Let RSpec/SpecFilePathFormat leverage ActiveSupport inflections when defined and configured

Fix #740

Author: corsonknowles

CHANGELOG.md

@@ -2,6 +2,8 @@
 
 ## Master (Unreleased)
 
+- Let `RSpec/SpecFilePathFormat` leverage ActiveSupport inflections when configured. ([@corsonknowles])
+
 ## 3.6.0 (2025-04-18)
 
 - Fix false positive in `RSpec/Pending`, where it would mark the default block `it` as an offense. ([@bquorning])

config/default.yml

@@ -924,6 +924,8 @@ RSpec/SpecFilePathFormat:
   IgnoreMethods: false
   IgnoreMetadata:
     type: routing
+  InflectorPath: "./config/initializers/inflections.rb"
+  UseActiveSupportInflections: false
   VersionAdded: '2.24'
   Reference: https://www.rubydoc.info/gems/rubocop-rspec/RuboCop/Cop/RSpec/SpecFilePathFormat
 

docs/modules/ROOT/pages/cops_rspec.adoc

@@ -5897,6 +5897,17 @@ my_class_spec.rb         # describe MyClass, '#method'
 whatever_spec.rb         # describe MyClass, type: :routing do; end
 ----
 
+[#_useactivesupportinflections_-true_-rspecspecfilepathformat]
+==== `UseActiveSupportInflections: true`
+
+[source,ruby]
+----
+# Enable to use ActiveSupport's inflector for custom acronyms
+# like HTTP, etc. Set to false by default.
+# The InflectorPath provides the path to the inflector file.
+# The default is ./config/initializers/inflections.rb.
+----
+
 [#configurable-attributes-rspecspecfilepathformat]
 === Configurable attributes
 
@@ -5922,6 +5933,14 @@ whatever_spec.rb         # describe MyClass, type: :routing do; end
 | IgnoreMetadata
 | `{"type" => "routing"}`
 | 
+
+| InflectorPath
+| `./config/initializers/inflections.rb`
+| String
+
+| UseActiveSupportInflections
+| `false`
+| Boolean
 |===
 
 [#references-rspecspecfilepathformat]

lib/rubocop/cop/rspec/spec_file_path_format.rb

@@ -32,13 +32,22 @@ module RSpec
       #   # good
       #   whatever_spec.rb         # describe MyClass, type: :routing do; end
       #
+      # @example `UseActiveSupportInflections: true`
+      #   # Enable to use ActiveSupport's inflector for custom acronyms
+      #   # like HTTP, etc. Set to false by default.
+      #   # The InflectorPath provides the path to the inflector file.
+      #   # The default is ./config/initializers/inflections.rb.
+      #
       class SpecFilePathFormat < Base
         include TopLevelGroup
         include Namespace
         include FileHelp
 
         MSG = 'Spec path should end with `%<suffix>s`.'
 
+        # Class instance variable to cache ActiveSupport availability
+        @activesupport_available = nil
+
         # @!method example_group_arguments(node)
         def_node_matcher :example_group_arguments, <<~PATTERN
           (block $(send #rspec? #ExampleGroups.all $_ $...) ...)
@@ -57,6 +66,28 @@ def on_top_level_example_group(node)
           end
         end
 
+        # For testing and debugging
+        def self.reset_activesupport_cache!
+          @activesupport_available = nil
+        end
+
+        def self.activesupport_inflections_available?(inflections)
+          return @activesupport_available unless @activesupport_available.nil?
+
+          @activesupport_available = begin
+            return false unless File.exist?(inflections)
+
+            require 'active_support/inflector'
+            require inflections
+
+            true
+          rescue LoadError, NameError
+            false
+          end
+        rescue StandardError
+          false
+        end
+
         private
 
         def ensure_correct_file_path(send_node, class_name, arguments)
@@ -106,10 +137,29 @@ def expected_path(constant)
         end
 
         def camel_to_snake_case(string)
-          string
-            .gsub(/([^A-Z])([A-Z]+)/, '\1_\2')
-            .gsub(/([A-Z])([A-Z][^A-Z\d]+)/, '\1_\2')
-            .downcase
+          if activesupport_inflections_available?
+            ActiveSupport::Inflector.underscore(string)
+          else
+            string
+              .gsub(/([^A-Z])([A-Z]+)/, '\1_\2')
+              .gsub(/([A-Z])([A-Z][^A-Z\d]+)/, '\1_\2')
+              .downcase
+          end
+        end
+
+        def inflector_path
+          cop_config.fetch('InflectorPath',
+                           './config/initializers/inflections.rb')
+        end
+
+        def activesupport_inflections_available?
+          return false unless use_activesupport_inflections?
+
+          self.class.activesupport_inflections_available?(inflector_path)
+        end
+
+        def use_activesupport_inflections?
+          cop_config.fetch('UseActiveSupportInflections', false)
         end
 
         def custom_transform