generate bundle: Add Image Digest Resolver Option

Add option to select the image digest resolver when rendering bundles with
image digests pinned. The set of supported tools is defined in the
`operator-manifest-tools` library (curretnly `crane`, `skopeo`, and `script`).

Fixes #6898

Signed-off-by: Adam Kaplan <adam.kaplan@redhat.com>

Author: adambkaplan

changelog/fragments/feat-image-digest-resolver.yaml

@@ -0,0 +1,10 @@
+entries:
+  - description: >
+      Add `--image-digest-resolver` option to the operator-sdk
+      `generate bundle` command. When using image digests in operator bundles,
+      this lets developers choose `crane`, `skopeo` or a custom script to
+      resolve image SHAs.
+    kind: "addition"
+
+    # Is this a breaking change?
+    breaking: false

internal/cmd/operator-sdk/generate/bundle/bundle.go

@@ -117,6 +117,7 @@ func (c *bundleCmd) setDefaults() (err error) {
 	if c.packageName, c.layout, err = genutil.GetPackageNameAndLayout(c.packageName); err != nil {
 		return err
 	}
+
 	return nil
 }
 
@@ -148,6 +149,23 @@ func (c bundleCmd) validateManifests() (err error) {
 		}
 	}
 
+	if c.useImageDigests {
+		if len(c.imageDigestResolver) == 0 {
+			return errors.New("--image-digest-resolver cannot be empty when using image digests")
+		}
+		isValid := false
+		for _, r := range imageresolver.GetResolverOptions() {
+			if c.imageDigestResolver == string(r) {
+				isValid = true
+				break
+			}
+		}
+		if !isValid {
+			return fmt.Errorf("--image-digest-resolver must be one of: %s", imageresolver.GetResolverOptions())
+		}
+
+	}
+
 	return nil
 }
 
@@ -311,9 +329,8 @@ func (c bundleCmd) pinImages(manifestPath string) error {
 	if err != nil {
 		return err
 	}
-	resolverArgs := make(map[string]string)
-	resolverArgs["usedefault"] = "true"
-	resolver, err := imageresolver.GetResolver(imageresolver.ResolverCrane, resolverArgs)
+
+	resolver, err := imageresolver.GetResolver(imageresolver.ResolverOption(c.imageDigestResolver), c.resolverArgs())
 	if err != nil {
 		return err
 	}
@@ -329,3 +346,16 @@ func (c bundleCmd) pinImages(manifestPath string) error {
 
 	return nil
 }
+
+func (c bundleCmd) resolverArgs() map[string]string {
+	resolverArgs := make(map[string]string)
+
+	switch c.imageDigestResolver {
+	case string(imageresolver.ResolverCrane):
+		resolverArgs["usedefault"] = "true"
+	case string(imageresolver.ResolverSkopeo):
+	case string(imageresolver.ResolverScript):
+	default:
+	}
+	return resolverArgs
+}

internal/cmd/operator-sdk/generate/bundle/cmd.go

@@ -52,6 +52,8 @@ type bundleCmd struct {
 
 	// Use Image Digests flag to toggle using traditional Image tags vs SHA Digests
 	useImageDigests bool
+	// Tool to use when resolving image digests. Defaults to crane.
+	imageDigestResolver string
 }
 
 // NewCmd returns the 'bundle' command configured for the new project layout.
@@ -144,6 +146,7 @@ func (c *bundleCmd) addFlagsTo(fs *pflag.FlagSet) {
 	fs.StringVar(&c.packageName, "package", "", "Bundle's package name")
 
 	fs.BoolVar(&c.useImageDigests, "use-image-digests", false, "Use SHA Digest for images")
+	fs.StringVar(&c.imageDigestResolver, "image-digest-resolver", "crane", "Resolver for image digests. Options are crane, skopeo, or script")
 }
 
 func (c bundleCmd) println(a ...interface{}) {