Provide interface and individual namespaces for brew CLI commands

Library/Homebrew/abstract_command.rb

@@ -0,0 +1,51 @@
+# typed: strong
+# frozen_string_literal: true
+
+module Homebrew
+  # Subclass this to implement a `brew` command. This is preferred to declaring a named function in the `Homebrew`
+  # module, because:
+  # - Each Command lives in an isolated namespace.
+  # - Each Command implements a defined interface.
+  # - `args` is available as an ivar, and thus does not need to be passed as an argument to helper methods.
+  #
+  # To subclass, implement a `run` method and provide a `cmd_args` block to document the command and its allowed args.
+  # To generate method signatures for command args, run `brew typecheck --update`.
+  class AbstractCommand
+    extend T::Helpers
+
+    abstract!
+
+    class << self
+      sig { returns(T.nilable(CLI::Parser)) }
+      attr_reader :parser
+
+      sig { returns(String) }
+      def command_name = T.must(name).split("::").fetch(-1).downcase
+
+      # @return the AbstractCommand subclass associated with the brew CLI command name.
+      sig { params(name: String).returns(T.nilable(T.class_of(AbstractCommand))) }
+      def command(name) = subclasses.find { _1.command_name == name }
+
+      private
+
+      sig { params(block: T.proc.bind(CLI::Parser).void).void }
+      def cmd_args(&block)
+        @parser = T.let(CLI::Parser.new(&block), T.nilable(CLI::Parser))
+      end
+    end
+
+    sig { returns(CLI::Args) }
+    attr_reader :args
+
+    sig { params(argv: T::Array[String]).void }
+    def initialize(argv = ARGV.freeze)
+      parser = self.class.parser
+      raise "Commands must include a `cmd_args` block" if parser.nil?
+
+      @args = T.let(parser.parse(argv), CLI::Args)
+    end
+
+    sig { abstract.void }
+    def run; end
+  end
+end

Library/Homebrew/brew.rb

@@ -59,6 +59,7 @@
 
   ENV["PATH"] = path.to_s
 
+  require "abstract_command"
   require "commands"
   require "settings"
 
@@ -83,7 +84,12 @@
   end
 
   if internal_cmd || Commands.external_ruby_v2_cmd_path(cmd)
-    Homebrew.send Commands.method_name(cmd)
+    cmd_class = Homebrew::AbstractCommand.command(T.must(cmd))
+    if cmd_class
+      cmd_class.new.run
+    else
+      Homebrew.public_send Commands.method_name(cmd)
+    end
   elsif (path = Commands.external_ruby_cmd_path(cmd))
     require?(path)
     exit Homebrew.failed? ? 1 : 0

Library/Homebrew/cli/args.rbi

@@ -0,0 +1,19 @@
+# typed: strict
+
+# This file contains global args as defined in `Homebrew::CLI::Parser.global_options`
+# `Command`-specific args are defined in the commands themselves, with type signatures
+# generated by the `Tapioca::Compilers::Args` compiler.
+
+class Homebrew::CLI::Args
+  sig { returns(T::Boolean) }
+  def debug?; end
+
+  sig { returns(T::Boolean) }
+  def help?; end
+
+  sig { returns(T::Boolean) }
+  def quiet?; end
+
+  sig { returns(T::Boolean) }
+  def verbose?; end
+end

Library/Homebrew/cli/parser.rb

@@ -248,12 +248,14 @@ def conflicts(*options)
         @conflicts << options.map { |option| option_to_name(option) }
       end
 
-      def option_to_name(option)
+      def self.option_to_name(option)
         option.sub(/\A--?(\[no-\])?/, "")
               .tr("-", "_")
               .delete("=")
       end
 
+      def option_to_name(option) = self.class.option_to_name(option)
+
       def name_to_option(name)
         if name.length == 1
           "-#{name}"