* Future, then a call setException() would likely also overflow.
     *
     * - If the stack overflowed after set()/setValue() stored its result, then a call to
     * setException() will be a no-op because the Future is already done.
     *
     * Both scenarios are bad: The output Future might never complete, or, if it does complete, it

There are, however, times when we cannot maintain complete compatibility.
If code depends on buggy (including insecure) behavior,
then fixing the bug will break that code.
New features can also have similar impacts:
enabling the HTTP/2 use by the HTTP client broke programs
connecting to servers with buggy HTTP/2 implementations.
These kinds of changes are unavoidable and

import importlib

import pytest
from fastapi.testclient import TestClient


@pytest.fixture(
    name="client",
    params=[
        pytest.param("tutorial004_py39"),
    ],
)
def get_client(request: pytest.FixtureRequest):
    mod = importlib.import_module(f"docs_src.extra_models.{request.param}")

    client = TestClient(mod.app)
    return client


def test_get_items(client: TestClient):

# Maintenance Mode

**This project is currently under maintenance and is not accepting new changes.**

- The codebase is in a maintenance-only state
- No new features, enhancements, or pull requests will be accepted
- Critical security fixes may be evaluated on a case-by-case basis
- Existing issues and pull requests will not be actively reviewed
- Community support continues on a best-effort basis through [Slack](https://slack.min.io)

import static com.google.common.collect.ReflectionFreeAssertThrows.assertThrows;
import static com.google.common.collect.testing.features.CollectionFeature.KNOWN_ORDER;
import static com.google.common.collect.testing.features.CollectionFeature.SERIALIZABLE;
import static com.google.common.collect.testing.features.MapFeature.ALLOWS_ANY_NULL_QUERIES;
import static com.google.common.truth.Truth.assertThat;
import static java.util.Collections.emptyList;

 * crawling and indexing documents, including incremental crawling capabilities, content
 * modification checking, and integration with the Fess search engine backend.
 *
 * <p>Key features include:</p>
 * <ul>
 * <li>Incremental crawling support with last-modified timestamp checking</li>
 * <li>Document expiration handling</li>
 * <li>Child URL extraction and queueing</li>

import static com.google.common.collect.ReflectionFreeAssertThrows.assertThrows;
import static com.google.common.collect.testing.features.CollectionFeature.KNOWN_ORDER;
import static com.google.common.collect.testing.features.CollectionFeature.SERIALIZABLE;
import static com.google.common.collect.testing.features.MapFeature.ALLOWS_ANY_NULL_QUERIES;
import static com.google.common.truth.Truth.assertThat;
import static java.util.Collections.emptySet;

from ...utils import needs_py310


@pytest.fixture(
    name="mod",
    params=[
        pytest.param("tutorial001_py39"),
        pytest.param("tutorial001_py310", marks=needs_py310),
    ],
)
def get_module(request: pytest.FixtureRequest):
    module = importlib.import_module(f"docs_src.encoder.{request.param}")
    return module


@pytest.fixture(name="client")
def get_client(mod: ModuleType):

import importlib
from types import ModuleType

import pytest
from fastapi.testclient import TestClient


@pytest.fixture(
    name="mod",
    params=[
        pytest.param("tutorial008d_py39"),
        pytest.param("tutorial008d_an_py39"),
    ],
)
def get_mod(request: pytest.FixtureRequest):
    mod = importlib.import_module(f"docs_src.dependencies.{request.param}")

    return mod

This includes `pydantic.v1`, which is no longer supported in Python 3.14 and above.

If you want to use the latest features of Python, you will need to make sure you use Pydantic v2.

///

If you have an old FastAPI app with Pydantic v1, here I'll show you how to migrate it to Pydantic v2, and the **features in FastAPI 0.119.0** to help you with a gradual migration.

## Official Guide { #official-guide }