Fetch formula resources before unlinking during upgrade.

Fixes #6374.

Library/Homebrew/cask/installer.rb

@@ -369,6 +369,7 @@ module Cask
             fi.show_header = true
             fi.verbose = verbose?
             fi.prelude
+            fi.fetch
             fi.install
             fi.finish
           end

Library/Homebrew/cmd/install.rb

@@ -326,6 +326,7 @@ module Homebrew
     fi.interactive          = args.interactive?
     fi.git                  = args.git?
     fi.prelude
+    fi.fetch
     fi.install
     fi.finish
   rescue FormulaInstallationAlreadyAttemptedError

Library/Homebrew/cmd/upgrade.rb

@@ -192,6 +192,8 @@ module Homebrew
     end
     oh1 "Upgrading #{Formatter.identifier(f.full_specified_name)} #{upgrade_version} #{fi.options.to_a.join(" ")}"
 
+    fi.fetch
+
     # first we unlink the currently active keg for this formula otherwise it is
     # possible for the existing build to interfere with the build we are about to
     # do! Seriously, it happens!

Library/Homebrew/formula.rb

@@ -1160,6 +1160,7 @@ class Formula
   # @private
   def brew
     @prefix_returns_versioned_prefix = true
+    active_spec.fetch
     stage do |staging|
       staging.retain! if Homebrew.args.keep_tmp?
       prepare_patches

Library/Homebrew/formula_installer.rb

@@ -600,6 +600,7 @@ class FormulaInstaller
     fi.installed_as_dependency = true
     fi.installed_on_request    = df.any_version_installed? && tab.installed_on_request
     fi.prelude
+    fi.fetch
     oh1 "Installing #{formula.full_name} dependency: #{Formatter.identifier(dep.name)}"
     fi.install
     fi.finish
@@ -946,14 +947,35 @@ class FormulaInstaller
     @show_summary_heading = true
   end
 
-  def pour
-    if (bottle_path = formula.local_bottle_path)
-      downloader = LocalBottleDownloadStrategy.new(bottle_path)
-    else
-      downloader = formula.bottle
-      downloader.fetch
-    end
+  def fetch_dependencies
+    deps = compute_dependencies
 
+    return if deps.empty? || ignore_deps?
+
+    deps.each do |dep, _|
+      dep.to_formula.resources.each(&:fetch)
+    end
+  end
+
+  def fetch
+    fetch_dependencies
+
+    return if only_deps?
+
+    downloader.fetch
+  end
+
+  def downloader
+    if (bottle_path = formula.local_bottle_path)
+      LocalBottleDownloadStrategy.new(bottle_path)
+    elsif pour_bottle?
+      formula.bottle
+    else
+      formula.downloader
+    end
+  end
+
+  def pour
     HOMEBREW_CELLAR.cd do
       downloader.stage
     end

Library/Homebrew/reinstall.rb

@@ -36,6 +36,7 @@ module Homebrew
       fi.installed_on_request    = tab.installed_on_request
     end
     fi.prelude
+    fi.fetch
 
     oh1 "Reinstalling #{Formatter.identifier(f.full_name)} #{options.to_a.join " "}"
 

Library/Homebrew/resource.rb

@@ -70,8 +70,8 @@ class Resource
   def stage(target = nil, &block)
     raise ArgumentError, "target directory or block is required" unless target || block
 
-    fetch
     prepare_patches
+
     unpack(target, &block)
   end
 

Library/Homebrew/test/formula_installer_bottle_spec.rb

@@ -23,7 +23,10 @@ describe FormulaInstaller do
     stub_formula_loader formula("gcc") { url "gcc-1.0" }
     stub_formula_loader formula("patchelf") { url "patchelf-1.0" }
     allow(Formula["patchelf"]).to receive(:latest_version_installed?).and_return(true)
-    described_class.new(formula).install
+
+    fi = FormulaInstaller.new(formula)
+    fi.fetch
+    fi.install
 
     keg = Keg.new(formula.prefix)
 

Library/Homebrew/test/formula_installer_spec.rb

@@ -21,6 +21,7 @@ describe FormulaInstaller do
 
     installer = described_class.new(formula)
 
+    installer.fetch
     installer.install
 
     keg = Keg.new(formula.prefix)
@@ -158,6 +159,7 @@ describe FormulaInstaller do
 
     it "shows audit problems if HOMEBREW_DEVELOPER is set" do
       ENV["HOMEBREW_DEVELOPER"] = "1"
+      formula_installer.fetch
       formula_installer.install
       expect(formula_installer).to receive(:audit_installed).and_call_original
       formula_installer.caveats

Library/Homebrew/test/formulary_spec.rb

@@ -149,6 +149,7 @@ describe Formulary do
       let(:installer) { FormulaInstaller.new(installed_formula) }
 
       it "returns a Formula when given a rack" do
+        installer.fetch
         installer.install
 
         f = described_class.from_rack(installed_formula.rack)
@@ -156,6 +157,7 @@ describe Formulary do
       end
 
       it "returns a Formula when given a Keg" do
+        installer.fetch
         installer.install
 
         keg = Keg.new(installed_formula.prefix)

Library/Homebrew/test/support/helper/spec/shared_context/integration_test.rb

@@ -177,6 +177,7 @@ RSpec.shared_context "integration test" do
     fi = FormulaInstaller.new(Formula[name])
     fi.build_bottle = build_bottle
     fi.prelude
+    fi.fetch
     fi.install
     fi.finish
   end