From ef8c34ece36adbb14cab6d628170930a2ae4b93c Mon Sep 17 00:00:00 2001
From: Maxim Ivanov <ivanovmg@gmail.com>
Date: Wed, 23 Dec 2020 00:39:40 +0700
Subject: [PATCH 1/2] REF: simplify logic in assert_produces_warning

---
 pandas/_testing.py | 116 +++++++++++++++++++++++++++++----------------
 1 file changed, 76 insertions(+), 40 deletions(-)

diff --git a/pandas/_testing.py b/pandas/_testing.py
index cad95ca571258..52ac90e84092c 100644
--- a/pandas/_testing.py
+++ b/pandas/_testing.py
@@ -16,6 +16,7 @@
     ContextManager,
     List,
     Optional,
+    Sequence,
     Tuple,
     Type,
     Union,
@@ -2715,65 +2716,100 @@ class for all warnings. To check that no warning is returned,
     __tracebackhide__ = True
 
     with warnings.catch_warnings(record=True) as w:
-
-        saw_warning = False
-        matched_message = False
-
         warnings.simplefilter(filter_level)
         yield w
-        extra_warnings = []
 
-        for actual_warning in w:
+        if expected_warning:
             expected_warning = cast(Type[Warning], expected_warning)
-            if expected_warning and issubclass(
-                actual_warning.category, expected_warning
+            _assert_caught_expected_warning(
+                caught_warnings=w,
+                expected_warning=expected_warning,
+                match=match,
+                check_stacklevel=check_stacklevel,
+            )
+
+        if raise_on_extra_warnings:
+            _assert_caught_no_extra_warnings(
+                caught_warnings=w,
+                expected_warning=expected_warning,
+            )
+
+
+def _assert_caught_expected_warning(
+    *,
+    caught_warnings: Sequence[warnings.WarningMessage],
+    expected_warning: Type[Warning],
+    match: Optional[str],
+    check_stacklevel: bool,
+) -> None:
+    """Assert that there was the expected warning among the caught warnings."""
+    saw_warning = False
+    matched_message = False
+
+    for actual_warning in caught_warnings:
+        if issubclass(actual_warning.category, expected_warning):
+            saw_warning = True
+
+            if check_stacklevel and issubclass(
+                actual_warning.category, (FutureWarning, DeprecationWarning)
             ):
-                saw_warning = True
+                _assert_raised_with_correct_stacklevel(actual_warning)
 
-                if check_stacklevel and issubclass(
-                    actual_warning.category, (FutureWarning, DeprecationWarning)
-                ):
-                    _assert_raised_with_correct_stacklevel(actual_warning)
+            if match is not None and re.search(match, str(actual_warning.message)):
+                matched_message = True
 
-                if match is not None and re.search(match, str(actual_warning.message)):
-                    matched_message = True
+    if not saw_warning:
+        raise AssertionError(
+            f"Did not see expected warning of class "
+            f"{repr(expected_warning.__name__)}"
+        )
 
-            else:
-                extra_warnings.append(
-                    (
-                        actual_warning.category.__name__,
-                        actual_warning.message,
-                        actual_warning.filename,
-                        actual_warning.lineno,
-                    )
-                )
+    if match and not matched_message:
+        raise AssertionError(
+            f"Did not see warning {repr(expected_warning.__name__)} "
+            f"matching {match}"
+        )
 
-        if expected_warning:
-            expected_warning = cast(Type[Warning], expected_warning)
-            if not saw_warning:
-                raise AssertionError(
-                    f"Did not see expected warning of class "
-                    f"{repr(expected_warning.__name__)}"
-                )
 
-            if match and not matched_message:
-                raise AssertionError(
-                    f"Did not see warning {repr(expected_warning.__name__)} "
-                    f"matching {match}"
+def _assert_caught_no_extra_warnings(
+    *,
+    caught_warnings: Sequence[warnings.WarningMessage],
+    expected_warning: Optional[Union[Type[Warning], bool]],
+):
+    extra_warnings = []
+
+    for actual_warning in caught_warnings:
+        if _is_unexpected_warning(actual_warning, expected_warning):
+            extra_warnings.append(
+                (
+                    actual_warning.category.__name__,
+                    actual_warning.message,
+                    actual_warning.filename,
+                    actual_warning.lineno,
                 )
-
-        if raise_on_extra_warnings and extra_warnings:
-            raise AssertionError(
-                f"Caused unexpected warning(s): {repr(extra_warnings)}"
             )
 
+    if extra_warnings:
+        raise AssertionError(f"Caused unexpected warning(s): {repr(extra_warnings)}")
+
+
+def _is_unexpected_warning(
+    actual_warning: warnings.WarningMessage,
+    expected_warning: Optional[Union[Type[Warning], bool]],
+) -> bool:
+    """Check if the actual warning issued is unexpected."""
+    if actual_warning and not expected_warning:
+        return True
+    expected_warning = cast(Type[Warning], expected_warning)
+    return bool(not issubclass(actual_warning.category, expected_warning))
+
 
 def _assert_raised_with_correct_stacklevel(
     actual_warning: warnings.WarningMessage,
 ) -> None:
     from inspect import getframeinfo, stack
 
-    caller = getframeinfo(stack()[3][0])
+    caller = getframeinfo(stack()[4][0])
     msg = (
         "Warning not set with correct stacklevel. "
         f"File where warning is raised: {actual_warning.filename} != "

From d31d485153645dce2e3ab52c5a9fb12d9b93bf65 Mon Sep 17 00:00:00 2001
From: Maxim Ivanov <ivanovmg@gmail.com>
Date: Wed, 23 Dec 2020 02:33:03 +0700
Subject: [PATCH 2/2] DOC: add docstring

---
 pandas/_testing.py | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/pandas/_testing.py b/pandas/_testing.py
index 52ac90e84092c..7786eeeb46797 100644
--- a/pandas/_testing.py
+++ b/pandas/_testing.py
@@ -2775,7 +2775,8 @@ def _assert_caught_no_extra_warnings(
     *,
     caught_warnings: Sequence[warnings.WarningMessage],
     expected_warning: Optional[Union[Type[Warning], bool]],
-):
+) -> None:
+    """Assert that no extra warnings apart from the expected ones are caught."""
     extra_warnings = []
 
     for actual_warning in caught_warnings: