///

FastAPI will now:

* **Validate** the data making sure that the max length is 50 characters
* Show a **clear error** for the client when the data is not valid
* **Document** the parameter in the OpenAPI schema *path operation* (so it will show up in the **automatic docs UI**)

The `initial` and `next` subdirectories of this directory are for release notes.

## For developers

Release notes should be added to `next` by editing existing files or creating
new files. **Do not add RELNOTE=yes comments in CLs.** Instead, add a file to
the CL (or ask the author to do so).

At the end of the development cycle, the files will be merged by being
concatenated in sorted order by pathname. Files in the directory matching the

/// note

If you don't know, check the [Async: *"In a hurry?"*](../../async.md#in-a-hurry){.internal-link target=_blank} section about `async` and `await` in the docs.

///

## Integrated with OpenAPI

All the request declarations, validations and requirements of your dependencies (and sub-dependencies) will be integrated in the same OpenAPI schema.

So, the interactive docs will have all the information from these dependencies too:

<img src="/img/tutorial/path-params/image02.png">

The same way, there are many compatible tools. Including code generation tools for many languages.

## Pydantic

All the data validation is performed under the hood by <a href="https://docs.pydantic.dev/" class="external-link" target="_blank">Pydantic</a>, so you get all the benefits from it. And you know you are in good hands.

   *
   * <p><b>Warning:</b> If the input future does not already implement {@code ListenableFuture}, the
   * returned future will emulate {@link ListenableFuture#addListener} by submitting a task to the
   * given executor at the first call to {@code addListener}. The task must be started by the
   * executor promptly, or else the returned {@code ListenableFuture} may fail to work. The task's

/*
 * Copyright (C) 2007 The Guava Authors
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,

   *
   * <p>The generated comparator is serializable if all the provided values are serializable.
   *
   * @param leastValue the value which the returned comparator should consider the "least" of all
   *     values
   * @param remainingValuesInOrder the rest of the values that the returned comparator will be able
   *     to compare, in the order the comparator should follow

/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *

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"License"); you may not use this file except in compliance
with the License.  You may obtain a copy of the License at

 *       Thread acquires its first hold (and releases its last remaining hold).
 *   <li>Before the lock is acquired, the lock is checked against the current set of acquired
 *       locks---to each of the acquired locks, an edge from the soon-to-be-acquired lock is either
 *       verified or created.
 *   <li>If a new edge needs to be created, the outgoing edges of the acquired locks are traversed