Correct path resolution to nested local dependencies

The tool failed to properly resolve nested local dependencies to jsonnet
bundles in different directory trees. This arises because the
installation command resolves and installs nested jsonnet local
dependencies relative to the root jsonnetfile, rather than track and
evaluate the installation path relative to the nested library's
jsonnetfile.

Consider a repository with multiple local jsonnet bundles in various
directory trees, organised as follows (lockfiles elided for brevity):

  /top/of/tree
   |- lib/module_A
     |- jsonnetfile.json
   |- lib/module_B
     |- jsonnetfile.json
   |- src/root_module
     |- jsonnetfile.json

The modules depend on each other as follows:

  ┌───────────────────┐   ┌───────────────────┐   ┌───────────────────┐
  │                   │   │                   │   │                   │
  │  src/root_module  │──>│   lib/module_A    │──>│   lib/module_B    │
  │                   │   │                   │   │                   │
  └───────────────────┘   └───────────────────┘   └───────────────────┘

where X ──> Y indicates bundle X depends on bundle Y, expressed by
adding a dependency of type local in bundle X's jsonnetfile.json, whose
path is the relative path from bundle X to bundle Y in the directory
structure. For example, src/root_module will express a local dependency
on path ../lib/module_A to depend on library module A.

Invoking jb install in src/root_module will result in an error:

  jb: error: failed to install packages: downloading: symlink destination path does not exist: %w:
    stat /top/of/tree/src/module_B: no such file or directory

This occurs because jsonnet-bundler improperly attempts to resolve the
nested dependency on library module B relative to the root module path,
i.e. src/root_module.  The correct behaviour is to perform such
resolution relative to the depending module's jsonnetfile.json, i.e.
relative to lib/module_A.

pkg/local.go

@@ -38,7 +38,7 @@ func NewLocalPackage(source *deps.Local) Interface {
 func (p *LocalPackage) Install(ctx context.Context, name, dir, version string) (lockVersion string, err error) {
 	wd, err := os.Getwd()
 	if err != nil {
-		return "", errors.Wrap(err, "failed to get current working directory: %w")
+		return "", errors.Wrap(err, "failed to get current working directory")
 	}
 
 	oldname := filepath.Join(wd, p.Source.Directory)
@@ -51,17 +51,17 @@ func (p *LocalPackage) Install(ctx context.Context, name, dir, version string) (
 
 	err = os.RemoveAll(newname)
 	if err != nil {
-		return "", errors.Wrap(err, "failed to clean previous destination path: %w")
+		return "", errors.Wrap(err, "failed to clean previous destination path")
 	}
 
 	_, err = os.Stat(oldname)
 	if os.IsNotExist(err) {
-		return "", errors.Wrap(err, "symlink destination path does not exist: %w")
+		return "", errors.Wrap(err, "symlink destination path does not exist")
 	}
 
 	err = os.Symlink(linkname, newname)
 	if err != nil {
-		return "", errors.Wrap(err, "failed to create symlink for local dependency: %w")
+		return "", errors.Wrap(err, "failed to create symlink for local dependency")
 	}
 
 	color.Magenta("LOCAL %s -> %s", name, oldname)

pkg/packages.go

@@ -52,7 +52,7 @@ var (
 func Ensure(direct v1.JsonnetFile, vendorDir string, oldLocks map[string]deps.Dependency) (map[string]deps.Dependency, error) {
 	// ensure all required files are in vendor
 	// This is the actual installation
-	locks, err := ensure(direct.Dependencies, vendorDir, oldLocks)
+	locks, err := ensure(direct.Dependencies, vendorDir, "", oldLocks)
 	if err != nil {
 		return nil, err
 	}
@@ -210,7 +210,7 @@ func known(deps map[string]deps.Dependency, p string) bool {
 	return false
 }
 
-func ensure(direct map[string]deps.Dependency, vendorDir string, locks map[string]deps.Dependency) (map[string]deps.Dependency, error) {
+func ensure(direct map[string]deps.Dependency, vendorDir, pathToParentModule string, locks map[string]deps.Dependency) (map[string]deps.Dependency, error) {
 	deps := make(map[string]deps.Dependency)
 
 	for _, d := range direct {
@@ -231,7 +231,7 @@ func ensure(direct map[string]deps.Dependency, vendorDir string, locks map[strin
 		dir := filepath.Join(vendorDir, d.Name())
 		os.RemoveAll(dir)
 
-		locked, err := download(d, vendorDir)
+		locked, err := download(d, vendorDir, pathToParentModule)
 		if err != nil {
 			return nil, errors.Wrap(err, "downloading")
 		}
@@ -257,7 +257,12 @@ func ensure(direct map[string]deps.Dependency, vendorDir string, locks map[strin
 			return nil, err
 		}
 
-		nested, err := ensure(f.Dependencies, vendorDir, locks)
+		absolutePath, err := filepath.EvalSymlinks(filepath.Join(vendorDir, d.Name()))
+		if err != nil {
+			return nil, err
+		}
+
+		nested, err := ensure(f.Dependencies, vendorDir, absolutePath, locks)
 		if err != nil {
 			return nil, err
 		}
@@ -274,13 +279,27 @@ func ensure(direct map[string]deps.Dependency, vendorDir string, locks map[strin
 
 // download retrieves a package from a remote upstream. The checksum of the
 // files is generated afterwards.
-func download(d deps.Dependency, vendorDir string) (*deps.Dependency, error) {
+func download(d deps.Dependency, vendorDir, pathToParentModule string) (*deps.Dependency, error) {
 	var p Interface
 	switch {
 	case d.Source.GitSource != nil:
 		p = NewGitPackage(d.Source.GitSource)
 	case d.Source.LocalSource != nil:
-		p = NewLocalPackage(d.Source.LocalSource)
+		wd, err := os.Getwd()
+		if err != nil {
+			return nil, fmt.Errorf("failed to get current working directory: %w", err)
+		}
+
+		// Resolve the relative path to the parent module. When a local
+		// dependency tree is resolved recursively, nested local dependencies
+		// with relative paths must be evaluated relative to their referencing
+		// jsonnetfile, rather than relative to the top-level jsonnetfile.
+		modulePath, err := filepath.Rel(wd, filepath.Join(pathToParentModule, d.Source.LocalSource.Directory))
+		if err != nil {
+			modulePath = d.Source.LocalSource.Directory
+		}
+
+		p = NewLocalPackage(&deps.Local{Directory: modulePath})
 	}
 
 	if p == nil {