Issue #118. Better error when trying to generate MHTML without a base_url specified.

Author: jashkenas

lib/jammit.rb

@@ -34,9 +34,10 @@ module Jammit
   # requested by a browser -- rendering a 404.
   class PackageNotFound < NameError; end
 
-  # Jammit raises a ConfigurationNotFound exception when you try to load the
-  # configuration of an assets.yml file that doesn't exist.
-  class ConfigurationNotFound < NameError; end
+  # Jammit raises a MissingConfiguration exception when you try to load the
+  # configuration of an assets.yml file that doesn't exist, or are missing 
+  # a piece of required configuration.
+  class MissingConfiguration < NameError; end
 
   # Jammit raises an OutputNotWritable exception if the output directory for
   # cached packages is locked.
@@ -64,7 +65,7 @@ class << self
   def self.load_configuration(config_path, soft=false)
     exists = config_path && File.exists?(config_path)
     return false if soft && !exists
-    raise ConfigurationNotFound, "could not find the \"#{config_path}\" configuration file" unless exists
+    raise MissingConfiguration, "could not find the \"#{config_path}\" configuration file" unless exists
     conf = YAML.load(ERB.new(File.read(config_path)).result)
 
     # Optionally overwrite configuration based on the environment.

lib/jammit/packager.rb

@@ -43,7 +43,8 @@ def precache_all(output_dir=nil, base_url=nil)
         cache(p, 'css', pack_stylesheets(p), output_dir)
         if Jammit.embed_assets
           cache(p, 'css', pack_stylesheets(p, :datauri), output_dir, :datauri)
-          if Jammit.mhtml_enabled && base_url
+          if Jammit.mhtml_enabled
+            raise MissingConfiguration, "A --base-url option is required in order to generate MHTML." unless base_url
             mtime = latest_mtime package_for(p, :css)[:paths]
             asset_url = "#{base_url}#{Jammit.asset_url(p, :css, :mhtml, mtime)}"
             cache(p, 'css', pack_stylesheets(p, :mhtml, asset_url), output_dir, :mhtml, mtime)

test/unit/test_configuration.rb

@@ -12,7 +12,7 @@ def teardown
   end
 
   def test_loading_a_nonexistent_file
-    assert_raises(ConfigurationNotFound) do
+    assert_raises(MissingConfiguration) do
       Jammit.load_configuration('nonexistent/assets.yml')
     end
   end

test/unit/test_packager.rb

@@ -113,7 +113,7 @@ def test_exceptions_for_unwritable_directories
 
   def test_package_helper
     FileUtils.rm_rf("test/public/assets/*")
-    Jammit.package! :config_file => "test/config/assets.yml"
+    Jammit.package! :config_file => "test/config/assets.yml", :base_url => "http://example.com/"
     assert File.exists?("test/public/assets/js_test.js")
     assert File.exists?("test/public/assets/css_test.css")
     FileUtils.rm_rf("test/public/assets")