fix(grouping): Correctly handle multiple threads in fingerprinting code

src/sentry/grouping/fingerprinting.py

@@ -57,6 +57,17 @@ class InvalidFingerprintingConfig(Exception):
     pass
 
 
+def get_crashing_thread(threads):
+    if len(threads) == 1:
+        return threads[0]
+    filtered = [x for x in threads if x and x.get("crashed")]
+    if len(filtered) == 1:
+        return filtered[0]
+    filtered = [x for x in threads if x and x.get("current")]
+    if len(filtered) == 1:
+        return filtered[0]
+
+
 class EventAccess:
     def __init__(self, event):
         self.event = event
@@ -139,8 +150,9 @@ def _push_frame(frame):
                 frames = get_path(self.event, "stacktrace", "frames", filter=True)
                 if not frames:
                     threads = get_path(self.event, "threads", "values", filter=True)
-                    if threads and len(threads) == 1:
-                        frames = get_path(threads, 0, "stacktrace", "frames")
+                    thread = get_crashing_thread(threads)
+                    if thread is not None:
+                        frames = get_path(thread, "stacktrace", "frames")
                 for frame in frames or ():
                     _push_frame(frame)
 

tests/sentry/grouping/fingerprint_inputs/fingerprint-two-threads.json

@@ -0,0 +1,66 @@
+{
+  "_fingerprinting_rules": [
+    {
+      "matchers": [
+        ["function", "main"]
+      ],
+      "fingerprint": ["in-main"]
+    }
+  ],
+  "threads": {
+    "values": [
+      {
+        "stacktrace": {
+          "frames": [
+            {
+              "function": "main",
+              "abs_path": "foo/baz.c",
+              "filename": "foo/baz.c",
+              "lineno": 1,
+              "in_app": true
+            }
+          ]
+        },
+        "name": "Main Thread",
+        "current": true,
+        "crashed": true,
+        "raw_stacktrace": {
+          "frames": [
+            {
+              "function": "<redacted>",
+              "lineno": 1,
+              "in_app": true
+            }
+          ]
+        },
+        "id": 42
+      },
+      {
+        "stacktrace": {
+          "frames": [
+            {
+              "function": "main",
+              "abs_path": "foo/baz.c",
+              "filename": "foo/baz.c",
+              "lineno": 1,
+              "in_app": true
+            }
+          ]
+        },
+        "name": "Other Thread",
+        "current": false,
+        "crashed": false,
+        "raw_stacktrace": {
+          "frames": [
+            {
+              "function": "<redacted>",
+              "lineno": 1,
+              "in_app": true
+            }
+          ]
+        },
+        "id": 43
+      }
+    ]
+  }
+}

tests/sentry/grouping/similarity/snapshots/test_features/test_similarity_extract_fingerprinting/fingerprint_two_threads.pysnap

@@ -0,0 +1,7 @@
+---
+created: '2021-10-09T08:58:47.042020Z'
+creator: sentry
+source: tests/sentry/grouping/similarity/test_features.py
+---
+similarity:2020-07-23:fingerprint:ident-shingle: "in-main"
+similarity:2020-07-23:stacktrace:frames-ident: [["filename","baz.c"],["function","main"]]

tests/sentry/grouping/snapshots/test_fingerprinting/test_event_hash_variant/fingerprint_two_threads.pysnap

@@ -0,0 +1,35 @@
+---
+created: '2021-10-09T08:26:55.655641Z'
+creator: sentry
+source: tests/sentry/grouping/test_fingerprinting.py
+---
+config:
+  rules:
+  - attributes: {}
+    fingerprint:
+    - in-main
+    matchers:
+    - - function
+      - main
+  version: 1
+fingerprint:
+- in-main
+title: <unlabeled event>
+variants:
+  app:
+    component:
+      contributes: false
+      contributes_to_similarity: true
+      hint: custom fingerprint takes precedence
+    type: component
+  custom-fingerprint:
+    matched_rule: function:"main" -> "in-main"
+    type: custom-fingerprint
+    values:
+    - in-main
+  system:
+    component:
+      contributes: false
+      contributes_to_similarity: true
+      hint: custom fingerprint takes precedence
+    type: component