PS: Hide the new nodes and enure that we still show the old return node.

Author: MathiasVP

powershell/ql/lib/semmle/code/powershell/dataflow/internal/DataFlowImplSpecific.qll

@@ -21,4 +21,6 @@ module PowershellDataFlow implements InputSig<Location> {
   class ParameterNode = Private::ParameterNodeImpl;
 
   Node exprNode(DataFlowExpr e) { result = Public::exprNode(e) }
+
+  predicate neverSkipInPathGraph = Private::neverSkipInPathGraph/1;
 }

powershell/ql/lib/semmle/code/powershell/dataflow/internal/DataFlowPrivate.qll

@@ -31,6 +31,9 @@ abstract class NodeImpl extends Node {
 
   /** Do not call: use `toString()` instead. */
   abstract string toStringImpl();
+
+  /** Holds if this node should be hidden from path explanations. */
+  predicate nodeIsHidden() { none() }
 }
 
 private class ExprNodeImpl extends ExprNode, NodeImpl {
@@ -284,7 +287,13 @@ private string approxKnownElementIndex(ConstantValue cv) {
 import Cached
 
 /** Holds if `n` should be hidden from path explanations. */
-predicate nodeIsHidden(Node n) { none() }
+predicate nodeIsHidden(Node n) { n.(NodeImpl).nodeIsHidden() }
+
+/**
+ * Holds if `n` should never be skipped over in the `PathGraph` and in path
+ * explanations.
+ */
+predicate neverSkipInPathGraph(Node n) { isReturned(n.(AstNode).getCfgNode()) }
 
 /** An SSA node. */
 abstract class SsaNode extends NodeImpl, TSsaNode {
@@ -795,6 +804,8 @@ private class ImplicitWrapNode extends TImplicitWrapNode, NodeImpl {
   override Location getLocationImpl() { result = n.getLocation() }
 
   override string toStringImpl() { result = "implicit unwrapping of " + n.toString() }
+
+  override predicate nodeIsHidden() { any() }
 }
 
 /**
@@ -829,6 +840,8 @@ private class ReturnNodeImpl extends TReturnNodeImpl, NodeImpl {
   override Location getLocationImpl() { result = scope.getLocation() }
 
   override string toStringImpl() { result = "return value for " + scope.toString() }
+
+  override predicate nodeIsHidden() { any() }
 }
 
 /** A node that performs a type cast. */

powershell/ql/test/library-tests/dataflow/returns/test.expected

@@ -1,48 +1,32 @@
 models
 edges
-| test.ps1:1:25:3:2 | return value for {...} | test.ps1:5:6:5:20 | callSourceOnce | provenance |  |
-| test.ps1:2:5:2:15 | Source | test.ps1:2:5:2:15 | implicit unwrapping of Source | provenance |  |
-| test.ps1:2:5:2:15 | implicit unwrapping of Source | test.ps1:1:25:3:2 | return value for {...} | provenance |  |
+| test.ps1:2:5:2:15 | Source | test.ps1:5:6:5:20 | callSourceOnce | provenance |  |
 | test.ps1:5:6:5:20 | callSourceOnce | test.ps1:6:6:6:8 | x | provenance |  |
-| test.ps1:8:26:11:2 | return value for {...} | test.ps1:13:6:13:21 | callSourceTwice | provenance |  |
-| test.ps1:9:5:9:15 | Source | test.ps1:9:5:9:15 | implicit unwrapping of Source | provenance |  |
-| test.ps1:9:5:9:15 | implicit unwrapping of Source | test.ps1:8:26:11:2 | return value for {...} | provenance |  |
-| test.ps1:10:5:10:15 | Source | test.ps1:10:5:10:15 | implicit unwrapping of Source | provenance |  |
-| test.ps1:10:5:10:15 | implicit unwrapping of Source | test.ps1:8:26:11:2 | return value for {...} | provenance |  |
+| test.ps1:9:5:9:15 | Source | test.ps1:13:6:13:21 | callSourceTwice | provenance |  |
+| test.ps1:10:5:10:15 | Source | test.ps1:13:6:13:21 | callSourceTwice | provenance |  |
 | test.ps1:13:6:13:21 | callSourceTwice | test.ps1:14:6:14:8 | x | provenance |  |
-| test.ps1:16:24:18:2 | return value for {...} | test.ps1:20:6:20:19 | returnSource1 | provenance |  |
-| test.ps1:17:12:17:22 | Source | test.ps1:17:12:17:22 | implicit unwrapping of Source | provenance |  |
-| test.ps1:17:12:17:22 | implicit unwrapping of Source | test.ps1:16:24:18:2 | return value for {...} | provenance |  |
+| test.ps1:17:12:17:22 | Source | test.ps1:20:6:20:19 | returnSource1 | provenance |  |
 | test.ps1:20:6:20:19 | returnSource1 | test.ps1:21:6:21:8 | x | provenance |  |
-| test.ps1:23:24:28:2 | return value for {...} | test.ps1:30:6:30:19 | returnSource2 | provenance |  |
-| test.ps1:24:10:24:20 | Source | test.ps1:25:5:25:7 | implicit unwrapping of x | provenance |  |
-| test.ps1:25:5:25:7 | implicit unwrapping of x | test.ps1:23:24:28:2 | return value for {...} | provenance |  |
-| test.ps1:26:10:26:20 | Source | test.ps1:27:12:27:14 | implicit unwrapping of y | provenance |  |
-| test.ps1:27:12:27:14 | implicit unwrapping of y | test.ps1:23:24:28:2 | return value for {...} | provenance |  |
+| test.ps1:24:10:24:20 | Source | test.ps1:25:5:25:7 | x | provenance |  |
+| test.ps1:25:5:25:7 | x | test.ps1:30:6:30:19 | returnSource2 | provenance |  |
+| test.ps1:26:10:26:20 | Source | test.ps1:27:12:27:14 | y | provenance |  |
+| test.ps1:27:12:27:14 | y | test.ps1:30:6:30:19 | returnSource2 | provenance |  |
 | test.ps1:30:6:30:19 | returnSource2 | test.ps1:31:6:31:8 | x | provenance |  |
 nodes
-| test.ps1:1:25:3:2 | return value for {...} | semmle.label | return value for {...} |
 | test.ps1:2:5:2:15 | Source | semmle.label | Source |
-| test.ps1:2:5:2:15 | implicit unwrapping of Source | semmle.label | implicit unwrapping of Source |
 | test.ps1:5:6:5:20 | callSourceOnce | semmle.label | callSourceOnce |
 | test.ps1:6:6:6:8 | x | semmle.label | x |
-| test.ps1:8:26:11:2 | return value for {...} | semmle.label | return value for {...} |
 | test.ps1:9:5:9:15 | Source | semmle.label | Source |
-| test.ps1:9:5:9:15 | implicit unwrapping of Source | semmle.label | implicit unwrapping of Source |
 | test.ps1:10:5:10:15 | Source | semmle.label | Source |
-| test.ps1:10:5:10:15 | implicit unwrapping of Source | semmle.label | implicit unwrapping of Source |
 | test.ps1:13:6:13:21 | callSourceTwice | semmle.label | callSourceTwice |
 | test.ps1:14:6:14:8 | x | semmle.label | x |
-| test.ps1:16:24:18:2 | return value for {...} | semmle.label | return value for {...} |
 | test.ps1:17:12:17:22 | Source | semmle.label | Source |
-| test.ps1:17:12:17:22 | implicit unwrapping of Source | semmle.label | implicit unwrapping of Source |
 | test.ps1:20:6:20:19 | returnSource1 | semmle.label | returnSource1 |
 | test.ps1:21:6:21:8 | x | semmle.label | x |
-| test.ps1:23:24:28:2 | return value for {...} | semmle.label | return value for {...} |
 | test.ps1:24:10:24:20 | Source | semmle.label | Source |
-| test.ps1:25:5:25:7 | implicit unwrapping of x | semmle.label | implicit unwrapping of x |
+| test.ps1:25:5:25:7 | x | semmle.label | x |
 | test.ps1:26:10:26:20 | Source | semmle.label | Source |
-| test.ps1:27:12:27:14 | implicit unwrapping of y | semmle.label | implicit unwrapping of y |
+| test.ps1:27:12:27:14 | y | semmle.label | y |
 | test.ps1:30:6:30:19 | returnSource2 | semmle.label | returnSource2 |
 | test.ps1:31:6:31:8 | x | semmle.label | x |
 subpaths