Prerequisites: Use system version of Node

We were incorrectly assuming consumers had the version of Node installed
that is declared in `Suspenders::NODE_LTS_VERSION`.

Because of this, we were generating a `.node-version` file with a
version that was not installed on the user's system. This was a problem
because when subsequent generators depending on Node where invoked, they
would raise the following:

```
No preset version installed for command node
Please install a version by running one of the following:

asdf install nodejs 20.11.1
```

To account for this, we [borrow][] from Rails, but modify slightly.
First, we look to see if `ENV["NODE_VERSION"]` is set. If not, we then
look to see if Node is installed, and set the version via `node
--version`. If neither of those values are present, we raise. This is
because we can't use a fallback value, since the consumer does not have
Node installed on their system.

Removes `Suspenders::NODE_LTS_VERSION` since it's no longer used as a
fallback.

Introduced [climate_control][] as a development dependency in order to
test this feature.

[borrow]: https://github.com/rails/rails/blob/d65fec4fd2a047533408cbbd4824b248adc0e3fd/railties/lib/rails/generators/app_base.rb#L521-L529
[climate_control]: https://github.com/thoughtbot/climate_control

Gemfile.lock

@@ -84,6 +84,7 @@ GEM
     base64 (0.1.1)
     bigdecimal (3.1.4)
     builder (3.2.4)
+    climate_control (1.2.0)
     concurrent-ruby (1.2.2)
     connection_pool (2.4.1)
     crass (1.0.6)
@@ -234,6 +235,7 @@ PLATFORMS
   x86_64-linux
 
 DEPENDENCIES
+  climate_control
   mocha
   puma
   sqlite3

lib/generators/suspenders/install/web_generator.rb

@@ -4,6 +4,7 @@ module Install
       class WebGenerator < Rails::Generators::Base
         include Suspenders::Generators::APIAppUnsupported
         include Suspenders::Generators::DatabaseUnsupported
+        include Suspenders::Generators::NodeNotInstalled
 
         source_root File.expand_path("../../../templates/install/web", __FILE__)
         desc <<~MARKDOWN

lib/generators/suspenders/prerequisites_generator.rb

@@ -1,13 +1,16 @@
 module Suspenders
   module Generators
     class PrerequisitesGenerator < Rails::Generators::Base
+      include Suspenders::Generators::Helpers
+      include Suspenders::Generators::NodeNotInstalled
+
       source_root File.expand_path("../../templates/prerequisites", __FILE__)
 
       desc <<~MARKDOWN
         Creates `.node-version` file set to the current LTS version.
       MARKDOWN
 
-      def node_version
+      def set_node_version
         template "node-version", ".node-version"
       end
     end

lib/generators/templates/prerequisites/node-version.tt

@@ -1 +1 @@
-<%= Suspenders::NODE_LTS_VERSION %>
+<%= node_version %>

lib/suspenders/cleanup/generate_readme.rb

@@ -16,6 +16,8 @@
 module Suspenders
   module Cleanup
     class GenerateReadme
+      include Suspenders::Generators::Helpers
+
       def self.perform(readme, app_name)
         new(readme, app_name).perform
       end
@@ -153,7 +155,7 @@ def prerequisites
 
         @file.write <<~MARKDOWN
           Ruby: `#{Suspenders::MINIMUM_RUBY_VERSION}`
-          Node: `#{Suspenders::NODE_LTS_VERSION}`
+          Node: `#{node_version}`
         MARKDOWN
 
         new_line

lib/suspenders/generators.rb

@@ -18,6 +18,10 @@ def default_test_helper_present?
       def rspec_test_helper_present?
         File.exist? Rails.root.join("spec/rails_helper.rb")
       end
+
+      def node_version
+        ENV["NODE_VERSION"] || `node --version`[/\d+\.\d+\.\d+/]
+      end
     end
 
     module APIAppUnsupported
@@ -46,6 +50,8 @@ def api_only_app?
     end
 
     module DatabaseUnsupported
+      include Helpers
+
       class Error < StandardError
         def message
           "This generator requires PostgreSQL"
@@ -72,5 +78,26 @@ def database_unsupported?
         end
       end
     end
+
+    module NodeNotInstalled
+      class Error < StandardError
+      end
+
+      extend ActiveSupport::Concern
+
+      included do
+        def raise_if_node_not_installed
+          if node_not_installed?
+            raise Suspenders::Generators::NodeNotInstalled::Error
+          end
+        end
+      end
+
+      private
+
+      def node_not_installed?
+        !node_version.present?
+      end
+    end
   end
 end

lib/suspenders/version.rb

@@ -2,5 +2,4 @@ module Suspenders
   VERSION = "3.0.0".freeze
   RAILS_VERSION = "~> 7.0".freeze
   MINIMUM_RUBY_VERSION = ">= 3.1".freeze
-  NODE_LTS_VERSION = "20.11.1".freeze
 end

suspenders.gemspec

@@ -27,6 +27,7 @@ Gem::Specification.new do |spec|
 
   spec.add_dependency "rails", Suspenders::RAILS_VERSION
 
+  spec.add_development_dependency "climate_control"
   spec.add_development_dependency "mocha"
   spec.add_development_dependency "standard"
 end

test/generators/suspenders/install/web_generator_test.rb

@@ -28,6 +28,16 @@ class WebGeneratorTest < Rails::Generators::TestCase
           end
         end
 
+        test "raises if Node is not installed" do
+          Object.any_instance.stubs(:`).returns("")
+
+          with_database "postgresql" do
+            assert_raises Suspenders::Generators::NodeNotInstalled::Error do
+              run_generator
+            end
+          end
+        end
+
         private
 
         def prepare_destination

test/generators/suspenders/prerequisites_generator_test.rb

@@ -1,4 +1,5 @@
 require "test_helper"
+require "climate_control"
 require "generators/suspenders/prerequisites_generator"
 
 module Suspenders
@@ -10,14 +11,36 @@ class PrerequisitesGeneratorTest < Rails::Generators::TestCase
       destination Rails.root
       teardown :restore_destination
 
-      test "generates .node-version file" do
+      test "generates .node-version file (from ENV)" do
+        ClimateControl.modify NODE_VERSION: "1.2.3" do
+          run_generator
+
+          assert_file app_root(".node-version") do |file|
+            assert_match(/1\.2\.3/, file)
+          end
+        end
+      end
+
+      test "generates .node-version file (from system)" do
+        Object.any_instance.stubs(:`).returns("v1.2.3\n")
+
         run_generator
 
         assert_file app_root(".node-version") do |file|
-          assert_match(/20\.11\.1/, file)
+          assert_match(/1\.2\.3/, file)
         end
       end
 
+      test "raises if node is not installed" do
+        Object.any_instance.stubs(:`).returns("")
+
+        assert_raises Suspenders::Generators::NodeNotInstalled::Error do
+          run_generator
+        end
+
+        assert_no_file app_root(".node-version")
+      end
+
       private
 
       def restore_destination

test/suspenders/cleanup/generate_readme_test.rb

@@ -6,6 +6,8 @@ module Suspenders
   module Cleanup
     class GenerateReadmeTest < ActiveSupport::TestCase
       test "generates README using generator descriptions" do
+        Object.any_instance.stubs(:`).returns("v1.2.3\n")
+
         Tempfile.create "README.md" do |readme|
           path = readme.path
 
@@ -18,7 +20,7 @@ class GenerateReadmeTest < ActiveSupport::TestCase
 
           assert_match "## Prerequisites", readme
           assert_match Suspenders::MINIMUM_RUBY_VERSION, readme
-          assert_match Suspenders::NODE_LTS_VERSION, readme
+          assert_match "Node: `1.2.3`", readme
 
           assert_match "## Configuration", readme
           assert_match "### Test", readme

test/suspenders_test.rb

@@ -12,8 +12,4 @@ class SuspendersTest < ActiveSupport::TestCase
   test "it has a Minimum Ruby version number" do
     assert Suspenders::MINIMUM_RUBY_VERSION
   end
-
-  test "it has a Node LTS version number" do
-    assert Suspenders::NODE_LTS_VERSION
-  end
 end