DEV: Disable the use of 'legacy' Ember assets (#17127)

Anyone still using `EMBER_CLI_PROD_ASSETS=0` in development or production will be gracefully switched to Ember CLI. In development, a repeated message will be logged to STDERR.

Similarly, passing `QUNIT_EMBER_CLI=0` to the qunit rake task will now do nothing. A warning will be printed, and ember-cli mode will be used. Note that we've chosen not to fail the task, so that existing plugin/theme CI jobs don't immediately start failing. We may switch to a hard fail in the coming days/weeks.

.github/workflows/tests.yml

@@ -31,7 +31,7 @@ jobs:
       fail-fast: false
 
       matrix:
-        build_type: [backend, frontend, frontend-legacy, annotations]
+        build_type: [backend, frontend, annotations]
         target: [core, plugins]
         exclude:
           - build_type: annotations
@@ -153,16 +153,6 @@ jobs:
         if: matrix.build_type == 'backend' && matrix.target == 'plugins'
         run: bin/rake plugin:spec
 
-      - name: Core QUnit (Legacy)
-        if: matrix.build_type == 'frontend-legacy' && matrix.target == 'core'
-        run: QUNIT_EMBER_CLI=0 bin/rake qunit:test['1200000']
-        timeout-minutes: 30
-
-      - name: Plugin QUnit (Legacy)
-        if: matrix.build_type == 'frontend-legacy' && matrix.target == 'plugins'
-        run: QUNIT_EMBER_CLI=0 bin/rake plugin:qunit['*','1200000']
-        timeout-minutes: 30
-
       - name: Plugin QUnit (Ember CLI)
         if: matrix.build_type == 'frontend' && (matrix.target == 'plugins' || matrix.target == 'core-plugins')
         run: QUNIT_EMBER_CLI=1 bin/rake plugin:qunit['*','1200000']

lib/ember_cli.rb

@@ -17,7 +17,10 @@ module EmberCli
   }
 
   def self.enabled?
-    ENV["EMBER_CLI_PROD_ASSETS"] != "0"
+    if !Rails.env.production? && ENV["EMBER_CLI_PROD_ASSETS"] == "0"
+      STDERR.puts "The 'legacy' ember environment is discontinued. Running with ember-cli assets. Remove the EMBER_CLI_PROD_ASSETS=0 flag."
+    end
+    true
   end
 
   def self.script_chunks

lib/tasks/assets.rake

@@ -4,6 +4,10 @@ if !defined?(EMBER_CLI)
   EMBER_CLI = EmberCli.enabled?
 end
 
+if ENV["EMBER_CLI_PROD_ASSETS"] == "0"
+  STDERR.puts "The 'legacy' ember environment is discontinued. Compiling with ember-cli assets..."
+end
+
 task 'assets:precompile:before' do
 
   require 'uglifier'

lib/tasks/qunit.rake

@@ -28,7 +28,11 @@ task "qunit:test", [:timeout, :qunit_path] do |_, args|
     false
   end
 
-  ember_cli = ENV['QUNIT_EMBER_CLI'] == "1"
+  if ENV['QUNIT_EMBER_CLI'] == "0"
+    puts "The 'legacy' ember environment is discontinued - running tests with ember-cli assets..."
+  end
+
+  ember_cli = true
 
   port = ENV['TEST_SERVER_PORT'] || 60099
   while !port_available? port