* installation
* activation
* update
* deactivation
* un-installation

When a plugin is installed we may want to check the license and make users agree. We may also want to unpack the given plugin in a particular location.

		version string
		format  string
		want    bool
	}{
		{1, "123", "fs", false},
		{2, "123", xlMetaFormat, false},
		{3, xlMetaVersion100, "test", false},
		{4, xlMetaVersion101, "hello", false},
		{5, xlMetaVersion100, xlMetaFormat, true},
		{6, xlMetaVersion101, xlMetaFormat, true},
	}
	for _, tt := range tests {
		if got := isXLMetaFormatValid(tt.version, tt.format); got != tt.want {

This is the driest thing I know.  Silence all round, if you please!
"William the Conqueror, whose cause was favoured by the pope, was
soon submitted to by the English, who wanted leaders, and had been
of late much accustomed to usurpation and conquest.  Edwin and
Morcar, the earls of Mercia and Northumbria--"'

  `Ugh!' said the Lory, with a shiver.

# 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):

{* ../../docs_src/bigger_applications/app_an_py310/internal/admin.py hl[3] title["app/internal/admin.py"] *}

But we still want to set a custom `prefix` when including the `APIRouter` so that all its *path operations* start with `/admin`, we want to secure it with the `dependencies` we already have for this project, and we want to include `tags` and `responses`.

     * <p>
     * This method is called by Maven during initialization to collect all custom enum values
     * that should be registered. The returned collection should contain all the enum values
     * that this provider wants to contribute.
     * <p>
     * The values returned by this method should be created using the appropriate factory methods
     * for the specific enum type, such as {@code language()}, {@code projectScope()}, or

This is probably not as important or necessary if you use `Annotated`.

///

Let's say that you want to declare the query parameter `q` as a required `str`.

And you don't need to declare anything else for that parameter, so you don't really need to use `Query`.

But you still need to use `Path` for the `item_id` path parameter. And you don't want to use `Annotated` for some reason.

## Decision

The *Build Tool Team* has decided to use Architectural Decision Records (aka ADR) to track decisions we want to follow.

The main logic with ADRs is to describe (architectural) decisions made:

* To provide best practices and solutions we (as the *build tool* team) want to promote.
* To avoid asking the same thing multiple times during code review.

  //
  // - @PolyNull means "@Nullable or @Nonnull"
  //   (That would be unsound for an input Iterable<@Nullable Foo>. So, if we wanted to use
  //   @PolyNull, we would have to restrict this method to non-null <T>. But it has users who pass
  //   iterables with null elements.)
  //
  // - @JointlyNullable means "@Nullable or no annotation"

<div class="screenshot">
<img src="/img/tutorial/header-param-models/image01.png">
</div>

## Forbid Extra Headers { #forbid-extra-headers }

In some special use cases (probably not very common), you might want to **restrict** the headers that you want to receive.

You can use Pydantic's model configuration to `forbid` any `extra` fields:

{* ../../docs_src/header_param_models/tutorial002_an_py310.py hl[10] *}