Attribute values > to_phlex_attribute_value, to_str, to_s (#629)

Fixes #569 

Attribute values can be any object that responds to
`to_phlex_attribute_value` or `to_str`, falling back to `to_s` if
neither is defined.

Signed-off-by: Joel Drapper <joel@drapper.me>
Co-authored-by: Joel Drapper <joel@drapper.me>

gd/phlex/sgml/attributes.rb

@@ -2,9 +2,21 @@
 
 include TestHelper
 
+class ToPhlexAttributeValueable
+	def to_phlex_attribute_value
+		"to_phlex_attribute_value"
+	end
+end
+
+class ToSable
+	def to_s
+		"to_s"
+	end
+end
+
 class ToStrable
 	def to_str
-		"foo"
+		"to_str"
 	end
 end
 
@@ -40,12 +52,28 @@ def to_str
 	expect(component.new).to_render %(<div class="bg-red-500 rounded"></div>)
 end
 
+test "with a to_phlex_attribute_value-able object" do
+	component = build_component_with_template do
+		div class: ToPhlexAttributeValueable.new
+	end
+
+	expect(component.new).to_render %(<div class="to_phlex_attribute_value"></div>)
+end
+
+test "with a to_s-able object" do
+	component = build_component_with_template do
+		div class: ToSable.new
+	end
+
+	expect(component.new).to_render %(<div class="to_s"></div>)
+end
+
 test "with a to_str-able object" do
 	component = build_component_with_template do
 		div class: ToStrable.new
 	end
 
-	expect(component.new).to_render %(<div class="foo"></div>)
+	expect(component.new).to_render %(<div class="to_str"></div>)
 end
 
 test "with numeric integer/float" do

lib/phlex/sgml.rb

@@ -427,7 +427,15 @@ def __build_attributes__(attributes, buffer:)
 				when Set
 					buffer << " " << name << '="' << Phlex::Escape.html_escape(v.to_a.compact.join(" ")) << '"'
 				else
-					buffer << " " << name << '="' << Phlex::Escape.html_escape(v.to_str) << '"'
+					value = if v.respond_to?(:to_phlex_attribute_value)
+						v.to_phlex_attribute_value
+					elsif v.respond_to?(:to_str)
+						v.to_str
+					else
+						v.to_s
+					end
+
+					buffer << " " << name << '="' << Phlex::Escape.html_escape(value) << '"'
 				end
 			end