[RF-DOCS] Update Rails Error Reporting Guide [ci skip]

guides/source/documents.yaml

@@ -175,7 +175,7 @@
     -
       name: Error Reporting in Rails Applications
       url: error_reporting.html
-      description: This guide introduces ways to manage exceptions that occur in Ruby on Rails applications.
+      description: This guide introduces ways to manage errors that occur in Ruby on Rails applications.
     -
       name: Debugging Rails Applications
       url: debugging_rails_applications.html

guides/source/error_reporting.md

@@ -3,7 +3,7 @@
 Error Reporting in Rails Applications
 ========================
 
-This guide introduces ways to manage exceptions that occur in Ruby on Rails applications.
+This guide introduces ways to manage errors in a Rails application.
 
 After reading this guide, you will know:
 
@@ -13,11 +13,16 @@ After reading this guide, you will know:
 --------------------------------------------------------------------------------
 
 Error Reporting
-------------------------
+---------------
 
-The Rails [error reporter](https://api.rubyonrails.org/classes/ActiveSupport/ErrorReporter.html) provides a standard way to collect exceptions that occur in your application and report them to your preferred service or location.
+The Rails [error
+reporter](https://api.rubyonrails.org/classes/ActiveSupport/ErrorReporter.html)
+provides a standard way to collect errors that occur in your application and
+report them to your preferred service or location (e.g. you could report the
+errors to a monitoring service such as
+Sentry).
 
-The error reporter aims to replace boilerplate error-handling code like this:
+It aims to replace boilerplate error-handling code like this:
 
 ```ruby
 begin
@@ -35,17 +40,32 @@ Rails.error.handle(SomethingIsBroken) do
 end
 ```
 
-Rails wraps all executions (such as HTTP requests, jobs, and `rails runner` invocations) in the error reporter, so any unhandled errors raised in your app will automatically be reported to your error-reporting service via their subscribers.
+Rails wraps all executions (such as HTTP
+requests,
+[jobs](active_job_basics.html), and [rails runner](command_line.html#bin-rails-runner) invocations) in the error reporter,
+so any unhandled errors raised in your app will automatically be reported to
+your error-reporting service via their subscribers.
 
-This means that third-party error-reporting libraries no longer need to insert a Rack middleware or do any monkey-patching to capture unhandled exceptions. Libraries that use ActiveSupport can also use this to non-intrusively report warnings that would previously have been lost in logs.
+This means that third-party error-reporting libraries no longer need to insert a
+[Rack](rails_on_rack.html) middleware or do any monkey-patching to capture
+unhandled errors. Libraries that use [Active
+Support](https://api.rubyonrails.org/classes/ActiveSupport.html) can also use
+this to non-intrusively report warnings that would previously have been lost in
+logs.
 
-Using the Rails' error reporter is not required. All other means of capturing errors still work.
+NOTE: Using the Rails error reporter is optional, as other means of capturing
+errors still work.
 
 ### Subscribing to the Reporter
 
-To use the error reporter, you need a _subscriber_. A subscriber is any object with a `report` method. When an error occurs in your application or is manually reported, the Rails error reporter will call this method with the error object and some options.
+To use the error reporter with an external service, you need a _subscriber_. A
+subscriber can be any Ruby object with a `report` method. When an error occurs
+in your application or is manually reported, the Rails error reporter will call
+this method with the error object and some options.
 
-Some error-reporting libraries, such as [Sentry's](https://github.com/getsentry/sentry-ruby/blob/e18ce4b6dcce2ebd37778c1e96164684a1e9ebfc/sentry-rails/lib/sentry/rails/error_subscriber.rb) and [Honeybadger's](https://docs.honeybadger.io/lib/ruby/integration-guides/rails-exception-tracking/), automatically register a subscriber for you. Consult your provider's documentation for more details.
+NOTE: Some error-reporting libraries, such as Sentry's
+and Honeybadger's,
+automatically register a subscriber for you.
 
 You may also create a custom subscriber. For example:
 
@@ -58,23 +78,51 @@ class ErrorSubscriber
 end
 ```
 
-After defining the subscriber class, register it by calling [`Rails.error.subscribe`](https://api.rubyonrails.org/classes/ActiveSupport/ErrorReporter.html#method-i-subscribe) method:
+After defining the subscriber class, you can register it by calling the
+[`Rails.error.subscribe`](https://api.rubyonrails.org/classes/ActiveSupport/ErrorReporter.html#method-i-subscribe)
+method:
 
 ```ruby
 Rails.error.subscribe(ErrorSubscriber.new)
 ```
 
-You can register as many subscribers as you wish. Rails will call them in turn, in the order in which they were registered.
+You can register as many subscribers as you wish. Rails will call them in the
+order in which they were registered.
+
+It is also possible to unregister a subscriber by calling
+[`Rails.error.unsubscribe`](https://api.rubyonrails.org/classes/ActiveSupport/ErrorReporter.html#method-i-unsubscribe).
+This may be useful if you'd like to replace or remove a subscriber added by one
+of your dependencies. Both `subscribe` and `unsubscribe` can take either a
+subscriber or a class as follows:
+
+```ruby
+subscriber = ErrorSubscriber.new
+Rails.error.unsubscribe(subscriber)
+# or
+Rails.error.unsubscribe(ErrorSubscriber)
+```
 
-NOTE: The Rails error-reporter will always call registered subscribers, regardless of your environment. However, many error-reporting services only report errors in production by default. You should configure and test your setup across environments as needed.
+NOTE: The Rails error reporter will always call registered subscribers,
+regardless of your environment. However, many error-reporting services only
+report errors in production by default. You should configure and test your setup
+across environments as needed.
 
 ### Using the Error Reporter
 
-There are three ways you can use the error reporter:
+Rails error reporter has four methods that allow you to report methods in
+different ways:
+
+* `Rails.error.handle`
+* `Rails.error.record`
+* `Rails.error.report`
+* `Rails.error.unexpected`
 
 #### Reporting and Swallowing Errors
 
-[`Rails.error.handle`](https://api.rubyonrails.org/classes/ActiveSupport/ErrorReporter.html#method-i-handle) will report any error raised within the block. It will then **swallow** the error, and the rest of your code outside the block will continue as normal.
+The
+[`Rails.error.handle`](https://api.rubyonrails.org/classes/ActiveSupport/ErrorReporter.html#method-i-handle)
+method will report any error raised within the block. It will then **swallow**
+the error, and the rest of your code outside the block will continue as normal.
 
 ```ruby
 result = Rails.error.handle do
@@ -84,7 +132,9 @@ result # => nil
 1 + 1 # This will be executed
 ```
 
-If no error is raised in the block, `Rails.error.handle` will return the result of the block, otherwise it will return `nil`. You can override this by providing a `fallback`:
+If no error is raised in the block, `Rails.error.handle` will return the result
+of the block, otherwise it will return `nil`. You can override this by providing
+a `fallback`:
 
 ```ruby
 user = Rails.error.handle(fallback: -> { User.anonymous }) do
@@ -94,7 +144,10 @@ end
 
 #### Reporting and Re-raising Errors
 
-[`Rails.error.record`](https://api.rubyonrails.org/classes/ActiveSupport/ErrorReporter.html#method-i-record) will report errors to all registered subscribers and then re-raise the error, meaning that the rest of your code won't execute.
+The
+[`Rails.error.record`](https://api.rubyonrails.org/classes/ActiveSupport/ErrorReporter.html#method-i-record)
+method will report errors to all registered subscribers and then **re-raise**
+the error, meaning that the rest of your code won't execute.
 
 ```ruby
 Rails.error.record do
@@ -103,11 +156,13 @@ end
 1 + 1 # This won't be executed
 ```
 
-If no error is raised in the block, `Rails.error.record` will return the result of the block.
+If no error is raised in the block, `Rails.error.record` will return the result
+of the block.
 
 #### Manually Reporting Errors
 
-You can also manually report errors by calling [`Rails.error.report`](https://api.rubyonrails.org/classes/ActiveSupport/ErrorReporter.html#method-i-report):
+You can also manually report errors by calling
+[`Rails.error.report`](https://api.rubyonrails.org/classes/ActiveSupport/ErrorReporter.html#method-i-report):
 
 ```ruby
 begin
@@ -117,39 +172,64 @@ rescue StandardError => e
 end
 ```
 
-Any options you pass will be passed on the error subscribers.
+Any options you pass will be passed on to the error subscribers.
 
-### Error-reporting Options
+#### Reporting Unexpected Errors
+
+You can report any unexpected error by calling
+[`Rails.error.unexpected`](https://api.rubyonrails.org/classes/ActiveSupport/ErrorReporter.html#method-i-unexpected").
 
-All 3 reporting APIs (`#handle`, `#record`, and `#report`) support the following options, which are then passed along to all registered subscribers:
+When called in production, this method will return nil after the error is
+reported and the execution of your code will continue.
 
-- `handled`: a `Boolean` to indicate if the error was handled. This is set to `true` by default. `#record` sets this to `false`.
-- `severity`: a `Symbol` describing the severity of the error. Expected values are: `:error`, `:warning`, and `:info`. `#handle` sets this to `:warning`, while `#record` sets it to `:error`.
-- `context`: a `Hash` to provide more context about the error, like request or user details
-- `source`: a `String` about the source of the error. The default source is `"application"`. Errors reported by internal libraries may set other sources; the Redis cache library may use `"redis_cache_store.active_support"`, for instance. Your subscriber can use the source to ignore errors you aren't interested in.
+When called in development, the error will be wrapped in a new error class (to
+ensure it's not being rescued higher in the stack) and surfaced to the developer
+for debugging.
+
+For example:
 
 ```ruby
-Rails.error.handle(context: { user_id: user.id }, severity: :info) do
+def edit
+  if published?
+    Rails.error.unexpected("[BUG] Attempting to edit a published article, that shouldn't be possible")
+    false
+  end
   # ...
 end
 ```
 
-### Filtering by Error Classes
+NOTE: This method is intended to gracefully handle any errors that may occur in
+production, but that aren't anticipated to be the result of typical use.
 
-With `Rails.error.handle` and `Rails.error.record`, you can also choose to only report errors of certain classes. For example:
+### Error-reporting Options
+
+The reporting APIs `#handle`, `#record`, and `#report` support the following
+options, which are then passed along to all registered subscribers:
+
+- `handled`: a `Boolean` to indicate if the error was handled. This is set to
+  `true` by default. `#record` sets this to `false`.
+- `severity`: a `Symbol` describing the severity of the error. Expected values
+  are: `:error`, `:warning`, and `:info`. `#handle` sets this to `:warning`,
+  while `#record` sets it to `:error`.
+- `context`: a `Hash` to provide more context about the error, like request or
+  user details
+- `source`: a `String` about the source of the error. The default source is
+  `"application"`. Errors reported by internal libraries may set other sources;
+  the Redis cache library may use `"redis_cache_store.active_support"`, for
+  instance. Your subscriber can use the source to ignore errors you aren't
+  interested in.
 
 ```ruby
-Rails.error.handle(IOError) do
-  1 + '1' # raises TypeError
+Rails.error.handle(context: { user_id: user.id }, severity: :info) do
+  # ...
 end
-1 + 1 # TypeErrors are not IOErrors, so this will *not* be executed
 ```
 
-Here, the `TypeError` will not be captured by the Rails error reporter. Only instances of  `IOError` and its descendants will be reported. Any other errors will be raised as normal.
-
 ### Setting Context Globally
 
-In addition to setting context through the `context` option, you can use the [`#set_context`](https://api.rubyonrails.org/classes/ActiveSupport/ErrorReporter.html#method-i-set_context) API. For example:
+In addition to setting context through the `context` option, you can use
+[`Rails.error.set_context`](https://api.rubyonrails.org/classes/ActiveSupport/ErrorReporter.html#method-i-set_context).
+For example:
 
 ```ruby
 Rails.error.set_context(section: "checkout", user_id: @user.id)
@@ -165,9 +245,44 @@ Rails.error.handle(context: { b: 3 }) { raise }
 # The reported context will be: {:a=>1, :b=>3}
 ```
 
-### For Libraries
+### Filtering by Error Classes
+
+With `Rails.error.handle` and `Rails.error.record`, you can also choose to only
+report errors of certain classes. For example:
+
+```ruby
+Rails.error.handle(IOError) do
+  1 + '1' # raises TypeError
+end
+1 + 1 # TypeErrors are not IOErrors, so this will *not* be executed
+```
+
+Here, the `TypeError` will not be captured by the Rails error reporter. Only
+instances of  `IOError` and its descendants will be reported. Any other errors
+will be raised as normal.
+
+### Disabling Notifications
+
+You can prevent a subscriber from being notified of errors for the duration of a
+block by calling
+[`Rails.error.disable`](https://api.rubyonrails.org/classes/ActiveSupport/ErrorReporter.html#method-i-disable).
+Similarly to `subscribe` and `unsubscribe`, you can pass in either the
+subscriber itself, or its class.
+
+```ruby
+Rails.error.disable(ErrorSubscriber) do
+  1 + '1' # TypeError will not be reported via the ErrorSubscriber
+end
+```
+
+NOTE: This can also be helpful for third-party error reporting services who may
+want to manage error handling a different way, or higher in the stack.
+
+Error-reporting Libraries
+------------------------
 
-Error-reporting libraries can register their subscribers in a `Railtie`:
+Error-reporting libraries can register their subscribers in a
+[Railtie](https://api.rubyonrails.org/classes/Rails/Railtie.html):
 
 ```ruby
 module MySdk
@@ -179,4 +294,7 @@ module MySdk
 end
 ```
 
-If you register an error subscriber, but still have other error mechanisms like a Rack middleware, you may end up with errors reported multiple times. You should either remove your other mechanisms or adjust your report functionality so it skips reporting an exception it has seen before.
+NOTE: If you register an error subscriber, but still have other error mechanisms
+like a Rack middleware, you may end up with errors reported multiple times. You
+should either remove your other mechanisms or adjust your report functionality
+so it skips reporting an error it has seen before.