fix: 3.11 now traces decorator lines as the decorators execute

See: https://bugs.python.org/issue46234

4 files changed, 38 insertions, 10 deletions

diff --git a/coverage/env.py b/coverage/env.py
index 64d93e21..cf2f9d26 100644
--- a/coverage/env.py
+++ b/coverage/env.py
@@ -100,6 +100,10 @@ class PYBEHAVIOR:
     # Some words are keywords in some places, identifiers in other places.
     soft_keywords = (PYVERSION >= (3, 10))
 
+    # CPython 3.11 now jumps to the decorator line again while executing
+    # the decorator.
+    trace_decorator_line_again = (PYVERSION > (3, 11, 0, 'alpha', 3, 0))
+
 
 # Coverage.py specifics.
 
diff --git a/coverage/parser.py b/coverage/parser.py
index 665360fa..a96964d4 100644
--- a/coverage/parser.py
+++ b/coverage/parser.py
@@ -944,10 +944,11 @@ class AstArcAnalyzer:
     def _handle_decorated(self, node):
         """Add arcs for things that can be decorated (classes and functions)."""
         main_line = last = node.lineno
-        if node.decorator_list:
+        decs = node.decorator_list
+        if decs:
             if env.PYBEHAVIOR.trace_decorated_def:
                 last = None
-            for dec_node in node.decorator_list:
+            for dec_node in decs:
                 dec_start = self.line_for_node(dec_node)
                 if last is not None and dec_start != last:
                     self.add_arc(last, dec_start)
@@ -955,6 +956,11 @@ class AstArcAnalyzer:
             if env.PYBEHAVIOR.trace_decorated_def:
                 self.add_arc(last, main_line)
                 last = main_line
+            if env.PYBEHAVIOR.trace_decorator_line_again:
+                for top, bot in zip(decs, decs[1:]):
+                    self.add_arc(self.line_for_node(bot), self.line_for_node(top))
+                self.add_arc(self.line_for_node(decs[0]), main_line)
+                self.add_arc(main_line, self.line_for_node(decs[-1]))
             # The definition line may have been missed, but we should have it
             # in `self.statements`.  For some constructs, `line_for_node` is
             # not what we'd think of as the first line in the statement, so map
diff --git a/tests/test_arcs.py b/tests/test_arcs.py
index 978a3731..0635fcbc 100644
--- a/tests/test_arcs.py
+++ b/tests/test_arcs.py
@@ -1664,6 +1664,13 @@ class DecoratorArcTest(CoverageTest):
     """Tests of arcs with decorators."""
 
     def test_function_decorator(self):
+        arcz = (
+            ".1 16 67 7A AE EF F. "     # main line
+            ".2 24 4.   -23 3-2 "       # decorators
+            "-6D D-6 "                  # my_function
+        )
+        if env.PYBEHAVIOR.trace_decorator_line_again:
+            arcz += "A7 76 6A "
         self.check_coverage("""\
             def decorator(arg):
                 def _dec(f):
@@ -1681,13 +1688,17 @@ class DecoratorArcTest(CoverageTest):
             a = 14
             my_function()
             """,
-            arcz=
-                ".1 16 67 7A AE EF F. "     # main line
-                ".2 24 4.   -23 3-2 "       # decorators
-                "-6D D-6 ",                 # my_function
+            arcz=arcz,
         )
 
     def test_class_decorator(self):
+        arcz = (
+            ".1 16 67 6D 7A AE E. "     # main line
+            ".2 24 4.   -23 3-2 "       # decorators
+            "-66 D-6 "                  # MyObject
+        )
+        if env.PYBEHAVIOR.trace_decorator_line_again:
+            arcz += "A7 76 6A "
         self.check_coverage("""\
             def decorator(arg):
                 def _dec(c):
@@ -1704,10 +1715,7 @@ class DecoratorArcTest(CoverageTest):
                 X = 13
             a = 14
             """,
-            arcz=
-                ".1 16 67 6D 7A AE E. "     # main line
-                ".2 24 4.   -23 3-2 "       # decorators
-                "-66 D-6 ",                 # MyObject
+            arcz=arcz,
         )
 
     def test_bug_466a(self):
@@ -1716,6 +1724,8 @@ class DecoratorArcTest(CoverageTest):
         arcz = ".1 1A A.  13 3.     -35 58 8-3 "
         if env.PYBEHAVIOR.trace_decorated_def:
             arcz = arcz.replace("3.", "34 4.")
+        if env.PYBEHAVIOR.trace_decorator_line_again:
+            arcz += "43 "
         self.check_coverage("""\
             class Parser(object):
 
@@ -1737,6 +1747,8 @@ class DecoratorArcTest(CoverageTest):
         arcz = ".1 1A A.  13 3.     -35 58 8-3 "
         if env.PYBEHAVIOR.trace_decorated_def:
             arcz = arcz.replace("3.", "34 4.")
+        if env.PYBEHAVIOR.trace_decorator_line_again:
+            arcz += "43 "
         self.check_coverage("""\
             class Parser(object):
 
@@ -1925,6 +1937,8 @@ class AsyncTest(CoverageTest):
         arcz = ".1 14 4.     .2 2.  -46 6-4 "
         if env.PYBEHAVIOR.trace_decorated_def:
             arcz = arcz.replace("4.", "45 5.")
+        if env.PYBEHAVIOR.trace_decorator_line_again:
+            arcz += "54 "
         self.check_coverage("""\
             def wrap(f):        # 1
                 return f
diff --git a/tests/test_parser.py b/tests/test_parser.py
index 1e509035..2393ccd1 100644
--- a/tests/test_parser.py
+++ b/tests/test_parser.py
@@ -240,6 +240,10 @@ class PythonParserTest(CoverageTest):
             expected_arcs.update(set(arcz_to_arcs("-46 6-4")))
             expected_exits.update({6: 1})
 
+        if env.PYBEHAVIOR.trace_decorator_line_again:
+            expected_arcs.update(set(arcz_to_arcs("54 98")))
+            expected_exits.update({9: 2, 5: 2})
+
         assert expected_statements == parser.statements
         assert expected_arcs == parser.arcs()
         assert expected_exits == parser.exit_counts()