From 2c78aaa89fffd3bd010ac487b2b65ace2aad8fd1 Mon Sep 17 00:00:00 2001
From: Dor-bl <59066376+Dor-bl@users.noreply.github.com>
Date: Sun, 13 Sep 2026 21:40:20 +0000
Subject: [PATCH] perf: optimize string formatting in format_stacktrace

Construct file and meth strings directly with conditional expressions
to avoid intermediate string object allocations and re-allocations
inside the stack trace loop in MobileErrorHandler.
---
 appium/webdriver/errorhandler.py         | 12 ++--
 test/unit/webdriver/errorhandler_test.py | 74 ++++++++++++++++++++++++
 2 files changed, 80 insertions(+), 6 deletions(-)
 create mode 100644 test/unit/webdriver/errorhandler_test.py

diff --git a/appium/webdriver/errorhandler.py b/appium/webdriver/errorhandler.py
index d074b01a..7f8fc435 100644
--- a/appium/webdriver/errorhandler.py
+++ b/appium/webdriver/errorhandler.py
@@ -69,12 +69,12 @@ def format_stacktrace(original: None | str | Sequence) -> list[str]:
                 continue
 
             line = frame.get('lineNumber', '')
-            file = frame.get('fileName', '<anonymous>')
-            if line:
-                file = f'{file}:{line}'
-            meth = frame.get('methodName', '<anonymous>')
-            if 'className' in frame:
-                meth = f'{frame["className"]}.{meth}'
+            file = f'{frame.get("fileName", "<anonymous>")}:{line}' if line else frame.get('fileName', '<anonymous>')
+            meth = (
+                f'{frame["className"]}.{frame.get("methodName", "<anonymous>")}'
+                if 'className' in frame
+                else frame.get('methodName', '<anonymous>')
+            )
             result.append(f'    at {meth} ({file})')
     except TypeError:
         pass
diff --git a/test/unit/webdriver/errorhandler_test.py b/test/unit/webdriver/errorhandler_test.py
new file mode 100644
index 00000000..b24ccf70
--- /dev/null
+++ b/test/unit/webdriver/errorhandler_test.py
@@ -0,0 +1,74 @@
+#!/usr/bin/env python
+
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+from appium.webdriver.errorhandler import format_stacktrace
+
+
+def test_format_stacktrace_empty() -> None:
+    assert format_stacktrace(None) == []
+    assert format_stacktrace('') == []
+    assert format_stacktrace([]) == []
+
+
+def test_format_stacktrace_string() -> None:
+    assert format_stacktrace('line1\nline2\nline3') == ['line1', 'line2', 'line3']
+
+
+def test_format_stacktrace_frames() -> None:
+    frames = [
+        {
+            'fileName': 'App.js',
+            'lineNumber': 100,
+            'methodName': 'handleClick',
+            'className': 'AppComponent',
+        },
+        {
+            'fileName': 'Server.py',
+            'lineNumber': 42,
+            'methodName': 'process',
+        },
+        {
+            'methodName': 'anonymous_func',
+            'className': 'Util',
+        },
+        {
+            'fileName': 'index.js',
+        },
+        {},
+    ]
+
+    expected = [
+        '    at AppComponent.handleClick (App.js:100)',
+        '    at process (Server.py:42)',
+        '    at Util.anonymous_func (<anonymous>)',
+        '    at <anonymous> (index.js)',
+        '    at <anonymous> (<anonymous>)',
+    ]
+
+    assert format_stacktrace(frames) == expected
+
+
+def test_format_stacktrace_non_dict_elements() -> None:
+    frames = [
+        'not a dict',
+        123,
+        {'fileName': 'test.py', 'lineNumber': 10, 'methodName': 'foo'},
+        None,
+    ]
+    expected = ['    at foo (test.py:10)']
+    assert format_stacktrace(frames) == expected
+
+
+def test_format_stacktrace_invalid_type() -> None:
+    assert format_stacktrace(123) == []