Correct configuration state priority merging

To ensure loaded data from configuration files override default
application values and CLI flags always take precedence over all other
loaded states the overall loading logic has been refactored.
It is achieved by implementing a command initialization function
(called before each command) that merges the configuration states in the
correct order.
Also the loading logic has been moved from `pkg/config/constants.go`
into the `pkg/config/config.go` file to better separate the purpose of
both files.

Epic GH-33
Resolves GH-68

Author: arcticicestudio

cmd/snowsaw/snowsaw.go

@@ -30,7 +30,12 @@ var (
 	// debug indicates if the `debug` flag has been set to enable configure the logging for the debug scope.
 	debug bool
 	// explicitConfigFilePath stores the path to the application configuration file when the `config` flag is specified.
+	// It takes precedence over the default application configuration paths.
 	explicitConfigFilePath string
+	// snowblockBaseDirs stores the comma-separated paths to the snowblock directories when the `basedirs` flag is
+	// specified.
+	// It takes precedence over the path of the application configuration file(s).
+	snowblockBaseDirs []string
 )
 
 // rootCmd is the root command of the application.
@@ -48,7 +53,7 @@ var rootCmd = &cobra.Command{
 // Run is the main application function that adds all child commands to the root command and sets flags appropriately.
 // This is called by `main.main()` and only needs to be run once for the root command.
 func Run() {
-	// Disable verbose errors to provide custom formatted CLI output via application-wide printer.
+	// Disable cobra's verbose errors and replace with custom formatted CLI logger from the `pkg/prt` package.
 	rootCmd.SilenceErrors = true
 
 	// Run the application with the given commands, flags and arguments and exit on any (downstream) error.
@@ -60,35 +65,39 @@ func Run() {
 
 func init() {
 	// Specify the functions to be run before each command gets executed.
-	cobra.OnInitialize(initDebugScope, initConfig, initPrinter)
+	cobra.OnInitialize(initDebugScope, initConfig, initPrinter, mergeConfigValues)
 
 	// Define global application flags.
-	rootCmd.PersistentFlags().StringVar(&explicitConfigFilePath, "config", "", "set the configuration file")
+	rootCmd.PersistentFlags().StringVar(&explicitConfigFilePath, "config", "", "path to the configuration file")
 	rootCmd.PersistentFlags().BoolVar(&debug, "debug", false, "enable debug information output")
+	rootCmd.PersistentFlags().StringSliceVarP(
+		&snowblockBaseDirs, "basedirs", "b", config.AppConfig.Snowblocks.Paths,
+		"comma-separated paths to snowblock base directories")
 
 	// Set the app version information for the automatically generated `version` flag.
 	rootCmd.Version = color.CyanString(config.Version)
 	rootCmd.SetVersionTemplate(`{{printf "%s\n" .Version}}`)
 
 	// Create and register all subcommands.
 	rootCmd.AddCommand(info.NewInfoCmd())
+	rootCmd.AddCommand(bootstrap.NewBootstrapCmd())
 }
 
 // initConfig searches and loads either the default application configuration file paths or the explicit file at the
 // given path specified through the global `config` flag.
 func initConfig() {
 	if explicitConfigFilePath != "" {
-		if err := builder.Load(file.NewFile(explicitConfigFilePath)).Into(&config.AppConfig); err != nil {
-			prt.Errorf("while loading custom application configuration file:\n%v", err)
+		if err := builder.Load(file.NewFile(explicitConfigFilePath)).Into(&config.AppConfig, false); err != nil {
+			prt.Errorf("Failed to load application configuration file: %v", err)
 			os.Exit(1)
 		}
 	} else {
 		b := builder.Load(config.AppConfigPaths...)
 		if len(b.Files) == 0 {
-			prt.Debugf("No configuration files found, using default application configuration.")
+			prt.Debugf("No configuration files found, using application defaults.")
 		}
-		if err := b.Into(&config.AppConfig); err != nil {
-			prt.Errorf("while loading application configuration files:\n%v", err)
+		if err := b.Into(&config.AppConfig, true); err != nil {
+			prt.Errorf("Failed to load application configuration file(s): %v", err)
 			os.Exit(1)
 		}
 	}
@@ -103,13 +112,36 @@ func initDebugScope() {
 
 // setPrinterVerbosityLevel configures the global CLI printer like the verbosity level.
 func initPrinter() {
-	lvl, err := prt.ParseVerbosityLevel(strings.ToUpper(config.AppConfig.LogLevel))
-	if err != nil {
-		prt.Debugf("Error while parsing log level from configuration: %v", err)
-		prt.Debugf("Using default INFO level as fallback")
-		prt.SetVerbosityLevel(prt.InfoVerbosity)
-	} else {
-		prt.Debugf("Using configured logger level: %s", strings.ToUpper(config.AppConfig.LogLevel))
-		prt.SetVerbosityLevel(lvl)
+	// The `debug` flag always takes precedence and overrides the application configuration value.
+	if !debug {
+		lvl, err := prt.ParseVerbosityLevel(strings.ToUpper(config.AppConfig.LogLevel))
+		if err != nil {
+			prt.Debugf("Error while parsing log level from configuration: %v", err)
+			prt.Debugf("Using default INFO level as fallback")
+			prt.SetVerbosityLevel(prt.InfoVerbosity)
+		} else {
+			prt.Debugf("Using configured logger level: %s", strings.ToUpper(config.AppConfig.LogLevel))
+			prt.SetVerbosityLevel(lvl)
+		}
+	}
+}
+
+// mergeConfigValues merges the specified (global) flags and merges the corresponding values with the default
+// application configuration values.
+// Since flags have the highest precedence their value will override application defaults as well as value from
+// loaded application configuration files.
+func mergeConfigValues() {
+	// Use configured or individual snowblock base directories if specified, otherwise fall back to the default directory.
+	if len(config.AppConfig.Snowblocks.BaseDirs) == 0 {
+		config.AppConfig.Snowblocks.BaseDirs = append(
+			config.AppConfig.Snowblocks.BaseDirs, config.DefaultSnowblocksBaseDirectoryName)
+	}
+	if len(snowblockBaseDirs) > 0 {
+		config.AppConfig.Snowblocks.BaseDirs = snowblockBaseDirs
+	}
+
+	// If the logging level has not been specified fall back to the default level.
+	if config.AppConfig.LogLevel == "" {
+		config.AppConfig.LogLevel = config.DefaultLoggingLevel
 	}
 }

magefile.go

@@ -208,7 +208,7 @@ func Test() {
 	mg.SerialDeps(unitTests)
 }
 
-// Test runs all unit tests with enabled race detection.
+// TestCover runs all unit tests with with coverage reports and enabled race detection.
 func TestCover() {
 	mg.SerialDeps(Clean)
 	// Ensure the required directory structure exists, `go test` doesn't create it automatically.

pkg/config/config.go

@@ -13,8 +13,52 @@
 // It provides a file abstraction to de/encode, load and validate YAML and JSON data using the builder design pattern.
 package config
 
+import (
+	"fmt"
+	"os"
+	"path/filepath"
+
+	"github.com/mitchellh/go-homedir"
+
+	"github.com/arcticicestudio/snowsaw/pkg/config/encoder"
+	"github.com/arcticicestudio/snowsaw/pkg/config/source/file"
+)
+
 // Config represents the application-wide configurations.
 type Config struct {
-	// LogLevel is the verbosity level of the application-wide logging behavior.
-	LogLevel string `json:"logLevel"`
+	// LogLevel is the application-wide logging verbosity level.
+	LogLevel string `json:"logLevel" yaml:"logLevel"`
+
+	// Snowblocks are general snowblocks configurations.
+	Snowblocks Snowblocks `json:"snowblocks,flow" yaml:"snowblocks,flow"`
+}
+
+// Snowblocks represents the general snowblocks configurations.
+type Snowblocks struct {
+	// BaseDirs are the paths of the snowblock base directories.
+	BaseDirs []string `json:"baseDirs,flow" yaml:"baseDirs,flow"`
+	// Paths are the paths of the snowblocks directories.
+	Paths []string `json:"paths,flow" yaml:"paths,flow"`
+}
+
+func init() {
+	AppConfigPaths = genConfigPaths()
+}
+
+func genConfigPaths() []*file.File {
+	var files []*file.File
+
+	// Include the user-level dotfile configuration from user's home directory.
+	home, err := homedir.Dir()
+	if err == nil {
+		files = append(files, file.NewFile(filepath.Join(home, fmt.Sprintf(".%s.%s", ProjectName, encoder.ExtensionsYaml))))
+	}
+
+	// A file placed in the current working directory takes precedence over the user-level configuration.
+	pwd, err := os.Getwd()
+	if err == nil {
+		files = append(files, file.NewFile(filepath.Join(pwd, fmt.Sprintf("%s.%s", ProjectName, encoder.ExtensionsYaml))))
+	}
+
+	return files
 }

pkg/config/constants.go

@@ -12,19 +12,22 @@
 package config
 
 import (
-	"fmt"
-	"os"
-	"path/filepath"
-
-	"github.com/mitchellh/go-homedir"
-
-	"github.com/arcticicestudio/snowsaw/pkg/config/encoder"
+	"github.com/arcticicestudio/snowsaw/pkg/api/snowblock"
 	"github.com/arcticicestudio/snowsaw/pkg/config/source/file"
+	"github.com/arcticicestudio/snowsaw/pkg/snowblock/task"
+	"github.com/arcticicestudio/snowsaw/pkg/snowblock/task/link"
 )
 
 const (
+	// DefaultLoggingLevel is the default application-wide level of logging the verbosity.
+	DefaultLoggingLevel = "info"
+
+	// DefaultSnowblocksBaseDirectoryName is the default name of the snowblocks base directory.
+	DefaultSnowblocksBaseDirectoryName = "snowblocks"
+
 	// PackageName is the name of this Go module
 	PackageName = "github.com/arcticicestudio/" + ProjectName
+
 	// ProjectName is the name of the project.
 	ProjectName = "snowsaw"
 )
@@ -42,28 +45,3 @@ var (
 	// Version is the application version.
 	Version = "0.0.0"
 )
-
-func init() {
-	AppConfig = Config{
-		LogLevel: "info",
-	}
-	AppConfigPaths = genConfigPaths()
-}
-
-func genConfigPaths() []*file.File {
-	var files []*file.File
-
-	// Include the user-level dotfile configuration from user's home directory.
-	home, err := homedir.Dir()
-	if err == nil {
-		files = append(files, file.NewFile(filepath.Join(home, fmt.Sprintf(".%s.%s", ProjectName, encoder.ExtensionsYaml))))
-	}
-
-	// A file placed in the current working directory takes precedence over the user-level configuration.
-	pwd, err := os.Getwd()
-	if err == nil {
-		files = append(files, file.NewFile(filepath.Join(pwd, fmt.Sprintf("%s.%s", ProjectName, encoder.ExtensionsYaml))))
-	}
-
-	return files
-}