Improve oci error message

pkg/cli/cmd/bicep/publish/publish.go

@@ -293,11 +293,37 @@ func (r *Runner) prepareDestination() (*remote.Repository, error) {
 	return dst, nil
 }
 
+// enhanceOCIError enhances the OCI registry error with detailed information about naming rules.
+// The 'br:' prefix indicates this is a Bicep OCI registry reference.
+// The target parameter should be the OCI reference without the 'br:' prefix (as stored in Runner.Target).
+func enhanceOCIError(target string, err error) error {
+	errMsg := err.Error()
+
+	const helpMessage = "The target must be a valid Bicep OCI registry reference in the form 'br:<OCI-registry-hostname>/<module-path>:<tag>'."
+
+	// Display the target with the 'br:' prefix to match what the user provided
+	displayTarget := "br:" + target
+
+	// Check if this is a known OCI validation error
+	if strings.Contains(errMsg, "invalid repository") ||
+		strings.Contains(errMsg, "invalid registry") ||
+		strings.Contains(errMsg, "invalid tag") ||
+		strings.Contains(errMsg, "missing registry or repository") ||
+		strings.Contains(errMsg, "invalid reference") {
+		return clierrors.MessageWithCause(err,
+			"Invalid OCI reference in target %q.\n\n"+helpMessage,
+			displayTarget)
+	}
+
+	// Return the original error if we don't recognize it
+	return err
+}
+
 // extractDestination extracts the host, repo, and tag from the target
 func (r *Runner) extractDestination() (*destination, error) {
 	ref, err := registry.ParseReference(r.Target)
 	if err != nil {
-		return nil, err
+		return nil, enhanceOCIError(r.Target, err)
 	}
 
 	host := ref.Host()

pkg/cli/cmd/bicep/publish/publish_test.go

@@ -23,6 +23,7 @@ import (
 	"net/http"
 	"net/url"
 	"reflect"
+	"strings"
 	"testing"
 
 	"github.com/opencontainers/go-digest"
@@ -98,6 +99,83 @@ func TestRunner_extractDestination(t *testing.T) {
 	}
 }
 
+func TestRunner_extractDestination_EnhancedErrors(t *testing.T) {
+	tests := []struct {
+		name                string
+		target              string
+		wantErr             bool
+		expectedErrContains []string
+	}{
+		{
+			name:    "uppercase in repository name",
+			target:  "localhost:5000/myregistry/Data/mySqlDatabases/kubernetes/kubernetesmysql:latest",
+			wantErr: true,
+			expectedErrContains: []string{
+				"Invalid OCI reference",
+				"br:",
+			},
+		},
+		{
+			name:    "uppercase at start of repository",
+			target:  "localhost:5000/MyRegistry/data:latest",
+			wantErr: true,
+			expectedErrContains: []string{
+				"Invalid OCI reference",
+				"br:",
+			},
+		},
+		{
+			name:    "invalid tag starting with hyphen",
+			target:  "localhost:5000/myregistry/data:-invalid",
+			wantErr: true,
+			expectedErrContains: []string{
+				"Invalid OCI reference",
+				"br:",
+			},
+		},
+		{
+			name:    "missing repository",
+			target:  "localhost:5000",
+			wantErr: true,
+			expectedErrContains: []string{
+				"Invalid OCI reference",
+				"br:",
+			},
+		},
+		{
+			name:    "valid lowercase repository",
+			target:  "localhost:5000/myregistry/data/mysqldatabases/kubernetes/kubernetesmysql:latest",
+			wantErr: false,
+		},
+		{
+			name:    "valid with hyphens and underscores",
+			target:  "localhost:5000/my-registry/my_data:v1.0.0",
+			wantErr: false,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			r := &Runner{
+				Target: tt.target,
+			}
+			_, err := r.extractDestination()
+			if (err != nil) != tt.wantErr {
+				t.Errorf("Runner.extractDestination() error = %v, wantErr %v", err, tt.wantErr)
+				return
+			}
+			if err != nil && tt.wantErr {
+				errStr := err.Error()
+				for _, expectedStr := range tt.expectedErrContains {
+					if !strings.Contains(errStr, expectedStr) {
+						t.Errorf("Runner.extractDestination() error = %q, expected to contain %q", errStr, expectedStr)
+					}
+				}
+			}
+		})
+	}
+}
+
 func Test_pushBlob(t *testing.T) {
 	tests := []struct {
 		name      string