Requirement: callers are responsible for invoking #satisfied?

This hack was necessary since requirements were not checked again
in the forked build process, but now they are, and calling it again
after the build environment has been set up can produce incorrect
results. In fact, if it happens to return false the second time,
the env modification will be skipped altogether.

Library/Homebrew/requirement.rb

@@ -43,8 +43,10 @@ class Requirement
 
   # Overriding #modify_build_environment is deprecated.
   # Pass a block to the the env DSL method instead.
+  # Note: #satisfied? should be called before invoking this method
+  # as the env modifications may depend on its side effects.
   def modify_build_environment
-    satisfied? and env.modify_build_environment(self)
+    env.modify_build_environment(self)
   end
 
   def env

Library/Homebrew/test/test_requirement.rb

@@ -81,6 +81,7 @@ class RequirementTests < Test::Unit::TestCase
     ENV.expects(:userpaths!)
     ENV.expects(:append).with("PATH", which_path.parent, ":")
 
+    req.satisfied?
     req.modify_build_environment
   end