Write Cache to disk if an exception occurs while processing the Environment - fix #4

lib/rscons/environment.rb

@@ -176,29 +176,31 @@ module Rscons
       cache.clear_checksum_cache!
       targets_processed = {}
       unless @targets.empty?
-        process_target = proc do |target|
-          targets_processed[target] ||= begin
-            @targets[target][:sources].each do |src|
-              if @targets.include?(src) and not targets_processed.include?(src)
-                process_target.call(src)
+        begin
+          process_target = proc do |target|
+            targets_processed[target] ||= begin
+              @targets[target][:sources].each do |src|
+                if @targets.include?(src) and not targets_processed.include?(src)
+                  process_target.call(src)
+                end
               end
+              result = run_builder(@targets[target][:builder],
+                                   target,
+                                   @targets[target][:sources],
+                                   cache,
+                                   @targets[target][:vars] || {})
+              unless result
+                raise BuildError.new("Failed to build #{target}")
+              end
+              result
             end
-            result = run_builder(@targets[target][:builder],
-                                 target,
-                                 @targets[target][:sources],
-                                 cache,
-                                 @targets[target][:vars] || {})
-            unless result
-              cache.write
-              raise BuildError.new("Failed to build #{target}")
-            end
-            result
           end
+          @targets.each do |target, target_params|
+            process_target.call(target)
+          end
+        ensure
+          cache.write
         end
-        @targets.each do |target, target_params|
-          process_target.call(target)
-        end
-        cache.write
       end
     end
 

spec/rscons/environment_spec.rb

@@ -176,6 +176,21 @@ module Rscons
 
         expect { env.process }.to raise_error BuildError, /Failed.to.build.main.o/
       end
+
+      it "writes the cache when the Builder raises an exception" do
+        env = Environment.new
+        env.Object("module.o", "module.c")
+
+        cache = "cache"
+        Cache.should_receive(:instance).and_return(cache)
+        cache.should_receive(:clear_checksum_cache!)
+        env.stub(:run_builder) do |builder, target, sources, cache, vars|
+          raise "Ruby exception thrown by builder"
+        end
+        cache.should_receive(:write)
+
+        expect { env.process }.to raise_error RuntimeError, /Ruby exception thrown by builder/
+      end
     end
 
     describe "#clear_targets" do