12 files changed, 69 insertions, 49 deletions
diff --git a/guides/source/3_2_release_notes.md b/guides/source/3_2_release_notes.md
index 3fccca8d5c..6570b19f97 100644
--- a/guides/source/3_2_release_notes.md
+++ b/guides/source/3_2_release_notes.md
@@ -295,7 +295,7 @@ Action Pack
     ```ruby
     @items.each do |item|
       content_tag_for(:li, item) do
-         Title: <%= item.title %>
+        Title: <%= item.title %>
       end
     end
     ```
diff --git a/guides/source/5_0_release_notes.md b/guides/source/5_0_release_notes.md
index 6d53e1c2b4..3805fd2a63 100644
--- a/guides/source/5_0_release_notes.md
+++ b/guides/source/5_0_release_notes.md
@@ -55,7 +55,7 @@ information.
 ### API Applications
 
 Rails can now be used to create slimmed down API only applications.
-This is useful for creating and serving APIs similar to [Twitter](https://dev.twitter.com) or [GitHub](https://developer.github.com) API, 
+This is useful for creating and serving APIs similar to [Twitter](https://dev.twitter.com) or [GitHub](https://developer.github.com) API,
 that can be used to serve public facing, as well as, for custom applications.
 
 You can generate a new api Rails app using:
@@ -77,7 +77,7 @@ This will do three main things:
   you generate a new resource.
 
 The application provides a base for APIs,
-that can then be [configured to pull in functionality](api_app.html) as suitable for the application's needs.  
+that can then be [configured to pull in functionality](api_app.html) as suitable for the application's needs.
 
 See the [Using Rails for API-only Applications](api_app.html) guide for more
 information.
diff --git a/guides/source/action_mailer_basics.md b/guides/source/action_mailer_basics.md
index ba26c922be..96ef9c4450 100644
--- a/guides/source/action_mailer_basics.md
+++ b/guides/source/action_mailer_basics.md
@@ -413,7 +413,7 @@ inside of Action Controller, so you can use all the same options, such as
 
 #### Caching mailer view
 
-You can do cache in mailer views like in application views using `cache` method.
+You can perform fragment caching in mailer views like in application views using the `cache` method.
 
 ```
 <% cache do %>
@@ -427,6 +427,9 @@ And in order to use this feature, you need to configure your application with th
   config.action_mailer.perform_caching = true
 ```
 
+Fragment caching is also supported in multipart emails.
+Read more about caching in the [Rails caching guide](caching_with_rails.html).
+
 ### Action Mailer Layouts
 
 Just like controller views, you can also have mailer layouts. The layout name
diff --git a/guides/source/active_job_basics.md b/guides/source/active_job_basics.md
index 2606bfe280..9fc95954bc 100644
--- a/guides/source/active_job_basics.md
+++ b/guides/source/active_job_basics.md
@@ -379,7 +379,7 @@ class GuestsCleanupJob < ApplicationJob
   queue_as :default
 
   rescue_from(ActiveRecord::RecordNotFound) do |exception|
-   # Do something with the exception
+    # Do something with the exception
   end
 
   def perform
diff --git a/guides/source/active_record_querying.md b/guides/source/active_record_querying.md
index 53cacfa6ea..678b80516f 100644
--- a/guides/source/active_record_querying.md
+++ b/guides/source/active_record_querying.md
@@ -1393,7 +1393,7 @@ end
 ```
 
 NOTE: The `default_scope` is also applied while creating/building a record
-when the scope arguments are given as a `Hash`. It is not applied while 
+when the scope arguments are given as a `Hash`. It is not applied while
 updating a record. E.g.:
 
 ```ruby
diff --git a/guides/source/active_support_core_extensions.md b/guides/source/active_support_core_extensions.md
index 4c37f6aba9..9f89e666dc 100644
--- a/guides/source/active_support_core_extensions.md
+++ b/guides/source/active_support_core_extensions.md
@@ -135,9 +135,9 @@ NOTE: Defined in `active_support/core_ext/object/blank.rb`.
 
 ### `duplicable?`
 
-In Ruby 2.4 most objects can be duplicated via `dup` or `clone` except 
+In Ruby 2.4 most objects can be duplicated via `dup` or `clone` except
 methods and certain numbers. Though Ruby 2.2 and 2.3 can't duplicate `nil`,
-`false`, `true`, and  symbols as well as instances `Float`, `Fixnum`, 
+`false`, `true`, and  symbols as well as instances `Float`, `Fixnum`,
 and `Bignum` instances.
 
 ```ruby
@@ -1709,7 +1709,7 @@ Specifically performs these transformations:
   * Capitalizes the first word.
 
 The capitalization of the first word can be turned off by setting the
-+:capitalize+ option to false (default is true).
+`:capitalize` option to false (default is true).
 
 ```ruby
 "name".humanize                         # => "Name"
@@ -1989,7 +1989,7 @@ Extensions to `BigDecimal`
 The method `to_s` provides a default specifier of "F". This means that a simple call to `to_s` will result in floating point representation instead of engineering notation:
 
 ```ruby
-BigDecimal.new(5.00, 6).to_s  # => "5.0"
+BigDecimal.new(5.00, 6).to_s       # => "5.0"
 ```
 
 and that symbol specifiers are also supported:
@@ -2359,7 +2359,7 @@ This method is similar in purpose to `Kernel#Array`, but there are some differen
 
 * If the argument responds to `to_ary` the method is invoked. `Kernel#Array` moves on to try `to_a` if the returned value is `nil`, but `Array.wrap` returns an array with the argument as its single element right away.
 * If the returned value from `to_ary` is neither `nil` nor an `Array` object, `Kernel#Array` raises an exception, while `Array.wrap` does not, it just returns the value.
-* It does not call `to_a` on the argument, if the argument does not respond to +to_ary+ it returns an array with the argument as its single element.
+* It does not call `to_a` on the argument, if the argument does not respond to `to_ary` it returns an array with the argument as its single element.
 
 The last point is particularly worth comparing for some enumerables:
 
@@ -3641,7 +3641,7 @@ Durations can be added to and subtracted from time objects:
 now = Time.current
 # => Mon, 09 Aug 2010 23:20:05 UTC +00:00
 now + 1.year
-#  => Tue, 09 Aug 2011 23:21:11 UTC +00:00
+# => Tue, 09 Aug 2011 23:21:11 UTC +00:00
 now - 1.week
 # => Mon, 02 Aug 2010 23:21:11 UTC +00:00
 ```
diff --git a/guides/source/association_basics.md b/guides/source/association_basics.md
index 1212ae53bc..b5bd24d027 100644
--- a/guides/source/association_basics.md
+++ b/guides/source/association_basics.md
@@ -663,11 +663,11 @@ By default, associations look for objects only within the current module's scope
 module MyApplication
   module Business
     class Supplier < ApplicationRecord
-       has_one :account
+      has_one :account
     end
 
     class Account < ApplicationRecord
-       belongs_to :supplier
+      belongs_to :supplier
     end
   end
 end
@@ -679,13 +679,13 @@ This will work fine, because both the `Supplier` and the `Account` class are def
 module MyApplication
   module Business
     class Supplier < ApplicationRecord
-       has_one :account
+      has_one :account
     end
   end
 
   module Billing
     class Account < ApplicationRecord
-       belongs_to :supplier
+      belongs_to :supplier
     end
   end
 end
@@ -697,14 +697,14 @@ To associate a model with a model in a different namespace, you must specify the
 module MyApplication
   module Business
     class Supplier < ApplicationRecord
-       has_one :account,
+      has_one :account,
         class_name: "MyApplication::Billing::Account"
     end
   end
 
   module Billing
     class Account < ApplicationRecord
-       belongs_to :supplier,
+      belongs_to :supplier,
         class_name: "MyApplication::Business::Supplier"
     end
   end
@@ -968,13 +968,12 @@ side of the association.
 Counter cache columns are added to the containing model's list of read-only attributes through `attr_readonly`.
 
 ##### `:dependent`
-Controls what happens to associated objects when their owner is destroyed:
+If you set the `:dependent` option to:
 
-* `:destroy` causes the associated objects to also be destroyed.
-* `:delete_all` causes the associated objects to be deleted directly from the database (callbacks are not executed).
-* `:nullify` causes the foreign keys to be set to `NULL` (callbacks are not executed).
-* `:restrict_with_exception` causes an exception to be raised if there are associated records.
-* `:restrict_with_error` causes an error to be added to the owner if there are associated objects.
+* `:destroy`, when the object is destroyed, `destroy` will be called on its
+associated objects.
+* `:delete`, when the object is destroyed, all its associated objects will be
+deleted directly from the database without calling their `destroy` method.
 
 WARNING: You should not specify this option on a `belongs_to` association that is connected with a `has_many` association on the other class. Doing so can lead to orphaned records in your database.
 
diff --git a/guides/source/caching_with_rails.md b/guides/source/caching_with_rails.md
index 6cdce5c2f4..910a531068 100644
--- a/guides/source/caching_with_rails.md
+++ b/guides/source/caching_with_rails.md
@@ -175,10 +175,28 @@ class Game < ApplicationRecord
 end
 ```
 
-With `touch` set to true, any action which changes `updated_at` for a game
+With `touch` set to `true`, any action which changes `updated_at` for a game
 record will also change it for the associated product, thereby expiring the
 cache.
 
+### Shared Partial Caching
+
+It is possible to share partials and associated caching between files with different mime types. For example shared partial caching allows template writers to share a partial between HTML and Javascript files. When templates are collected in the template resolver file paths they only include the template language extension and not the mime type. Because of this templates can be used for multiple mime types. Both HTML and JavaScript requests will respond to the following code:
+
+```ruby
+render(partial: 'hotels/hotel', collection: @hotels, cached: true)
+```
+
+Will load a file named `hotels/hotel.erb`.
+
+Another option is to include the full filename of the partial to render.
+
+```ruby
+render(partial: 'hotels/hotel.html.erb', collection: @hotels, cached: true)
+```
+
+Will load a file named `hotels/hotel.html.erb` in any file mime type, for example you could include this partial in a Javascript file.
+
 ### Managing dependencies
 
 In order to correctly invalidate the cache, you need to properly define the
@@ -272,7 +290,7 @@ Sometimes you need to cache a particular value or query result instead of cachin
 
 The most efficient way to implement low-level caching is using the `Rails.cache.fetch` method. This method does both reading and writing to the cache. When passed only a single argument, the key is fetched and value from the cache is returned. If a block is passed, that block will be executed in the event of a cache miss. The return value of the block will be written to the cache under the given cache key, and that return value will be returned. In case of cache hit, the cached value will be returned without executing the block.
 
-Consider the following example. An application has a `Product` model with an instance method that looks up the product’s price on a competing website. The data returned by this method would be perfect for low-level caching:
+Consider the following example. An application has a `Product` model with an instance method that looks up the product's price on a competing website. The data returned by this method would be perfect for low-level caching:
 
 ```ruby
 class Product < ApplicationRecord
@@ -284,7 +302,7 @@ class Product < ApplicationRecord
 end
 ```
 
-NOTE: Notice that in this example we used the `cache_key` method, so the resulting cache-key will be something like `products/233-20140225082222765838000/competing_price`. `cache_key` generates a string based on the model’s `id` and `updated_at` attributes. This is a common convention and has the benefit of invalidating the cache whenever the product is updated. In general, when you use low-level caching for instance level information, you need to generate a cache key.
+NOTE: Notice that in this example we used the `cache_key` method, so the resulting cache key will be something like `products/233-20140225082222765838000/competing_price`. `cache_key` generates a string based on the model's `id` and `updated_at` attributes. This is a common convention and has the benefit of invalidating the cache whenever the product is updated. In general, when you use low-level caching for instance level information, you need to generate a cache key.
 
 ### SQL Caching
 
@@ -387,9 +405,9 @@ store is not appropriate for large application deployments. However, it can
 work well for small, low traffic sites with only a couple of server processes,
 as well as development and test environments.
 
-New Rails projects are configured to use this implementation in development environment by default. 
+New Rails projects are configured to use this implementation in development environment by default.
 
-NOTE: Since processes will not share cache data when using `:memory_store`, 
+NOTE: Since processes will not share cache data when using `:memory_store`,
 it will not be possible to manually read, write or expire the cache via the Rails console.
 
 ### ActiveSupport::Cache::FileStore
@@ -580,7 +598,7 @@ Caching in Development
 ----------------------
 
 It's common to want to test the caching strategy of your application
-in development mode. Rails provides the rake task `dev:cache` to 
+in development mode. Rails provides the rake task `dev:cache` to
 easily toggle caching on/off.
 
 ```bash
diff --git a/guides/source/i18n.md b/guides/source/i18n.md
index dda16f755e..cb24822f86 100644
--- a/guides/source/i18n.md
+++ b/guides/source/i18n.md
@@ -105,7 +105,7 @@ This means, that in the `:en` locale, the key _hello_ will map to the _Hello wor
 
 The I18n library will use **English** as a **default locale**, i.e. if a different locale is not set, `:en` will be used for looking up translations.
 
-NOTE: The i18n library takes a **pragmatic approach** to locale keys (after [some discussion](http://groups.google.com/group/rails-i18n/browse_thread/thread/14dede2c7dbe9470/80eec34395f64f3c?hl=en)), including only the _locale_ ("language") part, like `:en`, `:pl`, not the _region_ part, like `:en-US` or `:en-GB`, which are traditionally used for separating "languages" and "regional setting" or "dialects". Many international applications use only the "language" element of a locale such as `:cs`, `:th` or `:es` (for Czech, Thai and Spanish). However, there are also regional differences within different language groups that may be important. For instance, in the `:en-US` locale you would have $ as a currency symbol, while in `:en-GB`, you would have £. Nothing stops you from separating regional and other settings in this way: you just have to provide full "English - United Kingdom" locale in a `:en-GB` dictionary. Few gems such as [Globalize3](https://github.com/globalize/globalize) may help you implement it.
+NOTE: The i18n library takes a **pragmatic approach** to locale keys (after [some discussion](https://groups.google.com/forum/#!topic/rails-i18n/FN7eLH2-lHA)), including only the _locale_ ("language") part, like `:en`, `:pl`, not the _region_ part, like `:en-US` or `:en-GB`, which are traditionally used for separating "languages" and "regional setting" or "dialects". Many international applications use only the "language" element of a locale such as `:cs`, `:th` or `:es` (for Czech, Thai and Spanish). However, there are also regional differences within different language groups that may be important. For instance, in the `:en-US` locale you would have $ as a currency symbol, while in `:en-GB`, you would have £. Nothing stops you from separating regional and other settings in this way: you just have to provide full "English - United Kingdom" locale in a `:en-GB` dictionary. Few gems such as [Globalize3](https://github.com/globalize/globalize) may help you implement it.
 
 The **translations load path** (`I18n.load_path`) is an array of paths to files that will be loaded automatically. Configuring this path allows for customization of translations directory structure and file naming scheme.
 
@@ -313,7 +313,7 @@ In general, this approach is far less reliable than using the language header an
 WARNING: You may be tempted to store the chosen locale in a _session_ or a *cookie*. However, **do not do this**. The locale should be transparent and a part of the URL. This way you won't break people's basic assumptions about the web itself: if you send a URL to a friend, they should see the same page and content as you. A fancy word for this would be that you're being [*RESTful*](https://en.wikipedia.org/wiki/Representational_State_Transfer). Read more about the RESTful approach in [Stefan Tilkov's articles](https://www.infoq.com/articles/rest-introduction). Sometimes there are exceptions to this rule and those are discussed below.
 
 Internationalization and Localization
------------------------------------
+-------------------------------------
 
 OK! Now you've initialized I18n support for your Ruby on Rails application and told it which locale to use and how to preserve it between requests.
 
@@ -371,7 +371,7 @@ end
 
 ```html+erb
 # app/views/home/index.html.erb
-<h1><%=t :hello_world %></h1>
+<h1><%= t :hello_world %></h1>
 <p><%= flash[:notice] %></p>
 ```
 
@@ -416,7 +416,7 @@ If your translations are stored in YAML files, certain keys must be escaped. The
 
 Examples:
 
-```erb
+```yaml
 # config/locales/en.yml
 en:
   success:
@@ -430,12 +430,12 @@ en:
 ```
 
 ```ruby
-I18n.t 'success.true' # => 'True!'
-I18n.t 'success.on' # => 'On!'
+I18n.t 'success.true'  # => 'True!'
+I18n.t 'success.on'    # => 'On!'
 I18n.t 'success.false' # => 'False!'
 I18n.t 'failure.false' # => Translation Missing
-I18n.t 'failure.off' # => Translation Missing
-I18n.t 'failure.true' # => Translation Missing
+I18n.t 'failure.off'   # => Translation Missing
+I18n.t 'failure.true'  # => Translation Missing
 ```
 
 ### Passing Variables to Translations
@@ -502,7 +502,7 @@ OK! Now let's add a timestamp to the view, so we can demo the **date/time locali
 
 ```erb
 # app/views/home/index.html.erb
-<h1><%=t :hello_world %></h1>
+<h1><%= t :hello_world %></h1>
 <p><%= flash[:notice] %></p>
 <p><%= l Time.now, format: :short %></p>
 ```
@@ -1050,7 +1050,7 @@ The Simple backend shipped with Active Support allows you to store translations
 
 For example a Ruby Hash providing translations can look like this:
 
-```yaml
+```ruby
 {
   pt: {
     foo: {
@@ -1187,7 +1187,7 @@ If you find your own locale (language) missing from our [example translations da
 Resources
 ---------
 
-* [Google group: rails-i18n](http://groups.google.com/group/rails-i18n) - The project's mailing list.
+* [Google group: rails-i18n](https://groups.google.com/forum/#!forum/rails-i18n) - The project's mailing list.
 * [GitHub: rails-i18n](https://github.com/svenfuchs/rails-i18n) - Code repository and issue tracker for the rails-i18n project. Most importantly you can find lots of [example translations](https://github.com/svenfuchs/rails-i18n/tree/master/rails/locale) for Rails that should work for your application in most cases.
 * [GitHub: i18n](https://github.com/svenfuchs/i18n) - Code repository and issue tracker for the i18n gem.
 
diff --git a/guides/source/kindle/toc.html.erb b/guides/source/kindle/toc.html.erb
index f310edd3a1..0f4228ed6b 100644
--- a/guides/source/kindle/toc.html.erb
+++ b/guides/source/kindle/toc.html.erb
@@ -14,7 +14,7 @@ Ruby on Rails Guides
         <% if document['work_in_progress']%>(WIP)<% end %>
       </li>
     <% end %>
-  </ul>  
+  </ul>
 <% end %>
 <hr />
 <ul>
diff --git a/guides/source/testing.md b/guides/source/testing.md
index 04cf1d751d..4ee3267261 100644
--- a/guides/source/testing.md
+++ b/guides/source/testing.md
@@ -928,7 +928,7 @@ each of the seven default actions, you can use the following command:
 $ bin/rails generate test_unit:scaffold article
 ...
 invoke  test_unit
-create test/controllers/articles_controller_test.rb
+create    test/controllers/articles_controller_test.rb
 ...
 ```
 
diff --git a/guides/source/working_with_javascript_in_rails.md b/guides/source/working_with_javascript_in_rails.md
index 6bce73ccad..27cef2bd27 100644
--- a/guides/source/working_with_javascript_in_rails.md
+++ b/guides/source/working_with_javascript_in_rails.md
@@ -24,11 +24,11 @@ In order to understand Ajax, you must first understand what a web browser does
 normally.
 
 When you type `http://localhost:3000` into your browser's address bar and hit
-'Go,' the browser (your 'client') makes a request to the server. It parses the
+'Go', the browser (your 'client') makes a request to the server. It parses the
 response, then fetches all associated assets, like JavaScript files,
 stylesheets and images. It then assembles the page. If you click a link, it
 does the same process: fetch the page, fetch the assets, put it all together,
-show you the results. This is called the 'request response cycle.'
+show you the results. This is called the 'request response cycle'.
 
 JavaScript can also make requests to the server, and parse the response. It
 also has the ability to update information on the page. Combining these two
@@ -57,7 +57,7 @@ will show you how Rails can help you write websites in this way, but it's
 all built on top of this fairly simple technique.
 
 Unobtrusive JavaScript
--------------------------------------
+----------------------
 
 Rails uses a technique called "Unobtrusive JavaScript" to handle attaching
 JavaScript to the DOM. This is generally considered to be a best-practice
@@ -139,7 +139,7 @@ JavaScript) in this style, and you can expect that many libraries will also
 follow this pattern.
 
 Built-in Helpers
-----------------------
+----------------
 
 ### Remote elements
 
@@ -372,9 +372,9 @@ is also useful for manipulating form data before serialization. The
 `ajax:beforeSend` event is also useful for adding custom request headers.
 
 If you stop the `ajax:aborted:file` event, the default behavior of allowing the
-browser to submit the form via normal means (i.e. non-AJAX submission) will be
+browser to submit the form via normal means (i.e. non-Ajax submission) will be
 canceled and the form will not be submitted at all. This is useful for
-implementing your own AJAX file upload workaround.
+implementing your own Ajax file upload workaround.
 
 ### Rails-ujs event handlers