# Development - Contributing

First, you might want to see the basic ways to [help FastAPI and get help](help-fastapi.md).

## Developing

If you already cloned the [fastapi repository](https://github.com/fastapi/fastapi) and you want to deep dive in the code, here are some guidelines to set up your environment.

### Install requirements

Create a virtual environment and install the required packages with [`uv`](https://github.com/astral-sh/uv):

This is because we want to include their *path operations* in the OpenAPI schema and the user interfaces.

As we cannot just isolate them and "mount" them independently of the rest, the *path operations* are "cloned" (re-created), not included directly.

///

## Configure the `entrypoint` in `pyproject.toml` { #configure-the-entrypoint-in-pyproject-toml }

      .assertFailure("canceled", "Canceled", "Socket closed", "Socket is closed")
  }

  @Test
  fun cancelAll() {
    val call = client.newCall(Request(server.url("/")))
    call.enqueue(callback)
    client.dispatcher.cancelAll()
    callback
      .await(server.url("/"))
      .assertFailure("canceled", "Canceled", "Socket closed", "Socket is closed")
  }

  @Test

  private static <X extends Throwable, V> AsyncFunction<X, V> unexpectedAsyncFunction() {
    return t -> {
      throw new AssertionError("Unexpected fallback", t);
    };
  }

  // catchingAsync tests cloned from the old withFallback tests:

  public void testCatchingAsync_inputDoesNotRaiseException() throws Exception {
    AsyncFunction<Throwable, Integer> fallback = unexpectedAsyncFunction();

  private static <X extends Throwable, V> AsyncFunction<X, V> unexpectedAsyncFunction() {
    return t -> {
      throw new AssertionError("Unexpected fallback", t);
    };
  }

  // catchingAsync tests cloned from the old withFallback tests:

  public void testCatchingAsync_inputDoesNotRaiseException() throws Exception {
    AsyncFunction<Throwable, Integer> fallback = unexpectedAsyncFunction();

          unlock();
        }
      }
    }

    /**
     * Removes an entry from within a table. All entries following the removed node can stay, but
     * all preceding ones need to be cloned.
     *
     * <p>This method does not decrement count for the removed entry, but does decrement count for
     * all partially collected entries which are skipped. As such callers which are modifying count

          unlock();
        }
      }
    }

    /**
     * Removes an entry from within a table. All entries following the removed node can stay, but
     * all preceding ones need to be cloned.
     *
     * <p>This method does not decrement count for the removed entry, but does decrement count for
     * all partially collected entries which are skipped. As such callers which are modifying count

        * When a `response_model` is declared, the same `response_model` type declaration won't be used as is, it will be "cloned" to create an new one (a cloned Pydantic `Field` with all the submodels cloned as well).

    Closer closer = new Closer(suppressor);

    IOException exception = new IOException();

    // c2 is added last, closed first
    TestCloseable c1 = closer.register(TestCloseable.normal());
    TestCloseable c2 = closer.register(TestCloseable.throwsOnClose(exception));

    try {
      closer.close();
    } catch (Throwable caught) {

  // Avoid infinite recursion if a closeable's close() method throws RejectedExecutionException and
  // is closed using the direct executor.
  public void testCloseThrowsRejectedExecutionException() throws Exception {
    doThrow(new RejectedExecutionException()).when(mockCloseable).close();
    ClosingFuture<Closeable> closingFuture =
        ClosingFuture.submit(