Use futures instead of promises.

Library/Homebrew/cmd/fetch.rb

@@ -240,23 +240,23 @@ def run
             $stdout.print Tty.hide_cursor
             $stdout.flush
 
-            output_message = lambda do |downloadable, promise|
-              status = case promise.state
+            output_message = lambda do |downloadable, future|
+              status = case future.state
               when :fulfilled
                 "#{Tty.green}✔︎#{Tty.reset}"
               when :rejected
                 "#{Tty.red}✘#{Tty.reset}"
-              when :pending
+              when :pending, :processing
                 "#{Tty.blue}#{spinner}#{Tty.reset}"
               else
-                raise promise.state
+                raise future.state.to_s
               end
 
               message = "#{downloadable.download_type.capitalize} #{downloadable.name}"
               $stdout.puts "#{status} #{message}"
               $stdout.flush
 
-              if promise.rejected? && (e = promise.reason).is_a?(ChecksumMismatchError)
+              if future.rejected? && (e = future.reason).is_a?(ChecksumMismatchError)
                 opoo "#{downloadable.download_type.capitalize} reports different checksum: #{e.expected}"
                 Homebrew.failed = true if downloadable.is_a?(Resource::Patch)
                 next 2
@@ -269,24 +269,24 @@ def run
               begin
                 finished_states = [:fulfilled, :rejected]
 
-                finished_downloads, remaining_downloads = remaining_downloads.partition do |_, promise|
-                  finished_states.include?(promise.state)
+                finished_downloads, remaining_downloads = remaining_downloads.partition do |_, future|
+                  finished_states.include?(future.state)
                 end
 
-                finished_downloads.each do |downloadable, promise|
+                finished_downloads.each do |downloadable, future|
                   previous_pending_line_count -= 1
                   print "\033[K"
                   $stdout.flush
-                  output_message.call(downloadable, promise)
+                  output_message.call(downloadable, future)
                 end
 
                 previous_pending_line_count = 0
-                remaining_downloads.each do |downloadable, promise|
+                remaining_downloads.each do |downloadable, future|
                   break if previous_pending_line_count >= [concurrency, (Tty.height - 1)].min
 
                   print "\033[K"
                   $stdout.flush
-                  previous_pending_line_count += output_message.call(downloadable, promise)
+                  previous_pending_line_count += output_message.call(downloadable, future)
                 end
 
                 if previous_pending_line_count.positive?
@@ -317,9 +317,7 @@ def downloads
       end
 
       def fetch_downloadable(downloadable)
-        downloadable.clear_cache if args.force?
-
-        downloads[downloadable] ||= download_queue.enqueue(RetryableDownload.new(downloadable))
+        downloads[downloadable] ||= download_queue.enqueue(RetryableDownload.new(downloadable), force: args.force?)
       end
     end
   end

Library/Homebrew/download_queue.rb

@@ -2,7 +2,7 @@
 # frozen_string_literal: true
 
 require "downloadable"
-require "concurrent/promise"
+require "concurrent/promises"
 require "concurrent/executors"
 
 module Homebrew
@@ -16,11 +16,16 @@ def initialize(size = 1)
       @pool = Concurrent::FixedThreadPool.new(size)
     end
 
-    sig { params(downloadable: Downloadable).returns(Concurrent::Promise) }
-    def enqueue(downloadable)
-      Concurrent::Promise.execute(executor: pool) do
-        downloadable.fetch(quiet: pool.max_length > 1)
+    sig { params(downloadable: Downloadable, force: T::Boolean).returns(Concurrent::Promises::Future) }
+    def enqueue(downloadable, force: false)
+      quiet = pool.max_length > 1
+      # Passing in arguments from outside into the future is a common  `concurrent-ruby` pattern.
+      # rubocop:disable Lint/ShadowingOuterLocalVariable
+      Concurrent::Promises.future_on(pool, downloadable, force, quiet) do |downloadable, force, quiet|
+        downloadable.clear_cache if force
+        downloadable.fetch(quiet:)
       end
+      # rubocop:enable Lint/ShadowingOuterLocalVariable
     end
 
     sig { void }