# `Tesla.Env`
[🔗](https://github.com/elixir-tesla/tesla/blob/v1.18.1/lib/tesla/env.ex#L1)

This module defines a `t:Tesla.Env.t/0` struct that stores all data related to request/response.

# `assigns`

```elixir
@type assigns() :: %{optional(atom()) => any()}
```

# `body`

```elixir
@type body() :: any()
```

# `client`

```elixir
@type client() :: Tesla.Client.t()
```

# `headers`

```elixir
@type headers() :: [{binary(), binary()}]
```

# `method`

```elixir
@type method() :: :head | :get | :delete | :trace | :options | :post | :put | :patch
```

# `opts`

```elixir
@type opts() :: keyword()
```

# `param`

```elixir
@type param() ::
  query_scalar()
  | query_scalar_list()
  | query_list()
  | %{optional(query_key()) => param()}
```

# `private`

```elixir
@type private() :: %{optional(atom()) => any()}
```

# `query`

```elixir
@type query() :: query_list() | query_string() | %{optional(query_key()) => param()}
```

Structured query params as a list or map, including nested maps.

## Examples

- `[{"param", "value"}]` will be translated to `?param=value`.
- `%{filters: %{page: 1}}` will be translated to `?filters%5Bpage%5D=1`
  (that is, `filters[page]` with brackets percent-encoded by default).

Map query params do not guarantee encoded parameter order when Tesla's default
URL builder encodes them directly. In `Tesla.Middleware.Query` `:modern` mode,
values matching `Tesla.OpenAPI.QueryParams` definitions are encoded in definition
order.

A `t:Tesla.OpenAPI.QueryString.t/0` value represents the entire URL query string and
must not be mixed with normal query params.

# `query_key`

```elixir
@type query_key() :: binary() | atom()
```

# `query_list`

```elixir
@type query_list() :: [query_pair()]
```

# `query_pair`

```elixir
@type query_pair() :: {query_key(), param()}
```

# `query_scalar`

```elixir
@type query_scalar() :: String.Chars.t()
```

# `query_scalar_list`

```elixir
@type query_scalar_list() :: [query_scalar()]
```

# `query_string`

```elixir
@type query_string() :: Tesla.OpenAPI.QueryString.t()
```

# `result`

```elixir
@type result() :: {:ok, t()} | {:error, any()}
```

# `runtime`

```elixir
@type runtime() ::
  {atom(), atom(), any()}
  | {atom(), atom()}
  | {:fn, (t() -> t())}
  | {:fn, (t(), stack() -> t())}
```

# `stack`

```elixir
@type stack() :: [runtime()]
```

# `status`

```elixir
@type status() :: integer() | nil
```

# `t`

```elixir
@type t() :: %Tesla.Env{
  __client__: client() | nil,
  __module__: atom() | nil,
  assigns: assigns(),
  body: body(),
  headers: headers(),
  method: method(),
  opts: opts(),
  private: private(),
  query: query(),
  status: status(),
  url: url()
}
```

Request/response state carried through the middleware pipeline.

## Fields

  * `:method` - method of request. Example: `:get`.
  * `:url` - request URL. Example: `"https://www.google.com"`.
  * `:query` - structured query params. See `t:query/0`.
    Query params passed in the URL, such as `"/get?param=value"`, are not
    parsed to the `:query` field.
  * `:headers` - list of request/response headers.
    Example: `[{"content-type", "application/json"}]`.
    Request headers are overridden by response headers when the adapter is called.
  * `:body` - request/response body.
    Request body is overridden by response body when the adapter is called.
  * `:status` - response status. Example: `200`.
  * `:opts` - list of options. Example: `[adapter: [recv_timeout: 30_000]]`.
  * `:assigns` - user data as a map for application-specific metadata.
  * `:private` - data reserved for libraries and middleware. Keys must be
    atoms. Prefix keys with the name of your project to avoid conflicts.
    The `tesla_` prefix is reserved for Tesla.

# `url`

```elixir
@type url() :: binary()
```

Request URL or request target.

Examples:

- `"https://www.google.com"`
- `"/users/1"` when used with `Tesla.Middleware.BaseUrl`

Callers are expected to pass a valid, already-encoded URL or request target.
`Tesla` does not automatically validate, normalize, or percent-encode the URL path.
Some middleware may rewrite `env.url`.

---

*Consult [api-reference.md](api-reference.md) for complete listing*