refactor: use a map instead of a slice

Packages are unique anyways so it makes sense to use a map to avoid having
duplicates.

For compatibility reasons custom json (un)marshallers hide this change from the
end user

cmd/jb/install.go

@@ -34,15 +34,15 @@ func installCommand(dir, jsonnetHome string, uris []string) int {
 	}
 
 	kingpin.FatalIfError(
-		os.MkdirAll(filepath.Join(dir, "vendor", ".tmp"), os.ModePerm),
-		"creating vendor/ folder")
+		os.MkdirAll(filepath.Join(dir, jsonnetHome, ".tmp"), os.ModePerm),
+		"creating vendor folder")
 
 	jsonnetFile, err := jsonnetfile.Load(filepath.Join(dir, jsonnetfile.File))
 	kingpin.FatalIfError(err, "failed to load jsonnetfile")
 
 	for _, u := range uris {
 		d := parseDependency(dir, u)
-		jsonnetFile.Dependencies = append(jsonnetFile.Dependencies, *d)
+		jsonnetFile.Dependencies[d.Name] = *d
 	}
 
 	lockFile, err := jsonnetfile.Load(filepath.Join(dir, jsonnetfile.LockFile))
@@ -50,12 +50,7 @@ func installCommand(dir, jsonnetHome string, uris []string) int {
 		kingpin.FatalIfError(err, "failed to load lockfile")
 	}
 
-	locks := make(map[string]spec.Dependency)
-	for _, d := range lockFile.Dependencies {
-		locks[d.Name] = d
-	}
-
-	locked, err := pkg.Ensure(jsonnetFile, jsonnetHome, locks)
+	locked, err := pkg.Ensure(jsonnetFile, jsonnetHome, lockFile.Dependencies)
 	kingpin.FatalIfError(err, "failed to install packages")
 
 	kingpin.FatalIfError(

pkg/jsonnetfile/jsonnetfile.go

@@ -66,6 +66,9 @@ func Load(filepath string) (spec.JsonnetFile, error) {
 	if err := json.Unmarshal(bytes, &m); err != nil {
 		return m, errors.Wrap(err, "failed to unmarshal file")
 	}
+	if m.Dependencies == nil {
+		m.Dependencies = make(map[string]spec.Dependency)
+	}
 
 	return m, nil
 }

pkg/packages.go

@@ -33,14 +33,15 @@ var (
 	VersionMismatch = errors.New("multiple colliding versions specified")
 )
 
-func Ensure(want spec.JsonnetFile, vendorDir string, locks map[string]spec.Dependency) ([]spec.Dependency, error) {
-	var list []spec.Dependency
+func Ensure(want spec.JsonnetFile, vendorDir string, locks map[string]spec.Dependency) (map[string]spec.Dependency, error) {
+	deps := make(map[string]spec.Dependency)
+
 	for _, d := range want.Dependencies {
 		l, present := locks[d.Name]
 
 		// already locked and the integrity is intact
 		if present && check(l, vendorDir) {
-			list = append(list, l)
+			deps[d.Name] = l
 			continue
 		}
 		expectedSum := d.Sum
@@ -54,12 +55,12 @@ func Ensure(want spec.JsonnetFile, vendorDir string, locks map[string]spec.Depen
 			return nil, errors.Wrap(err, "downloading")
 		}
 		if expectedSum != "" && d.Sum != expectedSum {
-			return fmt.Errorf("checksum mismatch for %s. Expected %s but got %s", d.Name, expectedSum, d.Sum)
+			return nil, fmt.Errorf("checksum mismatch for %s. Expected %s but got %s", d.Name, expectedSum, d.Sum)
 		}
-		list = append(list, *locked)
+		deps[d.Name] = *locked
 	}
 
-	for _, d := range list {
+	for _, d := range deps {
 		f, err := jsonnetfile.Load(filepath.Join(vendorDir, d.Name, jsonnetfile.File))
 		if err != nil {
 			if os.IsNotExist(err) {
@@ -73,10 +74,14 @@ func Ensure(want spec.JsonnetFile, vendorDir string, locks map[string]spec.Depen
 			return nil, err
 		}
 
-		list = append(list, nested...)
+		for _, d := range nested {
+			if _, ok := deps[d.Name]; !ok {
+				deps[d.Name] = d
+			}
+		}
 	}
 
-	return list, nil
+	return deps, nil
 }
 
 func download(d spec.Dependency, vendorDir string) (*spec.Dependency, error) {

spec/spec.go

@@ -14,10 +14,42 @@
 
 package spec
 
+import (
+	"encoding/json"
+	"sort"
+)
+
 type JsonnetFile struct {
+	Dependencies map[string]Dependency
+}
+
+type jsonFile struct {
 	Dependencies []Dependency `json:"dependencies"`
 }
 
+func (jf *JsonnetFile) UnmarshalJSON(data []byte) error {
+	var s jsonFile
+	if err := json.Unmarshal(data, &s); err != nil {
+		return err
+	}
+
+	jf.Dependencies = make(map[string]Dependency)
+	for _, d := range s.Dependencies {
+		jf.Dependencies[d.Name] = d
+	}
+	return nil
+}
+
+func (jf JsonnetFile) MarshalJSON() ([]byte, error) {
+	var s jsonFile
+	for _, d := range jf.Dependencies {
+		s.Dependencies = append(s.Dependencies, d)
+	}
+
+
+	return json.Marshal(s)
+}
+
 type Dependency struct {
 	Name      string `json:"name"`
 	Source    Source `json:"source"`