Python: support for with-definitions

Author: yoff

python/ql/src/experimental/dataflow/internal/DataFlowPrivate.qll

@@ -42,6 +42,19 @@ module EssaFlow {
     //   nodeTo is `x`, essa var
     nodeFrom.asCfgNode() = nodeTo.asEssaNode().getDefinition().(AssignmentDefinition).getValue()
     or
+    // With definition
+    //   `with f(42) as x:`
+    //   nodeFrom is `f(42)`, cfg node
+    //   nodeTo is `x`, essa var
+    exists(With with, ControlFlowNode contextManager, ControlFlowNode var |
+      nodeFrom.asCfgNode() = contextManager and
+      nodeTo.asEssaNode().getDefinition().(WithDefinition).getDefiningNode() = var and
+      // see `with_flow`
+      with.getContextExpr() = contextManager.getNode() and
+      with.getOptionalVars() = var.getNode() and
+      contextManager.strictlyDominates(var)
+    )
+    or
     // Use
     //   `y = 42`
     //   `x = f(y)`

python/ql/test/experimental/dataflow/regression/dataflow.expected

@@ -6,6 +6,7 @@
 | test.py:37:13:37:18 | ControlFlowNode for SOURCE | test.py:41:14:41:14 | ControlFlowNode for t |
 | test.py:76:9:76:14 | ControlFlowNode for SOURCE | test.py:78:10:78:10 | ControlFlowNode for t |
 | test.py:108:13:108:18 | ControlFlowNode for SOURCE | test.py:112:14:112:14 | ControlFlowNode for t |
+| test.py:139:10:139:15 | ControlFlowNode for SOURCE | test.py:140:14:140:14 | ControlFlowNode for t |
 | test.py:143:9:143:14 | ControlFlowNode for SOURCE | test.py:145:10:145:10 | ControlFlowNode for s |
 | test.py:158:9:158:14 | ControlFlowNode for SOURCE | test.py:160:14:160:14 | ControlFlowNode for t |
 | test.py:158:9:158:14 | ControlFlowNode for SOURCE | test.py:162:14:162:14 | ControlFlowNode for t |

python/ql/test/experimental/dataflow/regression/dataflow.ql

@@ -4,7 +4,6 @@ from
   DataFlow::Node source,
   DataFlow::Node sink
 where
-  // source != sink and 
   exists(TestConfiguration cfg | cfg.hasFlow(source, sink))
 select
   source, sink