# --show-toplevel", but that wouldn't work for non-git repos (like if someone
# downloaded TF as a zip archive).
export TFCI_GIT_DIR=$(cd $(dirname "$0"); realpath ../../)
cd "$TFCI_GIT_DIR"

# "TFCI" may optionally be set to the name of an env-type file with TFCI
# variables in it, OR may be left empty if the user has already exported the
# relevant variables in their environment. Because of 'set -o allexport' above

## An app with callbacks { #an-app-with-callbacks }

Let's see all this with an example.

Imagine you develop an app that allows creating invoices.

These invoices will have an `id`, `title` (optional), `customer`, and `total`.

The user of your API (an external developer) will create an invoice in your API with a POST request.

Then your API will (let's imagine):

Y también puedes declarar parámetros del cuerpo como opcionales, estableciendo el valor predeterminado a `None`:

{* ../../docs_src/body_multiple_params/tutorial001_an_py310.py hl[18:20] *}

## Múltiples parámetros del cuerpo

/// note | Nota

Ten en cuenta que, en este caso, el `item` que se tomaría del cuerpo es opcional. Ya que tiene un valor por defecto de `None`.

///

import org.codelibs.fess.Constants;
import org.codelibs.fess.dict.DictionaryException;
import org.codelibs.fess.dict.DictionaryFile;
import org.codelibs.fess.util.ComponentUtil;
import org.dbflute.optional.OptionalEntity;

/**
 * Dictionary file for protected words.
 * This class manages the reading, writing, and updating of protected words dictionary files.
 */

    // okhttp configured specifically.
    if (project.name == "okhttp") return@dependencies

    if (project.name == "mockwebserver3-junit5") {
      // JUnit 5's APIs need java.util.function.Function and java.util.Optional from API 24.
      androidSignature(rootProject.libs.signature.android.apilevel24) { artifact { type = "signature" } }
    } else {
      // Everything else requires Android API 21+.

import java.util.Set;
import org.jspecify.annotations.Nullable;

/**
 * CompactLinkedHashSet is an implementation of a Set, which a predictable iteration order that
 * matches the insertion order. All optional operations (adding and removing) are supported. All
 * elements, including {@code null}, are permitted.
 *
 * <p>{@code contains(x)}, {@code add(x)} and {@code remove(x)}, are all (expected and amortized)

# ----------------------------------------------------------------------------
# Maven Start Up Batch script
#
# Required ENV vars:
# ------------------
#   JAVA_HOME - location of a JDK home dir
#
# Optional ENV vars
# -----------------
#   M2_HOME - location of maven2's installed home dir
#   MAVEN_OPTS - parameters passed to the Java VM when running Maven
#     e.g. to debug Maven itself, use

E você também pode declarar parâmetros de corpo como opcionais, definindo o valor padrão com `None`:

{* ../../docs_src/body_multiple_params/tutorial001_py310.py hl[17:19] *}

/// note | Nota

Repare que, neste caso, o `item` que seria capturado a partir do corpo é opcional. Visto que ele possui `None` como valor padrão.

///

## Múltiplos parâmetros de corpo

                    Artifact artifact = node.getArtifact();

                    try {
                        if (node.filterTrail(filter)) {
                            // If it was optional and not a direct dependency,
                            // we don't add it or its children, just allow the update of the version and artifactScope
                            if (node.isChildOfRootNode() || !artifact.isOptional()) {

Pydantic, que es lo que impulsa toda la validación y serialización de datos en FastAPI, tiene un comportamiento especial cuando usas `Optional` o `Union[Something, None]` sin un valor por defecto, puedes leer más al respecto en la documentación de Pydantic sobre <a href="https://docs.pydantic.dev/2.3/usage/models/#required-optional-fields" class="external-link" target="_blank">Campos requeridos</a>.

///

/// tip | Consejo