ProtoBoeuf::AutoloaderGen will generate helper modules to autoload ou…

…r generated constants

Rakefile

@@ -7,7 +7,9 @@ require "rubocop/rake_task"
 RuboCop::RakeTask.new
 
 BASE_DIR = File.dirname(__FILE__)
-codegen_rb_files = ["lib/protoboeuf/codegen.rb"]
+LIB_DIR = File.expand_path(BASE_DIR, "lib")
+
+codegen_rb_files = ["lib/protoboeuf/codegen.rb", "lib/protoboeuf/autoloadergen.rb"]
 proto_files = Rake::FileList[File.join(BASE_DIR, "test/fixtures/*.proto")]
 rb_files = proto_files.pathmap("#{BASE_DIR}/test/fixtures/%n_pb.rb")
 
@@ -19,14 +21,17 @@ well_known_types = Rake::FileList[
 ]
 
 WELL_KNOWN_PB = well_known_types.pathmap("%X.rb")
+# For a directory like lib/protoboeuf/google/protobuf, create an autoloader in lib/protoboeuf/google/protobuf.rb
+WELL_KNOWN_AUTOLOADERS = well_known_types.pathmap("%d.rb").uniq
 
 # Clobber/clean rules
 rb_files.each { |x| CLOBBER.append(x) }
 CLOBBER.append(BENCHMARK_UPSTREAM_PB)
 CLOBBER.append(BENCHMARK_PROTOBOEUF_PB)
 CLOBBER.append(WELL_KNOWN_PB)
+CLOBBER.append(WELL_KNOWN_AUTOLOADERS)
 
-rule ".rb" => ["%X.proto"] + codegen_rb_files do |t|
+rule ".rb" => ["%X.proto"] + codegen_rb_files do |t| # codegen_rb_files = ["lib/protoboeuf/codegen.rb"]
   codegen_rb_files.each { |f| require_relative f }
 
   require "tempfile"
@@ -106,6 +111,28 @@ end
 desc "Regenerate protobuf files"
 task gen_proto: rb_files
 
+desc "Regenerate autoloader modules for well-known types"
+task well_known_autoloaders: [:well_known_types] + codegen_rb_files do
+  # Given lib/protoboeuf/google/protobuf/foo.rb and lib/protoboeuf/google/protobuf/bar.rb, generate
+  # lib/protoboeuf/google/protobuf.rb that looks like:
+  #
+  # module ProtoBoeuf
+  #   module Google
+  #     module Protobuf
+  #       autoload :FooMessage1, "proto_boeuf/google/protobuf/foo"
+  #       autoload :FooMessage2, "proto_boeuf/google/protobuf/foo"
+  #       autoload :BarConst1, "proto_boeuf/google/protobuf/bar"
+  #     end
+  #   end
+  # end
+
+  require_relative "lib/protoboeuf/autoloadergen"
+
+  WELL_KNOWN_AUTOLOADERS.each do |autoloader_rb_file|
+    File.binwrite(autoloader_rb_file, ProtoBoeuf::AutoloaderGen.new(autoloader_rb_file).to_ruby)
+  end
+end
+
 task test: [:gen_proto, :well_known_types]
 task default: :test
 

lib/protoboeuf/autoloadergen.rb

@@ -0,0 +1,95 @@
+# frozen_string_literal: true
+
+require "erb"
+require "syntax_tree"
+require "pathname"
+
+module ProtoBoeuf
+  class AutoloaderGen
+    # This class generates top-level autoloader modules for our well known types.  Given autogenerated .rb files like:
+    #   - lib/protoboeuf/google/protobuf/foo.rb
+    #   - lib/protoboeuf/google/protobuf/bar.rb
+    #
+    # generate lib/protoboeuf/google/protobuf.rb that looks like:
+    #
+    # module ProtoBoeuf
+    #   module Google
+    #     module Protobuf
+    #       autoload :FooMessage1, "protoboeuf/google/protobuf/foo"
+    #       autoload :FooMessage2, "protoboeuf/google/protobuf/foo"
+    #       autoload :BarConst1, "protoboeuf/google/protobuf/bar"
+    #     end
+    #   end
+    # end
+
+    BASE_LIB_DIR = File.expand_path("..", __dir__)
+
+    attr_reader :module_filename,
+      :child_ruby_filenames,
+      :autoloader_module_name,
+      :autoloader_module_parts,
+      :child_constants_by_filename
+
+    def initialize(module_filename)
+      @module_filename = module_filename
+      # Given lib/protoboeuf/google.rb, glob lib/protoboeuf/google/**/*.rb
+      @child_ruby_filenames = Dir[module_filename.pathmap("%X/**/*.rb")]
+      @autoloader_module_name = nil
+      @child_constants_by_filename = child_ruby_filenames.each_with_object({}) do |filename, constants|
+        child_constants = constants_for_child_ruby_filename(filename)
+        # For the autoloader_module_name we can just pick the first child constant we come across and take the first
+        # three parts.  For example, ProtoBoeuf::Google::Api::FieldBehavior would be ProtoBoeuf::Google::Api.
+        @autoloader_module_name = child_constants.first.split("::")[0..2].join("::") if @autoloader_module_name.nil?
+
+        # Make our absolute filename relative to the base lib directory for our autoload calls.
+        require_path = Pathname.new(filename).relative_path_from(BASE_LIB_DIR).sub_ext("")
+        constants[require_path] = child_constants
+      end
+
+      @autoloader_module_parts = @autoloader_module_name.split("::")
+    end
+
+    def to_ruby
+      SyntaxTree.format(ERB.new(<<~RUBY, trim_mode: "-").result(binding))
+        # frozen_string_literal: true
+        # rubocop:disable all
+
+        <%- autoloader_module_parts.each do |module_name| -%>
+          module <%= module_name %>
+        <%- end -%>
+
+        <%- child_constants_by_filename.each do |require_path, constant_names| -%>
+          <%- constant_names.each do |constant_name| -%>
+            autoload :<%= constant_name.split("::").last %>, "<%= require_path %>"
+          <%- end -%>
+        <%- end -%>
+
+        <%- autoloader_module_parts.each do |module_name| -%>
+          end
+        <%- end -%>
+      RUBY
+    end
+
+    private
+
+    def constants_for_child_ruby_filename(filename)
+      @constants_for_child_ruby_filename ||= {}
+
+      return @constants_for_child_ruby_filename[filename] if @constants_for_child_ruby_filename.key?(filename)
+
+      loaded = Module.new do
+        module_eval File.binread(filename)
+      end
+
+      @constants_for_child_ruby_filename[filename] = loaded::ProtoBoeuf::Google.constants.flat_map do |const_name|
+        mod = loaded::ProtoBoeuf::Google.const_get(const_name)
+        next unless mod.is_a?(Module)
+
+        # The top-level module will be our anonymous Module we created above
+        parent_module_name = mod.name.split("::")[1..].join("::")
+
+        mod.constants.map { |const_name| "#{parent_module_name}::#{const_name}" }
+      end
+    end
+  end
+end

lib/protoboeuf/google.rb

@@ -2,4 +2,10 @@
 
 # There isn't a clean 1:1 mapping between constants and *.rb files, so eager load instead of autoload.
 
-Dir[File.expand_path("google/**/*.rb", __dir__)].each { |file| require file }
+# Dir[File.expand_path("google/**/*.rb", __dir__)].each { |file| require file }
+module ProtoBoeuf
+  module Google
+    autoload :Api, "protoboeuf/google/api"
+    autoload :Protobuf, "protoboeuf/google/protobuf"
+  end
+end

test/gem_test.rb

@@ -18,6 +18,8 @@ def test_can_be_required
         ::ProtoBoeuf::CodeGen
         ::ProtoBoeuf::Google::Api::FieldBehavior
         ::ProtoBoeuf::Google::Protobuf::Any
+        ::ProtoBoeuf::Google::Protobuf::FileDescriptorProto
+        ::ProtoBoeuf::Google::Protobuf::FileDescriptorSet
 
         exit 0
       RUBY