Validate dir for pd.errors and pd.util (#57140)

* Ensure pandas.errors only imports its __all__

* Make public util API accessible

* Fix import

* Type input

doc/source/reference/index.rst

@@ -24,13 +24,14 @@ The following subpackages are public.
   `pandas-stubs <https://github.com/pandas-dev/pandas-stubs>`_ package
   which has classes in addition to those that occur in pandas for type-hinting.
 
-In addition, public functions in ``pandas.io`` and ``pandas.tseries`` submodules
-are mentioned in the documentation.
+In addition, public functions in ``pandas.io``, ``pandas.tseries``, ``pandas.util`` submodules
+are explicitly mentioned in the documentation. Further APIs in these modules are not guaranteed
+to be stable.
 
 
 .. warning::
 
-    The ``pandas.core``, ``pandas.compat``, and ``pandas.util`` top-level modules are PRIVATE. Stable functionality in such modules is not guaranteed.
+    The ``pandas.core``, ``pandas.compat`` top-level modules are PRIVATE. Stable functionality in such modules is not guaranteed.
 
 .. If you update this toctree, also update the manual toctree in the
 .. main index.rst.template

pandas/core/frame.py

@@ -60,6 +60,8 @@
 from pandas.errors import (
     ChainedAssignmentError,
     InvalidIndexError,
+)
+from pandas.errors.cow import (
     _chained_assignment_method_msg,
     _chained_assignment_msg,
     _chained_assignment_warning_method_msg,

pandas/core/generic.py

@@ -101,6 +101,8 @@
     InvalidIndexError,
     SettingWithCopyError,
     SettingWithCopyWarning,
+)
+from pandas.errors.cow import (
     _chained_assignment_method_msg,
     _chained_assignment_warning_method_msg,
     _check_cacher,

pandas/core/indexing.py

@@ -27,6 +27,8 @@
     IndexingError,
     InvalidIndexError,
     LossySetitemError,
+)
+from pandas.errors.cow import (
     _chained_assignment_msg,
     _chained_assignment_warning_msg,
     _check_cacher,

pandas/core/series.py

@@ -45,6 +45,8 @@
 from pandas.errors import (
     ChainedAssignmentError,
     InvalidIndexError,
+)
+from pandas.errors.cow import (
     _chained_assignment_method_msg,
     _chained_assignment_msg,
     _chained_assignment_warning_method_msg,

pandas/errors/__init__.py

@@ -475,81 +475,6 @@ class ChainedAssignmentError(Warning):
     """
 
 
-_chained_assignment_msg = (
-    "A value is trying to be set on a copy of a DataFrame or Series "
-    "through chained assignment.\n"
-    "When using the Copy-on-Write mode, such chained assignment never works "
-    "to update the original DataFrame or Series, because the intermediate "
-    "object on which we are setting values always behaves as a copy.\n\n"
-    "Try using '.loc[row_indexer, col_indexer] = value' instead, to perform "
-    "the assignment in a single step.\n\n"
-    "See the caveats in the documentation: "
-    "https://pandas.pydata.org/pandas-docs/stable/user_guide/"
-    "indexing.html#returning-a-view-versus-a-copy"
-)
-
-
-_chained_assignment_method_msg = (
-    "A value is trying to be set on a copy of a DataFrame or Series "
-    "through chained assignment using an inplace method.\n"
-    "When using the Copy-on-Write mode, such inplace method never works "
-    "to update the original DataFrame or Series, because the intermediate "
-    "object on which we are setting values always behaves as a copy.\n\n"
-    "For example, when doing 'df[col].method(value, inplace=True)', try "
-    "using 'df.method({col: value}, inplace=True)' instead, to perform "
-    "the operation inplace on the original object.\n\n"
-)
-
-
-_chained_assignment_warning_msg = (
-    "ChainedAssignmentError: behaviour will change in pandas 3.0!\n"
-    "You are setting values through chained assignment. Currently this works "
-    "in certain cases, but when using Copy-on-Write (which will become the "
-    "default behaviour in pandas 3.0) this will never work to update the "
-    "original DataFrame or Series, because the intermediate object on which "
-    "we are setting values will behave as a copy.\n"
-    "A typical example is when you are setting values in a column of a "
-    "DataFrame, like:\n\n"
-    'df["col"][row_indexer] = value\n\n'
-    'Use `df.loc[row_indexer, "col"] = values` instead, to perform the '
-    "assignment in a single step and ensure this keeps updating the original `df`.\n\n"
-    "See the caveats in the documentation: "
-    "https://pandas.pydata.org/pandas-docs/stable/user_guide/"
-    "indexing.html#returning-a-view-versus-a-copy\n"
-)
-
-
-_chained_assignment_warning_method_msg = (
-    "A value is trying to be set on a copy of a DataFrame or Series "
-    "through chained assignment using an inplace method.\n"
-    "The behavior will change in pandas 3.0. This inplace method will "
-    "never work because the intermediate object on which we are setting "
-    "values always behaves as a copy.\n\n"
-    "For example, when doing 'df[col].method(value, inplace=True)', try "
-    "using 'df.method({col: value}, inplace=True)' or "
-    "df[col] = df[col].method(value) instead, to perform "
-    "the operation inplace on the original object.\n\n"
-)
-
-
-def _check_cacher(obj) -> bool:
-    # This is a mess, selection paths that return a view set the _cacher attribute
-    # on the Series; most of them also set _item_cache which adds 1 to our relevant
-    # reference count, but iloc does not, so we have to check if we are actually
-    # in the item cache
-    if hasattr(obj, "_cacher"):
-        parent = obj._cacher[1]()
-        # parent could be dead
-        if parent is None:
-            return False
-        if hasattr(parent, "_item_cache"):
-            if obj._cacher[0] in parent._item_cache:
-                # Check if we are actually the item from item_cache, iloc creates a
-                # new object
-                return obj is parent._item_cache[obj._cacher[0]]
-    return False
-
-
 class NumExprClobberingError(NameError):
     """
     Exception raised when trying to use a built-in numexpr name as a variable name.
@@ -831,6 +756,7 @@ class InvalidComparison(Exception):
     "AbstractMethodError",
     "AttributeConflictWarning",
     "CategoricalConversionWarning",
+    "ChainedAssignmentError",
     "ClosedFileError",
     "CSSWarning",
     "DatabaseError",

pandas/errors/cow.py

@@ -0,0 +1,74 @@
+from typing import Any
+
+_chained_assignment_msg = (
+    "A value is trying to be set on a copy of a DataFrame or Series "
+    "through chained assignment.\n"
+    "When using the Copy-on-Write mode, such chained assignment never works "
+    "to update the original DataFrame or Series, because the intermediate "
+    "object on which we are setting values always behaves as a copy.\n\n"
+    "Try using '.loc[row_indexer, col_indexer] = value' instead, to perform "
+    "the assignment in a single step.\n\n"
+    "See the caveats in the documentation: "
+    "https://pandas.pydata.org/pandas-docs/stable/user_guide/"
+    "indexing.html#returning-a-view-versus-a-copy"
+)
+
+
+_chained_assignment_method_msg = (
+    "A value is trying to be set on a copy of a DataFrame or Series "
+    "through chained assignment using an inplace method.\n"
+    "When using the Copy-on-Write mode, such inplace method never works "
+    "to update the original DataFrame or Series, because the intermediate "
+    "object on which we are setting values always behaves as a copy.\n\n"
+    "For example, when doing 'df[col].method(value, inplace=True)', try "
+    "using 'df.method({col: value}, inplace=True)' instead, to perform "
+    "the operation inplace on the original object.\n\n"
+)
+
+
+_chained_assignment_warning_msg = (
+    "ChainedAssignmentError: behaviour will change in pandas 3.0!\n"
+    "You are setting values through chained assignment. Currently this works "
+    "in certain cases, but when using Copy-on-Write (which will become the "
+    "default behaviour in pandas 3.0) this will never work to update the "
+    "original DataFrame or Series, because the intermediate object on which "
+    "we are setting values will behave as a copy.\n"
+    "A typical example is when you are setting values in a column of a "
+    "DataFrame, like:\n\n"
+    'df["col"][row_indexer] = value\n\n'
+    'Use `df.loc[row_indexer, "col"] = values` instead, to perform the '
+    "assignment in a single step and ensure this keeps updating the original `df`.\n\n"
+    "See the caveats in the documentation: "
+    "https://pandas.pydata.org/pandas-docs/stable/user_guide/"
+    "indexing.html#returning-a-view-versus-a-copy\n"
+)
+
+_chained_assignment_warning_method_msg = (
+    "A value is trying to be set on a copy of a DataFrame or Series "
+    "through chained assignment using an inplace method.\n"
+    "The behavior will change in pandas 3.0. This inplace method will "
+    "never work because the intermediate object on which we are setting "
+    "values always behaves as a copy.\n\n"
+    "For example, when doing 'df[col].method(value, inplace=True)', try "
+    "using 'df.method({col: value}, inplace=True)' or "
+    "df[col] = df[col].method(value) instead, to perform "
+    "the operation inplace on the original object.\n\n"
+)
+
+
+def _check_cacher(obj: Any) -> bool:
+    # This is a mess, selection paths that return a view set the _cacher attribute
+    # on the Series; most of them also set _item_cache which adds 1 to our relevant
+    # reference count, but iloc does not, so we have to check if we are actually
+    # in the item cache
+    if hasattr(obj, "_cacher"):
+        parent = obj._cacher[1]()
+        # parent could be dead
+        if parent is None:
+            return False
+        if hasattr(parent, "_item_cache"):
+            if obj._cacher[0] in parent._item_cache:
+                # Check if we are actually the item from item_cache, iloc creates a
+                # new object
+                return obj is parent._item_cache[obj._cacher[0]]
+    return False

pandas/tests/api/test_api.py

@@ -357,6 +357,29 @@ def test_api_extensions(self):
         self.check(api_extensions, self.allowed_api_extensions)
 
 
+class TestErrors(Base):
+    def test_errors(self):
+        self.check(pd.errors, pd.errors.__all__, ignored=["ctypes", "cow"])
+
+
+class TestUtil(Base):
+    def test_util(self):
+        self.check(
+            pd.util,
+            ["hash_array", "hash_pandas_object"],
+            ignored=[
+                "_decorators",
+                "_test_decorators",
+                "_exceptions",
+                "_validators",
+                "capitalize_first_letter",
+                "version",
+                "_print_versions",
+                "_tester",
+            ],
+        )
+
+
 class TestTesting(Base):
     funcs = [
         "assert_frame_equal",

pandas/util/__init__.py

@@ -25,5 +25,9 @@ def __getattr__(key: str):
     raise AttributeError(f"module 'pandas.util' has no attribute '{key}'")
 
 
+def __dir__():
+    return list(globals().keys()) + ["hash_array", "hash_pandas_object"]
+
+
 def capitalize_first_letter(s: str) -> str:
     return s[:1].upper() + s[1:]