[lldb] Support expectedFlakey decorator in dotest

The dotest framework had an existing decorator to mark flakey tests. It
was not implemented and would simply run the underlying test. This
commit modifies the decorator to run the test multiple times in the case
of failure and only raises the test failure when all attempts fail.

Author: dmpots

lldb/packages/Python/lldbsuite/test/decorators.py

@@ -3,6 +3,7 @@
 from packaging import version
 import ctypes
 import locale
+import logging
 import os
 import platform
 import re
@@ -525,12 +526,24 @@ def expectedFailureWindows(bugnumber=None):
     return expectedFailureOS(["windows"], bugnumber)
 
 
-# TODO: This decorator does not do anything. Remove it.
-def expectedFlakey(expected_fn, bugnumber=None):
+# This decorator can be used to mark a test that can fail non-deterministically.
+# The decorator causes the underlying test to be re-run if it encounters a
+# failure. After `num_retries` attempts the test will be marked as a failure
+# if it has not yet passed.
+def expectedFlakey(expected_fn, bugnumber=None, num_retries=3):
     def expectedFailure_impl(func):
         @wraps(func)
         def wrapper(*args, **kwargs):
-            func(*args, **kwargs)
+            for i in range(1, num_retries+1):
+                try:
+                    return func(*args, **kwargs)
+                except Exception:
+                    logging.warning(
+                        f"expectedFlakey: test {func} failed attempt ({i}/{num_retries})"
+                    )
+                    # If the last attempt fails then re-raise the original failure.
+                    if i == num_retries:
+                        raise
 
         return wrapper