Improve error message when pulling a nonexistent catalog

pkg/catalog_next/pull.go

@@ -2,10 +2,12 @@ package catalognext
 
 import (
 	"context"
+	"errors"
 	"fmt"
 	"time"
 
 	"github.com/google/go-containerregistry/pkg/name"
+	"github.com/google/go-containerregistry/pkg/v1/remote/transport"
 
 	"github.com/docker/mcp-gateway/pkg/db"
 	"github.com/docker/mcp-gateway/pkg/oci"
@@ -41,6 +43,9 @@ func pullCatalog(ctx context.Context, dao db.DAO, ociService oci.Service, refStr
 
 	catalogArtifact, err := oci.ReadArtifact[CatalogArtifact](refStr, MCPCatalogArtifactType)
 	if err != nil {
+		if isNotFoundError(err) {
+			return nil, fmt.Errorf("catalog not found: %s", refStr)
+		}
 		return nil, fmt.Errorf("failed to read OCI catalog: %w", err)
 	}
 
@@ -88,3 +93,18 @@ func pullCatalog(ctx context.Context, dao db.DAO, ociService oci.Service, refStr
 
 	return &dbCatalog, nil
 }
+
+// isNotFoundError checks if the error is an OCI registry "not found" response
+// (MANIFEST_UNKNOWN or NAME_UNKNOWN).
+func isNotFoundError(err error) bool {
+	var transportErr *transport.Error
+	if !errors.As(err, &transportErr) {
+		return false
+	}
+	for _, diagnostic := range transportErr.Errors {
+		if diagnostic.Code == transport.ManifestUnknownErrorCode || diagnostic.Code == transport.NameUnknownErrorCode {
+			return true
+		}
+	}
+	return false
+}

pkg/catalog_next/pull_test.go

@@ -0,0 +1,63 @@
+package catalognext
+
+import (
+	"fmt"
+	"net/http"
+	"testing"
+
+	"github.com/google/go-containerregistry/pkg/v1/remote/transport"
+	"github.com/stretchr/testify/assert"
+)
+
+func TestIsNotFoundError(t *testing.T) {
+	tests := []struct {
+		name     string
+		err      error
+		expected bool
+	}{
+		{
+			name:     "manifest unknown",
+			err:      &transport.Error{Errors: []transport.Diagnostic{{Code: transport.ManifestUnknownErrorCode}}},
+			expected: true,
+		},
+		{
+			name:     "name unknown",
+			err:      &transport.Error{Errors: []transport.Diagnostic{{Code: transport.NameUnknownErrorCode}}},
+			expected: true,
+		},
+		{
+			name:     "wrapped manifest unknown",
+			err:      fmt.Errorf("fetch failed: %w", &transport.Error{Errors: []transport.Diagnostic{{Code: transport.ManifestUnknownErrorCode}}}),
+			expected: true,
+		},
+		{
+			name:     "unauthorized error",
+			err:      &transport.Error{Errors: []transport.Diagnostic{{Code: transport.UnauthorizedErrorCode}}},
+			expected: false,
+		},
+		{
+			name:     "non-transport error",
+			err:      fmt.Errorf("network timeout"),
+			expected: false,
+		},
+		{
+			name:     "transport error with no diagnostics",
+			err:      &transport.Error{StatusCode: http.StatusNotFound},
+			expected: false,
+		},
+		{
+			name: "multiple diagnostics with one match",
+			err: &transport.Error{Errors: []transport.Diagnostic{
+				{Code: transport.UnauthorizedErrorCode},
+				{Code: transport.ManifestUnknownErrorCode},
+			}},
+			expected: true,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			assert.Equal(t, tt.expected, isNotFoundError(tt.err))
+		})
+	}
+}