PYTHON-5677: ClientEncryption shouldn't try to load mongo crypt shared library

doc/changelog.rst

@@ -17,6 +17,9 @@ PyMongo 4.16 brings a number of changes including:
 - Fixed return type annotation for ``find_one_and_*`` methods on :class:`~pymongo.asynchronous.collection.AsyncCollection`
   and :class:`~pymongo.synchronous.collection.Collection` to include ``None``.
 - Added support for NumPy 1D-arrays in :class:`bson.binary.BinaryVector`.
+- Prevented :class:`~pymongo.encryption.ClientEncryption` from loading the crypt
+  shared library to fix "MongoCryptError: An existing crypt_shared library is
+  loaded by the application" unless the linked library search path is set.
 
 Changes in Version 4.15.5 (2025/XX/XX)
 --------------------------------------

pymongo/asynchronous/encryption.py

@@ -13,6 +13,7 @@
 # limitations under the License.
 
 """Support for explicit client-side field level encryption."""
+
 from __future__ import annotations
 
 import asyncio
@@ -714,10 +715,15 @@ def __init__(
         self._io_callbacks: Optional[_EncryptionIO] = _EncryptionIO(
             None, key_vault_coll, None, opts
         )
+
+        # Pass bypass_encryption=True to skip loading crypt_shared.
         self._encryption = AsyncExplicitEncrypter(
             self._io_callbacks,
             _create_mongocrypt_options(
-                kms_providers=kms_providers, schema_map=None, key_expiration_ms=key_expiration_ms
+                kms_providers=kms_providers,
+                schema_map=None,
+                key_expiration_ms=key_expiration_ms,
+                bypass_encryption=True,  # Don't load crypt_shared
             ),
         )
         # Use the same key vault collection as the callback.

pymongo/synchronous/encryption.py

@@ -13,6 +13,7 @@
 # limitations under the License.
 
 """Support for explicit client-side field level encryption."""
+
 from __future__ import annotations
 
 import contextlib
@@ -707,10 +708,15 @@ def __init__(
         self._io_callbacks: Optional[_EncryptionIO] = _EncryptionIO(
             None, key_vault_coll, None, opts
         )
+
+        # Pass bypass_encryption=True to skip loading crypt_shared.
         self._encryption = ExplicitEncrypter(
             self._io_callbacks,
             _create_mongocrypt_options(
-                kms_providers=kms_providers, schema_map=None, key_expiration_ms=key_expiration_ms
+                kms_providers=kms_providers,
+                schema_map=None,
+                key_expiration_ms=key_expiration_ms,
+                bypass_encryption=True,  # Don't load crypt_shared
             ),
         )
         # Use the same key vault collection as the callback.