Always pass a format to the ActionView::Template constructor

This means we can eliminate nil checks and remove some mutations from
the `decorate` method.

actionpack/test/dispatch/debug_exceptions_test.rb

@@ -39,7 +39,7 @@ class DebugExceptionsTest < ActionDispatch::IntegrationTest
     def call(env)
       env["action_dispatch.show_detailed_exceptions"] = @detailed
       req = ActionDispatch::Request.new(env)
-      template = ActionView::Template.new(File.read(__FILE__), __FILE__, ActionView::Template::Handlers::Raw.new, {})
+      template = ActionView::Template.new(File.read(__FILE__), __FILE__, ActionView::Template::Handlers::Raw.new, format: :html)
 
       case req.path
       when "/pass"

actionview/lib/action_view/template.rb

@@ -128,8 +128,11 @@ module ActionView
 
     attr_reader :variable
 
-    def initialize(source, identifier, handler, details)
-      format = details[:format] || (handler.default_format if handler.respond_to?(:default_format))
+    def initialize(source, identifier, handler, format: nil, **details)
+      unless format
+        ActiveSupport::Deprecation.warn "ActionView::Template#initialize requires a format parameter"
+        format = :html
+      end
 
       @source            = source
       @identifier        = identifier

actionview/lib/action_view/template/resolver.rb

@@ -196,7 +196,6 @@ module ActionView
       cached = nil
       templates.each do |t|
         t.locals         = locals
-        t.formats        = details[:formats]  || [:html] if t.formats.empty?
         t.variants       = details[:variants] || []      if t.variants.empty?
         t.virtual_path ||= (cached ||= build_path(*path_info))
       end
@@ -225,7 +224,7 @@ module ActionView
         template_paths = reject_files_external_to_app(template_paths) unless outside_app_allowed
 
         template_paths.map do |template|
-          handler, format, variant = extract_handler_and_format_and_variant(template)
+          handler, format, variant = extract_handler_and_format_and_variant(template, formats.first)
 
           FileTemplate.new(File.expand_path(template), handler,
             virtual_path: path.virtual,
@@ -292,7 +291,7 @@ module ActionView
       # Extract handler, formats and variant from path. If a format cannot be found neither
       # from the path, or the handler, we should return the array of formats given
       # to the resolver.
-      def extract_handler_and_format_and_variant(path)
+      def extract_handler_and_format_and_variant(path, query_format)
         pieces = File.basename(path).split(".")
         pieces.shift
 
@@ -300,9 +299,18 @@ module ActionView
 
         handler = Template.handler_for_extension(extension)
         format, variant = pieces.last.split(EXTENSIONS[:variants], 2) if pieces.last
-        format &&= Template::Types[format]
+        format = if format
+          Template::Types[format]
+        else
+          if handler.respond_to?(:default_format) # default_format can return nil
+            handler.default_format
+          else
+            query_format
+          end
+        end
 
-        [handler, format, variant]
+        # Template::Types[format] and handler.default_format can return nil
+        [handler, format || query_format, variant]
       end
   end
 

actionview/lib/action_view/testing/resolvers.rb

@@ -34,7 +34,7 @@ module ActionView #:nodoc:
         @hash.each do |_path, array|
           source, updated_at = array
           next unless query.match?(_path)
-          handler, format, variant = extract_handler_and_format_and_variant(_path)
+          handler, format, variant = extract_handler_and_format_and_variant(_path, :html)
           templates << Template.new(source, _path, handler,
             virtual_path: path.virtual,
             format: format,
@@ -49,7 +49,7 @@ module ActionView #:nodoc:
 
   class NullResolver < PathResolver
     def query(path, exts, _, _)
-      handler, format, variant = extract_handler_and_format_and_variant(path)
+      handler, format, variant = extract_handler_and_format_and_variant(path, :html)
       [ActionView::Template.new("Template generated by Null Resolver", path.virtual, handler, virtual_path: path.virtual, format: format, variant: variant)]
     end
   end

actionview/test/abstract_unit.rb

@@ -60,7 +60,7 @@ module RenderERBUtils
       string.strip,
       "test template",
       ActionView::Template.handler_for_extension(:erb),
-      {})
+      format: :html)
 
     view = ActionView::Base.with_empty_template_cache
     template.render(view.empty, {}).strip

actionview/test/template/template_test.rb

@@ -38,7 +38,8 @@ class TestERBTemplate < ActiveSupport::TestCase
         "<%= @virtual_path %>",
         "partial",
         ERBHandler,
-        virtual_path: "partial"
+        virtual_path: "partial",
+        format: :html
       )
     end
 
@@ -55,7 +56,8 @@ class TestERBTemplate < ActiveSupport::TestCase
     end
   end
 
-  def new_template(body = "<%= hello %>", details = { format: :html })
+  def new_template(body = "<%= hello %>", details = {})
+    details = { format: :html }.merge details
     ActionView::Template.new(body.dup, "hello template", details.fetch(:handler) { ERBHandler }, { virtual_path: "hello" }.merge!(details))
   end