[rail_inspector] Unify interface for files

Its difficult to test some of these classes because they load files very
internally. This commit does some refactoring to unify file lookup with
the goal being a future commit will extract most of this up a bunch of
layers.

Author: skipkayhil

tools/rail_inspector/lib/rail_inspector/configuring.rb

@@ -6,21 +6,42 @@
 
 module RailInspector
   class Configuring
-    class CachedParser
-      def initialize
-        @cache = {}
+    class Files
+      class Proxy
+        def initialize(pathname)
+          @pathname = pathname
+        end
+
+        def parse
+          @parse ||= Prism.parse_file(@pathname.to_s).value
+        end
+
+        def read
+          @pathname.read
+        end
+
+        def write(string)
+          @pathname.write(string)
+        end
+
+        def to_s
+          @pathname.to_s
+        end
       end
 
-      def call(path)
-        @cache[path] ||= Prism.parse_file(path.to_s).value
+      def initialize(root)
+        @root = Pathname.new(root)
+        @files = {}
       end
-    end
 
-    DOC_PATH = "guides/source/configuring.md"
-    APPLICATION_CONFIGURATION_PATH =
-      "railties/lib/rails/application/configuration.rb"
-    NEW_FRAMEWORK_DEFAULTS_PATH =
-      "railties/lib/rails/generators/rails/app/templates/config/initializers/new_framework_defaults_%{version}.rb.tt"
+      def []=(name, path)
+        @files[name] = Proxy.new(@root.join(path))
+      end
+
+      def method_missing(name, ...)
+        @files[name] || super
+      end
+    end
 
     class Doc
       attr_accessor :general_config, :versioned_defaults
@@ -45,12 +66,19 @@ def to_s
       end
     end
 
-    attr_reader :errors, :parser
+    attr_reader :errors, :files
 
     def initialize(rails_path)
       @errors = []
-      @parser = CachedParser.new
-      @rails_path = Pathname.new(rails_path)
+      @files = Files.new(rails_path)
+
+      @files[:application_configuration] = "railties/lib/rails/application/configuration.rb"
+      @files[:doc_path] = "guides/source/configuring.md"
+      @files[:rails_version] = "RAILS_VERSION"
+
+      @files[:new_framework_defaults] = "railties/lib/rails/generators/rails/app/templates/config/initializers/new_framework_defaults_%{version}.rb.tt" % {
+        version: rails_version.tr(".", "_")
+      }
     end
 
     def check
@@ -60,27 +88,15 @@ def check
     end
 
     def doc
-      @doc ||=
-        begin
-          content = File.read(doc_path)
-          Configuring::Doc.new(content)
-        end
-    end
-
-    def parse(relative_path)
-      parser.call(@rails_path.join(relative_path))
-    end
-
-    def read(relative_path)
-      File.read(@rails_path.join(relative_path))
+      @doc ||= Configuring::Doc.new(files.doc_path.read)
     end
 
     def rails_version
-      @rails_version ||= File.read(@rails_path.join("RAILS_VERSION")).to_f.to_s
+      @rails_version ||= files.rails_version.read.to_f.to_s
     end
 
     def write!
-      File.write(doc_path, doc.to_s)
+      files.doc_path.write(doc.to_s)
     end
 
     def error_message
@@ -90,10 +106,5 @@ def error_message
         "Make sure new configurations are added to configuring.md#rails-general-configuration in alphabetical order.\n" +
         "Errors may be autocorrectable with the --autocorrect flag"
     end
-
-    private
-      def doc_path
-        @rails_path.join(DOC_PATH)
-      end
   end
 end

tools/rail_inspector/lib/rail_inspector/configuring/check/framework_defaults.rb

@@ -37,12 +37,7 @@ def add_error(config)
             end
 
             def defaults_file_content
-              @defaults_file_content ||= checker.read(new_framework_defaults_path)
-            end
-
-            def new_framework_defaults_path
-              NEW_FRAMEWORK_DEFAULTS_PATH %
-                { version: checker.rails_version.tr(".", "_") }
+              @defaults_file_content ||= checker.files.new_framework_defaults.read
             end
         end
 
@@ -66,7 +61,7 @@ def check
 
         private
           def app_config_tree
-            checker.parse(APPLICATION_CONFIGURATION_PATH)
+            checker.files.application_configuration.parse
           end
 
           def check_defaults(defaults)
@@ -106,7 +101,7 @@ def check_defaults(defaults)
               end
 
             checker.errors << <<~MESSAGE unless config_diff.empty?
-              #{APPLICATION_CONFIGURATION_PATH}: Incorrect load_defaults docs
+              #{checker.files.application_configuration}: Incorrect load_defaults docs
               --- Expected
               +++ Actual
               #{config_diff.split("\n")[5..].join("\n")}

tools/rail_inspector/lib/rail_inspector/configuring/check/general_configuration.rb

@@ -21,7 +21,7 @@ def call
             APP_CONFIG_CONST = "Rails::Application::Configuration"
 
             def app_config_tree
-              @checker.parse(APPLICATION_CONFIGURATION_PATH)
+              @checker.files.application_configuration.parse
             end
         end