Refactored LibrariesManager.getLibrariesDir function

This helped to find out 2 places where the `installDir` was unnecessary.

Author: cmaglie

Diff for: arduino/libraries/librariesmanager/install.go

@@ -53,12 +53,9 @@ type LibraryInstallPlan struct {
 // install path, where the library should be installed and the possible library that is already
 // installed on the same folder and it's going to be replaced by the new one.
 func (lm *LibrariesManager) InstallPrerequisiteCheck(name string, version *semver.Version, installLocation libraries.LibraryLocation) (*LibraryInstallPlan, error) {
-	installDir := lm.getLibrariesDir(installLocation)
-	if installDir == nil {
-		if installLocation == libraries.User {
-			return nil, fmt.Errorf(tr("User directory not set"))
-		}
-		return nil, fmt.Errorf(tr("Builtin libraries directory not set"))
+	installDir, err := lm.getLibrariesDir(installLocation)
+	if err != nil {
+		return nil, err
 	}
 
 	libs := lm.FindByReference(&librariesindex.Reference{Name: name}, installLocation)
@@ -130,11 +127,6 @@ func (lm *LibrariesManager) Uninstall(lib *libraries.Library) error {
 
 // InstallZipLib installs a Zip library on the specified path.
 func (lm *LibrariesManager) InstallZipLib(ctx context.Context, archivePath *paths.Path, overwrite bool) error {
-	installDir := lm.getLibrariesDir(libraries.User)
-	if installDir == nil {
-		return fmt.Errorf(tr("User directory not set"))
-	}
-
 	// Clone library in a temporary directory
 	tmpDir, err := paths.MkTempDir("", "")
 	if err != nil {
@@ -207,11 +199,6 @@ func (lm *LibrariesManager) InstallZipLib(ctx context.Context, archivePath *path
 
 // InstallGitLib installs a library hosted on a git repository on the specified path.
 func (lm *LibrariesManager) InstallGitLib(gitURL string, overwrite bool) error {
-	installDir := lm.getLibrariesDir(libraries.User)
-	if installDir == nil {
-		return fmt.Errorf(tr("User directory not set"))
-	}
-
 	gitLibraryName, ref, err := parseGitURL(gitURL)
 	if err != nil {
 		return err

Diff for: arduino/libraries/librariesmanager/librariesmanager.go

@@ -16,6 +16,7 @@
 package librariesmanager
 
 import (
+	"errors"
 	"fmt"
 	"os"
 
@@ -140,13 +141,20 @@ func (lm *LibrariesManager) RescanLibraries() []*status.Status {
 	return statuses
 }
 
-func (lm *LibrariesManager) getLibrariesDir(installLocation libraries.LibraryLocation) *paths.Path {
+func (lm *LibrariesManager) getLibrariesDir(installLocation libraries.LibraryLocation) (*paths.Path, error) {
 	for _, dir := range lm.LibrariesDir {
 		if dir.Location == installLocation {
-			return dir.Path
+			return dir.Path, nil
 		}
 	}
-	return nil
+	switch installLocation {
+	case libraries.User:
+		return nil, errors.New(tr("user directory not set"))
+	case libraries.IDEBuiltIn:
+		return nil, errors.New(tr("built-in libraries directory not set"))
+	default:
+		return nil, fmt.Errorf("libraries directory not set: %s", installLocation.String())
+	}
 }
 
 // LoadLibrariesFromDir loads all libraries in the given directory. Returns