[ruby] Lower Array Creation for In Pattern Match (#5229)

Pattern match array creation is now lowered so that both reads and writes assign array indices to where each element much be read and written from.

Author: DavidBakerEffendi

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

@@ -1,12 +1,15 @@
 package io.joern.rubysrc2cpg.astcreation
 
 import io.joern.rubysrc2cpg.astcreation.RubyIntermediateAst.{
+  ArrayLiteral,
   ArrayPattern,
   BinaryExpression,
   BreakExpression,
   CaseExpression,
   ControlFlowStatement,
   DoWhileExpression,
+  DummyAst,
+  DynamicLiteral,
   ElseClause,
   ForExpression,
   IfExpression,
@@ -17,10 +20,9 @@ import io.joern.rubysrc2cpg.astcreation.RubyIntermediateAst.{
   NextExpression,
   OperatorAssignment,
   RescueExpression,
-  ReturnExpression,
   RubyExpression,
-  SimpleCall,
   SimpleIdentifier,
+  SimpleObjectInstantiation,
   SingleAssignment,
   SplattingRubyNode,
   StatementList,
@@ -32,18 +34,12 @@ import io.joern.rubysrc2cpg.astcreation.RubyIntermediateAst.{
   WhenClause,
   WhileExpression
 }
-import io.joern.rubysrc2cpg.parser.RubyJsonHelpers
+import io.joern.rubysrc2cpg.datastructures.BlockScope
 import io.joern.rubysrc2cpg.passes.Defines
-import io.joern.rubysrc2cpg.passes.Defines.RubyOperators
+import io.joern.rubysrc2cpg.passes.Defines.getBuiltInType
 import io.joern.x2cpg.{Ast, ValidationMode}
+import io.shiftleft.codepropertygraph.generated.nodes.{NewBlock, NewFieldIdentifier, NewLiteral, NewLocal}
 import io.shiftleft.codepropertygraph.generated.{ControlStructureTypes, DispatchTypes, Operators}
-import io.shiftleft.codepropertygraph.generated.nodes.{
-  NewBlock,
-  NewFieldIdentifier,
-  NewIdentifier,
-  NewLiteral,
-  NewLocal
-}
 
 trait AstForControlStructuresCreator(implicit withSchemaValidation: ValidationMode) { this: AstCreator =>
 
@@ -335,16 +331,67 @@ trait AstForControlStructuresCreator(implicit withSchemaValidation: ValidationMo
       ifElseChain.iterator.toList
     }
 
-    def generatedNode: StatementList = node.expression
-      .map { e =>
-        val tmp = SimpleIdentifier(None)(e.span.spanStart(this.tmpGen.fresh))
-        StatementList(
-          List(SingleAssignment(tmp, "=", e)(e.span)) ++
-            goCase(Some(tmp))
-        )(node.span)
+    val caseExpr = node.expression
+      .map {
+        case arrayLiteral: ArrayLiteral =>
+          val tmp             = SimpleIdentifier(None)(arrayLiteral.span.spanStart(this.tmpGen.fresh))
+          val arrayLiteralAst = DummyAst(astForTempArray(arrayLiteral))(arrayLiteral.span)
+          (tmp, arrayLiteralAst)
+        case e =>
+          val tmp = SimpleIdentifier(None)(e.span.spanStart(this.tmpGen.fresh))
+          (tmp, e)
       }
+      .map((tmp, e) => StatementList(List(SingleAssignment(tmp, "=", e)(e.span)) ++ goCase(Some(tmp)))(node.span))
       .getOrElse(StatementList(goCase(None))(node.span))
-    astsForStatement(generatedNode)
+
+    astsForStatement(caseExpr)
+  }
+
+  private def astForTempArray(node: ArrayLiteral): Ast = {
+    val tmp = this.tmpGen.fresh
+
+    def tmpRubyNode(tmpNode: Option[RubyExpression] = None) =
+      SimpleIdentifier()(tmpNode.map(_.span).getOrElse(node.span).spanStart(tmp))
+
+    def tmpAst(tmpNode: Option[RubyExpression] = None) = astForSimpleIdentifier(tmpRubyNode(tmpNode))
+
+    val block = blockNode(node, node.text, Defines.Any)
+    scope.pushNewScope(BlockScope(block))
+    val tmpLocal = NewLocal().name(tmp).code(tmp)
+    scope.addToScope(tmp, tmpLocal)
+
+    val arguments = if (node.text.startsWith("%")) {
+      val argumentsType =
+        if (node.isStringArray) getBuiltInType(Defines.String)
+        else getBuiltInType(Defines.Symbol)
+      node.elements.map {
+        case element @ StaticLiteral(_)               => StaticLiteral(argumentsType)(element.span)
+        case element @ DynamicLiteral(_, expressions) => DynamicLiteral(argumentsType, expressions)(element.span)
+        case element                                  => element
+      }
+    } else {
+      node.elements
+    }
+    val argumentAsts = arguments.zipWithIndex.map { case (arg, idx) =>
+      val indices     = StaticLiteral(getBuiltInType(Defines.Integer))(arg.span.spanStart(idx.toString)) :: Nil
+      val base        = tmpRubyNode(Option(arg))
+      val indexAccess = IndexAccess(base, indices)(arg.span.spanStart(s"${base.text}[$idx]"))
+      val assignment = SingleAssignment(indexAccess, "=", arg)(arg.span.spanStart(s"${indexAccess.text} = ${arg.text}"))
+      astForExpression(assignment)
+    }
+
+    val arrayInitCall = {
+      val base = SimpleIdentifier()(node.span.spanStart(Defines.Array))
+      astForExpression(SimpleObjectInstantiation(base, Nil)(node.span))
+    }
+
+    val assignment =
+      callNode(node, code(node), Operators.assignment, Operators.assignment, DispatchTypes.STATIC_DISPATCH)
+    val tmpAssignment = callAst(assignment, tmpAst() :: arrayInitCall :: Nil)
+    val tmpRetAst     = tmpAst(node.elements.lastOption)
+
+    scope.popScope()
+    blockAst(block, tmpAssignment +: argumentAsts :+ tmpRetAst)
   }
 
   private def astForOperatorAssignmentExpression(node: OperatorAssignment): Ast = {

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

@@ -63,6 +63,7 @@ trait AstForExpressionsCreator(implicit withSchemaValidation: ValidationMode) {
     case node: AccessModifier                   => astForSimpleIdentifier(node.toSimpleIdentifier)
     case node: ArrayPattern                     => astForArrayPattern(node)
     case node: DummyNode                        => Ast(node.node)
+    case node: DummyAst                         => node.ast
     case node: Unknown                          => astForUnknown(node)
     case x =>
       logger.warn(s"Unhandled expression of type ${x.getClass.getSimpleName}")

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

@@ -1,6 +1,7 @@
 package io.joern.rubysrc2cpg.astcreation
 
 import io.joern.rubysrc2cpg.passes.{Defines, GlobalTypes}
+import io.joern.x2cpg.Ast
 import io.shiftleft.codepropertygraph.generated.nodes.NewNode
 
 import java.util.Objects
@@ -621,6 +622,10 @@ object RubyIntermediateAst {
     */
   final case class DummyNode(node: NewNode)(span: TextSpan) extends RubyExpression(span)
 
+  /** A dummy class for wrapping around `Ast` and allowing it to integrate with RubyNode classes.
+    */
+  final case class DummyAst(ast: Ast)(span: TextSpan) extends RubyExpression(span)
+
   final case class UnaryExpression(op: String, expression: RubyExpression)(span: TextSpan) extends RubyExpression(span)
 
   final case class BinaryExpression(lhs: RubyExpression, op: String, rhs: RubyExpression)(span: TextSpan)

joern-cli/frontends/rubysrc2cpg/src/test/scala/io/joern/rubysrc2cpg/querying/CaseTests.scala

@@ -1,6 +1,5 @@
 package io.joern.rubysrc2cpg.querying
 
-import io.joern.rubysrc2cpg.passes.Defines.RubyOperators
 import io.joern.rubysrc2cpg.testfixtures.RubyCode2CpgFixture
 import io.shiftleft.codepropertygraph.generated.Operators
 import io.shiftleft.codepropertygraph.generated.nodes.*
@@ -115,11 +114,11 @@ class CaseTests extends RubyCode2CpgFixture {
 
     val block @ List(_) = cpg.method.name("class_for").block.astChildren.isBlock.l
 
-    val List(assign)   = block.astChildren.assignment.l;
+    val assign         = block.astChildren.assignment.head
     val List(lhs, rhs) = assign.argument.l
 
     lhs.start.isIdentifier.name.l shouldBe List("<tmp-0>")
-    rhs.start.isCall.code.l shouldBe List("[type, location]")
+    rhs.start.isBlock.code.l shouldBe List("[type, location]") // array lowering
 
     val headIf @ List(_)        = block.astChildren.isControlStructure.l
     val ifStmts @ List(_, _, _) = headIf.repeat(_.astChildren.order(3).astChildren.isControlStructure)(_.emit).l;
@@ -165,11 +164,11 @@ class CaseTests extends RubyCode2CpgFixture {
 
     val block @ List(_) = cpg.method.name("class_for").block.astChildren.isBlock.l
 
-    val List(assign, _, _) = block.astChildren.assignment.l;
-    val List(lhs, rhs)     = assign.argument.l
+    val assign         = block.astChildren.assignment.head
+    val List(lhs, rhs) = assign.argument.l
 
     lhs.start.isIdentifier.name.l shouldBe List("<tmp-0>")
-    rhs.start.isCall.code.l shouldBe List("[type, location]")
+    rhs.start.isBlock.code.l shouldBe List("[type, location]") // where the array lowering happens
 
     val headIf @ List(_)     = block.astChildren.isControlStructure.l
     val ifStmts @ List(_, _) = headIf.repeat(_.astChildren.order(3).astChildren.isControlStructure)(_.emit).l;