Change render to support any hash keys in locals

this lets you pass ruby keywords to templates:

    <%= render 'example', class: "cool" %>

    <%= render 'example', "spaces are" => "a-ok" %>

    <%= render 'example', Foo: "bar" %>

Previously you'd see confusing syntax errors like this:

    SyntaxError (.../_example.html.erb:1: syntax error, unexpected '='

Now you can reference invalid identifiers through local_assigns.

If you try to use an invalid keyword (e.g. class) in your template, you
get a syntax error on the line where you use it.

6 files changed, 47 insertions, 1 deletions

diff --git a/actionview/CHANGELOG.md b/actionview/CHANGELOG.md
index 8bd4e1e56c..e93745c3bf 100644
--- a/actionview/CHANGELOG.md
+++ b/actionview/CHANGELOG.md
@@ -1,3 +1,21 @@
+*   Render now accepts any keys for locals, including reserved words
+
+    Only locals with valid variable names get set directly. Others
+    will still be available in local_assigns.
+
+    Example of render with reserved words:
+
+    ```erb
+    <%= render "example", class: "text-center", message: "Hello world!" %>
+
+    <!-- _example.html.erb: -->
+    <%= tag.div class: local_assigns[:class] do %>
+      <p><%= message %></p>
+    <% end %>
+    ```
+
+    *Peter Schilling*, *Matthew Draper*
+
 *   Show cache hits and misses when rendering partials.
 
     Partials using the `cache` helper will show whether a render hit or missed
diff --git a/actionview/lib/action_view/template.rb b/actionview/lib/action_view/template.rb
index 513935cef0..c01dd1c028 100644
--- a/actionview/lib/action_view/template.rb
+++ b/actionview/lib/action_view/template.rb
@@ -1,5 +1,6 @@
 require "active_support/core_ext/object/try"
 require "active_support/core_ext/kernel/singleton_class"
+require "active_support/core_ext/module/delegation"
 require "thread"
 
 module ActionView
@@ -324,8 +325,13 @@ module ActionView
       end
 
       def locals_code #:nodoc:
+        # Only locals with valid variable names get set directly. Others will
+        # still be available in local_assigns.
+        locals = @locals.to_set - Module::DELEGATION_RESERVED_METHOD_NAMES
+        locals = locals.grep(/\A(?![A-Z0-9])(?:[[:alnum:]_]|[^\0-\177])+\z/)
+
         # Double assign to suppress the dreaded 'assigned but unused variable' warning
-        @locals.each_with_object("") { |key, code| code << "#{key} = #{key} = local_assigns[:#{key}];" }
+        locals.each_with_object("") { |key, code| code << "#{key} = #{key} = local_assigns[:#{key}];" }
       end
 
       def method_name #:nodoc:
diff --git a/actionview/test/fixtures/test/render_file_inspect_local_assigns.erb b/actionview/test/fixtures/test/render_file_inspect_local_assigns.erb
new file mode 100644
index 0000000000..aea5c351c5
--- /dev/null
+++ b/actionview/test/fixtures/test/render_file_inspect_local_assigns.erb
@@ -0,0 +1 @@
+<%= local_assigns.inspect.html_safe %>
\ No newline at end of file
diff --git a/actionview/test/fixtures/test/render_file_unicode_local.erb b/actionview/test/fixtures/test/render_file_unicode_local.erb
new file mode 100644
index 0000000000..cbfd040a76
--- /dev/null
+++ b/actionview/test/fixtures/test/render_file_unicode_local.erb
@@ -0,0 +1 @@
+<%= 🎃 %>
\ No newline at end of file
diff --git a/actionview/test/fixtures/test/render_file_with_ruby_keyword_locals.erb b/actionview/test/fixtures/test/render_file_with_ruby_keyword_locals.erb
new file mode 100644
index 0000000000..7e3fe6c6d9
--- /dev/null
+++ b/actionview/test/fixtures/test/render_file_with_ruby_keyword_locals.erb
@@ -0,0 +1 @@
+The class is <%= local_assigns[:class] %>
\ No newline at end of file
diff --git a/actionview/test/template/compiled_templates_test.rb b/actionview/test/template/compiled_templates_test.rb
index 7e3e5883b4..3ecac46d34 100644
--- a/actionview/test/template/compiled_templates_test.rb
+++ b/actionview/test/template/compiled_templates_test.rb
@@ -9,6 +9,25 @@ class CompiledTemplatesTest < ActiveSupport::TestCase
     assert_equal "This is nil: \n", render(template: "test/nil_return")
   end
 
+  def test_template_with_ruby_keyword_locals
+    assert_equal "The class is foo",
+      render(file: "test/render_file_with_ruby_keyword_locals", locals: { class: "foo" })
+  end
+
+  def test_template_with_invalid_identifier_locals
+    locals = {
+      foo: "bar",
+      Foo: "bar",
+      "d-a-s-h-e-s": "",
+      "white space": "",
+    }
+    assert_equal locals.inspect, render(file: "test/render_file_inspect_local_assigns", locals: locals)
+  end
+
+  def test_template_with_unicode_identifier
+    assert_equal "🎂", render(file: "test/render_file_unicode_local", locals: { 🎃: "🎂" })
+  end
+
   def test_template_gets_recompiled_when_using_different_keys_in_local_assigns
     assert_equal "one", render(file: "test/render_file_with_locals_and_default")
     assert_equal "two", render(file: "test/render_file_with_locals_and_default", locals: { secret: "two" })