[rubysrc2cpg] Decouple parser and ASTCreator (#3283)

* Fix bug in command line parsing

* Decouple parser and ASTCreator

* Also log error message

* Add missing import

---------

Co-authored-by: Fabian Yamaguchi <fabs@joern.io>

joern-cli/frontends/rubysrc2cpg/src/main/scala/io/joern/rubysrc2cpg/Main.scala

@@ -22,7 +22,7 @@ private object Frontend {
       programName("rubysrc2cpg"),
       opt[Unit]("enableDependencyDownload")
         .hidden()
-        .action((_, c) => c.withEnableDependencyDownload(false))
+        .action((_, c) => c.withEnableDependencyDownload(true))
         .text("enable dependency download for Unix System only")
     )
   }

joern-cli/frontends/rubysrc2cpg/src/main/scala/io/joern/rubysrc2cpg/astcreation/AntlrParser.scala

@@ -0,0 +1,16 @@
+package io.joern.rubysrc2cpg.astcreation
+
+import io.joern.rubysrc2cpg.parser.{RubyLexer, RubyParser}
+import org.antlr.v4.runtime.{CharStreams, CommonTokenStream, ParserRuleContext, Token}
+
+class AntlrParser {
+
+  def parse(filename: String): RubyParser.ProgramContext = {
+    val charStream  = CharStreams.fromFileName(filename)
+    val lexer       = new RubyLexer(charStream)
+    val tokenStream = new CommonTokenStream(lexer)
+    val parser      = new RubyParser(tokenStream)
+    parser.program()
+  }
+
+}

joern-cli/frontends/rubysrc2cpg/src/main/scala/io/joern/rubysrc2cpg/astcreation/AstCreator.scala

@@ -9,8 +9,8 @@ import io.joern.x2cpg.datastructures.{Global, Scope}
 import io.joern.x2cpg.{Ast, AstCreatorBase, AstNodeBuilder, Defines as XDefines}
 import io.shiftleft.codepropertygraph.generated.*
 import io.shiftleft.codepropertygraph.generated.nodes.*
+import org.antlr.v4.runtime.{ParserRuleContext, Token}
 import org.antlr.v4.runtime.tree.TerminalNode
-import org.antlr.v4.runtime.{CharStreams, CommonTokenStream, ParserRuleContext, Token}
 import org.slf4j.LoggerFactory
 import overflowdb.{BatchedUpdate, NodeOrDetachedNode}
 
@@ -19,6 +19,7 @@ import scala.collection.immutable.Seq
 import scala.collection.mutable
 import scala.collection.mutable.ListBuffer
 import scala.jdk.CollectionConverters.*
+import scala.util.{Failure, Success, Try}
 
 class AstCreator(
   protected val filename: String,
@@ -105,12 +106,19 @@ class AstCreator(
     methodAliases.getOrElse(name, name)
   }
   override def createAst(): BatchedUpdate.DiffGraphBuilder = {
-    val charStream  = CharStreams.fromFileName(filename)
-    val lexer       = new RubyLexer(charStream)
-    val tokenStream = new CommonTokenStream(lexer)
-    val parser      = new RubyParser(tokenStream)
-    val programCtx  = parser.program()
+    Try {
+      new AntlrParser().parse(filename)
+    } match {
+      case Success(programCtx) =>
+        createAstForProgramCtx(programCtx)
+      case Failure(exc) =>
+        logger.warn(s"Could not parse file: $filename, skipping")
+        logger.warn(exc.getMessage)
+        diffGraph
+    }
+  }
 
+  private def createAstForProgramCtx(programCtx: RubyParser.ProgramContext) = {
     val name     = ":program"
     val fullName = s"$relativeFilename:$name"
     val programMethod =