It was returning false in normal circumstances.
This broke the `head :ok and return if` construct.
Add appropriate test.

 - The request needs to be instance of ActionDispatch::Request or an
   object that responds to host, optional_port, protocol and
   symbolized_path_parameter.
 - This documentation was correctly added in
   https://github.com/rails/rails/commit/e3b3f416b57f5642ea25078485f7e9394ad04526
   but was changed to
   https://github.com/rails/rails/commit/e1ceae576e3911f3e6708b5d19a0e3ef63769eb7.
 - Fixes #16160.

Removed non-standard and unused require 'active_support/deprecation' from parts out of active_support.

This approach will avoid us to check for NoMethodError when trying to
decode

Add http_cache_forever to ActionController, so we can cache results
forever.
Things like static pages are a good candidate for this type of caching.

This cache only controls caching headers, so it is up to the browser to
cache those requests.

Non-string authenticity tokens raised NoMethodError when decoding the
masked token.

The methods `fresh_when` and `stale?` from ActionController::ConditionalGet
accept a single record as a short form for a hash. For instance

```ruby
  def show
    @article = Article.find(params[:id])
    fresh_when(@article)
  end
```

is just a short form for:

```ruby
  def show
    @article = Article.find(params[:id])
    fresh_when(etag: @article, last_modified: @article.created_at)
  end
```

This commit extends `fresh_when` and `stale?` to also accept a collection
of records, so that a short form similar to the one above can be used in
an `index` action. After this commit, the following code:

```ruby
def index
  @article = Article.all
  fresh_when(etag: @articles, last_modified: @articles.maximum(:created_at))
end
```

can be simply written as:

```ruby
def index
  @article = Article.all
  fresh_when(@articles)
end
```

PR #18772 changed the parameters of `stale?` to use `kwargs`.
[As for this comment](https://github.com/rails/rails/pull/18872/files#r24456288)
the default value for the `etag` parameter should be `record`, not `nil`.

This commit fixes the code and introduces a test that:

- passed before #18872
- fails on the current master (after #18772)
- passes again after setting the default value of `etag` to `record`.

Render arbitrary templates outside of controller actions

To have an easier way to setup a controller
instance with custom environment

Add `ActionController::Metal#set_request!` to set a request
on controller instance without calling dispatch.

It is clearer and closer to reality to use `@article.updated_at` as
the `:last_modified` parameter of `fresh_when` and `stale?`.

Using `@article.created_at` would result in the cache never expiring,
since the creation timestamp never changes.

[ci skip]

[ci skip]

This was used by the respond_to/respond_with implementation on this
file, which is now extracted to the responders gem.

This functionality has been extracted to the responders gem.

Commit 20fece14 introduced the `_status_code` method to fix calls to
`head :ok`. This method has been added on both ActionController::Metal
and ActionDispatch::Response.

As for the latter, this method is just equivalent to the `response_code`
one so commit aefec3c6 removed it from the `Reponse` object so call to
the `_status_code` method on an ActionController::Base instance would be
handled by the `Metal` class (which `Base` inherits from) but the status
code is not updated according to the response at this level.

The fix is to actually rely on `response_code` for ActionController::Base
instances but this method doesn't exist for bare Metal controllers so we
need to define it.

encapsulate env in the request so that we can eventually move away from
the env hash

this will help decouple us from using the rack env hash

- The single space response was added due to a bug in safari
  in https://github.com/rails/rails/commit/cb0f8fda9652c4d24d04693bdb82cecd3b067e5c
  and
  https://github.com/rails/rails/commit/807df4fcf021fc4d15972aa1c17ba7398d43ab0d.
- This was removed from the `render nothing: true` in
  https://github.com/rails/rails/pull/14883.
- Removing it from response of :head also. As :head is more obvious
  alternative to call `render nothing:
  true`(http://guides.rubyonrails.org/layouts_and_rendering.html#using-head-to-build-header-only-responses),
  removing it from head method also.
- Closes #18253.

Example does not work with session headers, should use request headers. [ci skip]

Add nodoc to some constants [skip ci]

This reverts commit da5cc10e.

Fixes #18091

See also https://github.com/rails/rails/pull/18003#commitcomment-9030909

As suggested in #16299([1]), this method should be a new public API for
retrieving unfiltered parameters from `ActionController::Parameters`
object, given that `Parameters#to_hash` will no longer work in Rails
5.0+ as we stop inheriting `Parameters` from `Hash`.

[1]: https://github.com/rails/rails/pull/16299#issuecomment-50220919

As discussed in #16299[1], this attribute is not thread safe and could
potentially create a security issue.

[1]: https://github.com/rails/rails/pull/16299#discussion_r15424533

See:
* https://github.com/rails/rails/pull/14903
* https://github.com/roidrage/lograge/issues/37

Some code by mxrguspxrt from #14903.