improve debuggability of cache.up_to_date? - close #46

spec/build_tests_spec.rb

@@ -91,6 +91,7 @@ end
 $LOAD_PATH.unshift(#{@owd.inspect} + "/lib")
 # force color off
 ENV["TERM"] = nil
+#{options[:ruby_setup_code]}
 EOF
     end
     stdout, stderr, status = nil, nil, nil
@@ -1273,6 +1274,69 @@ EOF
       expect(result.stderr).to eq ""
       expect(result.stdout).to eq ""
     end
+
+    context "debugging" do
+      it "prints a message when the target does not exist" do
+        test_dir("simple")
+        result = run_test(rsconsfile: "cache_debugging.rb")
+        expect(result.stdout).to match /Target foo\.o needs rebuilding because it does not exist on disk/
+      end
+
+      it "prints a message when there is no cached build information for the target" do
+        test_dir("simple")
+        FileUtils.touch("foo.o")
+        result = run_test(rsconsfile: "cache_debugging.rb")
+        expect(result.stdout).to match /Target foo\.o needs rebuilding because there is no cached build information for it/
+      end
+
+      it "prints a message when the target file has changed on disk" do
+        test_dir("simple")
+        result = run_test(rsconsfile: "cache_debugging.rb")
+        File.open("foo.o", "wb") {|fh| fh.puts "hi"}
+        result = run_test(rsconsfile: "cache_debugging.rb")
+        expect(result.stdout).to match /Target foo\.o needs rebuilding because it has been changed on disk since being built last/
+      end
+
+      it "prints a message when the command has changed" do
+        test_dir("simple")
+        result = run_test(rsconsfile: "cache_debugging.rb")
+        result = run_test(rsconsfile: "cache_debugging.rb", ruby_setup_code: %[ENV["command_change"] = "yes"])
+        expect(result.stdout).to match /Target foo\.o needs rebuilding because the command used to build it has changed/
+      end
+
+      it "prints a message when strict_deps is in use and the set of dependencies does not match" do
+        test_dir("simple")
+        result = run_test(rsconsfile: "cache_debugging.rb", ruby_setup_code: %[ENV["strict_deps1"] = "yes"])
+        result = run_test(rsconsfile: "cache_debugging.rb", ruby_setup_code: %[ENV["strict_deps2"] = "yes"])
+        expect(result.stdout).to match /Target foo\.o needs rebuilding because the :strict_deps option is given and the set of dependencies does not match the previous set of dependencies/
+      end
+
+      it "prints a message when there is a new dependency" do
+        test_dir("simple")
+        result = run_test(rsconsfile: "cache_debugging.rb")
+        result = run_test(rsconsfile: "cache_debugging.rb", ruby_setup_code: %[ENV["new_dep"] = "yes"])
+        expect(result.stdout).to match /Target foo\.o needs rebuilding because there are new dependencies/
+      end
+
+      it "prints a message when there is a new user-specified dependency" do
+        test_dir("simple")
+        result = run_test(rsconsfile: "cache_debugging.rb")
+        result = run_test(rsconsfile: "cache_debugging.rb", ruby_setup_code: %[ENV["new_user_dep"] = "yes"])
+        expect(result.stdout).to match /Target foo\.o needs rebuilding because the set of user-specified dependency files has changed/
+      end
+
+      it "prints a message when a dependency file has changed" do
+        test_dir("simple")
+        result = run_test(rsconsfile: "cache_debugging.rb")
+        f = File.read("simple.c", mode: "rb")
+        f += "\n"
+        File.open("simple.c", "wb") do |fh|
+          fh.write(f)
+        end
+        result = run_test(rsconsfile: "cache_debugging.rb")
+        expect(result.stdout).to match /Target foo\.o needs rebuilding because dependency file simple\.c has changed/
+      end
+    end
   end
 
   context "Object builder" do