chore(di): capture exception chain (#11771)

We augment the exception fields with known exception chaining attributes
to allow capturing exception chaining relations. The fields need to be
added manually because they are part of the BaseException built-in
fields and are not included in the object's __dict__ attribute.

## Checklist
- [x] PR author has checked that all the criteria below are met
- The PR description includes an overview of the change
- The PR description articulates the motivation for the change
- The change includes tests OR the PR description describes a testing
strategy
- The PR description notes risks associated with the change, if any
- Newly-added code is easy to change
- The change follows the [library release note
guidelines](https://ddtrace.readthedocs.io/en/stable/releasenotes.html)
- The change includes or references documentation updates if necessary
- Backport labels are set (if
[applicable](https://ddtrace.readthedocs.io/en/latest/contributing.html#backporting))

## Reviewer Checklist
- [ ] Reviewer has checked that all the criteria below are met 
- Title is accurate
- All changes are related to the pull request's stated goal
- Avoids breaking
[API](https://ddtrace.readthedocs.io/en/stable/versioning.html#interfaces)
changes
- Testing strategy adequately addresses listed risks
- Newly-added code is easy to change
- Release note makes sense to a user of the library
- If necessary, author has acknowledged and discussed the performance
implications of this PR as reported in the benchmarks PR comment
- Backport labels are set in a manner that is consistent with the
[release branch maintenance
policy](https://ddtrace.readthedocs.io/en/latest/contributing.html#backporting)

ddtrace/debugging/_signal/utils.py

@@ -304,6 +304,15 @@ def capture_value(
         }
 
     fields = get_fields(value)
+
+    # Capture exception chain for exceptions
+    if _isinstance(value, BaseException):
+        for attr in ("args", "__cause__", "__context__", "__suppress_context__"):
+            try:
+                fields[attr] = object.__getattribute__(value, attr)
+            except AttributeError:
+                pass
+
     captured_fields = {
         n: (
             capture_value(v, level=level - 1, maxlen=maxlen, maxsize=maxsize, maxfields=maxfields, stopping_cond=cond)

tests/debugging/exception/test_replay.py

@@ -161,8 +161,8 @@ def b_chain(bar):
                 m = 4
                 try:
                     a(bar % m)
-                except ValueError:
-                    raise KeyError("chain it")
+                except ValueError as exc:
+                    raise KeyError("chain it") from exc
 
         def c(foo=42):
             with self.trace("c"):

tests/debugging/test_debugger.py

@@ -210,7 +210,25 @@ def test_debugger_function_probe_on_function_with_exception():
 
     return_capture = snapshot_data["captures"]["return"]
     assert return_capture["arguments"] == {}
-    assert return_capture["locals"] == {"@exception": {"fields": {}, "type": "Exception"}}
+    assert return_capture["locals"] == {
+        "@exception": {
+            "type": "Exception",
+            "fields": {
+                "args": {
+                    "type": "tuple",
+                    "elements": [
+                        {"type": "str", "value": "'Hello'"},
+                        {"type": "str", "value": "'world!'"},
+                        {"type": "int", "value": "42"},
+                    ],
+                    "size": 3,
+                },
+                "__cause__": {"type": "NoneType", "isNull": True},
+                "__context__": {"type": "NoneType", "isNull": True},
+                "__suppress_context__": {"type": "bool", "value": "False"},
+            },
+        }
+    }
     assert return_capture["throwable"]["message"] == "'Hello', 'world!', 42"
     assert return_capture["throwable"]["type"] == "Exception"
 

tests/debugging/test_encoding.py

@@ -191,7 +191,21 @@ def _():
 
         exc = context.pop("throwable")
         assert context["arguments"] == {}
-        assert context["locals"] == {"@exception": {"type": "Exception", "fields": {}}}
+        assert context["locals"] == {
+            "@exception": {
+                "type": "Exception",
+                "fields": {
+                    "args": {
+                        "type": "tuple",
+                        "elements": [{"type": "str", "value": "'test'"}, {"type": "str", "value": "'me'"}],
+                        "size": 2,
+                    },
+                    "__cause__": {"type": "NoneType", "isNull": True},
+                    "__context__": {"type": "NoneType", "isNull": True},
+                    "__suppress_context__": {"type": "bool", "value": "False"},
+                },
+            }
+        }
         assert exc["message"] == "'test', 'me'"
         assert exc["type"] == "Exception"