# `Tesla.OpenAPI`
[🔗](https://github.com/elixir-tesla/tesla/blob/v1.22.0/lib/tesla/open_api.ex#L1)

Reference entry point for OpenAPI-compatible generated clients.

Tesla does not parse OpenAPI documents or generate operation modules. It
provides value objects and middleware hooks that generated clients can use
after they have already interpreted the OpenAPI document.

## Parameter Locations

| OpenAPI location | Tesla API |
| --- | --- |
| `path` | `Tesla.OpenAPI.PathTemplate`, `Tesla.OpenAPI.PathParam`, `Tesla.OpenAPI.PathParams`, and `Tesla.Middleware.PathParams` in `:modern` mode |
| `query` | `Tesla.OpenAPI.QueryParam`, `Tesla.OpenAPI.QueryParams`, and `Tesla.Middleware.Query` in `:modern` mode |
| `querystring` | `Tesla.OpenAPI.QueryString` passed as the request `:query` |
| `header` | `Tesla.OpenAPI.HeaderParam` and `Tesla.OpenAPI.HeaderParams.to_headers/2` |
| `cookie` | `Tesla.OpenAPI.CookieParam` and `Tesla.OpenAPI.CookieParams.to_headers/2` |

## Static Metadata And Dynamic Values

Generated clients should keep OpenAPI parameter definitions as module
attributes and pass only request values at runtime:

    defmodule MyApi.Operation.GetItem.Path do
      @path_template Tesla.OpenAPI.PathTemplate.new!("/items/{id}")

      @path_params Tesla.OpenAPI.PathParams.new!([
                     Tesla.OpenAPI.PathParam.new!("id")
                   ])

      def path_template, do: @path_template
      def path_params, do: @path_params
    end

    defmodule MyApi.Operation.GetItem.Query do
      @query_params Tesla.OpenAPI.QueryParams.new!([
                      Tesla.OpenAPI.QueryParam.new!("filter")
                    ])

      def query_params, do: @query_params
    end

    defmodule MyApi.Operation.GetItem do
      alias MyApi.Operation.GetItem.{Path, Query}

      @private Tesla.OpenAPI.merge_private([
                 Tesla.OpenAPI.PathTemplate.put_private(Path.path_template()),
                 Tesla.OpenAPI.PathParams.put_private(Path.path_params()),
                 Tesla.OpenAPI.QueryParams.put_private(Query.query_params())
               ])
    end

Path and query parameter collections are placed in `t:Tesla.Env.private/0`
because their middleware serializes them into the request URL. Header and
cookie parameter collections are applied before the request enters the
middleware stack and produce raw header tuples.

## Response Wrappers

Generated clients can define a local response module with
`Tesla.OpenAPI.Response`:

    defmodule MyApi.Response do
      use Tesla.OpenAPI.Response
    end

## Field Mapping

`in` chooses the Tesla API. It is not passed as an option to the value
objects. `style`, `explode`, and `allowReserved` become `:style`, `:explode`,
and `:allow_reserved` options where the corresponding parameter location
supports them.

See [Working with OpenAPI parameters](openapi-parameters.html) for a
generated-operation walkthrough, or the [OpenAPI Cheat Sheet](openapi.html)
for quick lookup while implementing generated clients.

# `merge_private`

```elixir
@spec merge_private([Tesla.Env.private()]) :: Tesla.Env.private()
```

Merges `t:Tesla.Env.private/0` maps from left to right.

---

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