Python: Implement OutNode

Also, fix test for local flow

python/ql/test/experimental/dataflow/global.ql

@@ -0,0 +1,36 @@
+import python
+import experimental.dataflow.DataFlow
+
+class SimpleConfig extends DataFlow::Configuration {
+  SimpleConfig() { this = "SimpleConfig" }
+
+  // TODO: make a test out of this
+  override predicate isSource(DataFlow::Node node) {
+    node.asEssaNode() instanceof EssaNodeDefinition
+  }
+
+  // TODO: make a test out of this
+  override predicate isSink(DataFlow::Node node) {
+    not exists(EssaDefinition succ |
+      node.asEssaNode().getDefinition() = pred(succ)
+    )
+  }
+
+  EssaDefinition pred(EssaDefinition n) {
+    // result = value(n.(EssaNodeDefinition))
+    // or
+    result = n.(EssaNodeRefinement).getInput()
+    or
+    result = n.(EssaEdgeRefinement).getInput()
+    or
+    result = n.(PhiFunction).getShortCircuitInput()
+  }
+}
+
+from
+  DataFlow::Node source,
+  DataFlow::Node sink
+where
+exists(SimpleConfig cfg | cfg.hasFlow(source, sink))
+select
+source, sink

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

@@ -1,4 +1,6 @@
-ERROR: Could not resolve module DataFlow (local.ql:5,3-11)
-ERROR: Could not resolve module DataFlow (local.ql:6,3-11)
-ERROR: Could not resolve module DataFlow (local.ql:8,3-11)
-ERROR: Could not resolve module semmle.code.python.dataflow.DataFlow (local.ql:2,8-44)
+| test.py:1:1:1:1 | GSSA Variable a | test.py:8:5:8:8 | GSSA Variable a |
+| test.py:1:5:1:5 | ControlFlowNode for IntegerLiteral | test.py:1:1:1:1 | GSSA Variable a |
+| test.py:2:5:2:5 | ControlFlowNode for a | test.py:2:1:2:1 | GSSA Variable b |
+| test.py:4:1:4:9 | ControlFlowNode for FunctionExpr | test.py:4:5:4:5 | GSSA Variable f |
+| test.py:5:7:5:11 | ControlFlowNode for BinaryExpr | test.py:5:3:5:3 | SSA variable y |
+| test.py:8:5:8:8 | ControlFlowNode for f() | test.py:8:1:8:1 | GSSA Variable c |