Handle delete statement in python frontend

cpg-core/src/main/kotlin/de/fraunhofer/aisec/cpg/graph/statements/expressions/DeleteExpression.kt

@@ -25,6 +25,7 @@
  */
 package de.fraunhofer.aisec.cpg.graph.statements.expressions
 
+import de.fraunhofer.aisec.cpg.graph.edges.ast.astEdgesOf
 import de.fraunhofer.aisec.cpg.graph.edges.ast.astOptionalEdgeOf
 import de.fraunhofer.aisec.cpg.graph.edges.unwrapping
 import java.util.Objects
@@ -34,11 +35,14 @@ class DeleteExpression : Expression() {
     @Relationship("OPERAND") var operandEdge = astOptionalEdgeOf<Expression>()
     var operand by unwrapping(DeleteExpression::operandEdge)
 
+    @Relationship(value = "TARGETS") var targetEdges = astEdgesOf<Expression>()
+    var targets by unwrapping(DeleteExpression::targetEdges)
+
     override fun equals(other: Any?): Boolean {
         if (this === other) return true
         if (other !is DeleteExpression) return false
-        return super.equals(other) && operand == other.operand
+        return super.equals(other) && operand == other.operand && targets == other.targets
     }
 
-    override fun hashCode() = Objects.hash(super.hashCode(), operand)
+    override fun hashCode() = Objects.hash(super.hashCode(), operand, targets)
 }

cpg-language-python/src/main/kotlin/de/fraunhofer/aisec/cpg/frontends/python/StatementHandler.kt

@@ -37,6 +37,7 @@ import de.fraunhofer.aisec.cpg.graph.statements.AssertStatement
 import de.fraunhofer.aisec.cpg.graph.statements.DeclarationStatement
 import de.fraunhofer.aisec.cpg.graph.statements.Statement
 import de.fraunhofer.aisec.cpg.graph.statements.expressions.Block
+import de.fraunhofer.aisec.cpg.graph.statements.expressions.DeleteExpression
 import de.fraunhofer.aisec.cpg.graph.statements.expressions.Expression
 import de.fraunhofer.aisec.cpg.graph.statements.expressions.MemberExpression
 import de.fraunhofer.aisec.cpg.graph.statements.expressions.ProblemExpression
@@ -67,7 +68,7 @@ class StatementHandler(frontend: PythonLanguageFrontend) :
             is Python.AST.Break -> newBreakStatement(rawNode = node)
             is Python.AST.Continue -> newContinueStatement(rawNode = node)
             is Python.AST.Assert -> handleAssert(node)
-            is Python.AST.Delete,
+            is Python.AST.Delete -> handleDelete(node)
             is Python.AST.Global,
             is Python.AST.Match,
             is Python.AST.Nonlocal,
@@ -83,6 +84,26 @@ class StatementHandler(frontend: PythonLanguageFrontend) :
         }
     }
 
+    /**
+     * Translates a Python [`Delete`](https://docs.python.org/3/library/ast.html#ast.Delete) into a
+     * [DeleteExpression].
+     */
+    private fun handleDelete(node: Python.AST.Delete): DeleteExpression {
+        val delete = newDeleteExpression(rawNode = node)
+        node.targets.forEach { target ->
+            if (target is Python.AST.Subscript) {
+                delete.targets.add(frontend.expressionHandler.handle(target))
+            } else {
+                delete.additionalProblems +=
+                    newProblemExpression(
+                        problem = "Delete is only supported for Subscript targets.",
+                        rawNode = target
+                    )
+            }
+        }
+        return delete
+    }
+
     /**
      * Translates a Python (https://docs.python.org/3/library/ast.html#ast.Assert] into a
      * [AssertStatement].

cpg-language-python/src/test/kotlin/de/fraunhofer/aisec/cpg/frontends/python/statementHandler/StatementHandlerTest.kt

@@ -29,14 +29,17 @@ import de.fraunhofer.aisec.cpg.TranslationResult
 import de.fraunhofer.aisec.cpg.frontends.python.PythonLanguage
 import de.fraunhofer.aisec.cpg.graph.*
 import de.fraunhofer.aisec.cpg.graph.statements.AssertStatement
+import de.fraunhofer.aisec.cpg.graph.statements.expressions.DeleteExpression
 import de.fraunhofer.aisec.cpg.graph.statements.expressions.Literal
+import de.fraunhofer.aisec.cpg.graph.statements.expressions.SubscriptExpression
 import de.fraunhofer.aisec.cpg.test.analyze
 import de.fraunhofer.aisec.cpg.test.analyzeAndGetFirstTU
 import de.fraunhofer.aisec.cpg.test.assertResolvedType
 import java.nio.file.Path
 import kotlin.test.Test
 import kotlin.test.assertEquals
 import kotlin.test.assertNotNull
+import kotlin.test.assertTrue
 import org.junit.jupiter.api.BeforeAll
 import org.junit.jupiter.api.TestInstance
 
@@ -123,4 +126,34 @@ class StatementHandlerTest {
         assertNotNull(message, "Assert statement should have a message")
         assertEquals("Test message", message.value, "The assert message is incorrect")
     }
+
+    @Test
+    fun testDeleteStatements() {
+        analyzeFile("delete.py")
+
+        val deleteExpressions = result.statements.filterIsInstance<DeleteExpression>()
+        assertEquals(4, deleteExpressions.size)
+
+        // Test for `del a`
+        val deleteStmt1 = deleteExpressions[0]
+        assertEquals(0, deleteStmt1.targets.size)
+        assertEquals(1, deleteStmt1.additionalProblems.size)
+
+        // Test for `del my_list[2]`
+        val deleteStmt2 = deleteExpressions[1]
+        assertEquals(1, deleteStmt2.targets.size)
+        assertTrue(deleteStmt2.targets.first() is SubscriptExpression)
+        assertTrue(deleteStmt2.additionalProblems.isEmpty())
+
+        // Test for `del my_dict['b']`
+        val deleteStmt3 = deleteExpressions[2]
+        assertEquals(1, deleteStmt3.targets.size)
+        assertTrue(deleteStmt3.targets.first() is SubscriptExpression)
+        assertTrue(deleteStmt3.additionalProblems.isEmpty())
+
+        // Test for `del obj.d`
+        val deleteStmt4 = deleteExpressions[3]
+        assertEquals(0, deleteStmt4.targets.size)
+        assertEquals(1, deleteStmt4.additionalProblems.size)
+    }
 }

cpg-language-python/src/test/resources/python/delete.py

@@ -0,0 +1,16 @@
+a = 5
+b = a
+del a
+
+my_list = [1, 2, 3]
+del my_list[2]
+
+my_dict = {'a': 1, 'b': 2}
+del my_dict['b']
+
+class MyClass:
+    def __init__(self):
+        self.d = 1
+
+obj = MyClass()
+del obj.d