interface Backend {
    fun nanoTime(): Long

    fun coordinatorNotify(taskRunner: TaskRunner)

    fun coordinatorWait(
      taskRunner: TaskRunner,
      nanos: Long,
    )

    fun <T> decorate(queue: BlockingQueue<T>): BlockingQueue<T>

    fun execute(
      taskRunner: TaskRunner,
      runnable: Runnable,
    )
  }

  class RealBackend(
    threadFactory: ThreadFactory,

  /**
   * Results are posted here as they occur. The find job is done when either one plan completes
   * successfully or all plans fail.
   */
  private val connectResults = taskRunner.backend.decorate(LinkedBlockingDeque<ConnectResult>())

  override fun find(): RealConnection {
    var firstException: IOException? = null
    try {
      while (tcpConnectsInFlight.isNotEmpty() || routePlanner.hasNext()) {

          <version>2.0.0+</version>
          <type>String</type>
          <defaultValue><![CDATA[]]></defaultValue>
          <description><![CDATA[If specified, identifies this phase as a dynamic phase to decorate the specified phase id, e.g. {@code after} or {@code before}.]]></description>
        </field>
        <field xml.attribute="true">
          <name>priority</name>
          <required>false</required>

          if (waitingCoordinatorInterrupted) {
            waitingCoordinatorInterrupted = false
            throw InterruptedException()
          }
        }

        override fun <T> decorate(queue: BlockingQueue<T>) = TaskFakerBlockingQueue(queue)
      },
      logger = logger,
    )

  /** Runs all tasks that are ready. Used by the test thread only. */
  fun runTasks() {

And it also includes a default exception handler for it.

To override it, import the `RequestValidationError` and use it with `@app.exception_handler(RequestValidationError)` to decorate the exception handler.

The exception handler will receive a `Request` and the exception.

{* ../../docs_src/handling_errors/tutorial004.py hl[2,14:16] *}

* <a href="https://docs.python.org/3/library/contextlib.html#contextlib.asynccontextmanager" class="external-link" target="_blank">`@contextlib.asynccontextmanager`</a>

using them to decorate a function with a single `yield`.

That's what **FastAPI** uses internally for dependencies with `yield`.

But you don't have to use the decorators for FastAPI dependencies (and you shouldn't).

import java.io.Serializable;

/**
 * An abstract base class for implementing the <a
 * href="http://en.wikipedia.org/wiki/Decorator_pattern">decorator pattern</a>. The {@link
 * #delegate()} method must be overridden to return the instance being decorated.
 *
 * <p>This class does <i>not</i> forward the {@code hashCode} and {@code equals} methods through to

import java.io.Serializable;

/**
 * An abstract base class for implementing the <a
 * href="http://en.wikipedia.org/wiki/Decorator_pattern">decorator pattern</a>. The {@link
 * #delegate()} method must be overridden to return the instance being decorated.
 *
 * <p>This class does <i>not</i> forward the {@code hashCode} and {@code equals} methods through to

Vous la mettez au dessus d'une fonction. Comme un joli chapeau décoratif (j'imagine que ce terme vient de là 🤷🏻‍♂).

Un "décorateur" prend la fonction en dessous et en fait quelque chose.

Dans notre cas, ce décorateur dit à **FastAPI** que la fonction en dessous correspond au **chemin** `/` avec l'**opération** `get`.

C'est le "**décorateur d'opération de chemin**".

///

You put it on top of a function. Like a pretty decorative hat (I guess that's where the term came from).

A "decorator" takes the function below and does something with it.

In our case, this decorator tells **FastAPI** that the function below corresponds to the **path** `/` with an **operation** `get`.

It is the "**path operation decorator**".

///

You can also use the other operations:

* `@app.post()`