Allow creating oci-archive and oci-dir without image name (#132)

In some cases, one want to create an oci-archive or oci-dir which never
pushed to registry.

Author: termoshtt

ocipkg/src/image/layout.rs

@@ -6,16 +6,15 @@ use anyhow::{bail, Context, Result};
 use oci_spec::image::{Descriptor, DescriptorBuilder, ImageIndex, ImageManifest, MediaType};
 use std::path::Path;
 
-/// Handler of [OCI Image Layout] with containing single manifest and its name.
+/// Handler of [OCI Image Layout] with containing single manifest
 ///
-/// - [OCI Image Layout] allows empty image name, i.e. no `org.opencontainers.image.ref.name` annotation, but this trait does not allow it.
 /// - [OCI Image Layout] allows containing multiple manifests in a single layout,
 ///   this trait assumes a single manifest in a single layout.
 ///
 /// [OCI Image Layout]: https://github.com/opencontainers/image-spec/blob/v1.1.0/image-layout.md
 ///
 pub trait Image {
-    /// The name of this image.
+    /// The name of this image. This fails if the image does not have name.
     fn get_name(&mut self) -> Result<ImageName>;
 
     /// Get blob content.

ocipkg/src/image/oci_archive.rs

@@ -14,12 +14,25 @@ use std::{
 
 /// Build an [OciArchive]
 pub struct OciArchiveBuilder {
-    image_name: ImageName,
+    image_name: Option<ImageName>,
     path: PathBuf,
     ar: tar::Builder<fs::File>,
 }
 
 impl OciArchiveBuilder {
+    pub fn new_unnamed(path: PathBuf) -> Result<Self> {
+        if path.exists() {
+            bail!("File already exists: {}", path.display());
+        }
+        let f = fs::File::create(&path)?;
+        let ar = tar::Builder::new(f);
+        Ok(Self {
+            ar,
+            path,
+            image_name: None,
+        })
+    }
+
     pub fn new(path: PathBuf, image_name: ImageName) -> Result<Self> {
         if path.exists() {
             bail!("File already exists: {}", path.display());
@@ -29,7 +42,7 @@ impl OciArchiveBuilder {
         Ok(Self {
             ar,
             path,
-            image_name,
+            image_name: Some(image_name),
         })
     }
 }
@@ -51,8 +64,12 @@ impl ImageBuilder for OciArchiveBuilder {
             .media_type(MediaType::ImageManifest)
             .size(size)
             .digest(digest.to_string())
-            .annotations(hashmap! {
-                "org.opencontainers.image.ref.name".to_string() => self.image_name.to_string()
+            .annotations(if let Some(name) = &self.image_name {
+                hashmap! {
+                    "org.opencontainers.image.ref.name".to_string() => name.to_string()
+                }
+            } else {
+                hashmap! {}
             })
             .build()?;
         let index = ImageIndexBuilder::default()

ocipkg/src/image/oci_dir.rs

@@ -16,7 +16,7 @@ use super::get_name_from_index;
 
 /// Build an [OciDir]
 pub struct OciDirBuilder {
-    image_name: ImageName,
+    image_name: Option<ImageName>,
     oci_dir_root: PathBuf,
     is_finished: bool,
 }
@@ -37,13 +37,25 @@ impl Drop for OciDirBuilder {
 }
 
 impl OciDirBuilder {
+    pub fn new_unnamed(oci_dir_root: PathBuf) -> Result<Self> {
+        if oci_dir_root.exists() {
+            bail!("oci-dir {} already exists", oci_dir_root.display());
+        }
+        fs::create_dir_all(&oci_dir_root)?;
+        Ok(Self {
+            image_name: None,
+            oci_dir_root,
+            is_finished: false,
+        })
+    }
+
     pub fn new(oci_dir_root: PathBuf, image_name: ImageName) -> Result<Self> {
         if oci_dir_root.exists() {
             bail!("oci-dir {} already exists", oci_dir_root.display());
         }
         fs::create_dir_all(&oci_dir_root)?;
         Ok(Self {
-            image_name,
+            image_name: Some(image_name),
             oci_dir_root,
             is_finished: false,
         })
@@ -68,8 +80,12 @@ impl ImageBuilder for OciDirBuilder {
             .media_type(MediaType::ImageManifest)
             .size(size)
             .digest(digest.to_string())
-            .annotations(hashmap! {
-                "org.opencontainers.image.ref.name".to_string() => self.image_name.to_string(),
+            .annotations(if let Some(name) = &self.image_name {
+                hashmap! {
+                    "org.opencontainers.image.ref.name".to_string() => name.to_string()
+                }
+            } else {
+                hashmap! {}
             })
             .build()?;
         let index = ImageIndexBuilder::default()