From b5363025a675d0b8f661333a87b31a817a79301d Mon Sep 17 00:00:00 2001
From: Markus Reiter <me@reitermark.us>
Date: Fri, 14 Aug 2020 02:26:29 +0200
Subject: [PATCH] Refactor and document `BuildEnvironment`.

---
 Library/Homebrew/build_environment.rb | 41 ++++++++++++++-------------
 Library/Homebrew/cmd/--env.rb         |  4 +--
 Library/Homebrew/exceptions.rb        |  2 +-
 Library/Homebrew/formula.rb           |  2 +-
 4 files changed, 26 insertions(+), 23 deletions(-)

diff --git a/Library/Homebrew/build_environment.rb b/Library/Homebrew/build_environment.rb
index ad0508d22a..ed6f319730 100644
--- a/Library/Homebrew/build_environment.rb
+++ b/Library/Homebrew/build_environment.rb
@@ -1,5 +1,8 @@
 # frozen_string_literal: true
 
+# Settings for the build environment.
+#
+# @api private
 class BuildEnvironment
   def initialize(*settings)
     @settings = Set.new(*settings)
@@ -23,35 +26,35 @@ class BuildEnvironment
     @settings.include? :userpaths
   end
 
+  # DSL for specifying build environment settings.
   module DSL
     def env(*settings)
       @env ||= BuildEnvironment.new
       @env.merge(settings)
     end
   end
-end
 
-module Homebrew
-  module_function
+  KEYS = %w[
+    CC CXX LD OBJC OBJCXX
+    HOMEBREW_CC HOMEBREW_CXX
+    CFLAGS CXXFLAGS CPPFLAGS LDFLAGS SDKROOT MAKEFLAGS
+    CMAKE_PREFIX_PATH CMAKE_INCLUDE_PATH CMAKE_LIBRARY_PATH CMAKE_FRAMEWORK_PATH
+    MACOSX_DEPLOYMENT_TARGET PKG_CONFIG_PATH PKG_CONFIG_LIBDIR
+    HOMEBREW_DEBUG HOMEBREW_MAKE_JOBS HOMEBREW_VERBOSE
+    HOMEBREW_SVN HOMEBREW_GIT
+    HOMEBREW_SDKROOT
+    MAKE GIT CPP
+    ACLOCAL_PATH PATH CPATH
+    LD_LIBRARY_PATH LD_RUN_PATH LD_PRELOAD LIBRARY_PATH
+  ].freeze
+  private_constant :KEYS
 
-  def build_env_keys(env)
-    %w[
-      CC CXX LD OBJC OBJCXX
-      HOMEBREW_CC HOMEBREW_CXX
-      CFLAGS CXXFLAGS CPPFLAGS LDFLAGS SDKROOT MAKEFLAGS
-      CMAKE_PREFIX_PATH CMAKE_INCLUDE_PATH CMAKE_LIBRARY_PATH CMAKE_FRAMEWORK_PATH
-      MACOSX_DEPLOYMENT_TARGET PKG_CONFIG_PATH PKG_CONFIG_LIBDIR
-      HOMEBREW_DEBUG HOMEBREW_MAKE_JOBS HOMEBREW_VERBOSE
-      HOMEBREW_SVN HOMEBREW_GIT
-      HOMEBREW_SDKROOT
-      MAKE GIT CPP
-      ACLOCAL_PATH PATH CPATH
-      LD_LIBRARY_PATH LD_RUN_PATH LD_PRELOAD LIBRARY_PATH
-    ].select { |key| env.key?(key) }
+  def self.keys(env)
+    KEYS & env.keys
   end
 
-  def dump_build_env(env, f = $stdout)
-    keys = build_env_keys(env)
+  def self.dump(env, f = $stdout)
+    keys = self.keys(env)
     keys -= %w[CC CXX OBJC OBJCXX] if env["CC"] == env["HOMEBREW_CC"]
 
     keys.each do |key|
diff --git a/Library/Homebrew/cmd/--env.rb b/Library/Homebrew/cmd/--env.rb
index 7586631754..80319d3053 100644
--- a/Library/Homebrew/cmd/--env.rb
+++ b/Library/Homebrew/cmd/--env.rb
@@ -43,9 +43,9 @@ module Homebrew
       Utils::Shell.from_path(args.shell)
     end
 
-    env_keys = build_env_keys(ENV)
+    env_keys = BuildEnvironment.keys(ENV)
     if shell.nil?
-      dump_build_env ENV
+      BuildEnvironment.dump ENV
     else
       env_keys.each do |key|
         puts Utils::Shell.export_value(key, ENV[key], shell)
diff --git a/Library/Homebrew/exceptions.rb b/Library/Homebrew/exceptions.rb
index f3fb93c6f0..7c6c862ad8 100644
--- a/Library/Homebrew/exceptions.rb
+++ b/Library/Homebrew/exceptions.rb
@@ -369,7 +369,7 @@ class BuildError < RuntimeError
       ohai "Configuration"
       SystemConfig.dump_verbose_config
       ohai "ENV"
-      Homebrew.dump_build_env(env)
+      BuildEnvironment.dump env
       puts
       onoe "#{formula.full_name} #{formula.version} did not build"
       unless (logs = Dir["#{formula.logs}/*"]).empty?
diff --git a/Library/Homebrew/formula.rb b/Library/Homebrew/formula.rb
index 5849baaa20..ddc6ec671a 100644
--- a/Library/Homebrew/formula.rb
+++ b/Library/Homebrew/formula.rb
@@ -2020,7 +2020,7 @@ class Formula
 
         SystemConfig.dump_verbose_config(log)
         log.puts
-        Homebrew.dump_build_env(env, log)
+        BuildEnvironment.dump env, log
 
         raise BuildError.new(self, cmd, args, env)
       end