Pre-build hooks do not respect modified key values for old-style builders

build_tests/build_dir/backward_compatible_build_hooks.rb

@@ -0,0 +1,22 @@
+class MyObject < Rscons::Builder
+  def run(target, sources, cache, env, vars)
+    env.run_builder(env.builders["Object"], target, sources, cache, vars)
+  end
+end
+
+Rscons::Environment.new(echo: :command) do |env|
+  env.add_builder(MyObject.new)
+  env.append('CPPPATH' => Dir['src/**/*/'].sort)
+  env.add_build_hook do |build_op|
+    if build_op[:builder].name == "MyObject" && build_op[:sources].first =~ %r{one\.c}
+      build_op[:vars]["CFLAGS"] << "-O1"
+      build_op[:sources] = ['src/two/two.c']
+    elsif build_op[:builder].name == "MyObject" && build_op[:target] =~ %r{two\.o}
+      new_vars = build_op[:vars].clone
+      new_vars["CFLAGS"] << "-O2"
+      build_op[:vars] = new_vars
+    end
+  end
+  env.MyObject('one.o', 'src/one/one.c')
+  env.MyObject('two.o', 'src/two/two.c')
+end

lib/rscons/environment.rb

@@ -615,7 +615,7 @@ module Rscons
 
       # Call the builder's #run method.
       if builder.method(:run).arity == 5
-        rv = builder.run(target, sources, cache, self, vars)
+        rv = builder.run(*build_operation.values_at(:target, :sources, :cache, :env, :vars))
       else
         rv = builder.run(build_operation)
       end

spec/build_tests_spec.rb

@@ -776,6 +776,18 @@ EOF
       result = run_test(rsconsfile: "bc_produces.rb")
       expect(result.stderr).to eq ""
     end
+
+    it 'supports build hooks to override construction variables' do
+      test_dir("build_dir")
+      result = run_test(rsconsfile: "backward_compatible_build_hooks.rb")
+      expect(result.stderr).to eq ""
+      expect(Set[*lines(result.stdout)]).to eq Set[
+        'gcc -c -o one.o -MMD -MF one.mf -Isrc/one/ -Isrc/two/ -O1 src/two/two.c',
+        'gcc -c -o two.o -MMD -MF two.mf -Isrc/one/ -Isrc/two/ -O2 src/two/two.c'
+      ]
+      expect(File.exists?('one.o')).to be_truthy
+      expect(File.exists?('two.o')).to be_truthy
+    end
   end
 
   context "CFile builder" do