# CHANGELOG
## v0.4.0 (2023-09-01)
Req v0.4.0 changes headers to be maps, adds request & response streaming, and improves steps.
### Change Headers to be Maps
Previously headers were lists of name/value tuples, e.g.:
```elixir
[{"content-type", "text/html"}]
```
This is a standard across the ecosystem (with minor difference that some Erlang libraries use
charlists instead of binaries.)
There are some problems with this particular choice though:
* We cannot use `headers[name]`
* We cannot use pattern matching
In short, this representation isn't very ergonomic to use.
Now headers are maps of string names and lists of values, e.g.:
```elixir
%{"content-type" => ["text/html"]}
```
This allows `headers[name]` usage:
```elixir
response.headers["content-type"]
#=> ["text/html"]
```
and pattern matching:
```elixir
case Req.request!(req) do
%{headers: %{"content-type" => ["application/json" <> _]}} ->
# handle JSON response
end
```
This is a major breaking change. If you cannot easily update your app
or your dependencies, do:
```elixir
# config/config.exs
config :req, legacy_headers_as_lists: true
```
This legacy fallback will be removed on Req 1.0.
There are two other changes to headers in this release.
Header names are now case-insensitive in functions like
`Req.Response.get_header/2`.
Trailer headers, or more precisely trailer fields or simply trailers, are now stored
in a separate `trailers` field on the `%Req.Response{}` struct as long as you use Finch 0.17+.
### Add Request Body Streaming
Req v0.4 adds official support for request body streaming by setting the request body to an
`enumerable`. Here's an example:
```elixir
iex> stream = Stream.duplicate("foo", 3)
iex> Req.post!("https://httpbin.org/post", body: stream).body["data"]
"foofoofoo"
```
The enumerable is passed through request steps and they may change it. For example,
the [`compress_body`] step gzips the request body on the fly.
### Add Response Body Streaming
Req v0.4 also adds response body streaming, via the `:into` option.
Here's an example where we download the first 20kb (by making a _range_ request, via the
[`put_range`] step) of Elixir release zip. We stream the response body into a function
and can handle each body chunk. The function receives a `{:data, data}, {req, resp}` and returns
a `{:cont | :halt, {req, resp}}` tuple.
```elixir
resp =
Req.get!(
url: "https://github.com/elixir-lang/elixir/releases/download/v1.15.4/elixir-otp-26.zip",
range: 0..20_000,
into: fn {:data, data}, {req, resp} ->
IO.inspect(byte_size(data), label: :chunk)
{:cont, {req, resp}}
end
)
# output: 17:07:38.131 [debug] redirecting to https://objects.githubusercontent.com/github-production-release-asset-2e6(...)
# output: chunk: 16384
# output: chunk: 3617
resp.status #=> 206
resp.headers["content-range"] #=> ["bytes 0-20000/6801977"]
resp.body #=> ""
```
Notice we only stream response _body_, that is, Req automatically handles HTTP response status and
headers. Once the stream is done, Req passes the response through response steps which allows
following redirects, retrying on errors, etc. Response `body` is set to empty string `""`
which is then ignored by [`decompress_body`], [`decode_body`], and similar steps. If you need
to decompress or decode incoming chunks, you need to do that in your custom `into: fun` function.
As the name `:into` implies, we can also stream response body into any [`Collectable`].
Here's a similar snippet to above where we stream to a file:
```elixir
resp =
Req.get!(
url: "https://github.com/elixir-lang/elixir/releases/download/v1.15.4/elixir-otp-26.zip",
range: 0..20_000,
into: File.stream!("elixit-otp-26.zip.1")
)
# output: 17:07:38.131 [debug] redirecting to (...)
resp.status #=> 206
resp.headers["content-range"] #=> ["bytes 0-20000/6801977"]
resp.body #=> %File.Stream{}
```
### Full CHANGELOG
* Change `request.headers` and `response.headers` to be maps.
* Ensure `request.headers` and `response.headers` are downcased.
Per [RFC 9110: HTTP Semantics](https://www.rfc-editor.org/rfc/rfc9110.html),
HTTP headers should be case-insensitive. However, per
[RFC 9113: HTTP/2](https://datatracker.ietf.org/doc/html/rfc9113) headers
must be sent downcased.
Req headers are now stored internally downcased and all accessor functions
like [`Req.Response.get_header/2`] are downcasing the given header name.
* Add `trailers` field to [`Req.Response`] struct. Trailer field is only filled in on Finch 0.17+.
* Make `request.registered_options` internal representation private.
* Make `request.options` internal representation private.
Currently `request.options` field is a map but it may change in the future.
One possible future change is using keywords lists internally which would
allow, for example, `Req.new(params: [a: 1]) |> Req.update(params: [b: 2])`
to keep duplicate `:params` in `request.options` which would then allow to
decide the duplicate key semantics on a per-step basis. And so, for example,
[`put_params`] would _merge_ params but most steps would simply use the
first value.
To have some room for manoeuvre in the future we should stop pattern
matching on `request.options`. Calling `request.options[key]`,
`put_in(request.options[key], value)`, and
`update_in(request.options[key], fun)` _is_ allowed.
* Fix typespecs for some functions
* Deprecate [`output`] step in favour of `into: File.stream!(path)`.
* Rename `follow_redirects` step to [`redirect`]
* [`redirect`]: Rename `:follow_redirects` option to `:redirect`.
* [`redirect`]: Rename `:location_trusted` option to `:redirect_trusted`.
* [`redirect`]: Change HTTP request method to GET only on POST requests that result in 301..303.
Previously we were changing the method to GET for all 3xx except 307 and 308.
* [`decompress_body`]: Remove support for `deflate` compression (which was broken)
* [`decompress_body`]: Don't crash on unknown codec
* [`decompress_body`]: Fix handling HEAD requests
* [`decompress_body`]: Re-calculate `content-length` header after decompresion
* [`decompress_body`]: Remove `content-encoding` header after decompression
* [`decode_body`]: Do not decode response with `content-encoding` header
* [`run_finch`]: Add `:inet6` option
* [`retry`]: Support `retry: :safe_transient` which retries HTTP 408/429/500/502/503/504
or exceptions with `reason` field set to `:timeout`/`:econnrefused`.
`:safe_transient` is the new default retry mode. (Previously we retried on 408/429/5xx and
_any_ exception.)
* [`retry`]: Support `retry: :transient` which is the same as `:safe_transient` except
it retries on all HTTP methods
* [`retry`]: Use `retry-after` header value on HTTP 503 Service Unavailable. Previously
only HTTP 429 Too Many Requests was using this header value.
* [`retry`]: Support `retry: &fun/2`. The function receives `request, response_or_exception`
and returns either:
* `true` - retry with the default delay
* `{:delay, milliseconds}` - retry with the given delay
* `false/nil` - don't retry
* [`retry`]: Deprecate `retry: :safe` in favour of `retry: :safe_transient`
* [`retry`]: Deprecate `retry: :never` in favour of `retry: false`
* [`Req.request/2`]: Improve error message on invalid arguments
* [`Req.update/2`]: Do not duplicate headers
* [`Req.update/2`]: Merge `:params`
* [`Req.Request`]: Fix displaying redacted basic authentication
* [`Req.Request`]: Add [`Req.Request.get_option/3`]
* [`Req.Request`]: Add [`Req.Request.fetch_option/2`]
* [`Req.Request`]: Add [`Req.Request.fetch_option!/2`]
* [`Req.Request`]: Add [`Req.Request.update_option/4`]
* [`Req.Request`]: Add [`Req.Request.delete_option/2`]
* [`Req.Response`]: Add [`Req.Response.delete_header/2`]
* [`Req.Response`]: Add [`Req.Response.update_private/4`]
## v0.3.11 (2023-07-24)
* Support `Req.get(options)`, `Req.post(options)`, etc
* Add [`Req.Request.new/1`]
* [`retry`]: Fix returning correct `private.req_retry_count`
## v0.3.10 (2023-06-20)
* [`decompress_body`]: No-op on non-binary response body
* [`decompress_body`]: Support multiple `content-encoding` headers
* [`decode_body`]: Remove `:extract` option
* Remove deprecated `Req.post!(url, body)` and similar functions
## v0.3.9 (2023-06-08)
* [`put_path_params`]: URI-encode path params
## v0.3.8 (2023-05-22)
* Add `:redact_auth` option to redact auth credentials, defaults to `true`.
* Soft-deprecate `Req.Request.run,run!` in favour of [`Req.Request.run_request/1`].
## v0.3.7 (2023-05-18)
* Deprecate setting headers to `%NaiveDateTime{}`, always use `%DateTime{}`.
* [`decode_body`]: Add `:decode_json` option
* [`follow_redirects`]: Add `:redirect_log_level`
* [`follow_redirects`]: Preserve HTTP method on 307/308 redirects
* [`run_finch`]: Allow `:finch_request` to perform the underlying request. This deprecates
passing 1-arity function `f(finch_request)` in favour of 4-arity
`f(request, finch_request, finch_name, finch_options)`.
## v0.3.6 (2023-03-06)
* [`run_finch`]: Fix setting `:hostname` option
* [`decode_body`]: Add `:extract` option to automatically extract archives (zip, tar, etc)
## v0.3.5 (2023-02-01)
* New step: [`put_path_params`]
* [`auth`]: Accept string
## v0.3.4 (2023-01-03)
* [`retry`]: Add `:retry_log_level` option
## v0.3.3 (2022-12-08)
* [`follow_redirects`]: Inherit scheme from previous location
* [`run_finch`]: Fix setting connect timeout
* [`run_finch`]: Add `:finch_request` option
## v0.3.2 (2022-11-14)
* [`decode_body`]: Decode JSON when response is json-api mime type
* [`put_params`]: Fix bug when params have been duplicated when retrying requeset
* [`retry`]: Remove `retry: :always` option
* [`retry`]: Soft-deprecate `retry: :never` in favour of `retry: false`
* [`run_finch`]: Add `:transport_opts`, `:proxy_headers`, `:proxy`, and `:client_settings` options
* `Req.Response.json/2`: Do not override content-type
## v0.3.1 (2022-09-09)
* [`encode_body`]: Set Accept header in JSON requests
* [`put_base_url`]: Fix merging with leading and/or trailing slashes
* Fix merging :adapter option
* Add get/2, post/2, put/2, patch/2, delete/2 and head/2
## v0.3.0 (2022-06-21)
Req v0.3.0 brings redesigned API, new steps, and improvements to existing steps.
### New API
The new API allows building a request struct with all the built-in steps. It can be then piped
to functions like `Req.get!/2`:
```elixir
iex> req = Req.new(base_url: "https://api.github.com")
iex> req |> Req.get!(url: "/repos/sneako/finch") |> then(& &1.body["description"])
"Elixir HTTP client, focused on performance"
iex> req |> Req.get(url: "/repos/elixir-mint/mint") |> then(& &1.body["description"])
"Functional HTTP client for Elixir with support for HTTP/1 and HTTP/2."
```
Setting body and encoding it to form/JSON is now done through `:body/:form/:json` options:
```elixir
iex> Req.post!("https://httpbin.org/anything", body: "hello!").body["data"]
"hello!"
iex> req = Req.new(url: "https://httpbin.org/anything")
iex> Req.post!(req, form: [x: 1]).body["form"]
%{"x" => "1"}
iex> Req.post!(req, json: %{x: 2}).body["form"]
%{"x" => 2}
```
### Improved Error Handling
Req now validates option names ensuring users didn't accidentally mistyped them.
If they did, it will try to give a helpful error message. Here are some examples:
```elixir
Req.request!(urll: "https://httpbin.org")
** (ArgumentError) unknown option :urll. Did you mean :url?
Req.new(bas_url: "https://httpbin.org")
** (ArgumentError) unknown option :bas_url. Did you mean :base_url?
```
Req also has a new option to handle HTTP errors (4xx/5xx). By default it will continue to
return the error responses:
```elixir
Req.get!("https://httpbin.org/status/404")
#=> %Req.Response{status: 404, ...}
```
but users can now pass `http_errors: :raise` to raise an exception instead:
```elixir
Req.get!("https://httpbin.org/status/404", http_errors: :raise)
** (RuntimeError) The requested URL returned error: 404
Response body: ""
```
This is especially useful in one-off scripts where we only really care about the
"happy path" but would still like to get a good error message when something
unexpected happened.
### Plugins
From the very beginning, Req could be extended with custom steps. To make using such custom steps
by others even easier, they can be packaged up into plugins.
Here are some examples:
* [`req_easyhtml`](https://github.com/wojtekmach/req_easyhtml)
* [`req_s3`](https://github.com/wojtekmach/req_s3)
* [`req_hex`](https://github.com/wojtekmach/req_hex)
* [`req_github_oauth`](https://github.com/wojtekmach/req_github_oauth)
And here's how they can be used:
```elixir
Mix.install([
{:req, "~> 0.3.0"},
{:req_easyhtml, github: "wojtekmach/req_easyhtml"},
{:req_s3, github: "wojtekmach/req_s3"},
{:req_hex, github: "wojtekmach/req_hex"},
{:req_github_oauth, github: "wojtekmach/req_github_oauth"}
])
req =
(Req.new(http_errors: :raise)
|> ReqEasyHTML.attach()
|> ReqS3.attach()
|> ReqHex.attach()
|> ReqGitHubOAuth.attach())
Req.get!(req, url: "https://elixir-lang.org").body[".entry-summary h5"]
#=>
# #EasyHTML[<h5>
# Elixir is a dynamic, functional language for building scalable and maintainable applications.
# </h5>]
Req.get!(req, url: "s3://ossci-datasets").body
#=>
# [
# "mnist/",
# "mnist/t10k-images-idx3-ubyte.gz",
# "mnist/t10k-labels-idx1-ubyte.gz",
# "mnist/train-images-idx3-ubyte.gz",
# "mnist/train-labels-idx1-ubyte.gz"
# ]
Req.get!(req, url: "https://repo.hex.pm/tarballs/req-0.1.0.tar").body["metadata.config"]["links"]
#=> %{"GitHub" => "https://github.com/wojtekmach/req"}
Req.get!(req, url: "https://api.github.com/user").body["login"]
# Outputs:
# paste this user code:
#
# 6C44-30A8
#
# at:
#
# https://github.com/login/device
#
# open browser window? [Yn]
# 15:22:28.350 [info] response: authorization_pending
# 15:22:33.519 [info] response: authorization_pending
# 15:22:38.678 [info] response: authorization_pending
#=> "wojtekmach"
Req.get!(req, url: "https://api.github.com/user").body["login"]
#=> "wojtekmach"
```
Notice all plugins can be attached to the same request struct which makes it really easy to
explore different endpoints.
See ["Writing Plugins" section in `Req.Request` module documentation](https://hexdocs.pm/req/Req.Request.html#module-writing-plugins)
for more information.
### Plug Integration
Req can now be used to easily test plugs using the `:plug` option:
```elixir
defmodule Echo do
def call(conn, _) do
"/" <> path = conn.request_path
Plug.Conn.send_resp(conn, 200, path)
end
end
test "echo" do
assert Req.get!("http:///hello", plug: Echo).body == "hello"
end
```
you can define plugs as functions too:
```elixir
test "echo" do
echo = fn conn ->
"/" <> path = conn.request_path
Plug.Conn.send_resp(conn, 200, path)
end
assert Req.get!("http:///hello", plug: echo).body == "hello"
end
```
which is particularly useful to create HTTP service mocks with tools like
[Bypass](https://github.com/PSPDFKit-labs/bypass).
### Request Adapters
While Req always used Finch as the underlying HTTP client, it was designed from the day one to
easily swap it out. This is now even easier with an `:adapter` option.
Here is a mock adapter that always returns a successful response:
```elixir
adapter = fn request ->
response = %Req.Response{status: 200, body: "it works!"}
{request, response}
end
Req.request!(url: "http://example", adapter: adapter).body
#=> "it works!"
```
Here is another one that uses the [`json/2`][resp_json] function to conveniently
return a JSON response:
[resp_json]: https://hexdocs.pm/req/Req.Response.html#json/2
```elixir
adapter = fn request ->
response = Req.Response.json(%{hello: 42})
{request, response}
end
resp = Req.request!(url: "http://example", adapter: adapter)
resp.headers
#=> [{"content-type", "application/json"}]
resp.body
#=> %{"hello" => 42}
```
And here is a naive Hackney-based adapter and how we can use it:
```elixir
hackney = fn request ->
case :hackney.request(
request.method,
URI.to_string(request.url),
request.headers,
request.body,
[:with_body]
) do
{:ok, status, headers, body} ->
headers = for {name, value} <- headers, do: {String.downcase(name), value}
response = %Req.Response{status: status, headers: headers, body: body}
{request, response}
{:error, reason} ->
{request, RuntimeError.exception(inspect(reason))}
end
end
Req.get!("https://api.github.com/repos/elixir-lang/elixir", adapter: hackney).body["description"]
#=> "Elixir is a dynamic, functional language designed for building scalable and maintainable applications"
```
See "Adapter" section in `Req.Request` module documentation for more information.
### Major changes
* Add high-level functional API: `Req.new(...) |> Req.request(...)`, `Req.new(...) |>
Req.get!(...)`, etc.
* Add `Req.Request.options` field that steps can read from. Also, make
all steps be arity 1.
When using "High-level" API, we now run all steps by default. (The
steps, by looking at request.options, can decide to be no-op.)
* Move low-level API to `Req.Request`
* Move built-in steps to `Req.Steps`
* Add step names
* Add `Req.head!/2`
* Add `Req.patch!/2`
* Add `Req.Request.adapter` field
* Add `Req.Request.merge_options/2`
* Add `Req.Request.register_options/2`
* Add `Req.Request.put_header/3`
* Add `Req.Request.put_headers/2`
* Add `Req.Request.put_new_header/3`
* Add `Req.Request.get_header/2`
* Add `Req.Request.update_private/4`
* Add `Req.Response.new/1`
* Add `Req.Response.json/2`
* Add `Req.Response.get_header/2`
* Add `Req.Response.put_header/3`
* Rename `put_if_modified_since` step to `cache`
* Rename `decompress` step to `decompress_body`
* Remove `put_default_steps` step
* Remove `run_steps` step
* Remove `put_default_headers` step
* Remove `encode_headers` step. The headers are now encoded in `Req.new/1` and `Req.request/2`
* Remove `Req.Request.unix_socket` field. Add option on `run_finch` step with the same name
instead.
* Require Elixir 1.12
### Step changes
* New step: [`put_plug`]
* New step: [`put_user_agent`] (replaces part of removed `put_default_headers`)
* New step: [`compressed`] (replaces part of removed `put_default_headers`)
* New step: [`compress_body`]
* New step: [`output`]
* New step: [`handle_http_errors`]
* [`put_base_url`]: Ignore base URL if given URL contains scheme
* [`run_finch`]: Add `:connect_options` which dynamically starts (or re-uses already started)
Finch pool with the given connection options.
* [`run_finch`]: Replace `:finch_options` with `:receive_timeout` and `:pool_timeout` options
* [`encode_body`]: Add `:form` and `:json` options (previously used as `{:form, data}` and
`{:json, data}`)
* [`cache`]: Include request method in cache key
* [`decompress_body`], [`compressed`]: Support Brotli
* [`decompress_body`], [`compressed`]: Support Zstandard
* [`decode_body`]: Support `decode_body: false` option to disable automatic body decoding
* [`follow_redirects`]: Change method to GET on 301..303 redirects
* [`follow_redirects`]: Don't send auth headers on redirect to different scheme/host/port
unless `location_trusted: true` is set
* [`retry`]: The `Retry-After` response header on HTTP 429 responses is now respected
* [`retry`]: The `:retry` option can now be set to `:safe` (default) to only retry GET/HEAD
requests on HTTP 408/429/5xx responses or exceptions, `:always` to always retry, `:never` to never
retry, and `fun` - a 1-arity function that accepts either a `Req.Response` or an exception
struct and returns boolean whether to retry
* [`retry`]: The `:retry_delay` option now accepts a function that takes a retry count (starting at 0)
and returns the delay. Defaults to a simple exponential backoff: 1s, 2s, 4s, 8s, ...
### Deprecations
* Deprecate calling `Req.post!(url, body)` in favour of `Req.post!(url, body: body)`.
Also, deprecate `Req.post!(url, {:form, data})` in favour of `Req.post!(url, form: data)`.
and `Req.post!(url, {:json, data})` in favour of `Req.post!(url, json: data)`. Same for
`Req.put!/2`.
* Deprecate setting `retry: [delay: delay, max_retries: max_retries]`
in favour of `retry_delay: delay, max_retries: max_retries`.
* Deprecate setting `cache: [dir: dir]` in favour of `cache_dir: dir`.
* Deprecate Req.build/3 in favour of manually building the struct.
## v0.2.2 (2022-04-04)
* Relax Finch version requirement
## v0.2.1 (2021-11-24)
* Add `:private` field to Response
* Update Finch to 0.9.1
## v0.2.0 (2021-11-08)
* Rename `normalize_headers` to `encode_headers`
* Rename `prepend_default_steps` to `put_default_steps`
* Rename `encode` and `decode` to `encode_body` and `decode_body`
* Rename `netrc` to `load_netrc`
* Rename `finch` step to `run_finch`
* Rename `if_modified_since` to `put_if_modified_since`
* Rename `range` to `put_range`
* Rename `params` to `put_params`
* Rename `request.uri` to `request.url`
* Change response/error step contract from `f(req, resp_err)` to `f({req, resp_err})`
* Support mime 2.x
* Add `Req.Response` struct
* Add `put!/3` and `delete!/2`
* Add `run_steps/2`
* Initial support for UNIX domain sockets
* Accept `{module, args}` and `module` as steps
* Ensure `get_private` and `put_private` have atom keys
* `put_default_steps`: Use MFArgs instead of captures for the default steps
* `put_if_modified_since`: Fix generating internet time
* `encode_headers`: Encode header values
* `retry`: Rename `:max_attempts` to `:max_retries`
## v0.1.1 (2021-07-16)
* Fix `append_request_steps/2` and `prepend_request_steps/2` (they did the opposite)
* Add `finch/1`
## v0.1.0 (2021-07-15)
* Initial release
[`auth`]: https://hexdocs.pm/req/Req.Steps.html#auth/1
[`cache`]: https://hexdocs.pm/req/Req.Steps.html#cache/1
[`compress_body`]: https://hexdocs.pm/req/Req.Steps.html#compress_body/1
[`compressed`]: https://hexdocs.pm/req/Req.Steps.html#compressed/1
[`decode_body`]: https://hexdocs.pm/req/Req.Steps.html#decode_body/1
[`decompress_body`]: https://hexdocs.pm/req/Req.Steps.html#decompress_body/1
[`compress_body`]: https://hexdocs.pm/req/Req.Steps.html#compress_body/1
[`encode_body`]: https://hexdocs.pm/req/Req.Steps.html#encode_body/1
[`redirect`]: https://hexdocs.pm/req/Req.Steps.html#redirect/1
[`handle_http_errors`]: https://hexdocs.pm/req/Req.Steps.html#handle_http_errors/1
[`output`]: https://hexdocs.pm/req/Req.Steps.html#output/1
[`put_base_url`]: https://hexdocs.pm/req/Req.Steps.html#put_base_url/1
[`put_params`]: https://hexdocs.pm/req/Req.Steps.html#put_params/1
[`put_path_params`]: https://hexdocs.pm/req/Req.Steps.html#put_path_params/1
[`put_plug`]: https://hexdocs.pm/req/Req.Steps.html#put_plug/1
[`put_user_agent`]: https://hexdocs.pm/req/Req.Steps.html#put_user_agent/1
[`put_range`]: https://hexdocs.pm/req/Req.Steps.html#put_range/1
[`retry`]: https://hexdocs.pm/req/Req.Steps.html#retry/1
[`run_finch`]: https://hexdocs.pm/req/Req.Steps.html#run_finch/1
[`Req.request/2`]: https://hexdocs.pm/req/Req.html#request/2
[`Req.update/2`]: https://hexdocs.pm/req/Req.html#update/2
[`Req.Request`]: https://hexdocs.pm/req/Req.Request.html
[`Req.Request.new/1`]: https://hexdocs.pm/req/Req.Request.html#new/1
[`Req.Request.run_request/1`]: https://hexdocs.pm/req/Req.Request.html#run_request/1
[`Req.Request.get_option/3`]: https://hexdocs.pm/req/Req.Request.html#get_option/3
[`Req.Request.fetch_option/2`]: https://hexdocs.pm/req/Req.Request.html#fetch_option/2
[`Req.Request.fetch_option!/2`]: https://hexdocs.pm/req/Req.Request.html#fetch_option!/2
[`Req.Request.update_option/4`]: https://hexdocs.pm/req/Req.Request.html#update_option/4
[`Req.Request.delete_option/2`]: https://hexdocs.pm/req/Req.Request.html#delete_option/2
[`Req.Request.update_private/4`]: https://hexdocs.pm/req/Req.Request.html#update_private/4
[`Req.Response`]: https://hexdocs.pm/req/Req.Response.html
[`Req.Response.get_header/2`]: https://hexdocs.pm/req/Req.Response.html#get_response/2
[`Req.Response.delete_header/2`]: https://hexdocs.pm/req/Req.Response.html#delete_header/2
[`Req.Response.update_private/4`]: https://hexdocs.pm/req/Req.Response.html#update_private/4
[`Req.Steps`]: https://hexdocs.pm/req/Req.Steps.html
[`Collectable`]: https://hexdocs.pm/elixir/Collectable.html
