Python: test shared CFG node reachability

Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>

Author: yoff

python/ql/test/library-tests/ControlFlow/shared-cfg-reachability/StrictlyReachesTest.expected

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+/**
+ * Inline-expectations test for node reachability in the shared CFG facade.
+ */
+
+import python
+import semmle.python.controlflow.internal.Cfg as Cfg
+import utils.test.InlineExpectationsTest
+
+private Cfg::NameNode namedNode(string id) { result.getId() = id }
+
+private Call reachabilityCase(string category, string sourceId, string destinationId) {
+  result.getFunc().(Name).getId() = "__reachability_case__" and
+  category = result.getPositionalArg(0).(StringLiteral).getText() and
+  sourceId = result.getPositionalArg(1).(StringLiteral).getText() and
+  destinationId = result.getPositionalArg(2).(StringLiteral).getText()
+}
+
+module StrictlyReachesTest implements TestSig {
+  string getARelevantTag() { result = ["reaches", "not-reaches"] }
+
+  predicate hasActualResult(Location location, string element, string tag, string value) {
+    exists(
+      Call marker, string sourceId, string destinationId, Cfg::NameNode source,
+      Cfg::NameNode destination
+    |
+      marker = reachabilityCase(value, sourceId, destinationId) and
+      source = namedNode(sourceId) and
+      source.isStore() and
+      destination = namedNode(destinationId) and
+      destination.isStore() and
+      location = marker.getLocation() and
+      element = marker.toString() and
+      (
+        tag = "reaches" and
+        source.strictlyReaches(destination)
+        or
+        tag = "not-reaches" and
+        not source.strictlyReaches(destination)
+      )
+    )
+  }
+}
+
+import MakeTest<StrictlyReachesTest>

python/ql/test/library-tests/ControlFlow/shared-cfg-reachability/StrictlyReachesTest.ql

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+module_anchor = 0
+
+
+def linear():
+    same_first = 1
+    same_second = same_first + 1
+    return same_second
+
+
+def branch(branch_condition):
+    branch_entry = 0
+    if branch_condition:
+        branch_left = 1
+    else:
+        branch_right = 2
+    branch_join = branch_entry
+    return branch_join
+
+
+def loop(loop_condition):
+    loop_seed = 0
+    while loop_condition:
+        loop_body = loop_seed
+        loop_latch = loop_body
+    after_loop = loop_seed
+    return after_loop
+
+
+def first_scope():
+    first_scope_start = 0
+    first_scope_end = first_scope_start + 1
+    return first_scope_end
+
+
+def second_scope():
+    second_scope_node = 0
+    return second_scope_node
+
+
+__reachability_case__("same-block-forward", "same_first", "same_second")  # $ reaches=same-block-forward
+__reachability_case__("same-block-reverse", "same_second", "same_first")  # $ not-reaches=same-block-reverse
+__reachability_case__("branch-left-to-join", "branch_left", "branch_join")  # $ reaches=branch-left-to-join
+__reachability_case__("branch-right-to-join", "branch_right", "branch_join")  # $ reaches=branch-right-to-join
+__reachability_case__("branch-siblings", "branch_left", "branch_right")  # $ not-reaches=branch-siblings
+__reachability_case__("loop-backedge", "loop_latch", "loop_body")  # $ reaches=loop-backedge
+__reachability_case__("loop-exit", "loop_body", "after_loop")  # $ reaches=loop-exit
+__reachability_case__("distinct-scopes", "first_scope_start", "second_scope_node")  # $ not-reaches=distinct-scopes