DEV: Add a spec for `assets:precompile:js_processor` (#23220)

lib/discourse_js_processor.rb

@@ -6,9 +6,6 @@ class DiscourseJsProcessor
   class TranspileError < StandardError
   end
 
-  JS_PROCESSOR_PATH =
-    Rails.env.production? ? "tmp/js-processor.js" : "tmp/js-processor/#{Process.pid}.js"
-
   # To generate a list of babel plugins used by ember-cli, set
   # babel: { debug: true } in ember-cli-build.js, then run `yarn ember build -prod`
   DISCOURSE_COMMON_BABEL_PLUGINS = [
@@ -101,6 +98,9 @@ class DiscourseJsProcessor
   end
 
   class Transpiler
+    JS_PROCESSOR_PATH =
+      Rails.env.production? ? "tmp/js-processor.js" : "tmp/js-processor/#{Process.pid}.js"
+
     @mutex = Mutex.new
     @ctx_init = Mutex.new
     @processor_mutex = Mutex.new
@@ -121,6 +121,7 @@ class DiscourseJsProcessor
         "app/assets/javascripts/js-processor.js",
         "--outfile=#{JS_PROCESSOR_PATH}",
       )
+      JS_PROCESSOR_PATH
     end
 
     def self.create_new_context

lib/tasks/assets.rake

@@ -301,7 +301,8 @@ task "assets:precompile:compress_js": "environment" do
 end
 
 task "assets:precompile:js_processor": "environment" do
-  DiscourseJsProcessor::Transpiler.generate_js_processor
+  path = DiscourseJsProcessor::Transpiler.generate_js_processor
+  puts "Compiled js-processor: #{path}"
 end
 
 # Run these tasks **before** Rails' "assets:precompile" task

spec/tasks/assets_precompile_spec.rb

@@ -0,0 +1,18 @@
+# frozen_string_literal: true
+
+RSpec.describe "assets:precompile" do
+  before do
+    Rake::Task.clear
+    Discourse::Application.load_tasks
+  end
+
+  describe "assets:precompile:js_processor" do
+    it "compiles the js processor" do
+      out = capture_stdout { Rake::Task["assets:precompile:js_processor"].invoke }
+
+      expect(out).to match(%r{Compiled js-processor: tmp/js-processor})
+      path = out.match(/: (.+)/)[1]
+      expect(File.exist?(path)).to eq(true)
+    end
+  end
+end