fix up builders to properly use variable overrides

lib/rscons/builders/cfile.rb

@@ -32,7 +32,7 @@ module Rscons
           else
             raise "Unknown source file #{sources.first.inspect} for CFile builder"
           end
-        command = env.build_command(env["#{cmd}_CMD"], vars)
+        command = env.build_command("${#{cmd}_CMD}", vars)
         standard_build("#{cmd} #{target}", target, command, sources, env, cache)
       end
     end

lib/rscons/builders/disassemble.rb

@@ -12,7 +12,7 @@ module Rscons
 
       def run(target, sources, cache, env, vars)
         vars = vars.merge("_SOURCES" => sources)
-        command = env.build_command(env["DISASM_CMD"], vars)
+        command = env.build_command("${DISASM_CMD}", vars)
         unless cache.up_to_date?(target, command, sources, env)
           cache.mkdir_p(File.dirname(target))
           return false unless env.execute("Disassemble #{target}", command, options: {out: target})

lib/rscons/builders/library.rb

@@ -13,13 +13,13 @@ module Rscons
 
       def run(target, sources, cache, env, vars)
         # build sources to linkable objects
-        objects = env.build_sources(sources, [env['OBJSUFFIX'], env['LIBSUFFIX']].flatten, cache, vars)
+        objects = env.build_sources(sources, env.expand_varref(["${OBJSUFFIX}", "${LIBSUFFIX}"], vars).flatten, cache, vars)
         if objects
           vars = vars.merge({
             '_TARGET' => target,
             '_SOURCES' => objects,
           })
-          command = env.build_command(env['ARCMD'], vars)
+          command = env.build_command("${ARCMD}", vars)
           standard_build("AR #{target}", target, command, objects, env, cache)
         end
       end

lib/rscons/builders/object.rb

@@ -58,11 +58,11 @@ module Rscons
           '_DEPFILE' => Rscons.set_suffix(target, '.mf'),
         })
         com_prefix = KNOWN_SUFFIXES.find do |compiler, suffix_var|
-          sources.first.end_with?(*env[suffix_var])
+          sources.first.end_with?(*env.expand_varref("${#{suffix_var}}"))
         end.tap do |v|
           v.nil? and raise "Error: unknown input file type: #{sources.first.inspect}"
         end.first
-        command = env.build_command(env["#{com_prefix}CMD"], vars)
+        command = env.build_command("${#{com_prefix}CMD}", vars)
         unless cache.up_to_date?(target, command, sources, env)
           cache.mkdir_p(File.dirname(target))
           FileUtils.rm_f(target)

lib/rscons/builders/preprocess.rb

@@ -9,15 +9,15 @@ module Rscons
       end
 
       def run(target, sources, cache, env, vars)
-        pp_cc = if sources.find {|s| s.end_with?(*env["CXXSUFFIX"])}
+        pp_cc = if sources.find {|s| s.end_with?(*env.expand_varref("${CXXSUFFIX}", vars))}
-                  env["CXX"]
+                  "${CXX}"
                 else
-                  env["CC"]
+                  "${CC}"
                 end
         vars = vars.merge("_PREPROCESS_CC" => pp_cc,
                           "_TARGET" => target,
                           "_SOURCES" => sources)
-        command = env.build_command(env["CPP_CMD"], vars)
+        command = env.build_command("${CPP_CMD}", vars)
         standard_build("Preprocess #{target}", target, command, sources, env, cache)
       end
     end

lib/rscons/builders/program.rb

@@ -17,23 +17,24 @@ module Rscons
 
       def run(target, sources, cache, env, vars)
         # build sources to linkable objects
-        objects = env.build_sources(sources, [env['OBJSUFFIX'], env['LIBSUFFIX']].flatten, cache, vars)
+        objects = env.build_sources(sources, env.expand_varref(["${OBJSUFFIX}", "${LIBSUFFIX}"], vars).flatten, cache, vars)
         return false unless objects
-        ld = if env["LD"]
+        ld = env.expand_varref("${LD}", vars)
-               env["LD"]
+        ld = if ld != ""
-             elsif sources.find {|s| s.end_with?(*env["DSUFFIX"])}
+               ld
-               env["DC"]
+             elsif sources.find {|s| s.end_with?(*env.expand_varref("${DSUFFIX}", vars))}
-             elsif sources.find {|s| s.end_with?(*env["CXXSUFFIX"])}
+               "${DC}"
-               env["CXX"]
+             elsif sources.find {|s| s.end_with?(*env.expand_varref("${CXXSUFFIX}", vars))}
+               "${CXX}"
              else
-               env["CC"]
+               "${CC}"
              end
         vars = vars.merge({
           '_TARGET' => target,
           '_SOURCES' => objects,
           'LD' => ld,
         })
-        command = env.build_command(env['LDCMD'], vars)
+        command = env.build_command("${LDCMD}", vars)
         standard_build("LD #{target}", target, command, objects, env, cache)
       end
     end

lib/rscons/varset.rb

@@ -83,7 +83,7 @@ module Rscons
         if varref =~ /^(.*)\$\{([^}]+)\}(.*)$/
           prefix, varname, suffix = $1, $2, $3
           varval = expand_varref(self[varname])
-          if varval.is_a?(String)
+          if varval.is_a?(String) or varval.nil?
             expand_varref("#{prefix}#{varval}#{suffix}")
           elsif varval.is_a?(Array)
             varval.map {|vv| expand_varref("#{prefix}#{vv}#{suffix}")}.flatten

spec/rscons/environment_spec.rb

@@ -223,6 +223,7 @@ module Rscons
         env["path"] = ["dir1", "dir2"]
         env["flags"] = ["-x", "-y", "${specialflag}"]
         env["specialflag"] = "-z"
+        env["foo"] = {}
         env.expand_varref(["-p${path}", "${flags}"]).should == ["-pdir1", "-pdir2", "-x", "-y", "-z"]
         env.expand_varref("foo").should == "foo"
         expect {env.expand_varref("${foo}")}.to raise_error /expand.a.variable.reference/

spec/rscons/varset_spec.rb

@@ -125,7 +125,8 @@ module Rscons
                      "CC" => "gcc",
                      "CPPPATH" => ["dir1", "dir2"],
                      "compiler" => "${CC}",
-                     "cmd" => ["${CC}", "-c", "${CFLAGS}", "-I${CPPPATH}"])
+                     "cmd" => ["${CC}", "-c", "${CFLAGS}", "-I${CPPPATH}"],
+                     "hash" => {})
       it "expands to the string itself if the string is not a variable reference" do
         v.expand_varref("CC").should == "CC"
         v.expand_varref("CPPPATH").should == "CPPPATH"
@@ -151,8 +152,11 @@ module Rscons
           "cflag: -O2, cpppath: dir2, compiler: gcc",
         ]
       end
-      it "raises an error when a variable reference refers to a non-existent variable" do
+      it "returns an empty string when a variable reference refers to a non-existent variable" do
-        expect { v.expand_varref("${not_here}") }.to raise_error /I do not know how to expand a variable reference to a NilClass/
+        expect(v.expand_varref("${not_here}")).to eq("")
+      end
+      it "raises an error when a variable reference refers to an unhandled type" do
+        expect { v.expand_varref("${hash}") }.to raise_error /I do not know how to expand a variable reference to a Hash/
       end
     end
   end