fix: Improve trimming of Swift function names (#72335)

Some Swift for Windows function names were trimmed to incorrect tokens
in the UI, resulting in hard-to-read stack traces. For instance, some
functions were shown as `"throws"` and closures were shown as `"#1"`.

This change fixes the former issue by using the correct function name.
Closures are now displayed as `"closure in <function name>"`, and
initialization expressions are displayed as `"initializer expression of
<value>"`, improving the user experience when browsing stack traces.

### Legal Boilerplate

Look, I get it. The entity doing business as "Sentry" was incorporated
in the State of Delaware in 2015 as Functional Software, Inc. and is
gonna need some rights from me in order to utilize my contributions in
this here PR. So here's the deal: I retain all rights, title and
interest in and to my contributions, and by keeping this boilerplate
intact I confirm that Sentry can use, modify, copy, and redistribute my
contributions, under Sentry's choice of terms.

Author: Steelskin

src/sentry/stacktraces/functions.py

@@ -228,19 +228,40 @@ def process_generics(value, start):
     #
     # ["unsigned", "int", "whatever"] -> whatever
     # ["@objc", "whatever", "->", "int"] -> whatever
-    try:
-        func_token = tokens[tokens.index("⟿") - 1]
-    except ValueError:
-        if tokens:
+    if function.find("initialization expression of") != -1:
+        # Swift initializer expression.
+        last_of_index = len(tokens) - 1 - tokens[::-1].index("of")
+        func_token = tokens[last_of_index + 1]
+        if func_token == "static":
+            # Static initializer expression, the object is the next token.
+            func_token = tokens[last_of_index + 2]
+        if func_token.startswith(":"):
+            # Trim the colon from the function name.
+            func_token = func_token[1:]
+        func_token = "initializer expression of " + func_token
+    elif tokens:
+        try:
+            last_arrow_index = len(tokens) - 1 - tokens[::-1].index("⟿")
+            func_token = tokens[last_arrow_index - 1]
+            if func_token == "throws":
+                # Throwing Swift function, the function name is the previous token.
+                func_token = tokens[last_arrow_index - 2]
+        except (ValueError, IndexError):
+            # No arrow, use the last token.
+            last_arrow_index = -1
             func_token = tokens[-1]
-        else:
-            func_token = None
+    else:
+        func_token = None
 
     if func_token:
         if func_token.startswith("@") and platform in ("cocoa", "swift"):
             # Found a Swift attribute instead of a function name, must be an
             # anonymous function
             func_token = ("thunk for " if is_thunk else "") + "closure"
+        elif "closure" in tokens and func_token != "closure":
+            # Found a closure.
+            func_token = "closure in " + func_token
+
         function = (
             func_token.replace("⟨", "<")
             .replace("◯", "()")

tests/sentry/grouping/snapshots/test_variants/test_event_hash_variant/newstyle@2019_04_05/in_app_in_ui.pysnap

@@ -4,7 +4,7 @@ creator: sentry
 source: tests/sentry/grouping/test_variants.py
 ---
 app:
-  hash: "9b037f38798ea127aac3e8b8e1e1024a"
+  hash: "61c031e5e187212561f67b5567f8ae47"
   component:
     app*
       exception*
@@ -122,7 +122,7 @@ app:
             filename*
               "mediaslideshow+extensions.swift"
             function* (isolated function)
-              "MediaSlideshow.toSources"
+              "closure in MediaSlideshow.toSources"
           frame*
             filename*
               "mediaslideshow+extensions.swift"
@@ -147,7 +147,7 @@ app:
           "EXC_BREAKPOINT"
 --------------------------------------------------------------------------
 system:
-  hash: "fe8b15fe322c91ede2fc48363fe43587"
+  hash: "7c47e696e27052f4849cb07e99cf649e"
   component:
     system*
       exception*
@@ -265,7 +265,7 @@ system:
             filename*
               "mediaslideshow+extensions.swift"
             function* (isolated function)
-              "MediaSlideshow.toSources"
+              "closure in MediaSlideshow.toSources"
           frame*
             filename*
               "mediaslideshow+extensions.swift"

tests/sentry/stacktraces/test_functions.py

@@ -103,6 +103,30 @@
         ],
         ["pthread_cond_timedwait@@GLIBC_2.3.2", "pthread_cond_timedwait"],
         ["glob64@GLIBC_2.2", "glob64"],
+        [
+            "static Namespace.ThrowingFunction() throws -> Namespace.ExitValue?",
+            "Namespace.ThrowingFunction",
+        ],
+        [
+            "closure #1 @Swift.MainActor () -> () in static Foo.CallFunction(args: [Swift.String]) -> ()",
+            "closure in Foo.CallFunction",
+        ],
+        [
+            "closure #1 () -> () in Bar.PostTask(() -> ()) -> ()",
+            "closure in Bar.PostTask",
+        ],
+        [
+            "closure #1 @Sendable () -> Swift.String in variable initialization expression of static Namespace.Class.var : Namespace.Parent",
+            "closure in initializer expression of Namespace.Class.var",
+        ],
+        [
+            "variable initialization expression of static Namespace.Class.var : Namespace.Parent",
+            "initializer expression of Namespace.Class.var",
+        ],
+        [
+            "closure #1 () -> () in variable initialization expression of static (extension in SpaceCreation):Namespace.Class.var : Namespace.Parent",
+            "closure in initializer expression of Namespace.Class.var",
+        ],
     ],
 )
 def test_trim_native_function_name(input, output):
@@ -142,14 +166,13 @@ def test_trim_csharp_function_name(input, output):
             "partial apply for thunk for @escaping @callee_guaranteed (@guaranteed SomeType, @guaranteed [String : SomeType2], @guaranteed SomeType3) -> ()",
             "thunk for closure",
         ],
-        [  # "closure ... in ..." functions are converted to containing
-            # function. We might want to change this in the future
+        [
             "closure #1 (T1) in foo(bar: T2)",
-            "foo",
+            "closure in foo",
         ],
         [
             "partial apply for closure #1 () in closure #2 (T1) in f1(_: T2, arg: T3)",
-            "f1",
+            "closure in f1",
         ],
     ],
 )