Run brew fetch before brew install

This will parallelise fetching of formulae and casks in `brew bundle`.

Author: MikeMcQuaid

Library/Homebrew/bundle/cask_installer.rb

@@ -74,6 +74,10 @@ def self.install!(name, preinstall: true, no_upgrade: false, verbose: false, for
         result
       end
 
+      def self.installable_or_upgradable?(name, no_upgrade: false, **options)
+        !cask_installed?(name) || upgrading?(no_upgrade, name, options)
+      end
+
       private_class_method def self.postinstall_change_state!(name:, options:, verbose:)
         postinstall = options.fetch(:postinstall, nil)
         return true if postinstall.blank?

Library/Homebrew/bundle/installer.rb

@@ -20,7 +20,9 @@ def self.install!(entries, global: false, file: nil, no_lock: false, no_upgrade:
         success = 0
         failure = 0
 
-        entries.each do |entry|
+        installable_entries = entries.filter_map do |entry|
+          next if Homebrew::Bundle::Skipper.skip? entry
+
           name = entry.name
           args = [name]
           options = {}
@@ -52,9 +54,26 @@ def self.install!(entries, global: false, file: nil, no_lock: false, no_upgrade:
             options = entry.options
             Homebrew::Bundle::TapInstaller
           end
-
           next if cls.nil?
-          next if Homebrew::Bundle::Skipper.skip? entry
+
+          { name:, args:, options:, verb:, type:, cls: }
+        end
+
+        if (fetchable_names = fetchable_formulae_and_casks(installable_entries, no_upgrade:).presence)
+          fetchable_names_joined = fetchable_names.join(", ")
+          Formatter.success("Fetching #{fetchable_names_joined}") unless quiet
+          unless Bundle.brew("fetch", *fetchable_names, verbose:)
+            $stderr.puts Formatter.error "`brew bundle` failed! Failed to fetch #{fetchable_names_joined}"
+            return false
+          end
+        end
+
+        installable_entries.each do |entry|
+          name = entry.fetch(:name)
+          args = entry.fetch(:args)
+          options = entry.fetch(:options)
+          verb = entry.fetch(:verb)
+          cls = entry.fetch(:cls)
 
           preinstall = if cls.preinstall!(*args, **options, no_upgrade:, verbose:)
             puts Formatter.success("#{verb} #{name}")
@@ -86,6 +105,24 @@ def self.install!(entries, global: false, file: nil, no_lock: false, no_upgrade:
 
         true
       end
+
+      def self.fetchable_formulae_and_casks(entries, no_upgrade:)
+        entries.filter_map do |entry|
+          name = entry.fetch(:name)
+          options = entry.fetch(:options)
+
+          case entry.fetch(:type)
+          when :brew
+            next if Homebrew::Bundle::FormulaInstaller.formula_installed_and_up_to_date?(name, no_upgrade:)
+
+            name
+          when :cask
+            next unless Homebrew::Bundle::CaskInstaller.installable_or_upgradable?(name, no_upgrade:, **options)
+
+            options.fetch(:full_name, name)
+          end
+        end
+      end
     end
   end
 end

Library/Homebrew/test/bundle/installer_spec.rb

@@ -0,0 +1,49 @@
+# frozen_string_literal: true
+
+require "bundle"
+require "bundle/dsl"
+require "bundle/installer"
+
+RSpec.describe Homebrew::Bundle::Installer do
+  let(:formula_entry) { Homebrew::Bundle::Dsl::Entry.new(:brew, "mysql") }
+  let(:cask_options) { { args: {}, full_name: "homebrew/cask/google-chrome" } }
+  let(:cask_entry) { Homebrew::Bundle::Dsl::Entry.new(:cask, "google-chrome", cask_options) }
+
+  before do
+    allow(Homebrew::Bundle::Skipper).to receive(:skip?).and_return(false)
+    allow(Homebrew::Bundle::FormulaInstaller).to receive_messages(formula_upgradable?: false, install!: true)
+    allow(Homebrew::Bundle::CaskInstaller).to receive_messages(cask_upgradable?: false, install!: true)
+  end
+
+  it "prefetches installable formulae and casks before installing" do
+    allow(Homebrew::Bundle::FormulaInstaller).to receive(:formula_installed_and_up_to_date?)
+      .with("mysql", no_upgrade: false).and_return(false)
+    allow(Homebrew::Bundle::CaskInstaller).to receive(:installable_or_upgradable?)
+      .with("google-chrome", no_upgrade: false, **cask_options).and_return(true)
+
+    expect(Homebrew::Bundle).to receive(:brew)
+      .with("fetch", "mysql", "homebrew/cask/google-chrome", verbose: false)
+      .ordered
+      .and_return(true)
+    expect(Homebrew::Bundle::FormulaInstaller).to receive(:preinstall!)
+      .with("mysql", no_upgrade: false, verbose: false)
+      .ordered
+      .and_return(true)
+    expect(Homebrew::Bundle::CaskInstaller).to receive(:preinstall!)
+      .with("google-chrome", **cask_options, no_upgrade: false, verbose: false)
+      .ordered
+      .and_return(true)
+
+    described_class.install!([formula_entry, cask_entry], verbose: false, force: false, quiet: true)
+  end
+
+  it "skips fetching when no formulae or casks need installation or upgrade" do
+    allow(Homebrew::Bundle::FormulaInstaller).to receive(:formula_installed_and_up_to_date?)
+      .with("mysql", no_upgrade: true).and_return(true)
+    allow(Homebrew::Bundle::FormulaInstaller).to receive(:preinstall!).and_return(false)
+
+    expect(Homebrew::Bundle).not_to receive(:brew).with("fetch", any_args)
+
+    described_class.install!([formula_entry], no_upgrade: true, quiet: true)
+  end
+end