fix(er): include nonlocals in snapshots (#11894)

We include nonlocal variables in snapshots to provide for better
visibility into exception occurrences.

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[applicable](https://ddtrace.readthedocs.io/en/latest/contributing.html#backporting))

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(cherry picked from commit d7927e6)

ddtrace/debugging/_safety.py

@@ -1,5 +1,6 @@
 from inspect import CO_VARARGS
 from inspect import CO_VARKEYWORDS
+from itertools import chain
 from types import FrameType
 from typing import Any
 from typing import Dict
@@ -23,11 +24,11 @@ def get_args(frame: FrameType) -> Iterator[Tuple[str, Any]]:
 
 def get_locals(frame: FrameType) -> Iterator[Tuple[str, Any]]:
     code = frame.f_code
+    _locals = frame.f_locals
     nargs = code.co_argcount + bool(code.co_flags & CO_VARARGS) + bool(code.co_flags & CO_VARKEYWORDS)
-    names = code.co_varnames[nargs:]
-    values = (frame.f_locals.get(name) for name in names)
-
-    return zip(names, values)
+    return (
+        (name, _locals.get(name)) for name in chain(code.co_varnames[nargs:], code.co_freevars, code.co_cellvars)
+    )  # include freevars and cellvars
 
 
 def get_globals(frame: FrameType) -> Iterator[Tuple[str, Any]]:

releasenotes/notes/fix-er-include-nonlocals-bbeecfbbbde35496.yaml

@@ -0,0 +1,4 @@
+---
+fixes:
+  - |
+    exception replay: include missing nonlocal variables in snapshot log messages.

tests/debugging/exception/test_replay.py

@@ -294,3 +294,23 @@ def c(foo=42):
             self.assert_span_count(6)
             # no new snapshots
             assert len(uploader.collector.queue) == 3
+
+    def test_debugger_exception_in_closure(self):
+        def b():
+            with self.trace("b"):
+                nonloc = 4
+
+                def a(v):
+                    if nonloc:
+                        raise ValueError("hello", v)
+
+                a(nonloc)
+
+        with exception_replay() as uploader:
+            with with_rate_limiter(RateLimiter(limit_rate=1, raise_on_exceed=False)):
+                with pytest.raises(ValueError):
+                    b()
+
+            assert all(
+                s.line_capture["locals"]["nonloc"] == {"type": "int", "value": "4"} for s in uploader.collector.queue
+            )

tests/debugging/test_safety.py

@@ -15,7 +15,10 @@ def assert_args(args):
         assert set(dict(_safety.get_args(inspect.currentframe().f_back)).keys()) == args
 
     def assert_locals(_locals):
-        assert set(dict(_safety.get_locals(inspect.currentframe().f_back)).keys()) == _locals
+        assert set(dict(_safety.get_locals(inspect.currentframe().f_back)).keys()) == _locals | {
+            "assert_args",
+            "assert_locals",
+        }
 
     def assert_globals(_globals):
         assert set(dict(_safety.get_globals(inspect.currentframe().f_back)).keys()) == _globals