PYTHON-5670 Restore minimal support for Python 3.9 (#2640)

Author: blink1073

.evergreen/generated_configs/tasks.yml

@@ -242,6 +242,98 @@ tasks:
           TEST_MIN_DEPS: "1"
     tags: [test-min-deps, sharded_cluster-auth-ssl]
 
+  # Min support tests
+  - name: test-min-support-python3.9-standalone-noauth-nossl
+    commands:
+      - func: run server
+      - func: run tests
+        vars:
+          UV_PYTHON: "3.9"
+          AUTH: noauth
+          SSL: nossl
+          TOPOLOGY: standalone
+    tags: [test-min-support]
+  - name: test-min-support-python3.9-replica-set-noauth-ssl
+    commands:
+      - func: run server
+      - func: run tests
+        vars:
+          UV_PYTHON: "3.9"
+          AUTH: noauth
+          SSL: ssl
+          TOPOLOGY: replica_set
+    tags: [test-min-support]
+  - name: test-min-support-python3.9-sharded-cluster-auth-ssl
+    commands:
+      - func: run server
+      - func: run tests
+        vars:
+          UV_PYTHON: "3.9"
+          AUTH: auth
+          SSL: ssl
+          TOPOLOGY: sharded_cluster
+    tags: [test-min-support]
+  - name: test-min-support-pypy3.9-standalone-noauth-nossl
+    commands:
+      - func: run server
+      - func: run tests
+        vars:
+          UV_PYTHON: pypy3.9
+          AUTH: noauth
+          SSL: nossl
+          TOPOLOGY: standalone
+    tags: [test-min-support]
+  - name: test-min-support-pypy3.9-replica-set-noauth-ssl
+    commands:
+      - func: run server
+      - func: run tests
+        vars:
+          UV_PYTHON: pypy3.9
+          AUTH: noauth
+          SSL: ssl
+          TOPOLOGY: replica_set
+    tags: [test-min-support]
+  - name: test-min-support-pypy3.9-sharded-cluster-auth-ssl
+    commands:
+      - func: run server
+      - func: run tests
+        vars:
+          UV_PYTHON: pypy3.9
+          AUTH: auth
+          SSL: ssl
+          TOPOLOGY: sharded_cluster
+    tags: [test-min-support]
+  - name: test-min-support-pypy3.10-standalone-noauth-nossl
+    commands:
+      - func: run server
+      - func: run tests
+        vars:
+          UV_PYTHON: pypy3.10
+          AUTH: noauth
+          SSL: nossl
+          TOPOLOGY: standalone
+    tags: [test-min-support]
+  - name: test-min-support-pypy3.10-replica-set-noauth-ssl
+    commands:
+      - func: run server
+      - func: run tests
+        vars:
+          UV_PYTHON: pypy3.10
+          AUTH: noauth
+          SSL: ssl
+          TOPOLOGY: replica_set
+    tags: [test-min-support]
+  - name: test-min-support-pypy3.10-sharded-cluster-auth-ssl
+    commands:
+      - func: run server
+      - func: run tests
+        vars:
+          UV_PYTHON: pypy3.10
+          AUTH: auth
+          SSL: ssl
+          TOPOLOGY: sharded_cluster
+    tags: [test-min-support]
+
   # Mod wsgi tests
   - name: mod-wsgi-replica-set-python3.10
     commands:

.evergreen/generated_configs/variants.yml

@@ -326,6 +326,14 @@ buildvariants:
     expansions:
       TEST_NAME: load_balancer
 
+  # Min support tests
+  - name: min-support-rhel8
+    tasks:
+      - name: .test-min-support
+    display_name: Min Support RHEL8
+    run_on:
+      - rhel87-small
+
   # Mockupdb tests
   - name: mockupdb-rhel8
     tasks:

.evergreen/scripts/generate_config.py

@@ -502,6 +502,12 @@ def create_aws_auth_variants():
     return variants
 
 
+def create_min_support_variants():
+    host = HOSTS["rhel8"]
+    name = get_variant_name("Min Support", host=host)
+    return [create_variant([".test-min-support"], name, host=host)]
+
+
 def create_no_server_variants():
     host = HOSTS["rhel8"]
     name = get_variant_name("No server", host=host)
@@ -897,6 +903,24 @@ def _create_ocsp_tasks(algo, variant, server_type, base_task_name):
     return tasks
 
 
+def create_min_support_tasks():
+    server_func = FunctionCall(func="run server")
+    from generate_config_utils import MIN_SUPPORT_VERSIONS
+
+    tasks = []
+    for python, topology in product(MIN_SUPPORT_VERSIONS, TOPOLOGIES):
+        auth, ssl = get_standard_auth_ssl(topology)
+        vars = dict(UV_PYTHON=python, AUTH=auth, SSL=ssl, TOPOLOGY=topology)
+        test_func = FunctionCall(func="run tests", vars=vars)
+        task_name = get_task_name(
+            "test-min-support", python=python, topology=topology, auth=auth, ssl=ssl
+        )
+        tags = ["test-min-support"]
+        commands = [server_func, test_func]
+        tasks.append(EvgTask(name=task_name, tags=tags, commands=commands))
+    return tasks
+
+
 def create_aws_lambda_tasks():
     assume_func = FunctionCall(func="assume ec2 role")
     vars = dict(TEST_NAME="aws_lambda")

.evergreen/scripts/generate_config_utils.py

@@ -24,6 +24,7 @@
 ALL_VERSIONS = ["4.2", "4.4", "5.0", "6.0", "7.0", "8.0", "rapid", "latest"]
 CPYTHONS = ["3.10", "3.11", "3.12", "3.13", "3.14t", "3.14"]
 PYPYS = ["pypy3.11"]
+MIN_SUPPORT_VERSIONS = ["3.9", "pypy3.9", "pypy3.10"]
 ALL_PYTHONS = CPYTHONS + PYPYS
 MIN_MAX_PYTHON = [CPYTHONS[0], CPYTHONS[-1]]
 BATCHTIME_WEEK = 10080

.github/workflows/dist.yml

@@ -83,6 +83,7 @@ jobs:
       - name: Assert all versions in wheelhouse
         if: ${{ ! startsWith(matrix.buildplat[1], 'macos') }}
         run: |
+          ls wheelhouse/*cp39*.whl
           ls wheelhouse/*cp310*.whl
           ls wheelhouse/*cp311*.whl
           ls wheelhouse/*cp312*.whl
@@ -110,7 +111,7 @@ jobs:
       - uses: actions/setup-python@v6
         with:
           # Build sdist on lowest supported Python
-          python-version: "3.10"
+          python-version: "3.9"
 
       - name: Build SDist
         run: |

.github/workflows/test-python.yml

@@ -208,7 +208,7 @@ jobs:
           cache: 'pip'
           cache-dependency-path: 'pyproject.toml'
           # Build sdist on lowest supported Python
-          python-version: "3.10"
+          python-version: "3.9"
       - name: Build SDist
         shell: bash
         run: |
@@ -242,7 +242,7 @@ jobs:
             cache: 'pip'
             cache-dependency-path: 'sdist/test/pyproject.toml'
             # Test sdist on lowest supported Python
-            python-version: "3.10"
+            python-version: "3.9"
         - id: setup-mongodb
           uses: mongodb-labs/drivers-evergreen-tools@master
         - name: Run connect test from sdist
@@ -266,7 +266,7 @@ jobs:
         - name: Install uv
           uses: astral-sh/setup-uv@681c641aba71e4a1c380be3ab5e12ad51f415867 # v7
           with:
-            python-version: "3.10"
+            python-version: "3.9"
         - id: setup-mongodb
           uses: mongodb-labs/drivers-evergreen-tools@master
           with:

CONTRIBUTING.md

@@ -16,7 +16,7 @@ be of interest or that has already been addressed.
 
 ## Supported Interpreters
 
-PyMongo supports CPython 3.10+ and PyPy3.10+. Language features not
+PyMongo supports CPython 3.9+ and PyPy3.9+. Language features not
 supported by all interpreters can not be used.
 
 ## Style Guide

README.md

@@ -97,7 +97,7 @@ package that is incompatible with PyMongo.
 
 ## Dependencies
 
-PyMongo supports CPython 3.10+ and PyPy3.10+.
+PyMongo supports CPython 3.9+ and PyPy3.9+.
 
 Required dependencies:
 

doc/changelog.rst

@@ -6,14 +6,11 @@ Changes in Version 4.16.0 (XXXX/XX/XX)
 
 PyMongo 4.16 brings a number of changes including:
 
-.. warning:: PyMongo 4.16 drops support for Python 3.9 and PyPy 3.10: Python 3.10+ or PyPy 3.11+ is now required.
-
-- Dropped support for Python 3.9 and PyPy 3.10.
 - Removed invalid documents from :class:`bson.errors.InvalidDocument` error messages as
   doing so may leak sensitive user data.
   Instead, invalid documents are stored in :attr:`bson.errors.InvalidDocument.document`.
-- PyMongo now requires ``dnspython>=2.6.1``, since ``dnspython`` 1.0 is no longer maintained and is incompatible with
-  Python 3.10+.  The minimum version is ``2.6.1`` to account for `CVE-2023-29483 <https://www.cve.org/CVERecord?id=CVE-2023-29483>`_.
+- PyMongo now requires ``dnspython>=2.6.1``, since ``dnspython`` 1.0 is no longer maintained.
+  The minimum version is ``2.6.1`` to account for `CVE-2023-29483 <https://www.cve.org/CVERecord?id=CVE-2023-29483>`_.
 - Removed support for Eventlet.
   Eventlet is actively being sunset by its maintainers and has compatibility issues with PyMongo's dnspython dependency.
 - Use Zstandard support from the standard library for Python 3.14+, and use ``backports.zstd`` for older versions.

gridfs/asynchronous/grid_file.py

@@ -46,6 +46,7 @@
 from pymongo.asynchronous.collection import AsyncCollection
 from pymongo.asynchronous.cursor import AsyncCursor
 from pymongo.asynchronous.database import AsyncDatabase
+from pymongo.asynchronous.helpers import anext
 from pymongo.common import validate_string
 from pymongo.errors import (
     BulkWriteError,