Audit correct uses_from_macos usage with RuboCop

- This builds on @jonchang's work that started in #6265.
- We now use `uses_from_macos` to declare dependencies that are implicit
  on macOS because they ship with macOS, but they're needed on Linux. We
  have to be sure that the dependencies people specify as
  `uses_from_macos` are actually shipped with macOS. So, we maintain a
  safelist of those dependencies and check against it.
- Also add more legitimate `uses_from_macos` dependencies to the list.
- This is runnable with `brew audit --only-cops=FormulaAudit/UsesFromMacos`.
- It produces different number of failures on macOS vs. Linux, because
  apparently we've not synced Homebrew/linuxbrew-core upstream thoroughly
  enough yet.
- Originally this was designed as a `--strict` audit, but we flipped it
  to be a normal audit because - to quote Mike - this is "sufficiently
  robust" now.

Library/Homebrew/rubocops.rb

@@ -18,5 +18,6 @@ require "rubocops/options"
 require "rubocops/urls"
 require "rubocops/lines"
 require "rubocops/class"
+require "rubocops/uses_from_macos"
 
 require "rubocops/rubocop-cask"

Library/Homebrew/rubocops/uses_from_macos.rb

@@ -0,0 +1,52 @@
+# frozen_string_literal: true
+
+require "rubocops/extend/formula"
+
+module RuboCop
+  module Cop
+    module FormulaAudit
+      # This cop audits `uses_from_macos` dependencies in formulae
+      class UsesFromMacos < FormulaCop
+        ALLOWED_USES_FROM_MACOS_DEPS = %w[
+          bison
+          bzip2
+          curl
+          expat
+          expect
+          flex
+          groff
+          libffi
+          libxml2
+          libxslt
+          ncurses
+          m4
+          perl
+          php
+          python@2
+          ruby
+          sqlite
+          texinfo
+          unzip
+          vim
+          xz
+          zlib
+          zsh
+        ].freeze
+
+        def audit_formula(_node, _class_node, _parent_class_node, body_node)
+          find_method_with_args(body_node, :uses_from_macos, /^"(.+)"/).each do |method|
+            dep = if parameters(method).first.class == RuboCop::AST::StrNode
+              parameters(method).first
+            elsif parameters(method).first.class == RuboCop::AST::HashNode
+              parameters(method).first.keys.first
+            end
+
+            next if ALLOWED_USES_FROM_MACOS_DEPS.include?(string_content(dep))
+
+            problem "`uses_from_macos` should only be used for macOS dependencies, not #{string_content(dep)}."
+          end
+        end
+      end
+    end
+  end
+end

Library/Homebrew/test/.rubocop_todo.yml

@@ -48,6 +48,7 @@ RSpec/FilePath:
     - 'rubocops/options_spec.rb'
     - 'rubocops/patches_spec.rb'
     - 'rubocops/text_spec.rb'
+    - 'rubocops/uses_from_macos_spec.rb'
     - 'search_spec.rb'
     - 'string_spec.rb'
     - 'system_command_result_spec.rb'

Library/Homebrew/test/rubocops/uses_from_macos_spec.rb

@@ -0,0 +1,19 @@
+# frozen_string_literal: true
+
+require "rubocops/uses_from_macos"
+
+describe RuboCop::Cop::FormulaAudit::UsesFromMacos do
+  subject(:cop) { described_class.new }
+
+  it "when auditing uses_from_macos dependencies" do
+    expect_offense(<<~RUBY)
+      class Foo < Formula
+        url "https://brew.sh/foo-1.0.tgz"
+        homepage "https://brew.sh"
+
+        uses_from_macos "postgresql"
+        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `uses_from_macos` should only be used for macOS dependencies, not postgresql.
+      end
+    RUBY
+  end
+end