Python: Add dataflow test for a,b = b,a

Also enables a single test to output more than one OK

Author: RasmusWL

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

@@ -131,6 +131,8 @@ edges
 | test.py:276:28:276:33 | ControlFlowNode for SOURCE | test.py:276:10:276:34 | ControlFlowNode for second() |
 | test.py:335:12:335:17 | ControlFlowNode for SOURCE | test.py:335:10:335:18 | ControlFlowNode for f() |
 | test.py:339:28:339:33 | ControlFlowNode for SOURCE | test.py:339:10:339:34 | ControlFlowNode for second() |
+| test.py:372:9:372:14 | ControlFlowNode for SOURCE | test.py:374:10:374:10 | ControlFlowNode for a |
+| test.py:372:9:372:14 | ControlFlowNode for SOURCE | test.py:379:10:379:10 | ControlFlowNode for b |
 nodes
 | datamodel.py:13:1:13:6 | GSSA Variable SOURCE | semmle.label | GSSA Variable SOURCE |
 | datamodel.py:13:10:13:17 | ControlFlowNode for Str | semmle.label | ControlFlowNode for Str |
@@ -260,6 +262,9 @@ nodes
 | test.py:335:12:335:17 | ControlFlowNode for SOURCE | semmle.label | ControlFlowNode for SOURCE |
 | test.py:339:10:339:34 | ControlFlowNode for second() | semmle.label | ControlFlowNode for second() |
 | test.py:339:28:339:33 | ControlFlowNode for SOURCE | semmle.label | ControlFlowNode for SOURCE |
+| test.py:372:9:372:14 | ControlFlowNode for SOURCE | semmle.label | ControlFlowNode for SOURCE |
+| test.py:374:10:374:10 | ControlFlowNode for a | semmle.label | ControlFlowNode for a |
+| test.py:379:10:379:10 | ControlFlowNode for b | semmle.label | ControlFlowNode for b |
 #select
 | datamodel.py:38:6:38:17 | ControlFlowNode for f() | datamodel.py:13:10:13:17 | ControlFlowNode for Str | datamodel.py:38:6:38:17 | ControlFlowNode for f() | <message> |
 | datamodel.py:38:6:38:17 | ControlFlowNode for f() | datamodel.py:38:8:38:13 | ControlFlowNode for SOURCE | datamodel.py:38:6:38:17 | ControlFlowNode for f() | <message> |
@@ -301,3 +306,5 @@ nodes
 | test.py:276:10:276:34 | ControlFlowNode for second() | test.py:276:28:276:33 | ControlFlowNode for SOURCE | test.py:276:10:276:34 | ControlFlowNode for second() | <message> |
 | test.py:335:10:335:18 | ControlFlowNode for f() | test.py:335:12:335:17 | ControlFlowNode for SOURCE | test.py:335:10:335:18 | ControlFlowNode for f() | <message> |
 | test.py:339:10:339:34 | ControlFlowNode for second() | test.py:339:28:339:33 | ControlFlowNode for SOURCE | test.py:339:10:339:34 | ControlFlowNode for second() | <message> |
+| test.py:374:10:374:10 | ControlFlowNode for a | test.py:372:9:372:14 | ControlFlowNode for SOURCE | test.py:374:10:374:10 | ControlFlowNode for a | <message> |
+| test.py:379:10:379:10 | ControlFlowNode for b | test.py:372:9:372:14 | ControlFlowNode for SOURCE | test.py:379:10:379:10 | ControlFlowNode for b | <message> |

python/ql/test/experimental/dataflow/coverage/test.py

@@ -366,3 +366,14 @@ def test_lambda_extra_keyword():
 def test_lambda_extra_keyword_flow():
     f_extra_keyword_flow = lambda **a : [*a][0] # return the name of the first extra keyword argument
     SINK(f_extra_keyword_flow(**{SOURCE: None})) # Flow missing
+
+
+def test_swap():
+    a = SOURCE
+    b = NONSOURCE
+    SINK(a)
+    SINK_F(b)
+
+    a, b = b, a
+    SINK_F(a)
+    SINK(b)

python/ql/test/experimental/dataflow/coverage/validTest.py

@@ -1,8 +1,8 @@
-def check_output(s, f):
-    if s == "OK\n":
+def check_output(outtext, f):
+    if all(s == "OK" for s in outtext.splitlines()):
         pass
     else:
-        raise RuntimeError("Function failed", s, f)
+        raise RuntimeError("Function failed", outtext, f)
 
 def check_test_function(f):
     from io import StringIO