From f08b313f962c60cc4f88913e9c9fd4dc1e7d7c07 Mon Sep 17 00:00:00 2001
From: Christian Banse <oxisto@clouditor.io>
Date: Mon, 9 Sep 2024 15:43:34 +0200
Subject: [PATCH] More comments

---
 .../aisec/cpg/graph/DeclarationBuilder.kt     |  2 +-
 .../aisec/cpg/helpers/SubgraphWalker.kt       | 21 +++++++++++++++--
 .../cpg/frontends/python/StatementHandler.kt  | 23 ++++++++++++++-----
 3 files changed, 37 insertions(+), 9 deletions(-)

diff --git a/cpg-core/src/main/kotlin/de/fraunhofer/aisec/cpg/graph/DeclarationBuilder.kt b/cpg-core/src/main/kotlin/de/fraunhofer/aisec/cpg/graph/DeclarationBuilder.kt
index e24ce7ff18..c2e429edfd 100644
--- a/cpg-core/src/main/kotlin/de/fraunhofer/aisec/cpg/graph/DeclarationBuilder.kt
+++ b/cpg-core/src/main/kotlin/de/fraunhofer/aisec/cpg/graph/DeclarationBuilder.kt
@@ -107,7 +107,7 @@ fun MetadataProvider.newOperatorDeclaration(
     operatorCode: String,
     recordDeclaration: RecordDeclaration? = null,
     rawNode: Any? = null
-): MethodDeclaration {
+): OperatorDeclaration {
     val node = OperatorDeclaration()
     node.applyMetadata(this, name, rawNode, defaultNamespace = recordDeclaration?.name)
 
diff --git a/cpg-core/src/main/kotlin/de/fraunhofer/aisec/cpg/helpers/SubgraphWalker.kt b/cpg-core/src/main/kotlin/de/fraunhofer/aisec/cpg/helpers/SubgraphWalker.kt
index 4960d1677c..e5821b00d7 100644
--- a/cpg-core/src/main/kotlin/de/fraunhofer/aisec/cpg/helpers/SubgraphWalker.kt
+++ b/cpg-core/src/main/kotlin/de/fraunhofer/aisec/cpg/helpers/SubgraphWalker.kt
@@ -346,8 +346,26 @@ object SubgraphWalker {
     }
 }
 
+/**
+ * Tries to replace the [old] expression with a [new] one, given the [parent].
+ *
+ * There are two things to consider:
+ * - First, this only works if [parent] is either an [ArgumentHolder] or [StatementHolder].
+ *   Otherwise, we cannot instruct the parent to exchange the node
+ * - Second, since exchanging the node has influence on their edges (such as EOG, DFG, etc.), we
+ *   only support a replacement very early in the pass system. To be specific, we only allow
+ *   replacement before any DFG edges are set. We are re-wiring EOG edges, but nothing else. If one
+ *   tries to replace a node with existing [Node.nextDFG] or [Node.prevDFG], we fail.
+ */
 context(ContextProvider)
 fun SubgraphWalker.ScopedWalker.replace(parent: Node?, old: Expression, new: Expression): Boolean {
+    // We do not allow to replace nodes where the DFG (or other dependent nodes, such as PDG have
+    // been set). The reason for that is that these edges contain a lot of information on the edges
+    // themselves and replacing this edge would be very complicated.
+    if (old.prevDFG.isNotEmpty() || old.nextDFG.isNotEmpty()) {
+        return false
+    }
+
     val success =
         when (parent) {
             is ArgumentHolder -> parent.replace(old, new)
@@ -359,13 +377,12 @@ fun SubgraphWalker.ScopedWalker.replace(parent: Node?, old: Expression, new: Exp
                 return false
             }
         }
-
     if (!success) {
         Pass.log.error(
             "Replacing expression $old was not successful. Further analysis might not be entirely accurate."
         )
     } else {
-        // Store any eventual EOG nodes and disconnect old node
+        // Store any eventual EOG/DFG nodes and disconnect old node
         val oldPrevEOG = old.prevEOG.toMutableList()
         val oldNextEOG = old.nextEOG.toMutableList()
         old.disconnectFromGraph()
diff --git a/cpg-language-python/src/main/kotlin/de/fraunhofer/aisec/cpg/frontends/python/StatementHandler.kt b/cpg-language-python/src/main/kotlin/de/fraunhofer/aisec/cpg/frontends/python/StatementHandler.kt
index 48532c8c1e..4b874063be 100644
--- a/cpg-language-python/src/main/kotlin/de/fraunhofer/aisec/cpg/frontends/python/StatementHandler.kt
+++ b/cpg-language-python/src/main/kotlin/de/fraunhofer/aisec/cpg/frontends/python/StatementHandler.kt
@@ -39,6 +39,7 @@ 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
 import de.fraunhofer.aisec.cpg.graph.types.FunctionType
+import de.fraunhofer.aisec.cpg.helpers.Util
 import kotlin.collections.plusAssign
 
 class StatementHandler(frontend: PythonLanguageFrontend) :
@@ -300,12 +301,22 @@ class StatementHandler(frontend: PythonLanguageFrontend) :
                         rawNode = s
                     )
                 } else if (language is HasOperatorOverloading && s.name.isKnownOperatorName) {
-                    newOperatorDeclaration(
-                        name = s.name,
-                        recordDeclaration = recordDeclaration,
-                        operatorCode = language.operatorCodeFor(s.name) ?: "",
-                        rawNode = s
-                    )
+                    var decl =
+                        newOperatorDeclaration(
+                            name = s.name,
+                            recordDeclaration = recordDeclaration,
+                            operatorCode = language.operatorCodeFor(s.name) ?: "",
+                            rawNode = s
+                        )
+                    if (decl.operatorCode == "") {
+                        Util.warnWithFileLocation(
+                            decl,
+                            log,
+                            "Could not find operator code for operator {}. This will most likely result in a failure",
+                            s.name
+                        )
+                    }
+                    decl
                 } else {
                     newMethodDeclaration(
                         name = s.name,