config: permit values to skip transformation

if the given value is already of the type the transform is expected to
produce, then just let it pass through

lib/new_relic/agent/configuration/default_source.rb

@@ -308,6 +308,7 @@ def self.enforce_fallback(allowed_values: nil, fallback: nil)
  :type => String,
  :allowed_from_server => false,
  :transform => proc { |v| v.is_a?(String) ? v.split(';') : v },
+ :transformed_type => Array,
  :description => 'Specify the [application name](/docs/apm/new-relic-apm/installation-configuration/name-your-application) used to aggregate data in the New Relic UI. To report data to [multiple apps at the same time](/docs/apm/new-relic-apm/installation-configuration/using-multiple-names-app), specify a list of names separated by a semicolon `;`. For example, `MyApp` or `MyStagingApp;Instance1`.'
  },
  :license_key => {
@@ -463,6 +464,7 @@ def self.enforce_fallback(allowed_values: nil, fallback: nil)
  :public => true,
  :type => String,
  :allowed_from_server => false,
+ :transformed_type => Hash, # NOTE: :labels is a special case and transformed in manager.rb without a :transform key
  :description => 'A dictionary of [label names](/docs/data-analysis/user-interface-functions/labels-categories-organize-your-apps-servers) and values that will be applied to the data sent from this agent. May also be expressed as a semicolon-delimited `;` string of colon-separated `:` pairs. For example, `Server:One;Data Center:Primary`.'
  },
  :log_file_name => {
@@ -1008,6 +1010,7 @@ def self.enforce_fallback(allowed_values: nil, fallback: nil)
  :type => Array,
  :allowed_from_server => false,
  :transform => DefaultSource.method(:convert_to_regexp_list),
+ :transformed_type => Array,
  :description => 'List of allowed endpoints to include in audit log.'
  },
  :'audit_log.path' => {
@@ -1089,6 +1092,7 @@ def self.enforce_fallback(allowed_values: nil, fallback: nil)
  :type => Array,
  :allowed_from_server => false,
  :transform => proc { |arr| NewRelic::Agent.add_automatic_method_tracers(arr) },
+ :transformed_type => Array,
  :description => <<~DESCRIPTION
  An array of `CLASS#METHOD` (for instance methods) and/or `CLASS.METHOD` (for class methods) strings representing Ruby methods that the agent can automatically add custom instrumentation to. This doesn't require any modifications of the source code that defines the methods.
 
@@ -1587,6 +1591,7 @@ def self.notify
  :type => Array,
  :allowed_from_server => false,
  :transform => DefaultSource.method(:convert_to_regexp_list),
+ :transformed_type => Array,
  :description => %Q(Specifies a list of hostname patterns separated by commas that will match gRPC hostnames that traffic is to be ignored by New Relic for. New Relic's gRPC client instrumentation will ignore traffic streamed to a host matching any of these patterns, and New Relic's gRPC server instrumentation will ignore traffic for a server running on a host whose hostname matches any of these patterns. By default, no traffic is ignored when gRPC instrumentation is itself enabled. For example, `"private.com$,exception.*"`)
  },
  :'instrumentation.grpc_server' => {
@@ -1933,6 +1938,7 @@ def self.notify
  :type => Array,
  :allowed_from_server => false,
  :transform => DefaultSource.method(:convert_to_regexp_list),
+ :transformed_type => Array,
  :description => 'Specify an Array of Rake tasks to automatically instrument. ' \
  'This configuration option converts the Array to a RegEx list. If you\'d like ' \
  'to allow all tasks by default, use `rake.tasks: [.+]`. No rake tasks will be ' \
@@ -1953,6 +1959,7 @@ def self.notify
  :type => Array,
  :allowed_from_server => true,
  :transform => DefaultSource.method(:convert_to_regexp_list),
+ :transformed_type => Array,
  :description => 'Define transactions you want the agent to ignore, by specifying a list of patterns matching the URI you want to ignore. For more detail, see [the docs on ignoring specific transactions](/docs/agents/ruby-agent/api-guides/ignoring-specific-transactions/#config-ignoring).'
  },
  # Serverless
@@ -1962,6 +1969,7 @@ def self.notify
  :type => Boolean,
  :allowed_from_server => false,
  :transform => proc { |bool| NewRelic::Agent::ServerlessHandler.env_var_set? || bool },
+ :transformed_type => Boolean,
  :description => 'If `true`, the agent will operate in a streamlined mode suitable for use with short-lived ' \
  'serverless functions. NOTE: Only AWS Lambda functions are supported currently and this ' \
  "option is not intended for use without [New Relic's Ruby Lambda layer](https://docs.newrelic.com/docs/serverless-function-monitoring/aws-lambda-monitoring/get-started/monitoring-aws-lambda-serverless-monitoring/) offering."
@@ -2080,6 +2088,7 @@ def self.notify
  :type => Array,
  :allowed_from_server => false,
  :transform => DefaultSource.method(:convert_to_constant_list),
+ :transformed_type => Array,
  :description => 'Specify a list of exceptions you do not want the agent to strip when [strip_exception_messages](#strip_exception_messages-enabled) is `true`. Separate exceptions with a comma. For example, `"ImportantException,PreserveMessageException"`.'
  },
  # Thread profiler

lib/new_relic/agent/configuration/manager.rb

@@ -215,7 +215,7 @@ def type_coerce(key, value, category)
  # convert bool to string for regex usage and bool hash lookup
  value = value.to_s if type == Boolean
  if value.class != String
- return value if category == :test
+ return value if category == :test || likely_transformed_already?(key, value)
 
  return default_with_warning(key, value, "Expected to receive a value of type #{type} but " \
  "received #{value.class}.")
@@ -233,6 +233,10 @@ def type_coerce(key, value, category)
  procedure.call(value)
  end
 
+ def likely_transformed_already?(key, value)
+ DEFAULTS.dig(key, :transformed_type) == value.class
+ end
+
  def default_with_warning(key, value, msg)
  default = default_without_warning(key)
  NewRelic::Agent.logger.warn "Received an invalid '#{value}' value for the '#{key}' configuration " \