diff --git a/Library/Homebrew/cmd/--cellar.rb b/Library/Homebrew/cmd/--cellar.rb
index 096c31bbd6..e12fcc5655 100644
--- a/Library/Homebrew/cmd/--cellar.rb
+++ b/Library/Homebrew/cmd/--cellar.rb
@@ -25,7 +25,7 @@ module Homebrew
     if Homebrew.args.named.blank?
       puts HOMEBREW_CELLAR
     else
-      puts ARGV.resolved_formulae.map(&:rack)
+      puts Homebrew.args.resolved_formulae.map(&:rack)
     end
   end
 end
diff --git a/Library/Homebrew/cmd/--prefix.rb b/Library/Homebrew/cmd/--prefix.rb
index 6969a00b26..4d8655fb6a 100644
--- a/Library/Homebrew/cmd/--prefix.rb
+++ b/Library/Homebrew/cmd/--prefix.rb
@@ -25,7 +25,7 @@ module Homebrew
     if Homebrew.args.named.blank?
       puts HOMEBREW_PREFIX
     else
-      puts ARGV.resolved_formulae.map { |f|
+      puts Homebrew.args.resolved_formulae.map { |f|
         f.opt_prefix.exist? ? f.opt_prefix : f.installed_prefix
       }
     end
diff --git a/Library/Homebrew/cmd/gist-logs.rb b/Library/Homebrew/cmd/gist-logs.rb
index 72e867d133..a62e420451 100644
--- a/Library/Homebrew/cmd/gist-logs.rb
+++ b/Library/Homebrew/cmd/gist-logs.rb
@@ -142,10 +142,10 @@ module Homebrew
   end
 
   def gist_logs
-    raise FormulaUnspecifiedError if ARGV.resolved_formulae.length != 1
+    raise FormulaUnspecifiedError if Homebrew.args.resolved_formulae.length != 1
 
     Install.perform_preinstall_checks(all_fatal: true)
     Install.perform_build_from_source_checks(all_fatal: true)
-    gistify_logs(ARGV.resolved_formulae.first)
+    gistify_logs(Homebrew.args.resolved_formulae.first)
   end
 end
diff --git a/Library/Homebrew/cmd/migrate.rb b/Library/Homebrew/cmd/migrate.rb
index cce46897c7..d5b6b7308d 100644
--- a/Library/Homebrew/cmd/migrate.rb
+++ b/Library/Homebrew/cmd/migrate.rb
@@ -27,7 +27,7 @@ module Homebrew
 
     raise FormulaUnspecifiedError if Homebrew.args.named.blank?
 
-    ARGV.resolved_formulae.each do |f|
+    Homebrew.args.resolved_formulae.each do |f|
       if f.oldname
         unless (rack = HOMEBREW_CELLAR/f.oldname).exist? && !rack.subdirs.empty?
           raise NoSuchKegError, f.oldname
diff --git a/Library/Homebrew/cmd/missing.rb b/Library/Homebrew/cmd/missing.rb
index 027b5110dc..4b51ed3439 100644
--- a/Library/Homebrew/cmd/missing.rb
+++ b/Library/Homebrew/cmd/missing.rb
@@ -33,7 +33,7 @@ module Homebrew
     ff = if Homebrew.args.named.blank?
       Formula.installed.sort
     else
-      ARGV.resolved_formulae.sort
+      Homebrew.args.resolved_formulae.sort
     end
 
     ff.each do |f|
diff --git a/Library/Homebrew/cmd/outdated.rb b/Library/Homebrew/cmd/outdated.rb
index c6161d8707..c27713a236 100644
--- a/Library/Homebrew/cmd/outdated.rb
+++ b/Library/Homebrew/cmd/outdated.rb
@@ -35,10 +35,10 @@ module Homebrew
   def outdated
     outdated_args.parse
 
-    formulae = if ARGV.resolved_formulae.empty?
+    formulae = if Homebrew.args.resolved_formulae.blank?
       Formula.installed
     else
-      ARGV.resolved_formulae
+      Homebrew.args.resolved_formulae
     end
     if args.json
       raise UsageError, "Invalid JSON version: #{args.json}" unless ["v1", true].include? args.json
@@ -47,7 +47,7 @@ module Homebrew
     else
       outdated = print_outdated(formulae)
     end
-    Homebrew.failed = !ARGV.resolved_formulae.empty? && !outdated.empty?
+    Homebrew.failed = Homebrew.args.resolved_formulae.present? && !outdated.empty?
   end
 
   def print_outdated(formulae)
diff --git a/Library/Homebrew/cmd/pin.rb b/Library/Homebrew/cmd/pin.rb
index 33ae70e439..76cc6130c2 100644
--- a/Library/Homebrew/cmd/pin.rb
+++ b/Library/Homebrew/cmd/pin.rb
@@ -23,7 +23,7 @@ module Homebrew
 
     raise FormulaUnspecifiedError if args.remaining.empty?
 
-    ARGV.resolved_formulae.each do |f|
+    Homebrew.args.resolved_formulae.each do |f|
       if f.pinned?
         opoo "#{f.name} already pinned"
       elsif !f.pinnable?
diff --git a/Library/Homebrew/cmd/postinstall.rb b/Library/Homebrew/cmd/postinstall.rb
index fd20bec0fb..dcecd0f937 100644
--- a/Library/Homebrew/cmd/postinstall.rb
+++ b/Library/Homebrew/cmd/postinstall.rb
@@ -25,7 +25,7 @@ module Homebrew
 
     raise KegUnspecifiedError if args.remaining.empty?
 
-    ARGV.resolved_formulae.each do |f|
+    Homebrew.args.resolved_formulae.each do |f|
       ohai "Postinstalling #{f}"
       fi = FormulaInstaller.new(f)
       fi.post_install
diff --git a/Library/Homebrew/cmd/reinstall.rb b/Library/Homebrew/cmd/reinstall.rb
index 67acf71b4d..6b0f6ea588 100644
--- a/Library/Homebrew/cmd/reinstall.rb
+++ b/Library/Homebrew/cmd/reinstall.rb
@@ -53,7 +53,7 @@ module Homebrew
 
     Install.perform_preinstall_checks
 
-    ARGV.resolved_formulae.each do |f|
+    Homebrew.args.resolved_formulae.each do |f|
       if f.pinned?
         onoe "#{f.full_name} is pinned. You must unpin it to reinstall."
         next
diff --git a/Library/Homebrew/cmd/unpin.rb b/Library/Homebrew/cmd/unpin.rb
index 2ffd949893..6bd17b27f2 100644
--- a/Library/Homebrew/cmd/unpin.rb
+++ b/Library/Homebrew/cmd/unpin.rb
@@ -24,7 +24,7 @@ module Homebrew
 
     raise FormulaUnspecifiedError if args.remaining.empty?
 
-    ARGV.resolved_formulae.each do |f|
+    Homebrew.args.resolved_formulae.each do |f|
       if f.pinned?
         f.unpin
       elsif !f.pinnable?
diff --git a/Library/Homebrew/cmd/upgrade.rb b/Library/Homebrew/cmd/upgrade.rb
index 29ffe5bd7f..9ef1e5f877 100644
--- a/Library/Homebrew/cmd/upgrade.rb
+++ b/Library/Homebrew/cmd/upgrade.rb
@@ -68,11 +68,11 @@ module Homebrew
 
       exit 0 if outdated.empty?
     else
-      outdated = ARGV.resolved_formulae.select do |f|
+      outdated = Homebrew.args.resolved_formulae.select do |f|
         f.outdated?(fetch_head: args.fetch_HEAD?)
       end
 
-      (ARGV.resolved_formulae - outdated).each do |f|
+      (Homebrew.args.resolved_formulae - outdated).each do |f|
         versions = f.installed_kegs.map(&:version)
         if versions.empty?
           ofail "#{f.full_specified_name} not installed"
diff --git a/Library/Homebrew/dev-cmd/audit.rb b/Library/Homebrew/dev-cmd/audit.rb
index 13a706a333..0da9155ed5 100644
--- a/Library/Homebrew/dev-cmd/audit.rb
+++ b/Library/Homebrew/dev-cmd/audit.rb
@@ -83,8 +83,8 @@ module Homebrew
       ff = Formula
       files = Tap.map(&:formula_dir)
     else
-      ff = ARGV.resolved_formulae
-      files = ARGV.resolved_formulae.map(&:path)
+      ff = Homebrew.args.resolved_formulae
+      files = Homebrew.args.resolved_formulae.map(&:path)
     end
 
     only_cops = args.only_cops
diff --git a/Library/Homebrew/dev-cmd/bottle.rb b/Library/Homebrew/dev-cmd/bottle.rb
index b870e8d9ae..3495d428ef 100644
--- a/Library/Homebrew/dev-cmd/bottle.rb
+++ b/Library/Homebrew/dev-cmd/bottle.rb
@@ -89,7 +89,7 @@ module Homebrew
     raise KegUnspecifiedError if args.remaining.empty?
 
     ensure_relocation_formulae_installed! unless args.skip_relocation?
-    ARGV.resolved_formulae.each do |f|
+    Homebrew.args.resolved_formulae.each do |f|
       bottle_formula f
     end
   end
diff --git a/Library/Homebrew/dev-cmd/formula.rb b/Library/Homebrew/dev-cmd/formula.rb
index 1bb5fba2f9..b018489e6d 100644
--- a/Library/Homebrew/dev-cmd/formula.rb
+++ b/Library/Homebrew/dev-cmd/formula.rb
@@ -23,6 +23,6 @@ module Homebrew
 
     raise FormulaUnspecifiedError if Homebrew.args.named.blank?
 
-    ARGV.resolved_formulae.each { |f| puts f.path }
+    Homebrew.args.resolved_formulae.each { |f| puts f.path }
   end
 end
diff --git a/Library/Homebrew/dev-cmd/test.rb b/Library/Homebrew/dev-cmd/test.rb
index 47ae4412b3..72b912789c 100644
--- a/Library/Homebrew/dev-cmd/test.rb
+++ b/Library/Homebrew/dev-cmd/test.rb
@@ -38,7 +38,7 @@ module Homebrew
 
     require "formula_assertions"
 
-    ARGV.resolved_formulae.each do |f|
+    Homebrew.args.resolved_formulae.each do |f|
       # Cannot test uninstalled formulae
       unless f.latest_version_installed?
         ofail "Testing requires the latest version of #{f.full_name}"
diff --git a/Library/Homebrew/extend/ARGV.rb b/Library/Homebrew/extend/ARGV.rb
index f8447dc52f..575c5c62a4 100644
--- a/Library/Homebrew/extend/ARGV.rb
+++ b/Library/Homebrew/extend/ARGV.rb
@@ -6,10 +6,6 @@ module HomebrewArgvExtension
     self - options_only
   end
 
-  def options_only
-    select { |arg| arg.start_with?("-") }
-  end
-
   def flags_only
     select { |arg| arg.start_with?("--") }
   end
@@ -26,14 +22,6 @@ module HomebrewArgvExtension
     end.uniq(&:name)
   end
 
-  def resolved_formulae
-    require "formula"
-    # TODO: use @instance variable to ||= cache when moving to CLI::Parser
-    (downcased_unique_named - casks).map do |name|
-      Formulary.resolve(name, spec: spec(nil))
-    end.uniq(&:name)
-  end
-
   def casks
     # TODO: use @instance variable to ||= cache when moving to CLI::Parser
     downcased_unique_named.grep HOMEBREW_CASK_TAP_CASK_REGEX
@@ -118,18 +106,10 @@ module HomebrewArgvExtension
     formulae.any? { |argv_f| argv_f.full_name == f.full_name }
   end
 
-  def flag?(flag)
-    options_only.include?(flag) || switch?(flag[2, 1])
-  end
-
   def force_bottle?
     include?("--force-bottle")
   end
 
-  def fetch_head?
-    include? "--fetch-HEAD"
-  end
-
   def cc
     value "cc"
   end
@@ -153,6 +133,14 @@ module HomebrewArgvExtension
 
   private
 
+  def options_only
+    select { |arg| arg.start_with?("-") }
+  end
+
+  def flag?(flag)
+    options_only.include?(flag) || switch?(flag[2, 1])
+  end
+
   # e.g. `foo -ns -i --bar` has three switches: `n`, `s` and `i`
   def switch?(char)
     return false if char.length > 1
diff --git a/Library/Homebrew/postinstall.rb b/Library/Homebrew/postinstall.rb
index fe4e006019..0eb610839d 100644
--- a/Library/Homebrew/postinstall.rb
+++ b/Library/Homebrew/postinstall.rb
@@ -24,6 +24,7 @@ begin
   trap("INT", old_trap)
 
   formula = Homebrew.args.resolved_formulae.first
+  formula.extend(Debrew::Formula) if Homebrew.args.debug?
   formula.run_post_install
 rescue Exception => e # rubocop:disable Lint/RescueException
   error_pipe.puts e.to_json
diff --git a/Library/Homebrew/test.rb b/Library/Homebrew/test.rb
index 838556e17f..c4b6403e86 100644
--- a/Library/Homebrew/test.rb
+++ b/Library/Homebrew/test.rb
@@ -9,10 +9,20 @@ require "debrew"
 require "formula_assertions"
 require "fcntl"
 require "socket"
+require "cli/parser"
+
+def test_args
+  Homebrew::CLI::Parser.new do
+    switch :force
+    switch :verbose
+    switch :debug
+  end
+end
 
 TEST_TIMEOUT_SECONDS = 5 * 60
 
 begin
+  test_args.parse
   error_pipe = UNIXSocket.open(ENV["HOMEBREW_ERROR_PIPE"], &:recv_io)
   error_pipe.fcntl(Fcntl::F_SETFD, Fcntl::FD_CLOEXEC)
 
@@ -21,9 +31,9 @@ begin
 
   trap("INT", old_trap)
 
-  formula = ARGV.resolved_formulae.first
+  formula = Homebrew.args.resolved_formulae.first
   formula.extend(Homebrew::Assertions)
-  formula.extend(Debrew::Formula) if ARGV.debug?
+  formula.extend(Debrew::Formula) if Homebrew.args.debug?
 
   # tests can also return false to indicate failure
   Timeout.timeout TEST_TIMEOUT_SECONDS do
diff --git a/Library/Homebrew/test/ARGV_spec.rb b/Library/Homebrew/test/ARGV_spec.rb
index b8ccd4d831..1fa852f60e 100644
--- a/Library/Homebrew/test/ARGV_spec.rb
+++ b/Library/Homebrew/test/ARGV_spec.rb
@@ -47,7 +47,7 @@ describe HomebrewArgvExtension do
     let(:argv) { ["--foo", "-vds", "a", "b", "cdefg"] }
 
     it "returns an array of option arguments" do
-      expect(subject.options_only).to eq ["--foo", "-vds"]
+      expect(subject.send("options_only")).to eq ["--foo", "-vds"]
     end
   end
 
@@ -87,18 +87,18 @@ describe HomebrewArgvExtension do
     let(:argv) { ["--foo", "-bq", "--bar"] }
 
     it "returns true if the given string is a flag" do
-      expect(subject.flag?("--foo")).to eq true
-      expect(subject.flag?("--bar")).to eq true
+      expect(subject.send("flag?", "--foo")).to eq true
+      expect(subject.send("flag?", "--bar")).to eq true
     end
 
     it "returns true if there is a switch with the same initial character" do
-      expect(subject.flag?("--baz")).to eq true
-      expect(subject.flag?("--qux")).to eq true
+      expect(subject.send("flag?", "--baz")).to eq true
+      expect(subject.send("flag?", "--qux")).to eq true
     end
 
     it "returns false if there is no matching flag" do
-      expect(subject.flag?("--frotz")).to eq false
-      expect(subject.flag?("--debug")).to eq false
+      expect(subject.send("flag?", "--frotz")).to eq false
+      expect(subject.send("flag?", "--debug")).to eq false
     end
   end