Improving coding style

* Refactored RPMLayerAnalyzer for better code reuse
* Updated differs.go to initialize Analyzers map with constant keys
* moved layerAnalyzers vector from root.go to differs.go

Signed-off-by: David Cassany <dcassany@suse.de>

Author: davidcassany

cmd/root.go

@@ -59,8 +59,6 @@ const (
 	RemotePrefix = "remote://"
 )
 
-var layerAnalyzers = [...]string{"layer", "aptlayer", "rpmlayer"}
-
 var RootCmd = &cobra.Command{
 	Use:   "container-diff",
 	Short: "container-diff is a tool for analyzing and comparing container images",
@@ -270,7 +268,7 @@ func getExtractPathForName(name string) (string, error) {
 
 func includeLayers() bool {
 	for _, t := range types {
-		for _, a := range layerAnalyzers {
+		for _, a := range differs.LayerAnalyzers {
 			if t == a {
 				return true
 			}

differs/differs.go

@@ -24,6 +24,17 @@ import (
 	"github.com/sirupsen/logrus"
 )
 
+const historyAnalyzer = "history"
+const metadataAnalyzer = "metadata"
+const fileAnalyzer = "file"
+const layerAnalyzer = "layer"
+const aptAnalyzer = "apt"
+const aptLayerAnalyzer = "aptlayer"
+const rpmAnalyzer = "rpm"
+const rpmLayerAnalyzer = "rpmlayer"
+const pipAnalyzer = "pip"
+const nodeAnalyzer = "node"
+
 type DiffRequest struct {
 	Image1    pkgutil.Image
 	Image2    pkgutil.Image
@@ -42,18 +53,20 @@ type Analyzer interface {
 }
 
 var Analyzers = map[string]Analyzer{
-	"history":  HistoryAnalyzer{},
-	"metadata": MetadataAnalyzer{},
-	"file":     FileAnalyzer{},
-	"layer":    FileLayerAnalyzer{},
-	"apt":      AptAnalyzer{},
-	"aptlayer": AptLayerAnalyzer{},
-	"rpm":      RPMAnalyzer{},
-	"rpmlayer": RPMLayerAnalyzer{},
-	"pip":      PipAnalyzer{},
-	"node":     NodeAnalyzer{},
+	historyAnalyzer:  HistoryAnalyzer{},
+	metadataAnalyzer: MetadataAnalyzer{},
+	fileAnalyzer:     FileAnalyzer{},
+	layerAnalyzer:    FileLayerAnalyzer{},
+	aptAnalyzer:      AptAnalyzer{},
+	aptLayerAnalyzer: AptLayerAnalyzer{},
+	rpmAnalyzer:      RPMAnalyzer{},
+	rpmLayerAnalyzer: RPMLayerAnalyzer{},
+	pipAnalyzer:      PipAnalyzer{},
+	nodeAnalyzer:     NodeAnalyzer{},
 }
 
+var LayerAnalyzers = [...]string{layerAnalyzer, aptLayerAnalyzer, rpmLayerAnalyzer}
+
 func (req DiffRequest) GetDiff() (map[string]util.Result, error) {
 	img1 := req.Image1
 	img2 := req.Image2

differs/rpm_diff.go

@@ -102,7 +102,7 @@ func (a RPMAnalyzer) getPackages(image pkgutil.Image) (map[string]util.PackageIn
 
 	packages, err := rpmDataFromImageFS(image)
 	if err != nil {
-		logrus.Info("Running RPM binary from image in a container")
+		logrus.Info("Couldn't retrieve RPM data from extracted filesystem; running query in container")
 		return rpmDataFromContainer(image.Image)
 	}
 	return packages, err
@@ -111,30 +111,22 @@ func (a RPMAnalyzer) getPackages(image pkgutil.Image) (map[string]util.PackageIn
 // rpmDataFromImageFS runs a local rpm binary, if any, to query the image
 // rpmdb and returns a map of installed packages.
 func rpmDataFromImageFS(image pkgutil.Image) (map[string]util.PackageInfo, error) {
-	packages := make(map[string]util.PackageInfo)
-	// Check there is an executable rpm tool in host
-	if err := exec.Command("rpm", "--version").Run(); err != nil {
-		logrus.Warn("No RPM binary in host")
-		return packages, err
-	}
-	dbPath, err := rpmDBPath(image.FSPath)
+	dbPath, err := rpmEnvCheck(image.FSPath)
 	if err != nil {
 		logrus.Warnf("Couldn't find RPM database: %s", err.Error())
-		return packages, err
-	}
-	cmdArgs := append([]string{"--root", image.FSPath, "--dbpath", dbPath}, rpmCmd[1:]...)
-	out, err := exec.Command(rpmCmd[0], cmdArgs...).Output()
-	if err != nil {
-		logrus.Warnf("RPM call failed: %s", err.Error())
-		return packages, err
+		return nil, err
 	}
-	output := strings.Split(string(out), "\n")
-	return parsePackageData(output)
+	return rpmDataFromFS(image.FSPath, dbPath)
 }
 
-// rpmDBPath tries to get the RPM database path from the /usr/lib/rpm/macros
-// file in the image rootfs.
-func rpmDBPath(rootFSPath string) (string, error) {
+// rpmEnvCheck checks there is an rpm binary in the host and tries to
+// get the RPM database path from the /usr/lib/rpm/macros file in the
+// image rootfs
+func rpmEnvCheck(rootFSPath string) (string, error) {
+	if err := exec.Command("rpm", "--version").Run(); err != nil {
+		logrus.Warn("No RPM binary in host")
+		return "", err
+	}
 	imgMacrosFile, err := os.Open(filepath.Join(rootFSPath, rpmMacros))
 	if err != nil {
 		return "", err
@@ -408,7 +400,7 @@ func (a RPMLayerAnalyzer) getPackages(image pkgutil.Image) ([]map[string]util.Pa
 
 	packages, err := rpmDataFromLayerFS(image)
 	if err != nil {
-		logrus.Info("Running RPM binary from image in a container")
+		logrus.Info("Couldn't retrieve RPM data from extracted filesystem; running query in container")
 		return rpmDataFromLayeredContainers(image.Image)
 	}
 	return packages, err
@@ -418,37 +410,42 @@ func (a RPMLayerAnalyzer) getPackages(image pkgutil.Image) ([]map[string]util.Pa
 // rpmdb and returns an array of maps of installed packages.
 func rpmDataFromLayerFS(image pkgutil.Image) ([]map[string]util.PackageInfo, error) {
 	var packages []map[string]util.PackageInfo
-	// Check there is an executable rpm tool in host
-	if err := exec.Command("rpm", "--version").Run(); err != nil {
-		logrus.Warn("No RPM binary in host")
-		return packages, err
-	}
-	dbPath, err := rpmDBPath(image.FSPath)
+	dbPath, err := rpmEnvCheck(image.FSPath)
 	if err != nil {
 		logrus.Warnf("Couldn't find RPM database: %s", err.Error())
 		return packages, err
 	}
 	for _, layer := range image.Layers {
-		layerPackages := make(map[string]util.PackageInfo)
-		//query only layers that include the rpm database
-		if _, err := os.Stat(filepath.Join(layer.FSPath, dbPath)); err == nil {
-			cmdArgs := append([]string{"--root", layer.FSPath, "--dbpath", dbPath}, rpmCmd[1:]...)
-			out, err := exec.Command(rpmCmd[0], cmdArgs...).Output()
-			if err != nil {
-				logrus.Warnf("RPM call failed: %s", err.Error())
-				return packages, err
-			}
-			layerPackages, err = parsePackageData(strings.Split(string(out), "\n"))
-			if err != nil {
-				return packages, err
-			}
+		layerPackages, err := rpmDataFromFS(layer.FSPath, dbPath)
+		if err != nil {
+			return packages, err
 		}
 		packages = append(packages, layerPackages)
 	}
 
 	return packages, nil
 }
 
+// rpmDataFromFS runs a local rpm binary to query the image
+// rpmdb and returns a map of installed packages.
+func rpmDataFromFS(fsPath string, dbPath string) (map[string]util.PackageInfo, error) {
+	packages := make(map[string]util.PackageInfo)
+	if _, err := os.Stat(filepath.Join(fsPath, dbPath)); err == nil {
+		cmdArgs := append([]string{"--root", fsPath, "--dbpath", dbPath}, rpmCmd[1:]...)
+		out, err := exec.Command(rpmCmd[0], cmdArgs...).Output()
+		if err != nil {
+			logrus.Warnf("RPM call failed: %s", err.Error())
+			return packages, err
+		}
+		output := strings.Split(string(out), "\n")
+		packages, err := parsePackageData(output)
+		if err != nil {
+			return packages, err
+		}
+	}
+	return packages, nil
+}
+
 // rpmDataFromLayeredContainers runs a tmp image in a container for each layer,
 // queries the data of installed rpm packages and returns an array of maps of
 // packages.