Support inline tags (#755)

Based on [issue](#750)

Adding support of inline tag declaration
Examples:
```
h1 'Hello'
```
will render:
```
<h1>Hello</h1>
```

```
div do
  h1 'Hello', class: 'title'
end
```
will render:
```
<div><h1 class="title">Hello</h1></div>
```

lib/phlex.rb

@@ -26,6 +26,7 @@ module Phlex
 	Escape = ERB::Escape
 	ATTRIBUTE_CACHE = FIFO.new
 	SUPPORTS_FIBER_STORAGE = RUBY_ENGINE == "ruby"
+	Null = Object.new.freeze
 end
 
 def 💪

lib/phlex/elements.rb

@@ -32,12 +32,20 @@ def register_element(method_name, tag: method_name.name.tr("_", "-"))
 		class_eval(<<-RUBY, __FILE__, __LINE__ + 1)
 			# frozen_string_literal: true
 
-			def #{method_name}(**attributes, &block)
+			def #{method_name}(content = Phlex::Null, **attributes, &block)
 				context = @_context
 				buffer = context.buffer
 				fragment = context.fragments
 				target_found = false
 
+				if content != Phlex::Null && !content.is_a?(String)
+					raise ArgumentError.new("Only String allowed for inline tags content")
+				end
+
+				if block && content != Phlex::Null
+					raise ArgumentError.new("Using inline and block syntax at same time is forbidden")
+				end
+
 				if fragment
 					return if fragment.length == 0 # we found all our fragments already
 
@@ -59,15 +67,23 @@ def #{method_name}(**attributes, &block)
 						buffer << "<#{tag}" << (Phlex::ATTRIBUTE_CACHE[attributes] ||= __attributes__(attributes)) << ">"
 						yield_content(&block)
 						buffer << "</#{tag}>"
-					else # without content block
+					elsif content != Phlex::Null # with inline content
+						buffer << "<#{tag}" << (Phlex::ATTRIBUTE_CACHE[attributes] ||= __attributes__(attributes)) << ">"
+						plain(content)
+						buffer << "</#{tag}>"
+					else # without content
 						buffer << "<#{tag}" << (Phlex::ATTRIBUTE_CACHE[attributes] ||= __attributes__(attributes)) << "></#{tag}>"
 					end
 				else # without attributes
 					if block # with content block
 						buffer << "<#{tag}>"
 						yield_content(&block)
 						buffer << "</#{tag}>"
-					else # without content block
+					elsif content != Phlex::Null # with inline content
+						buffer << "<#{tag}>"
+						plain(content)
+						buffer << "</#{tag}>"
+					else # without content
 						buffer << "<#{tag}></#{tag}>"
 					end
 				end

test/phlex/view/renderable/render.rb

@@ -91,5 +91,87 @@ def view_template(&block)
 				end
 			end
 		end
+
+		with "inline tag method call" do
+			with "simple inline tag" do
+				view do
+					def view_template
+						h1 "Hello", class: "title"
+					end
+				end
+
+				it "renders a new instance of that view" do
+					expect(output).to be == "<h1 class=\"title\">Hello</h1>"
+				end
+			end
+
+			with "regular nesting" do
+				view do
+					def view_template
+						div class: "first" do
+							div class: "second" do
+								div "Hello", class: "third"
+							end
+						end
+					end
+				end
+
+				it "renders a new instance of that view" do
+					expect(output).to be == "<div class=\"first\"><div class=\"second\"><div class=\"third\">Hello</div></div></div>"
+				end
+			end
+
+			with "contain block" do
+				view do
+					def block_div
+						proc { div "Hello" }
+					end
+
+					def view_template
+						div block_div
+					end
+				end
+
+				it "raise argument error" do
+					expect { output }.to raise_exception(ArgumentError, message: be == "Only String allowed for inline tags content")
+				end
+			end
+
+			with "contain nil argument" do
+				view do
+					def view_template
+						h1 div "Hello"
+					end
+				end
+
+				it "raise argument error" do
+					expect { output }.to raise_exception(ArgumentError, message: be == "Only String allowed for inline tags content")
+				end
+			end
+
+			with "both block and inline arguments" do
+				view do
+					def view_template
+						h1("Hello") { "Hello" }
+					end
+				end
+
+				it "raise argument error" do
+					expect { output }.to raise_exception(ArgumentError, message: be == "Using inline and block syntax at same time is forbidden")
+				end
+			end
+
+			with "non string content" do
+				view do
+					def view_template
+						div :hello, class: "first"
+					end
+				end
+
+				it "raises argument error" do
+					expect { output }.to raise_exception(ArgumentError, message: be == "Only String allowed for inline tags content")
+				end
+			end
+		end
 	end
 end