PYTHON-4840 Add evergreen tests for free-threaded Python 3.13t (#2048)

.evergreen/config.yml

@@ -116,7 +116,6 @@ functions:
         content_type: text/html
         display_name: "Coverage Report HTML"
 
-
   "upload mo artifacts":
     - command: ec2.assume_role
       params:
@@ -300,6 +299,15 @@ functions:
           - .evergreen/scripts/run-with-env.sh
           - .evergreen/scripts/run-tests.sh
 
+  "run direct tests":
+    - command: subprocess.exec
+      type: test
+      params:
+        working_dir: "src"
+        binary: bash
+        include_expansions_in_env: ["PYTHON_BINARY"]
+        args: [ .evergreen/scripts/run-direct-tests.sh ]
+
   "run enterprise auth tests":
     - command: subprocess.exec
       type: test
@@ -920,6 +928,15 @@ tasks:
       commands:
         - func: "run tests"
 
+    - name: "free-threading"
+      tags: ["free-threading"]
+      commands:
+        - func: "bootstrap mongo-orchestration"
+          vars:
+            VERSION: "8.0"
+            TOPOLOGY: "replica_set"
+        - func: "run direct tests"
+
     - name: "atlas-connect"
       tags: ["atlas-connect"]
       commands:

.evergreen/generated_configs/variants.yml

@@ -627,6 +627,32 @@ buildvariants:
       AUTH: auth
       PYTHON_BINARY: /opt/python/pypy3.10/bin/python3
 
+  # Free threaded tests
+  - name: free-threaded-rhel8-python3.13t
+    tasks:
+      - name: .free-threading
+    display_name: Free-threaded RHEL8 Python3.13t
+    run_on:
+      - rhel87-small
+    expansions:
+      PYTHON_BINARY: /opt/python/3.13t/bin/python3
+  - name: free-threaded-macos-python3.13t
+    tasks:
+      - name: .free-threading
+    display_name: Free-threaded macOS Python3.13t
+    run_on:
+      - macos-14
+    expansions:
+      PYTHON_BINARY: /Library/Frameworks/PythonT.Framework/Versions/3.13/bin/python3t
+  - name: free-threaded-macos-arm64-python3.13t
+    tasks:
+      - name: .free-threading
+    display_name: Free-threaded macOS Arm64 Python3.13t
+    run_on:
+      - macos-14-arm64
+    expansions:
+      PYTHON_BINARY: /Library/Frameworks/PythonT.Framework/Versions/3.13/bin/python3t
+
   # Green framework tests
   - name: green-eventlet-rhel8-python3.9
     tasks:

.evergreen/scripts/generate_config.py

@@ -146,12 +146,16 @@ def get_python_binary(python: str, host: Host) -> str:
         else:
             base = "C:/python"
         python = python.replace(".", "")
+        if python == "313t":
+            return f"{base}/Python313/python3.13t.exe"
         return f"{base}/Python{python}/python.exe"
 
     if name in ["rhel8", "ubuntu22", "ubuntu20", "rhel7"]:
         return f"/opt/python/{python}/bin/python3"
 
     if name in ["macos", "macos-arm64"]:
+        if python == "3.13t":
+            return "/Library/Frameworks/PythonT.Framework/Versions/3.13/bin/python3t"
         return f"/Library/Frameworks/Python.Framework/Versions/{python}/bin/python3"
 
     raise ValueError(f"no match found for python {python} on {name}")
@@ -318,6 +322,21 @@ def create_server_variants() -> list[BuildVariant]:
     return variants
 
 
+def create_free_threaded_variants() -> list[BuildVariant]:
+    variants = []
+    for host_name in ("rhel8", "macos", "macos-arm64", "win64"):
+        if host_name == "win64":
+            # TODO: PYTHON-5027
+            continue
+        tasks = [".free-threading"]
+        host = HOSTS[host_name]
+        python = "3.13t"
+        display_name = get_display_name("Free-threaded", host, python=python)
+        variant = create_variant(tasks, display_name, python=python, host=host)
+        variants.append(variant)
+    return variants
+
+
 def create_encryption_variants() -> list[BuildVariant]:
     variants = []
     tags = ["encryption_tag"]

.evergreen/scripts/run-direct-tests.sh

@@ -0,0 +1,10 @@
+#!/bin/bash
+set -x
+. .evergreen/utils.sh
+
+. .evergreen/scripts/env.sh
+createvirtualenv "$PYTHON_BINARY" .venv
+
+export PYMONGO_C_EXT_MUST_BUILD=1
+pip install -e ".[test]"
+pytest -v

doc/changelog.rst

@@ -16,6 +16,7 @@ PyMongo 4.11 brings a number of changes including:
 - pymongocrypt>=1.12 is now required for :ref:`In-Use Encryption` support.
 - Added support for free-threaded Python with the GIL disabled. For more information see:
   `Free-threaded CPython <https://docs.python.org/3.13/whatsnew/3.13.html#whatsnew313-free-threaded-cpython>`_.
+  We do not yet support free-threaded Python on Windows (`PYTHON-5027`_) or with In-Use Encryption (`PYTHON-5024`_).
 - :attr:`~pymongo.asynchronous.mongo_client.AsyncMongoClient.address` and
   :attr:`~pymongo.mongo_client.MongoClient.address` now correctly block when called on unconnected clients
   until either connection succeeds or a server selection timeout error is raised.
@@ -42,6 +43,8 @@ See the `PyMongo 4.11 release notes in JIRA`_ for the list of resolved issues
 in this release.
 
 .. _PyMongo 4.11 release notes in JIRA: https://jira.mongodb.org/secure/ReleaseNote.jspa?projectId=10004&version=40784
+.. _PYTHON-5027: https://jira.mongodb.org/browse/PYTHON-5027
+.. _PYTHON-5024: https://jira.mongodb.org/browse/PYTHON-5024
 
 Changes in Version 4.10.1 (2024/10/01)
 --------------------------------------