Add invariants

registry/storage/driver/azure/azure.go

@@ -262,6 +262,8 @@ func (d *driver) List(ctx context.Context, path string) ([]string, error) {
 		path = ""
 	}
 
+	// Invairant: path is not "/".
+
 	blobs, err := d.listBlobs(ctx, path)
 	if err != nil {
 		return blobs, err
@@ -400,13 +402,19 @@ func directDescendants(blobs []string, prefix string) []string {
 }
 
 func (d *driver) listBlobs(ctx context.Context, virtPath string) ([]string, error) {
+	// Invairant: virtPath is not "/"
+
 	if virtPath != "" && !strings.HasSuffix(virtPath, "/") { // containerify the path
 		virtPath += "/"
 	}
 
+	// Invairant: virtPath is "" or ends with "/"
+
 	out := []string{}
 	listPrefix := d.blobName(virtPath)
 
+	// Invairant: listPrefix starts with a "/" and ends with a "/" (or is "/")
+
 	pager := d.client.NewListBlobsFlatPager(&container.ListBlobsFlatOptions{
 		Prefix: &listPrefix,
 	})
@@ -425,6 +433,7 @@ func (d *driver) listBlobs(ctx context.Context, virtPath string) ([]string, erro
 			// In those cases, there is no root prefix to replace and we must actually add a "/" to all
 			// results in order to keep them as valid paths as recognized by storagedriver.PathRegexp
 			if !strings.HasPrefix(name, "/") { // add leading '/'
+				// Assertion: Unreachable code, as the name starts with listPrefix and listPrefix starts with a "/".
 				name = "/" + name
 			}
 			out = append(out, name)
@@ -435,6 +444,8 @@ func (d *driver) listBlobs(ctx context.Context, virtPath string) ([]string, erro
 }
 
 func (d *driver) blobName(path string) string {
+	// Invariant: path is any string.
+
 	// avoid returning an empty blob name.
 	// this will happen when rootDirectory is unset, and path == "/",
 	// which is what we get from the storage driver health check Stat call.
@@ -445,6 +456,8 @@ func (d *driver) blobName(path string) string {
 	trimmedRoot := strings.TrimRight(d.rootDirectory, "/")
 	trimmedPath := strings.TrimLeft(path, "/")
 	return trimmedRoot + "/" + trimmedPath
+
+	// Invairant: the returned string starts with a "/".
 }
 
 func is404(err error) bool {