Add a middleware to modify the error context before it is sent to subscribers.

Middleware is added to a stack of callables run on an error’s execution context before passing to subscribers. Allows creation of entries in error context that are shared by all subscribers.

A context middleware receives the same parameters as report. It must return a hash - the middleware stack returns the hash after it has run through all middlewares. A middleware can mutate or replace the hash.

Rails.error.add_middleware(-> (error, context) { context.merge({ foo: :bar }) })

# File activesupport/lib/active_support/error_reporter.rb, line 218
def add_middleware(middleware)
  @context_middlewares.use(middleware)
end

Prevent a subscriber from being notified of errors for the duration of the block. You may pass in the subscriber itself, or its class.

This can be helpful for error reporting service integrations, when they wish to handle any errors higher in the stack.

# File activesupport/lib/active_support/error_reporter.rb, line 186
def disable(subscriber)
  disabled_subscribers = (ActiveSupport::IsolatedExecutionState[self] ||= [])
  disabled_subscribers << subscriber
  begin
    yield
  ensure
    disabled_subscribers.delete(subscriber)
  end
end

Evaluates the given block, reporting and swallowing any unhandled error. If no error is raised, returns the return value of the block. Otherwise, returns the result of fallback.call, or nil if fallback is not specified.

# Will report a TypeError to all subscribers and return nil.
Rails.error.handle do
  1 + '1'
end

Can be restricted to handle only specific error classes:

maybe_tags = Rails.error.handle(Redis::BaseError) { redis.get("tags") }

Options¶ ↑

• :severity - This value is passed along to subscribers to indicate how important the error report is. Can be :error, :warning, or :info. Defaults to :warning.

• :context - Extra information that is passed along to subscribers. For example:

  Rails.error.handle(context: { section: "admin" }) do
    # ...
  end
  

• :fallback - A callable that provides handle‘s return value when an unhandled error is raised. For example:

  user = Rails.error.handle(fallback: -> { User.anonymous }) do
    User.find_by(params)
  end
  

• :source - This value is passed along to subscribers to indicate the source of the error. Subscribers can use this value to ignore certain errors. Defaults to "application".

# File activesupport/lib/active_support/error_reporter.rb, line 79
def handle(*error_classes, severity: :warning, context: {}, fallback: nil, source: DEFAULT_SOURCE)
  error_classes = DEFAULT_RESCUE if error_classes.empty?
  yield
rescue *error_classes => error
  report(error, handled: true, severity: severity, context: context, source: source)
  fallback.call if fallback
end

Evaluates the given block, reporting and re-raising any unhandled error. If no error is raised, returns the return value of the block.

# Will report a TypeError to all subscribers and re-raise it.
Rails.error.record do
  1 + '1'
end

Can be restricted to handle only specific error classes:

tags = Rails.error.record(Redis::BaseError) { redis.get("tags") }

Options¶ ↑

• :severity - This value is passed along to subscribers to indicate how important the error report is. Can be :error, :warning, or :info. Defaults to :error.

• :context - Extra information that is passed along to subscribers. For example:

  Rails.error.record(context: { section: "admin" }) do
    # ...
  end
  

• :source - This value is passed along to subscribers to indicate the source of the error. Subscribers can use this value to ignore certain errors. Defaults to "application".

# File activesupport/lib/active_support/error_reporter.rb, line 115
def record(*error_classes, severity: :error, context: {}, source: DEFAULT_SOURCE)
  error_classes = DEFAULT_RESCUE if error_classes.empty?
  yield
rescue *error_classes => error
  report(error, handled: false, severity: severity, context: context, source: source)
  raise
end

Report an error directly to subscribers. You can use this method when the block-based handle and record methods are not suitable.

Rails.error.report(error)

The error argument must be an instance of Exception.

Rails.error.report(Exception.new("Something went wrong"))

Otherwise you can use unexpected to report an error which does accept a string argument.

# File activesupport/lib/active_support/error_reporter.rb, line 233
def report(error, handled: true, severity: handled ? :warning : :error, context: {}, source: DEFAULT_SOURCE)
  return if error.instance_variable_defined?(:@__rails_error_reported)
  raise ArgumentError, "Reported error must be an Exception, got: #{error.inspect}" unless error.is_a?(Exception)

  ensure_backtrace(error)

  unless SEVERITIES.include?(severity)
    raise ArgumentError, "severity must be one of #{SEVERITIES.map(&:inspect).join(", ")}, got: #{severity.inspect}"
  end

  full_context = @context_middlewares.execute(
    error,
    context: ActiveSupport::ExecutionContext.to_h.merge(context || {}),
    handled:,
    severity:,
    source:
  )

  disabled_subscribers = ActiveSupport::IsolatedExecutionState[self]
  @subscribers.each do |subscriber|
    unless disabled_subscribers&.any? { |s| s === subscriber }
      subscriber.report(error, handled: handled, severity: severity, context: full_context, source: source)
    end
  rescue => subscriber_error
    if logger
      logger.fatal(
        "Error subscriber raised an error: #{subscriber_error.message} (#{subscriber_error.class})\n" +
        subscriber_error.backtrace.join("\n")
      )
    else
      raise
    end
  end

  while error
    unless error.frozen?
      error.instance_variable_set(:@__rails_error_reported, true)
    end
    error = error.cause
  end

  nil
end

Update the execution context that is accessible to error subscribers. Any context passed to handle, record, or report will be merged with the context set here.

Rails.error.set_context(section: "checkout", user_id: @user.id)

# File activesupport/lib/active_support/error_reporter.rb, line 202
def set_context(...)
  ActiveSupport::ExecutionContext.set(...)
end

Register a new error subscriber. The subscriber must respond to

report(Exception, handled: Boolean, severity: (:error OR :warning OR :info), context: Hash, source: String)

The report method should never raise an error.

# File activesupport/lib/active_support/error_reporter.rb, line 162
def subscribe(subscriber)
  unless subscriber.respond_to?(:report)
    raise ArgumentError, "Error subscribers must respond to #report"
  end
  @subscribers << subscriber
end

Either report the given error when in production, or raise it when in development or test.

When called in production, after the error is reported, this method will return nil and execution will continue.

When called in development, the original error is wrapped in a different error class to ensure it’s not being rescued higher in the stack and will be surfaced to the developer.

This method is intended for reporting violated assertions about preconditions, or similar cases that can and should be gracefully handled in production, but that aren’t supposed to happen.

The error can be either an exception instance or a String.

example:

  def edit
    if published?
      Rails.error.unexpected("[BUG] Attempting to edit a published article, that shouldn't be possible")
      return false
    end
    # ...
  end

# File activesupport/lib/active_support/error_reporter.rb, line 146
def unexpected(error, severity: :warning, context: {}, source: DEFAULT_SOURCE)
  error = RuntimeError.new(error) if error.is_a?(String)

  if @debug_mode
    ensure_backtrace(error)
    raise UnexpectedError, "#{error.class.name}: #{error.message}", error.backtrace, cause: error
  else
    report(error, handled: true, severity: severity, context: context, source: source)
  end
end

Unregister an error subscriber. Accepts either a subscriber or a class.

subscriber = MyErrorSubscriber.new
Rails.error.subscribe(subscriber)

Rails.error.unsubscribe(subscriber)
# or
Rails.error.unsubscribe(MyErrorSubscriber)

# File activesupport/lib/active_support/error_reporter.rb, line 177
def unsubscribe(subscriber)
  @subscribers.delete_if { |s| subscriber === s }
end