Ruby: Improve native extension loading for preview versions

Rakefile

@@ -159,6 +159,13 @@ namespace :prism do
       puts "Vendoring '#{file}' Prism file to #{vendored_file_path}"
       FileUtils.cp_r(prism_bundle_path + "/#{file}", prism_vendor_path)
     end
+
+    prism_ast_header = "#{prism_vendor_path}/include/prism/ast.h"
+
+    unless File.exist?(prism_ast_header)
+      puts "Generating Prism template files..."
+      system("ruby #{prism_vendor_path}/templates/template.rb", exception: true)
+    end
   end
 
   desc "Clean vendored Prism in vendor/prism/"

ext/herb/extconf.rb

@@ -2,10 +2,6 @@
 
 require "mkmf"
 
-Dir.chdir(File.expand_path("../..", __dir__)) do
-  system("rake templates", exception: true)
-end
-
 extension_name = "herb"
 
 include_path = File.expand_path("../../src/include", __dir__)

lib/herb.rb

@@ -31,9 +31,36 @@
 
 begin
   major, minor, _patch = RUBY_VERSION.split(".") #: [String, String, String]
-  require_relative "herb/#{major}.#{minor}/herb"
-rescue LoadError
-  require_relative "herb/herb"
+
+  if RUBY_PATCHLEVEL == -1
+    require_relative "herb/herb"
+  else
+    begin
+      require_relative "herb/#{major}.#{minor}/herb"
+    rescue LoadError
+      require_relative "herb/herb"
+    end
+  end
+rescue LoadError => e
+  raise LoadError, <<~MESSAGE
+    Failed to load the Herb native extension.
+
+    Tried to load: #{e.message.split(" -- ").last}
+
+    This can happen when:
+      1. You're using a preview/development version of Ruby (RUBY_PATCHLEVEL=#{RUBY_PATCHLEVEL})
+      2. The native extension wasn't compiled during gem installation
+      3. Required build tools (C compiler) were missing during installation
+
+    To fix, try reinstalling with source compilation:
+      gem install herb --platform ruby
+
+    If compilation fails, install a C compiler first:
+      - macOS:          xcode-select --install
+      - Ubuntu/Debian:  apt-get install build-essential
+      - Fedora/RHEL:    dnf install make gcc
+      - Alpine:         apk add build-base
+  MESSAGE
 end
 
 module Herb