Skip instrumentation in run_validators when no validators present

CHANGELOG.md

@@ -9,6 +9,7 @@
 * [#2664](https://github.com/ruby-grape/grape/pull/2664): Drop `test-prof` dependency - [@ericproulx](https://github.com/ericproulx).
 * [#2665](https://github.com/ruby-grape/grape/pull/2665): Pass `attrs` directly to `AttributesIterator` instead of `validator` - [@ericproulx](https://github.com/ericproulx).
 * [#2657](https://github.com/ruby-grape/grape/pull/2657): Instantiate validators at definition time - [@ericproulx](https://github.com/ericproulx).
+* [#2667](https://github.com/ruby-grape/grape/pull/2667): Skip instrumentation in run_validators when no validators present - [@ericproulx](https://github.com/ericproulx).
 * Your contribution here.
 
 #### Fixes

UPGRADING.md

@@ -3,6 +3,10 @@ Upgrading Grape
 
 ### Upgrading to >= 3.2
 
+#### `endpoint_run_validators.grape` notification no longer fired when there are no validators
+
+`ActiveSupport::Notifications` subscribers listening to `endpoint_run_validators.grape` will no longer receive an event for endpoints that have no validators. If you rely on this notification to measure every request, subscribe to `endpoint_run.grape` instead, which always fires.
+
 #### Custom validators: use `default_message_key` and `validation_error!`
 
 Validators are now instantiated once at definition time and frozen. Any setup should happen in `initialize`, not in `validate_param!`.

lib/grape/endpoint.rb

@@ -207,6 +207,8 @@ def execute
 
     def run_validators(request:)
       validators = inheritable_setting.route[:saved_validations]
+      return if validators.empty?
+
       validation_errors = []
 
       Grape::Validations::ParamScopeTracker.track do

spec/grape/endpoint_spec.rb

@@ -1062,9 +1062,6 @@ def memoized
         have_attributes(name: 'endpoint_run_filters.grape', payload: { endpoint: a_kind_of(described_class),
                                                                        filters: [],
                                                                        type: :before_validation }),
-        have_attributes(name: 'endpoint_run_validators.grape', payload: { endpoint: a_kind_of(described_class),
-                                                                          validators: [],
-                                                                          request: a_kind_of(Grape::Request) }),
         have_attributes(name: 'endpoint_run_filters.grape', payload: { endpoint: a_kind_of(described_class),
                                                                        filters: [],
                                                                        type: :after_validation }),
@@ -1091,9 +1088,6 @@ def memoized
         have_attributes(name: 'endpoint_run_filters.grape', payload: { endpoint: a_kind_of(described_class),
                                                                        filters: [],
                                                                        type: :before_validation }),
-        have_attributes(name: 'endpoint_run_validators.grape', payload: { endpoint: a_kind_of(described_class),
-                                                                          validators: [],
-                                                                          request: a_kind_of(Grape::Request) }),
         have_attributes(name: 'endpoint_run_filters.grape', payload: { endpoint: a_kind_of(described_class),
                                                                        filters: [],
                                                                        type: :after_validation }),