follow coderabbitai: add sentinel error and improve error handling

On-behalf-of: Gerald Morrison (SAP) <gerald.morrison@sap.com>
Signed-off-by: Gerald Morrison (SAP) <gerald.morrison@sap.com>

Author: morrison-sap

bindings/go/constructor/construct.go

@@ -30,6 +30,11 @@ import (
 // e.g. because the component version already exists in the target repository.
 var ErrShouldSkipConstruction = errors.New("should skip construction")
 
+// ErrDigestProcessorNotFound is returned by ResourceDigestProcessorProvider.GetDigestProcessor when no digest
+// processor is available for the given access type. This is distinct from operational errors (e.g. plugin start
+// failures) and signals that digest processing should be skipped for the resource.
+var ErrDigestProcessorNotFound = errors.New("digest processor not found")
+
 const AttributeDescriptor string = "constructor/descriptor"
 
 type Constructor interface {
@@ -425,9 +430,11 @@ func (c *DefaultConstructor) processResource(ctx context.Context, targetRepo Tar
 					if res, err = digestProcessor.ProcessResourceDigest(ctx, res, creds); err != nil {
 						return nil, fmt.Errorf("error processing resource %q with digest processor: %w", resource.ToIdentity(), err)
 					}
-				} else {
-					logger.Debug("no digest processor found for resource, skipping digest processing", "error", err)
+				} else if errors.Is(err, ErrDigestProcessorNotFound) {
+					logger.Debug("no digest processor found for resource, skipping digest processing")
 					err = nil
+				} else {
+					return nil, fmt.Errorf("error getting digest processor for resource %q: %w", resource.ToIdentity(), err)
 				}
 			}
 		}

bindings/go/constructor/construct_resource_test.go

@@ -538,7 +538,7 @@ func TestConstructWithResourceDigest(t *testing.T) {
 
 func TestConstructWithResourceAccessSucceedsWhenNoDigestProcessorRegistered(t *testing.T) {
 	mockDigestProvider := &mockDigestProcessorProvider{
-		err: fmt.Errorf("no digest processor registered for access type"),
+		err: fmt.Errorf("no digest processor registered for access type: %w", ErrDigestProcessorNotFound),
 	}
 
 	constructor := setupTestComponent(t, `
@@ -547,7 +547,7 @@ func TestConstructWithResourceAccessSucceedsWhenNoDigestProcessorRegistered(t *t
         relation: external
         type: helmChart
         access:
-          type: helm/v1
+          type: Helm/v1
           helmRepository: https://charts.example.com
           helmChart: my-chart:1.0.0
 `)
@@ -579,6 +579,37 @@ func TestConstructWithResourceAccessSucceedsWhenNoDigestProcessorRegistered(t *t
 	assert.Len(t, mockTargetRepo.addedVersions, 1)
 }
 
+func TestConstructWithResourceAccessFailsOnDigestProcessorError(t *testing.T) {
+	mockDigestProvider := &mockDigestProcessorProvider{
+		err: fmt.Errorf("plugin process crashed"),
+	}
+
+	constructor := setupTestComponent(t, `
+      - name: test-resource
+        version: v1.0.0
+        relation: external
+        type: helmChart
+        access:
+          type: Helm/v1
+          helmRepository: https://charts.example.com
+          helmChart: my-chart:1.0.0
+`)
+
+	mockTargetRepo := newMockTargetRepository()
+
+	opts := Options{
+		TargetRepositoryProvider:        &mockTargetRepositoryProvider{repo: mockTargetRepo},
+		ResourceDigestProcessorProvider: mockDigestProvider,
+	}
+
+	constructorInstance := NewDefaultConstructor(constructor, opts)
+
+	err := constructorInstance.Construct(t.Context())
+	require.Error(t, err)
+	assert.Contains(t, err.Error(), "error getting digest processor")
+	assert.Contains(t, err.Error(), "plugin process crashed")
+}
+
 func TestConstructWithInvalidInputMethod(t *testing.T) {
 	constructor := setupTestComponent(t, `
       - name: test-resource

bindings/go/plugin/manager/registries/digestprocessor/registry.go

@@ -137,7 +137,7 @@ func (r *RepositoryRegistry) GetPlugin(ctx context.Context, spec runtime.Typed)
 	if ok := r.scheme.IsRegistered(typ); ok {
 		p, ok := r.internalDigestProcessorPlugins[typ]
 		if !ok {
-			return nil, fmt.Errorf("no internal plugin registered for type %v", typ)
+			return nil, fmt.Errorf("no internal plugin registered for type %v: %w", typ, constructor.ErrDigestProcessorNotFound)
 		}
 
 		return p, nil
@@ -154,7 +154,7 @@ func (r *RepositoryRegistry) GetPlugin(ctx context.Context, spec runtime.Typed)
 func (r *RepositoryRegistry) getPlugin(ctx context.Context, typ runtime.Type) (digestprocessorv1.ResourceDigestProcessorContract, error) {
 	plugin, ok := r.registry[typ]
 	if !ok {
-		return nil, fmt.Errorf("failed to get plugin for typ %q", typ)
+		return nil, fmt.Errorf("failed to get plugin for typ %q: %w", typ, constructor.ErrDigestProcessorNotFound)
 	}
 
 	if existingPlugin, ok := r.constructedPlugins[plugin.ID]; ok {