Add parallel option

CHANGELOG.md

@@ -11,6 +11,11 @@ Prefix your message with one of the following:
 - [Security] in case of vulnerabilities.
 -->
 
+## Unreleased
+
+- [Added] Add `parallel` option to `I18nJS.call` to parallelize file export when
+  `:locale` placeholder is used.
+
 ## v4.2.3 - Mar 29, 2023
 
 - [Fixed] Load plugins when running `i18n lint:*` commands.

i18n-js.gemspec

@@ -37,10 +37,12 @@ Gem::Specification.new do |spec|
   spec.executables   = spec.files.grep(%r{^exe/}) {|f| File.basename(f) }
   spec.require_paths = ["lib"]
 
+  spec.add_dependency "concurrent-ruby", "~> 1.0", ">= 1.3.1"
   spec.add_dependency "glob", ">= 0.4.0"
   spec.add_dependency "i18n"
 
   spec.add_development_dependency "activesupport"
+  spec.add_development_dependency "faker"
   spec.add_development_dependency "minitest"
   spec.add_development_dependency "minitest-utils"
   spec.add_development_dependency "mocha"

lib/i18n-js.rb

@@ -8,6 +8,7 @@
 require "optparse"
 require "erb"
 require "digest/md5"
+require "concurrent-ruby"
 
 require_relative "i18n-js/schema"
 require_relative "i18n-js/version"
@@ -18,7 +19,7 @@
 module I18nJS
   MissingConfigError = Class.new(StandardError)
 
-  def self.call(config_file: nil, config: nil)
+  def self.call(config_file: nil, config: nil, parallel: false)
     if !config_file && !config
       raise MissingConfigError,
             "you must set either `config_file` or `config`"
@@ -32,7 +33,9 @@ def self.call(config_file: nil, config: nil)
 
     exported_files = []
 
-    config[:translations].each {|group| exported_files += export_group(group) }
+    config[:translations].each do |group|
+      exported_files += export_group(group, parallel:)
+    end
 
     plugins.each do |plugin|
       plugin.after_export(files: exported_files.dup) if plugin.enabled?
@@ -41,7 +44,7 @@ def self.call(config_file: nil, config: nil)
     exported_files
   end
 
-  def self.export_group(group)
+  def self.export_group(group, parallel: false)
     filtered_translations = Glob.filter(translations, group[:patterns])
     filtered_translations =
       plugins.reduce(filtered_translations) do |buffer, plugin|
@@ -57,10 +60,24 @@ def self.export_group(group)
     exported_files = []
 
     if output_file_path.include?(":locale")
-      filtered_translations.each_key do |locale|
-        locale_file_path = output_file_path.gsub(":locale", locale.to_s)
-        exported_files << write_file(locale_file_path,
-                                     locale => filtered_translations[locale])
+      if parallel
+        promises = []
+        filtered_translations.each_key do |locale|
+          promises <<
+            Concurrent::Promises.future(
+              output_file_path.gsub(":locale", locale.to_s),
+              locale => filtered_translations[locale]
+            ) do |locale_file_path, translations|
+              write_file(locale_file_path, translations)
+            end
+        end
+        exported_files = Concurrent::Promises.zip(*promises).value!
+      else
+        filtered_translations.each_key do |locale|
+          locale_file_path = output_file_path.gsub(":locale", locale.to_s)
+          exported_files << write_file(locale_file_path,
+                                       locale => filtered_translations[locale])
+        end
       end
     else
       exported_files << write_file(output_file_path, filtered_translations)

test/benchmarks/parallel_export.rb

@@ -0,0 +1,30 @@
+require "bundler/setup"
+
+require "faker"
+require "i18n"
+require "yaml"
+require "i18n-js"
+require "benchmark"
+
+(1..100).each do |i|
+  File.open("test/fixtures/bench/bench_#{i}.yml", "w") do |f|
+    strings = {}
+    5_000.times do
+      strings[Faker::Lorem.words(number: 4).join("_")] = Faker::Lorem.sentence
+    end
+    f.write({"x#{i}": strings}.to_yaml)
+  end
+end
+
+I18n.load_path = Dir["test/fixtures/bench/*.yml"]
+I18n.backend.load_translations
+
+Benchmark.bm(7) do |bench|
+  bench.report("baseline") do
+    I18nJS.call(config_file: "./test/config/locale_placeholder.yml")
+  end
+  bench.report("parallel") do
+    I18nJS.call(config_file: "./test/config/locale_placeholder.yml",
+                parallel: true)
+  end
+end

test/fixtures/bench/.gitignore

@@ -0,0 +1 @@
+*.yml

test/i18n-js/exporter_test.rb

@@ -96,6 +96,26 @@ class ExporterTest < Minitest::Test
                      "test/output/pt.json"
   end
 
+  test "exports multiple files using :locale in parallel" do
+    I18n.load_path << Dir["./test/fixtures/yml/*.yml"]
+    actual_files =
+      I18nJS.call(config_file: "./test/config/locale_placeholder.yml",
+                  parallel: true)
+
+    expected_files = [
+      "test/output/en.json",
+      "test/output/es.json",
+      "test/output/pt.json"
+    ]
+
+    assert_exported_files expected_files,
+                          actual_files
+    assert_json_file "test/fixtures/expected/multiple_files/es.json",
+                     "test/output/es.json"
+    assert_json_file "test/fixtures/expected/multiple_files/pt.json",
+                     "test/output/pt.json"
+  end
+
   test "exports multiple files using :locale as dirname" do
     I18n.load_path << Dir["./test/fixtures/yml/*.yml"]
     actual_files =