Use 'defer' mechanism to close log and project

Currently the main program closes the log files and the
project explicitly. That isn't a problem, but it doesn't
scale well if additional things need to be released. In
order to improve that this patch changes the main prograim
so that it uses the 'defer' mechanism, which will be easier
to use inf later patches that will need to release other
resources.

Change-Id: I033bd3440309de25d6a4ffaad53787a744adfec6
Signed-off-by: Juan Hernandez <[email protected]>

tools/src/ovc/main.go

@@ -33,7 +33,7 @@ type ToolFunc func(project *build.Project) error
 
 // This index contains the mapping from names to tool functions.
 //
-var toolsIndex = map[string]ToolFunc{
+var tools = map[string]ToolFunc{
 	"build":  buildTool,
 	"clean":  cleanTool,
 	"deploy": deployTool,
@@ -47,47 +47,45 @@ func main() {
 		fmt.Fprintf(os.Stderr, "Usage: %s TOOL [ARGS...]\n", filepath.Base(os.Args[0]))
 		os.Exit(1)
 	}
-	toolName := os.Args[1]
+	name := os.Args[1]
 
 	// Find the function that corresponds to the tool name:
-	toolFunc := toolsIndex[toolName]
-	if toolFunc == nil {
-		fmt.Fprintf(os.Stderr, "Can't find tool named '%s'.\n", toolName)
+	tool := tools[name]
+	if tool == nil {
+		fmt.Fprintf(os.Stderr, "Can't find tool named '%s'.\n", name)
 		os.Exit(1)
 	}
 
+	// Run the tool inside a different function, so that we can take
+	// advantage of the 'defer' mechanism:
+	os.Exit(run(name, tool))
+}
+
+func run(name string, tool ToolFunc) int {
 	// Open the log:
-	log.Open(toolName)
+	log.Open(name)
 	log.Info("Log file is '%s'", log.Path())
+	defer log.Close()
 
 	// Load the project:
 	path, _ := filepath.Abs("project.conf")
 	log.Info("Loading project file '%s'", path)
 	project, err := build.LoadProject(path)
 	if err != nil {
 		log.Error("%s", err)
-		os.Exit(1)
+		return 1
 	}
+	defer project.Close()
 
-	// Call the tool function, and close the project regardless of
-	// the result:
-	log.Debug("Running tool '%s'", toolName)
-	err = toolFunc(project)
-	project.Close()
-
-	// Report the result:
-	var code int
+	// Call the tool function:
+	log.Debug("Running tool '%s'", name)
+	err = tool(project)
 	if err != nil {
 		log.Error("%s", err)
 		log.Error("Tool failed, check log file '%s' for details", log.Path())
-		code = 1
+		return 1
 	} else {
 		log.Info("Tool finished successfully")
-		code = 0
+		return 0
 	}
-	log.Debug("Exit code is %d", code)
-
-	// Close the log and exit:
-	log.Close()
-	os.Exit(code)
 }