpressionList COMMA splattingArgument
  # operatorExpressionListWithSplattingArgumentIndexingArgumentList
- | (indexingArgument COMMA? NL*)*
+ | indexingArgument (COMMA? NL* indexingArgument)*
  #indexingArgumentIndexingArgumentList
  | associationList COMMA?
  # associationListIndexingArgumentList
@@ -324,7 +324,7 @@ primaryValue
  # singletonMethodDefinition
  | DEF definedMethodName (LPAREN parameterList? RPAREN)? EQ NL* statement
  # endlessMethodDefinition
- | MINUSGT lambdaExpressionParameterList block
+ | MINUSGT lambdaExpressionParameterList? block
  # lambdaExpression
 
  // Control structures
@@ -428,7 +428,7 @@ primaryValue
 
 lambdaExpressionParameterList
  : LPAREN blockParameterList? RPAREN
- | blockParameterList?
+ | blockParameterList
  ;
 
 // Non-nested calls
@@ -498,11 +498,22 @@ blockParameterList
  ;
 
 mandatoryOrOptionalOrGroupedParameterList
- : (mandatoryOrOptionalParameter | groupedParameterList) (COMMA NL* (mandatoryOrOptionalParameter | groupedParameterList))*
+ : mandatoryOrOptionalOrGroupedParameter (COMMA NL* mandatoryOrOptionalOrGroupedParameter)*
+ ;
+
+mandatoryOrOptionalOrGroupedParameter
+ : mandatoryParameter
+ | optionalParameter
+ | groupedParameterList
  ;
 
 mandatoryOrGroupedParameterList
- : (mandatoryParameter | groupedParameterList) (COMMA NL* (mandatoryParameter | groupedParameterList))*
+ : mandatoryOrGroupedParameter (COMMA NL* mandatoryOrGroupedParameter)*
+ ;
+
+mandatoryOrGroupedParameter
+ : mandatoryParameter
+ | groupedParameterList
  ;
 
 groupedParameterList

joern-cli/frontends/rubysrc2cpg/src/main/scala/io/joern/rubysrc2cpg/parser/AntlrContextHelpers.scala

@@ -211,12 +211,12 @@ object AntlrContextHelpers {
  ctx: MandatoryOrOptionalOrGroupedParameterListContext
  ) {
  def parameters: List[ParserRuleContext] =
- ctx.mandatoryOrOptionalParameter().asScala.toList ++ ctx.groupedParameterList().asScala.toList
+ ctx.mandatoryOrOptionalOrGroupedParameter().asScala.toList
  }
 
  sealed implicit class MandatoryOrGroupedParameterListContextHelper(ctx: MandatoryOrGroupedParameterListContext) {
  def parameters: List[ParserRuleContext] =
- ctx.mandatoryParameter().asScala.toList ++ ctx.groupedParameterList().asScala.toList
+ ctx.mandatoryOrGroupedParameter().asScala.toList
  }
 
  sealed implicit class GroupedParameterListContextHelper(ctx: GroupedParameterListContext) {

joern-cli/frontends/rubysrc2cpg/src/main/scala/io/joern/rubysrc2cpg/parser/AstPrinter.scala

@@ -694,10 +694,12 @@ class AstPrinter extends RubyParserBaseVisitor[String] {
  override def visitLambdaExpression(ctx: RubyParser.LambdaExpressionContext): String = {
  val outputSb = new StringBuilder(ctx.MINUSGT.getText)
 
- val params = Option(ctx.lambdaExpressionParameterList().blockParameterList())
- .fold(List())(_.parameters)
- .map(visit)
- .mkString(",")
+ val params = Option(ctx.lambdaExpressionParameterList()) match {
+ case Some(parameterList) =>
+ Option(parameterList.blockParameterList()).fold(List())(_.parameters).map(visit).mkString(",")
+ case None => ""
+ }
+
  val body = visit(ctx.block())
 
  if params != "" then outputSb.append(s"($params)")

joern-cli/frontends/rubysrc2cpg/src/main/scala/io/joern/rubysrc2cpg/parser/RubyNodeCreator.scala

@@ -772,8 +772,11 @@ class RubyNodeCreator(variableNameGen: FreshNameGenerator[String] = FreshNameGen
  }
 
  override def visitLambdaExpression(ctx: RubyParser.LambdaExpressionContext): RubyExpression = {
- val parameters =
- Option(ctx.lambdaExpressionParameterList().blockParameterList()).fold(List())(_.parameters).map(visit)
+ val parameters = Option(ctx.lambdaExpressionParameterList()) match {
+ case Some(parameterList) => Option(parameterList.blockParameterList()).fold(List())(_.parameters).map(visit)
+ case None => List()
+ }
+
  val body = visit(ctx.block()).asInstanceOf[Block]
  ProcOrLambdaExpr(Block(parameters, body)(ctx.toTextSpan))(ctx.toTextSpan)
  }

joern-cli/frontends/rubysrc2cpg/src/test/scala/io/joern/rubysrc2cpg/parser/DoBlockParserTests.scala

@@ -5,17 +5,35 @@ import org.scalatest.matchers.should.Matchers
 
 class DoBlockParserTests extends RubyParserFixture with Matchers {
  "fixme" ignore {
- test("f { |a, (b, c), d| }") // syntax error
  test(
  "break foo arg do |bar| end"
  ) // syntax error - possibly false syntax error due to just having a code sample starting with break which our parser doesn't allow
  test("yield foo arg do |bar| end") // syntax error
  test("a.b do | ; c | end") // syntax error
- test("f { |a, (b, *, c)| }")
- test("a { |b, c=1, *d, e, &f| }")
  }
 
  "Some block" in {
+ test(
+ "f { |a, (b, *, c)| }",
+ """f {
+ |{|a,(b, c, *)|}
+ |}""".stripMargin
+ )
+
+ test(
+ "a { |b, c=1, *d, e, &f| }",
+ """a {
+ |{|b,c=1,*d,&f,e|}
+ |}""".stripMargin
+ )
+
+ test(
+ "f { |a, (b, c), d| }",
+ """f {
+ |{|a,(b, c),d|}
+ |}""".stripMargin
+ )
+
  test(
  "a { |b, *c, d| }",
  """a {