Update lockfile api for package source (#1266)

## Summary
Update lockfile api for package source as suggested in
#1264 (comment)

## How was it tested?
devbox run build
devbox update

Author: LucilleH

internal/devpkg/package.go

@@ -403,7 +403,7 @@ func (p *Package) Versioned() string {
 }
 
 func (p *Package) IsLegacy() bool {
-	return p.isDevboxPackage() && !p.isVersioned() && p.lockfile.Source(p.Raw) == ""
+	return p.isDevboxPackage() && !p.isVersioned() && p.lockfile.Get(p.Raw).GetSource() == ""
 }
 
 func (p *Package) LegacyToVersioned() string {

internal/devpkg/package_test.go

@@ -119,8 +119,8 @@ func (l *lockfile) LegacyNixpkgsPath(pkg string) string {
 	)
 }
 
-func (l *lockfile) Source(pkg string) string {
-	return ""
+func (l *lockfile) Get(pkg string) *lock.Package {
+	return nil
 }
 
 func (l *lockfile) Resolve(pkg string) (*lock.Package, error) {

internal/lock/interfaces.go

@@ -11,8 +11,8 @@ type devboxProject interface {
 }
 
 type Locker interface {
+	Get(string) *Package
 	LegacyNixpkgsPath(string) string
 	ProjectDir() string
 	Resolve(string) (*Package, error)
-	Source(string) string
 }

internal/lock/lockfile.go

@@ -17,10 +17,6 @@ import (
 )
 
 const lockFileVersion = "1"
-const (
-	nixpkgSource       string = "nixpkg"
-	devboxSearchSource string = "devbox-search"
-)
 
 // Lightly inspired by package-lock.json
 type File struct {
@@ -32,27 +28,6 @@ type File struct {
 	Packages map[string]*Package `json:"packages"`
 }
 
-type Package struct {
-	LastModified  string `json:"last_modified,omitempty"`
-	PluginVersion string `json:"plugin_version,omitempty"`
-	Resolved      string `json:"resolved,omitempty"`
-	Source        string `json:"source,omitempty"`
-	Version       string `json:"version,omitempty"`
-	// Systems is keyed by the system name
-	Systems map[string]*SystemInfo `json:"systems,omitempty"`
-}
-
-type SystemInfo struct {
-	// StorePath is the input-addressed path for the nix package in /nix/store
-	// It is the cache key in the Binary Cache Store (cache.nixos.org)
-	// It is of the form <hash>-<name>-<version>
-	// <name> may be different from the canonicalName so we store the full store path.
-	StorePath string `json:"store_path,omitempty"`
-	// CAStorePath is the content-addressed path for the nix package in /nix/store
-	// It is of the form <hash>-<name>-<version>
-	CAStorePath string `json:"ca_store_path,omitempty"`
-}
-
 func GetFile(project devboxProject) (*File, error) {
 	lockFile := &File{
 		devboxProject: project,
@@ -130,12 +105,12 @@ func (l *File) LegacyNixpkgsPath(pkg string) string {
 	)
 }
 
-func (l *File) Source(pkg string) string {
+func (l *File) Get(pkg string) *Package {
 	entry, hasEntry := l.Packages[pkg]
 	if !hasEntry || entry.Resolved == "" {
-		return ""
+		return nil
 	}
-	return entry.Source
+	return entry
 }
 
 // This probably belongs in input.go but can't add it there because it will

internal/lock/package.go

@@ -0,0 +1,37 @@
+// Copyright 2023 Jetpack Technologies Inc and contributors. All rights reserved.
+// Use of this source code is governed by the license in the LICENSE file.
+
+package lock
+
+const (
+	nixpkgSource       string = "nixpkg"
+	devboxSearchSource string = "devbox-search"
+)
+
+type Package struct {
+	LastModified  string `json:"last_modified,omitempty"`
+	PluginVersion string `json:"plugin_version,omitempty"`
+	Resolved      string `json:"resolved,omitempty"`
+	Source        string `json:"source,omitempty"`
+	Version       string `json:"version,omitempty"`
+	// Systems is keyed by the system name
+	Systems map[string]*SystemInfo `json:"systems,omitempty"`
+}
+
+type SystemInfo struct {
+	// StorePath is the input-addressed path for the nix package in /nix/store
+	// It is the cache key in the Binary Cache Store (cache.nixos.org)
+	// It is of the form <hash>-<name>-<version>
+	// <name> may be different from the canonicalName so we store the full store path.
+	StorePath string `json:"store_path,omitempty"`
+	// CAStorePath is the content-addressed path for the nix package in /nix/store
+	// It is of the form <hash>-<name>-<version>
+	CAStorePath string `json:"ca_store_path,omitempty"`
+}
+
+func (p *Package) GetSource() string {
+	if p == nil {
+		return ""
+	}
+	return p.Source
+}