address review

pymongo/auth_aws.py

@@ -15,7 +15,6 @@
 """MONGODB-AWS Authentication helpers."""
 from __future__ import annotations
 
-import importlib.util
 from typing import TYPE_CHECKING, Any, Mapping, Type
 
 import bson
@@ -27,19 +26,18 @@
     from pymongo.auth import MongoCredential
     from pymongo.pool import Connection
 
-_HAVE_MONGODB_AWS = importlib.util.find_spec("pymongo_auth_aws") is not None
-
 
 def _authenticate_aws(credentials: MongoCredential, conn: Connection) -> None:
     """Authenticate using MONGODB-AWS."""
-    if not _HAVE_MONGODB_AWS:
+    try:
+        import pymongo_auth_aws  # type:ignore[import]
+    except ImportError:
         raise ConfigurationError(
             "MONGODB-AWS authentication requires pymongo-auth-aws: "
             "install with: python -m pip install 'pymongo[aws]'"
-        )
+        ) from None
 
-    # Delayed imports.
-    import pymongo_auth_aws  # type:ignore[import]
+    # Delayed import.
     from pymongo_auth_aws.auth import (  # type:ignore[import]
         set_cached_credentials,
         set_use_cached_credentials,

pymongo/compression_support.py

@@ -13,22 +13,44 @@
 # limitations under the License.
 from __future__ import annotations
 
-import importlib.util
 import warnings
 from typing import Any, Iterable, Optional, Union
 
 from pymongo.hello import HelloCompat
 from pymongo.helpers import _SENSITIVE_COMMANDS
 
-_HAVE_SNAPPY = importlib.util.find_spec("snappy") is not None
-_HAVE_ZLIB = importlib.util.find_spec("zlib") is not None
-_HAVE_ZSTD = importlib.util.find_spec("zstandard") is not None
-
 _SUPPORTED_COMPRESSORS = {"snappy", "zlib", "zstd"}
 _NO_COMPRESSION = {HelloCompat.CMD, HelloCompat.LEGACY_CMD}
 _NO_COMPRESSION.update(_SENSITIVE_COMMANDS)
 
 
+def _have_snappy() -> bool:
+    try:
+        import snappy  # type:ignore[import]  # noqa: F401
+
+        return True
+    except ImportError:
+        return False
+
+
+def _have_zlib() -> bool:
+    try:
+        import zlib  # noqa: F401
+
+        return True
+    except ImportError:
+        return False
+
+
+def _have_zstd() -> bool:
+    try:
+        import zstandard  # type:ignore[import]  # noqa: F401
+
+        return True
+    except ImportError:
+        return False
+
+
 def validate_compressors(dummy: Any, value: Union[str, Iterable[str]]) -> list[str]:
     try:
         # `value` is string.
@@ -41,21 +63,21 @@ def validate_compressors(dummy: Any, value: Union[str, Iterable[str]]) -> list[s
         if compressor not in _SUPPORTED_COMPRESSORS:
             compressors.remove(compressor)
             warnings.warn(f"Unsupported compressor: {compressor}", stacklevel=2)
-        elif compressor == "snappy" and not _HAVE_SNAPPY:
+        elif compressor == "snappy" and not _have_snappy():
             compressors.remove(compressor)
             warnings.warn(
                 "Wire protocol compression with snappy is not available. "
                 "You must install the python-snappy module for snappy support.",
                 stacklevel=2,
             )
-        elif compressor == "zlib" and not _HAVE_ZLIB:
+        elif compressor == "zlib" and not _have_zlib():
             compressors.remove(compressor)
             warnings.warn(
                 "Wire protocol compression with zlib is not available. "
                 "The zlib module is not available.",
                 stacklevel=2,
             )
-        elif compressor == "zstd" and not _HAVE_ZSTD:
+        elif compressor == "zstd" and not _have_zstd():
             compressors.remove(compressor)
             warnings.warn(
                 "Wire protocol compression with zstandard is not available. "

pymongo/pyopenssl_context.py

@@ -25,6 +25,7 @@
 from ipaddress import ip_address as _ip_address
 from typing import TYPE_CHECKING, Any, Callable, Optional, TypeVar, Union
 
+import cryptography.x509 as x509  # type:ignore[import]
 from OpenSSL import SSL as _SSL
 from OpenSSL import crypto as _crypto
 
@@ -39,7 +40,6 @@
 if TYPE_CHECKING:
     from ssl import VerifyMode
 
-    from cryptography.x509 import Certificate
 
 _T = TypeVar("_T")
 
@@ -179,7 +179,7 @@ class _CallbackData:
     """Data class which is passed to the OCSP callback."""
 
     def __init__(self) -> None:
-        self.trusted_ca_certs: Optional[list[Certificate]] = None
+        self.trusted_ca_certs: Optional[list[x509.Certificate]] = None
         self.check_ocsp_endpoint: Optional[bool] = None
         self.ocsp_response_cache = _OCSPCache()
 
@@ -331,7 +331,6 @@ def _load_wincerts(self, store: str) -> None:
         """Attempt to load CA certs from Windows trust store."""
         cert_store = self._ctx.get_cert_store()
         oid = _stdlibssl.Purpose.SERVER_AUTH.oid
-        import cryptography.x509 as x509
 
         for cert, encoding, trust in _stdlibssl.enum_certificates(store):  # type: ignore
             if encoding == "x509_asn":
@@ -401,7 +400,6 @@ def wrap_socket(
             # XXX: Do this in a callback registered with
             # SSLContext.set_info_callback? See Twisted for an example.
             if self.check_hostname and server_hostname is not None:
-                import service_identity
                 import service_identity.pyopenssl
 
                 try:

pymongo/srv_resolver.py

@@ -15,7 +15,6 @@
 """Support for resolving hosts and options from mongodb+srv:// URIs."""
 from __future__ import annotations
 
-import importlib.util
 import ipaddress
 import random
 from typing import TYPE_CHECKING, Any, Optional, Union
@@ -26,7 +25,14 @@
 if TYPE_CHECKING:
     from dns import resolver
 
-_HAVE_DNSPYTHON = importlib.util.find_spec("dns") is not None
+
+def _have_dnspython() -> bool:
+    try:
+        import dns  # type:ignore[import]  # noqa: F401
+
+        return True
+    except ImportError:
+        return False
 
 
 # dnspython can return bytes or str from various parts

pymongo/uri_parser.py

@@ -40,7 +40,7 @@
     get_validated_options,
 )
 from pymongo.errors import ConfigurationError, InvalidURI
-from pymongo.srv_resolver import _HAVE_DNSPYTHON, _SrvResolver
+from pymongo.srv_resolver import _have_dnspython, _SrvResolver
 from pymongo.typings import _Address
 
 if TYPE_CHECKING:
@@ -472,7 +472,7 @@ def parse_uri(
         is_srv = False
         scheme_free = uri[SCHEME_LEN:]
     elif uri.startswith(SRV_SCHEME):
-        if not _HAVE_DNSPYTHON:
+        if not _have_dnspython():
             python_path = sys.executable or "python"
             raise ConfigurationError(
                 'The "dnspython" module must be '

test/test_client.py

@@ -86,7 +86,7 @@
 from pymongo.client_options import ClientOptions
 from pymongo.command_cursor import CommandCursor
 from pymongo.common import _UUID_REPRESENTATIONS, CONNECT_TIMEOUT
-from pymongo.compression_support import _HAVE_SNAPPY, _HAVE_ZSTD
+from pymongo.compression_support import _have_snappy, _have_zstd
 from pymongo.cursor import Cursor, CursorType
 from pymongo.database import Database
 from pymongo.driver_info import DriverInfo
@@ -1558,7 +1558,7 @@ def compression_settings(client):
         self.assertEqual(opts.compressors, ["zlib"])
         self.assertEqual(opts.zlib_compression_level, -1)
 
-        if not _HAVE_SNAPPY:
+        if not _have_snappy():
             uri = "mongodb://localhost:27017/?compressors=snappy"
             client = MongoClient(uri, connect=False)
             opts = compression_settings(client)
@@ -1573,7 +1573,7 @@ def compression_settings(client):
             opts = compression_settings(client)
             self.assertEqual(opts.compressors, ["snappy", "zlib"])
 
-        if not _HAVE_ZSTD:
+        if not _have_zstd():
             uri = "mongodb://localhost:27017/?compressors=zstd"
             client = MongoClient(uri, connect=False)
             opts = compression_settings(client)

test/test_srv_polling.py

@@ -28,7 +28,7 @@
 from pymongo import common
 from pymongo.errors import ConfigurationError
 from pymongo.mongo_client import MongoClient
-from pymongo.srv_resolver import _HAVE_DNSPYTHON
+from pymongo.srv_resolver import _have_dnspython
 
 WAIT_TIME = 0.1
 
@@ -148,7 +148,7 @@ def predicate():
         return True
 
     def run_scenario(self, dns_response, expect_change):
-        self.assertEqual(_HAVE_DNSPYTHON, True)
+        self.assertEqual(_have_dnspython(), True)
         if callable(dns_response):
             dns_resolver_response = dns_response
         else:

test/test_uri_spec.py

@@ -27,7 +27,7 @@
 from test import clear_warning_registry, unittest
 
 from pymongo.common import INTERNAL_URI_OPTION_NAME_MAP, validate
-from pymongo.compression_support import _HAVE_SNAPPY
+from pymongo.compression_support import _have_snappy
 from pymongo.uri_parser import SRV_SCHEME, parse_uri
 
 CONN_STRING_TEST_PATH = os.path.join(
@@ -95,7 +95,7 @@ def modified_test_scenario(*args, **kwargs):
 def create_test(test, test_workdir):
     def run_scenario(self):
         compressors = (test.get("options") or {}).get("compressors", [])
-        if "snappy" in compressors and not _HAVE_SNAPPY:
+        if "snappy" in compressors and not _have_snappy:
             self.skipTest("This test needs the snappy module.")
         valid = True
         warning = False