phlex-ruby · joeldrapper · Mar 2, 2024 · Mar 2, 2024 · Mar 2, 2024 · Mar 2, 2024
diff --git a/lib/phlex/context.rb b/lib/phlex/context.rb
@@ -5,9 +5,12 @@ class Phlex::Context
 	def initialize
 		@buffer = +""
 		@capturing = false
+		@fragment = nil
+		@in_target_fragment = false
+		@found_target_fragment = false
 	end
 
-	attr_accessor :buffer, :capturing
+	attr_accessor :buffer, :capturing, :fragment, :in_target_fragment, :found_target_fragment
 
 	# Added for backwards compatibility with phlex-rails. We can remove this with 2.0
 	def target

diff --git a/lib/phlex/elements.rb b/lib/phlex/elements.rb
@@ -42,7 +42,26 @@ def register_element(method_name, tag: method_name.name.tr("_", "-"), deprecated
 
 			def #{method_name}(**attributes, &block)
 				#{deprecation}
-				buffer = @_context.buffer
+
+				context = @_context
+				buffer = context.buffer
+				fragment = context.fragment
+				end_find = false
+
+				if fragment
+					in_target_fragment = context.in_target_fragment
+
+					if !in_target_fragment
+					  if !context.found_target_fragment && attributes[:id] == fragment
+							context.in_target_fragment = true
+							context.found_target_fragment = true
+							end_find = true
+						else
+							yield if block
+							return nil
+						end
+					end
+				end
 
 				if attributes.length > 0 # with attributes
 					if block # with content block
@@ -64,6 +83,9 @@ def #{method_name}(**attributes, &block)
 
 				#{'flush' if tag == 'head'}
 
+				# I think we can actually throw from here.
+				context.in_target_fragment = false if end_find
+
 				nil
 			end
 
@@ -90,7 +112,21 @@ def register_void_element(method_name, tag: method_name.name.tr("_", "-"), depre
 
 			def #{method_name}(**attributes)
 				#{deprecation}
-				buffer = @_context.buffer
+				context = @_context
+				buffer = context.buffer
+				fragment = context.fragment
+
+				if fragment
+					in_target_fragment = context.in_target_fragment
+
+					if !in_target_fragment
+					  if !context.found_target_fragment && attributes[:id] == fragment
+							context.found_target_fragment = true
+						else
+							return nil
+						end
+					end
+				end
 
 				if attributes.length > 0 # with attributes
 					buffer << "<#{tag}" << (Phlex::ATTRIBUTE_CACHE[respond_to?(:process_attributes) ? (attributes.hash + self.class.hash) : attributes.hash] || __attributes__(**attributes)) << ">"

diff --git a/lib/phlex/html.rb b/lib/phlex/html.rb
@@ -29,7 +29,10 @@ def __unbuffered_class__
 
 		# Output an HTML doctype.
 		def doctype
-			@_context.buffer << "<!DOCTYPE html>"
+			context = @_context
+			return if context.fragment && !context.in_target_fragment
+
+			context.buffer << "<!DOCTYPE html>"
 			nil
 		end
 

diff --git a/lib/phlex/sgml.rb b/lib/phlex/sgml.rb
@@ -95,18 +95,19 @@ def await(task)
 		end
 
 		# Renders the view and returns the buffer. The default buffer is a mutable String.
-		def call(buffer = +"", context: Phlex::Context.new, view_context: nil, parent: nil, &block)
-			__final_call__(buffer, context: context, view_context: view_context, parent: parent, &block).tap do
+		def call(buffer = +"", context: Phlex::Context.new, view_context: nil, parent: nil, fragment: nil, &block)
+			__final_call__(buffer, context: context, view_context: view_context, parent: parent, fragment: fragment, &block).tap do
 				self.class.rendered_at_least_once!
 			end
 		end
 
 		# @api private
-		def __final_call__(buffer = +"", context: Phlex::Context.new, view_context: nil, parent: nil, &block)
+		def __final_call__(buffer = +"", context: Phlex::Context.new, view_context: nil, parent: nil, fragment: nil, &block)
 			@_buffer = buffer
 			@_context = context
 			@_view_context = view_context
 			@_parent = parent
+			@_context.fragment = fragment if fragment
 
 			block ||= @_content_block
 
@@ -139,6 +140,9 @@ def __final_call__(buffer = +"", context: Phlex::Context.new, view_context: nil,
 		# @return [nil]
 		# @see #format_object
 		def plain(content)
+			context = @_context
+			return if context.fragment && !context.in_target_fragment
+
 			unless __text__(content)
 				raise ArgumentError, "You've passed an object to plain that is not handled by format_object. See https://rubydoc.info/gems/phlex/Phlex/SGML#format_object-instance_method for more information"
 			end
@@ -150,7 +154,10 @@ def plain(content)
 		# @return [nil]
 		# @yield If a block is given, it yields the block with no arguments.
 		def whitespace(&block)
-			buffer = @_context.buffer
+			context = @_context
+			return if context.fragment && !context.in_target_fragment
+
+			buffer = context.buffer
 
 			buffer << " "
 
@@ -165,7 +172,10 @@ def whitespace(&block)
 		# Output an HTML comment.
 		# @return [nil]
 		def comment(&block)
-			buffer = @_context.buffer
+			context = @_context
+			return if context.fragment && !context.in_target_fragment
+
+			buffer = context.buffer
 
 			buffer << "<!-- "
 			yield_content(&block)
@@ -180,7 +190,10 @@ def comment(&block)
 		def unsafe_raw(content = nil)
 			return nil unless content
 
-			@_context.buffer << content
+			context = @_context
+			return if context.fragment && !context.in_target_fragment
+
+			context.buffer << content
 			nil
 		end
 

diff --git a/test/phlex/selective_rendering.rb b/test/phlex/selective_rendering.rb
@@ -0,0 +1,55 @@
+# frozen_string_literal: true
+
+class StandardElementExample < Phlex::HTML
+	def view_template
+		doctype
+		div {
+			comment { h1(id: "target") }
+			h1 { "Before" }
+			img(src: "before.jpg")
+			whitespace
+			comment { "This is a comment" }
+			h1(id: "target") {
+				plain "Hello"
+				strong { "World" }
+				img(src: "image.jpg")
+			}
+			img(src: "after.jpg")
+			h1(id: "target") { "After" }
+		}
+	end
+end
+
+class VoidElementExample < Phlex::HTML
+	def view_template
+		doctype
+		div {
+			comment { h1(id: "target") }
+			h1 { "Before" }
+			img(src: "before.jpg")
+			whitespace
+			comment { "This is a comment" }
+			h1 {
+				plain "Hello"
+				strong { "World" }
+				img(id: "target", src: "image.jpg")
+			}
+			img(src: "after.jpg")
+			h1(id: "target") { "After" }
+		}
+	end
+end
+
+describe Phlex::HTML do
+	it "renders the just the target fragment" do
+		expect(
+			StandardElementExample.new.call(fragment: "target")
+		).to be == %(<h1 id="target">Hello<strong>World</strong><img src="image.jpg"></h1>)
+	end
+
+	it "works with void elements" do
+		expect(
+			VoidElementExample.new.call(fragment: "target")
+		).to be == %(<img id="target" src="image.jpg">)
+	end
+end