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

@@ -32,6 +32,12 @@ 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
@@ -57,8 +63,67 @@ def on_top_level_example_group(node)
           end
         end
 
+        # For testing and debugging
+        def self.reset_activesupport_cache!
+          ActiveSupportInflector.reset_cache!
+        end
+
         private
 
+        # Inflector module that uses ActiveSupport for advanced inflection rules
+        module ActiveSupportInflector
+          def self.call(string)
+            ActiveSupport::Inflector.underscore(string)
+          end
+
+          def self.available?(cop_config)
+            return @available unless @available.nil?
+
+            unless cop_config.fetch('UseActiveSupportInflections', false)
+              return @available = false
+            end
+
+            unless File.exist?(inflector_path(cop_config))
+              return @available = false
+            end
+
+            @available = begin
+              require 'active_support/inflector'
+              require inflector_path(cop_config)
+              true
+            rescue LoadError, StandardError
+              false
+            end
+          end
+
+          def self.inflector_path(cop_config)
+            cop_config.fetch('InflectorPath',
+                             './config/initializers/inflections.rb')
+          end
+
+          def self.reset_cache!
+            @available = nil
+          end
+        end
+
+        # Inflector module that uses basic regex-based conversion
+        module DefaultInflector
+          def self.call(string)
+            string
+              .gsub(/([^A-Z])([A-Z]+)/, '\1_\2')
+              .gsub(/([A-Z])([A-Z][^A-Z\d]+)/, '\1_\2')
+              .downcase
+          end
+        end
+
+        def inflector
+          @inflector ||= if ActiveSupportInflector.available?(cop_config)
+                           ActiveSupportInflector
+                         else
+                           DefaultInflector
+                         end
+        end
+
         def ensure_correct_file_path(send_node, class_name, arguments)
           pattern = correct_path_pattern(class_name, arguments)
           return if filename_ends_with?(pattern)
@@ -106,10 +171,7 @@ 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
+          inflector.call(string)
         end
 
         def custom_transform