Allow reuse of installed packages in other scopes

When installing a package that already exists into a scope (env or global) -
it will now reference the previously vendored files and not require a --force flag.
If --force is provided, the files will always be re-vendored.

Closes #728
Signed-off-by: Oren Shomron <shomron@gmail.com>

pkg/registry/cache.go

@@ -64,6 +64,28 @@ func CacheDependency(a app.App, checker InstalledChecker, d pkg.Descriptor, cust
 		return nil, err
 	}
 
+	libSpec, err := r.ResolveLibrarySpec(d.Name, d.Version)
+	if err != nil {
+		return nil, errors.Wrapf(err, "resolving package metadata: %v", d)
+	}
+
+	// Check whether this library version is already installed
+	var qualified = d
+	qualified.Version = libSpec.Version
+	ok, err := checker.IsInstalled(qualified)
+	if err != nil {
+		return nil, errors.Wrapf(err, "checking package installed status: %v", qualified)
+	}
+
+	if ok && !force {
+		// We will reuse the currently installed package files
+		return &app.LibraryConfig{
+			Registry: d.Registry,
+			Name:     d.Name,
+			Version:  libSpec.Version,
+		}, nil
+	}
+
 	// Get all directories and files first, then write to disk. This
 	// protects us from failing with a half-cached dependency because of
 	// a network failure.
@@ -87,18 +109,6 @@ func CacheDependency(a app.App, checker InstalledChecker, d pkg.Descriptor, cust
 	// Make triple-sure the library references the correct registry, as it is known in this app.
 	libRef.Registry = d.Registry
 
-	// Check whether this library version is already installed
-	var qualified = d
-	qualified.Version = libRef.Version
-	ok, err := checker.IsInstalled(qualified)
-	if err != nil {
-		return nil, errors.Wrapf(err, "checking package installed status")
-	}
-	if ok && !force {
-		return nil, errors.Errorf("package '%s/%s@%s' already exists.",
-			libRef.Registry, libRef.Name, libRef.Version)
-	}
-
 	// Add library to app specification, but wait to write it out until
 	// the end, in case one of the network calls fails.
 	log.Infof("Retrieved %d files", len(files))

pkg/registry/github.go

@@ -321,6 +321,9 @@ func (gh *GitHub) ResolveLibrarySpec(partName, libRefSpec string) (*parts.Spec,
 		return nil, err
 	}
 
+	// For GitHub repositories, the SHA is the correct version, not what is written in the spec file.
+	parts.Version = resolvedSHA
+
 	return parts, nil
 }
 

pkg/registry/github_test.go

@@ -377,6 +377,7 @@ func TestGithub_ResolveLibrarySpec(t *testing.T) {
 		APIVersion:  "0.0.1",
 		Kind:        "ksonnet.io/parts",
 		Name:        "apache",
+		Version:     "54321",
 		Description: "part description",
 		Author:      "author",
 		Contributors: parts.ContributorSpecs{