Fix several issues around i18n and resource metadata.

There are a few things changing here. One is that we always dup metadata before using it - this prevents a class of nasty bugs where after the first resource list build, blocks had been deleted from metadata hashes, meaning they would no longer be applied. Now they will always stick around. Then, I made sure that whenever we render a file, we save the previous I18n.locale and restore it afterwards, in case people change locale from blocks. This should help in some weird cases where files are rendered recursively. Finally, I've added a :lang option that can be used from "page" or "proxy" to allow people to specify the language for one or more files without having to pass a block that sets I18n.locale directly, which should make that pattern much cleaner. This fixes #809 and may also fix middleman/middleman-blog#106.

middleman-core/lib/middleman-core/core_extensions/rendering.rb

@@ -128,6 +128,9 @@ module Middleman
 
           # Store last engine for later (could be inside nested renders)
           @current_engine, engine_was = engine, @current_engine
+          old_locale = ::I18n.locale
+
+          I18n.locale = opts[:lang] if opts[:lang]
 
           # Use a dup of self as a context so that instance variables set within
           # the template don't persist for other templates.
@@ -165,6 +168,7 @@ module Middleman
         ensure
           # Pop all the saved variables from earlier as we may be returning to a
           # previous render (layouts, partials, nested layouts).
+          ::I18n.locale = old_locale
           @current_engine = engine_was
           @content_blocks = nil
           @current_locs = nil

middleman-core/lib/middleman-core/sitemap/resource.rb

@@ -76,6 +76,7 @@ module Middleman
       # Merge in new metadata specific to this resource.
       # @param [Hash] metadata A metadata block like provides_metadata_for_path takes
       def add_metadata(metadata={}, &block)
+        metadata = metadata.dup
         if metadata.has_key?(:blocks)
           @local_metadata[:blocks] << metadata.delete(:blocks)
         end

middleman-core/lib/middleman-core/sitemap/store.rb

@@ -113,7 +113,7 @@ module Middleman
         provides_metadata.inject(blank_metadata) do |result, (callback, matcher)|
           next result if matcher && !source_file.match(matcher)
 
-          metadata = callback.call(source_file)
+          metadata = callback.call(source_file).dup
 
           if metadata.has_key?(:blocks)
             result[:blocks] << metadata[:blocks]
@@ -152,7 +152,7 @@ module Middleman
             next result unless File.fnmatch("/" + Util.strip_leading_slash(matcher), "/#{request_path}")
           end
 
-          metadata = callback.call(request_path)
+          metadata = callback.call(request_path).dup
 
           result[:blocks] += Array(metadata.delete(:blocks))
 

middleman-more/features/i18n_force_locale.feature

@@ -0,0 +1,13 @@
+Feature: i18n manually setting locale
+
+  Scenario: Setting I18n.locale in a block (see issue #809) or with the :lang option
+    Given the Server is running at "i18n-force-locale"
+    When I go to "/en/index.html"
+    Then I should see "Hello"
+    Then I should see "I18n.locale: en"
+    When I go to "/es/index.html"
+    Then I should see "Hola"
+    Then I should see "I18n.locale: es"
+    When I go to "/fr/index.html"
+    Then I should see "Bonjour"
+    Then I should see "I18n.locale: fr"

middleman-more/fixtures/i18n-force-locale/config.rb

@@ -0,0 +1,13 @@
+[:en, :es].each do |locale|
+  proxy "/#{locale}/index.html", "index.html", :ignore => true do
+    ::I18n.locale = locale
+  end
+end
+
+proxy "/fr/index.html", "index.html", :lang => :fr
+
+activate :i18n
+
+# This is what breaks i18n, just because it adds a resource list manipulator that 
+# forces a rebuild of the resource list.
+activate :asset_hash

middleman-more/fixtures/i18n-force-locale/locales/en.yml

@@ -0,0 +1,3 @@
+---
+en:
+  hello: "Hello"

middleman-more/fixtures/i18n-force-locale/locales/es.yml

@@ -0,0 +1,3 @@
+---
+es:
+  hello: "Hola"

middleman-more/fixtures/i18n-force-locale/locales/fr.yml

@@ -0,0 +1,3 @@
+---
+fr:
+  hello: "Bonjour"

middleman-more/fixtures/i18n-force-locale/source/index.haml

@@ -0,0 +1,2 @@
+Greeting: #{I18n.t 'hello'}
+I18n.locale: #{I18n.locale}

middleman-more/lib/middleman-more/core_extensions/i18n.rb

@@ -60,13 +60,15 @@ module Middleman
             end
 
             instance_vars = Proc.new do
-              ::I18n.locale = lang
               @lang         = lang
               @page_id      = page_id
             end
 
-            locals = { :lang => lang, :page_id => page_id }
-            { :blocks => [instance_vars], :locals => locals }
+            locals = { :lang => lang,
+              :page_id => page_id }
+            { :blocks => [instance_vars],
+              :locals => locals,
+              :options => { :lang => lang } }
           end
 
           @app.sitemap.register_resource_list_manipulator(
@@ -111,6 +113,7 @@ module Middleman
 
             page_id = File.basename(resource.path, File.extname(resource.path))
 
+            old_locale = ::I18n.locale
             langs.map do |lang|
               ::I18n.locale = lang
 
@@ -139,6 +142,8 @@ module Middleman
 
               new_resources << p
             end
+            ::I18n.locale = old_locale
+
           end
 
           resources + new_resources