Ensure yarn and bun version fallback

zzak · byroot · commit be7f922d7d5c · 2025-06-22T11:00:57.000+01:00
If we allow the `version` methods to return nil, it's possible to end up
in a situation where Dockerfile contains something like

```
ARG BUN_VERSION=
```

This can occur when bun or yarn are not installed locally on the current
version of node, and using a version manager like `nodenv`.

In this case, `rails new` would previously raise an error:

```
nodenv: yarn: command not found

The `yarn' command exists in these Node versions:
  20.15.0

E

Error:
AppGeneratorTest#test_css_option_with_cssbundling_gem_does_not_force_jsbundling_gem:
NoMethodError: undefined method '&gt;=' for nil
    lib/rails/generators/app_base.rb:550:in 'Rails::Generators::AppBase#yarn_through_corepack?'
    lib/rails/generators/rails/app/templates/Dockerfile.tt:41:in 'Thor::Actions#template'
```

By ensuring we fallback to a non-nil value we can ensure this case
doesn't occur.

&lt;details&gt;
&lt;summary&gt;Full example:&lt;/summary&gt;

```
$ bundle exec railties/exe/rails new ~/code/apps/TestApp_EsBuild_Tailwind_Pg -j=esbuild -c=tailwind -d=postgresql --dev

nodenv: yarn: command not found

The `yarn' command exists in these Node versions:
  20.15.0

nodenv: yarn: command not found

The `yarn' command exists in these Node versions:
  20.15.0

nodenv: yarn: command not found

The `yarn' command exists in these Node versions:
  20.15.0

bundler: failed to load command: railties/exe/rails (railties/exe/rails)
/home/zzak/code/rails/railties/lib/rails/generators/app_base.rb:550:in 'Rails::Generators::AppBase#yarn_through_corepack?': undefined method '&gt;=' for nil (NoMethodError)

        dockerfile_yarn_version &gt;= "2"
                                ^^
        from /home/zzak/code/rails/railties/lib/rails/generators/rails/app/templates/Dockerfile.tt:41:in 'Thor::Actions#template'
        from /home/zzak/.rbenv/versions/3.4.4/lib/ruby/3.4.0/erb.rb:429:in 'Kernel#eval'
        from /home/zzak/.rbenv/versions/3.4.4/lib/ruby/3.4.0/erb.rb:429:in 'ERB#result'
        from /home/zzak/.rbenv/versions/3.4.4/lib/ruby/gems/3.4.0/gems/thor-1.3.2/lib/thor/actions/file_manipulation.rb:128:in 'block in Thor::Actions#template'
        from /home/zzak/.rbenv/versions/3.4.4/lib/ruby/gems/3.4.0/gems/thor-1.3.2/lib/thor/actions/create_file.rb:54:in 'Thor::Actions::CreateFile#render'
        from /home/zzak/.rbenv/versions/3.4.4/lib/ruby/gems/3.4.0/gems/thor-1.3.2/lib/thor/actions/create_file.rb:64:in 'block (2 levels) in Thor::Actions::CreateFile#invoke!'
        from /home/zzak/.rbenv/versions/3.4.4/lib/ruby/gems/3.4.0/gems/thor-1.3.2/lib/thor/actions/create_file.rb:64:in 'IO.open'
        from /home/zzak/.rbenv/versions/3.4.4/lib/ruby/gems/3.4.0/gems/thor-1.3.2/lib/thor/actions/create_file.rb:64:in 'block in Thor::Actions::CreateFile#invoke!'
        from /home/zzak/.rbenv/versions/3.4.4/lib/ruby/gems/3.4.0/gems/thor-1.3.2/lib/thor/actions/empty_directory.rb:117:in 'Thor::Actions::EmptyDirectory#invoke_with_conflict_check'
        from /home/zzak/.rbenv/versions/3.4.4/lib/ruby/gems/3.4.0/gems/thor-1.3.2/lib/thor/actions/create_file.rb:61:in 'Thor::Actions::CreateFile#invoke!'
        from /home/zzak/.rbenv/versions/3.4.4/lib/ruby/gems/3.4.0/gems/thor-1.3.2/lib/thor/actions.rb:93:in 'Thor::Actions#action'
        from /home/zzak/.rbenv/versions/3.4.4/lib/ruby/gems/3.4.0/gems/thor-1.3.2/lib/thor/actions/create_file.rb:25:in 'Thor::Actions#create_file'
        from /home/zzak/.rbenv/versions/3.4.4/lib/ruby/gems/3.4.0/gems/thor-1.3.2/lib/thor/actions/file_manipulation.rb:124:in 'Thor::Actions#template'
        from /home/zzak/code/rails/railties/lib/rails/generators/rails/app/app_generator.rb:20:in 'Rails::ActionMethods#template'
        from /home/zzak/code/rails/railties/lib/rails/generators/rails/app/app_generator.rb:79:in 'Rails::AppBuilder#dockerfiles'
        from /home/zzak/code/rails/railties/lib/rails/generators/app_base.rb:174:in 'Kernel#public_send'
        from /home/zzak/code/rails/railties/lib/rails/generators/app_base.rb:174:in 'Rails::Generators::AppBase#build'
        from /home/zzak/code/rails/railties/lib/rails/generators/rails/app/app_generator.rb:402:in 'Rails::Generators::AppGenerator#create_dockerfiles'
        from /home/zzak/.rbenv/versions/3.4.4/lib/ruby/gems/3.4.0/gems/thor-1.3.2/lib/thor/command.rb:28:in 'Thor::Command#run'
        from /home/zzak/.rbenv/versions/3.4.4/lib/ruby/gems/3.4.0/gems/thor-1.3.2/lib/thor/invocation.rb:127:in 'Thor::Invocation#invoke_command'
        from /home/zzak/.rbenv/versions/3.4.4/lib/ruby/gems/3.4.0/gems/thor-1.3.2/lib/thor/invocation.rb:134:in 'block in Thor::Invocation#invoke_all'
        from /home/zzak/.rbenv/versions/3.4.4/lib/ruby/gems/3.4.0/gems/thor-1.3.2/lib/thor/invocation.rb:134:in 'Hash#each'
        from /home/zzak/.rbenv/versions/3.4.4/lib/ruby/gems/3.4.0/gems/thor-1.3.2/lib/thor/invocation.rb:134:in 'Enumerable#map'
        from /home/zzak/.rbenv/versions/3.4.4/lib/ruby/gems/3.4.0/gems/thor-1.3.2/lib/thor/invocation.rb:134:in 'Thor::Invocation#invoke_all'
        from /home/zzak/.rbenv/versions/3.4.4/lib/ruby/gems/3.4.0/gems/thor-1.3.2/lib/thor/group.rb:243:in 'Thor::Group.dispatch'
        from /home/zzak/.rbenv/versions/3.4.4/lib/ruby/gems/3.4.0/gems/thor-1.3.2/lib/thor/base.rb:584:in 'Thor::Base::ClassMethods#start'
        from /home/zzak/code/rails/railties/lib/rails/commands/application/application_command.rb:28:in 'Rails::Command::ApplicationCommand#perform'
        from /home/zzak/.rbenv/versions/3.4.4/lib/ruby/gems/3.4.0/gems/thor-1.3.2/lib/thor/command.rb:28:in 'Thor::Command#run'
        from /home/zzak/.rbenv/versions/3.4.4/lib/ruby/gems/3.4.0/gems/thor-1.3.2/lib/thor/invocation.rb:127:in 'Thor::Invocation#invoke_command'
        from /home/zzak/code/rails/railties/lib/rails/command/base.rb:176:in 'Rails::Command::Base#invoke_command'
        from /home/zzak/.rbenv/versions/3.4.4/lib/ruby/gems/3.4.0/gems/thor-1.3.2/lib/thor.rb:538:in 'Thor.dispatch'
        from /home/zzak/code/rails/railties/lib/rails/command/base.rb:71:in 'Rails::Command::Base.perform'
        from /home/zzak/code/rails/railties/lib/rails/command.rb:65:in 'block in Rails::Command.invoke'
        from /home/zzak/code/rails/railties/lib/rails/command.rb:143:in 'Rails::Command.with_argv'
        from /home/zzak/code/rails/railties/lib/rails/command.rb:63:in 'Rails::Command.invoke'
        from /home/zzak/code/rails/railties/lib/rails/cli.rb:20:in '&lt;top (required)&gt;'
        from /home/zzak/.rbenv/versions/3.4.4/lib/ruby/3.4.0/bundled_gems.rb:82:in 'Kernel.require'
        from /home/zzak/.rbenv/versions/3.4.4/lib/ruby/3.4.0/bundled_gems.rb:82:in 'block (2 levels) in Kernel#replace_require'
        from railties/exe/rails:10:in '&lt;top (required)&gt;'
        from /home/zzak/.rbenv/versions/3.4.4/lib/ruby/gems/3.4.0/gems/bundler-2.6.2/lib/bundler/cli/exec.rb:59:in 'Kernel.load'
        from /home/zzak/.rbenv/versions/3.4.4/lib/ruby/gems/3.4.0/gems/bundler-2.6.2/lib/bundler/cli/exec.rb:59:in 'Bundler::CLI::Exec#kernel_load'
        from /home/zzak/.rbenv/versions/3.4.4/lib/ruby/gems/3.4.0/gems/bundler-2.6.2/lib/bundler/cli/exec.rb:23:in 'Bundler::CLI::Exec#run'
        from /home/zzak/.rbenv/versions/3.4.4/lib/ruby/gems/3.4.0/gems/bundler-2.6.2/lib/bundler/cli.rb:452:in 'Bundler::CLI#exec'
        from /home/zzak/.rbenv/versions/3.4.4/lib/ruby/gems/3.4.0/gems/bundler-2.6.2/lib/bundler/vendor/thor/lib/thor/command.rb:28:in 'Bundler::Thor::Command#run'
        from /home/zzak/.rbenv/versions/3.4.4/lib/ruby/gems/3.4.0/gems/bundler-2.6.2/lib/bundler/vendor/thor/lib/thor/invocation.rb:127:in 'Bundler::Thor::Invocation#invoke_command'
        from /home/zzak/.rbenv/versions/3.4.4/lib/ruby/gems/3.4.0/gems/bundler-2.6.2/lib/bundler/vendor/thor/lib/thor.rb:538:in 'Bundler::Thor.dispatch'
        from /home/zzak/.rbenv/versions/3.4.4/lib/ruby/gems/3.4.0/gems/bundler-2.6.2/lib/bundler/cli.rb:35:in 'Bundler::CLI.dispatch'
        from /home/zzak/.rbenv/versions/3.4.4/lib/ruby/gems/3.4.0/gems/bundler-2.6.2/lib/bundler/vendor/thor/lib/thor/base.rb:584:in 'Bundler::Thor::Base::ClassMethods#start'
        from /home/zzak/.rbenv/versions/3.4.4/lib/ruby/gems/3.4.0/gems/bundler-2.6.2/lib/bundler/cli.rb:29:in 'Bundler::CLI.start'
        from /home/zzak/.rbenv/versions/3.4.4/lib/ruby/gems/3.4.0/gems/bundler-2.6.2/exe/bundle:28:in 'block in &lt;top (required)&gt;'
        from /home/zzak/.rbenv/versions/3.4.4/lib/ruby/gems/3.4.0/gems/bundler-2.6.2/lib/bundler/friendly_errors.rb:117:in 'Bundler.with_friendly_errors'
        from /home/zzak/.rbenv/versions/3.4.4/lib/ruby/gems/3.4.0/gems/bundler-2.6.2/exe/bundle:20:in '&lt;top (required)&gt;'
        from /home/zzak/.rbenv/versions/3.4.4/bin/bundle:25:in 'Kernel#load'
        from /home/zzak/.rbenv/versions/3.4.4/bin/bundle:25:in '&lt;main&gt;'
[ble: exit 1]
```

&lt;/details&gt;
diff --git a/railties/lib/rails/generators/app_base.rb b/railties/lib/rails/generators/app_base.rb
@@ -540,20 +540,27 @@ def node_version
       end
 
       def dockerfile_yarn_version
-        using_node? and `yarn --version`[/\d+\.\d+\.\d+/]
-      rescue
-        "latest"
+        version = begin
+          `yarn --version`[/\d+\.\d+\.\d+/]
+        rescue
+          nil
+        end
+
+        version || "latest"
       end
 
       def yarn_through_corepack?
-        true if dockerfile_yarn_version == "latest"
-        dockerfile_yarn_version >= "2"
+        using_node? and "#{dockerfile_yarn_version}" >= "2"
       end
 
       def dockerfile_bun_version
-        using_bun? and `bun --version`[/\d+\.\d+\.\d+/]
-      rescue
-        BUN_VERSION
+        version = begin
+          `bun --version`[/\d+\.\d+\.\d+/]
+        rescue
+          nil
+        end
+
+        version || BUN_VERSION
       end
 
       def dockerfile_binfile_fixups
diff --git a/railties/test/generators/app_generator_test.rb b/railties/test/generators/app_generator_test.rb
@@ -925,6 +925,22 @@ def test_esbuild_option_with_js_argument
     assert_gem "jsbundling-rails"
   end
 
+  def test_esbuild_without_yarn_installed
+    generator([destination_root], javascript: "esbuild")
+
+    # fallback to latest when yarn is not installed
+    generator.stub :dockerfile_yarn_version, "latest" do
+      quietly { generator.invoke_all }
+    end
+
+    assert_gem "jsbundling-rails"
+    assert_file "Dockerfile" do |content|
+      assert_match(/ARG YARN_VERSION=latest/, content)
+
+      assert_match("RUN corepack enable && yarn set version $YARN_VERSION", content)
+    end
+  end
+
   def test_bun_option
     generator([destination_root], javascript: "bun")
 
@@ -949,6 +965,23 @@ def test_bun_option_with_js_argument
     assert_gem "jsbundling-rails"
   end
 
+  def test_bun_without_bun_installed
+    generator([destination_root], javascript: "bun")
+    bun_version = generator.class.const_get(:BUN_VERSION)
+
+    # fallback to constant when bun is not installed
+    generator.stub :dockerfile_bun_version, bun_version do
+      quietly { generator.invoke_all }
+    end
+
+    assert_gem "jsbundling-rails"
+    assert_file "Dockerfile" do |content|
+      assert_match(/ARG BUN_VERSION=#{bun_version}/, content)
+
+      assert_match("RUN bun install --frozen-lockfile", content)
+    end
+  end
+
   def test_skip_javascript_option_with_skip_javascript_argument
     run_generator [destination_root, "--skip-javascript"]
     assert_no_gem "stimulus-rails"
