Allow queue to be used for task finished. (#276)

fixtures/async/a_condition.rb

@@ -0,0 +1,103 @@
+# frozen_string_literal: true
+
+# Released under the MIT License.
+# Copyright, 2018-2022, by Samuel Williams.
+
+require 'async/variable'
+
+module Async
+	ACondition = Sus::Shared("a condition") do
+		let(:condition) {subject.new}
+
+		it 'can signal waiting task' do
+			state = nil
+
+			reactor.async do
+				state = :waiting
+				condition.wait
+				state = :resumed
+			end
+
+			expect(state).to be == :waiting
+
+			condition.signal
+
+			reactor.yield
+
+			expect(state).to be == :resumed
+		end
+
+		it 'should be able to signal stopped task' do
+			expect(condition).to be(:empty?)
+			expect(condition).not.to be(:waiting?)
+
+			task = reactor.async do
+				condition.wait
+			end
+
+			expect(condition).not.to be(:empty?)
+			expect(condition).to be(:waiting?)
+
+			task.stop
+
+			condition.signal
+		end
+
+		it 'resumes tasks in order' do
+			order = []
+
+			5.times do |i|
+				task = reactor.async do
+					condition.wait
+					order << i
+				end
+			end
+
+			condition.signal
+
+			reactor.yield
+
+			expect(order).to be == [0, 1, 2, 3, 4]
+		end
+
+		with "timeout" do
+			let(:ready) {Async::Variable.new(condition)}
+			let(:waiting) {Async::Variable.new(subject.new)}
+
+			def before
+				@state = nil
+
+				@task = reactor.async do |task|
+					task.with_timeout(0.01) do
+						begin
+							@state = :waiting
+							waiting.resolve
+
+							ready.wait
+							@state = :signalled
+						rescue Async::TimeoutError
+							@state = :timeout
+						end
+					end
+				end
+
+				super
+			end
+
+			it 'can timeout while waiting' do
+				@task.wait
+
+				expect(@state).to be == :timeout
+			end
+
+			it 'can signal while waiting' do
+				waiting.wait
+				ready.resolve
+
+				@task.wait
+
+				expect(@state).to be == :signalled
+			end
+		end
+	end
+end

lib/async/condition.rb

@@ -40,12 +40,16 @@ def wait
 			end
 		end
 
-		# Is any fiber waiting on this notification?
-		# @returns [Boolean]
+		# @deprecated Replaced by {#waiting?}
 		def empty?
 			@waiting.empty?
 		end
 
+		# @returns [Boolean] Is any fiber waiting on this notification?
+		def waiting?
+			@waiting.size > 0
+		end
+
 		# Signal to a given task that it should resume operations.
 		# @parameter value [Object | Nil] The value to return to the waiting fibers.
 		def signal(value = nil)

lib/async/queue.rb

@@ -9,16 +9,19 @@
 
 module Async
 	# A queue which allows items to be processed in order.
+	#
+	# It has a compatible interface with {Notification} and {Condition}, except that it's multi-value.
+	#
 	# @public Since `stable-v1`.
-	class Queue < Notification
+	class Queue
 		# Create a new queue.
 		#
 		# @parameter parent [Interface(:async) | Nil] The parent task to use for async operations.
-		def initialize(parent: nil)
-			super()
-
+		# @parameter available [Notification] The notification to use for signaling when items are available.
+		def initialize(parent: nil, available: Notification.new)
 			@items = []
 			@parent = parent
+			@available = available
 		end
 
 		# @attribute [Array] The items in the queue.
@@ -38,20 +41,20 @@ def empty?
 		def <<(item)
 			@items << item
 
-			self.signal unless self.empty?
+			@available.signal unless self.empty?
 		end
 
 		# Add multiple items to the queue.
 		def enqueue(*items)
 			@items.concat(items)
 
-			self.signal unless self.empty?
+			@available.signal unless self.empty?
 		end
 
 		# Remove and return the next item from the queue.
 		def dequeue
 			while @items.empty?
-				self.wait
+				@available.wait
 			end
 
 			@items.shift
@@ -77,6 +80,16 @@ def each
 				yield item
 			end
 		end
+
+		# Signal the queue with a value, the same as {#enqueue}.
+		def signal(value)
+			self.enqueue(value)
+		end
+
+		# Wait for an item to be available, the same as {#dequeue}.
+		def wait
+			self.dequeue
+		end
 	end
 
 	# A queue which limits the number of items that can be enqueued.
@@ -85,12 +98,12 @@ class LimitedQueue < Queue
 		# Create a new limited queue.
 		#
 		# @parameter limit [Integer] The maximum number of items that can be enqueued.
-		def initialize(limit = 1, **options)
+		# @parameter full [Notification] The notification to use for signaling when the queue is full.
+		def initialize(limit = 1, full: Notification.new, **options)
 			super(**options)
 
 			@limit = limit
-
-			@full = Notification.new
+			@full = full
 		end
 
 		# @attribute [Integer] The maximum number of items that can be enqueued.
@@ -128,7 +141,7 @@ def enqueue(*items)
 				available = @limit - @items.size
 				@items.concat(items.shift(available))
 
-				self.signal unless self.empty?
+				@available.signal unless self.empty?
 			end
 		end
 

test/async/condition.rb

@@ -7,7 +7,7 @@
 require 'sus/fixtures/async'
 require 'async/condition'
 
-require 'a_condition'
+require 'async/a_condition'
 
 describe Async::Condition do
 	include Sus::Fixtures::Async::ReactorContext
@@ -52,5 +52,5 @@
 		expect(consumer.status).to be == :completed
 	end
 
-	it_behaves_like ACondition
+	it_behaves_like Async::ACondition
 end

test/async/notification.rb

@@ -6,7 +6,7 @@
 require 'sus/fixtures/async'
 require 'async/notification'
 
-require 'a_condition'
+require 'async/a_condition'
 
 describe Async::Notification do
 	include Sus::Fixtures::Async::ReactorContext
@@ -47,5 +47,5 @@
 		]
 	end
 
-	it_behaves_like ACondition
+	it_behaves_like Async::ACondition
 end

test/async/queue.rb

@@ -87,12 +87,44 @@
 		end
 	end
 
+	with '#signal' do
+		it 'can signal with an item' do
+			queue.signal(:item)
+			expect(queue.dequeue).to be == :item
+		end
+	end
+
+	with '#wait' do
+		it 'can wait for an item' do
+			reactor.async do |task|
+				queue.enqueue(:item)
+			end
+
+			expect(queue.wait).to be == :item
+		end
+	end
+
 	with 'an empty queue' do
 		it "is expected to be empty" do
 			expect(queue).to be(:empty?)
 		end
 	end
 
+	with 'task finishing queue' do
+		it 'can signal task completion' do
+			3.times do
+				Async(finished: queue) do
+					:result
+				end
+			end
+
+			3.times do
+				task = queue.dequeue
+				expect(task.wait).to be == :result
+			end
+		end
+	end
+
 	with 'semaphore' do
 		let(:capacity) {2}
 		let(:semaphore) {Async::Semaphore.new(capacity)}