Add warning when attempting to cache referential data when no driver …

…supports it

Signed-off-by: Max Smythe <smythe@google.com>

constraint/pkg/client/client.go

@@ -39,6 +39,11 @@ type Client struct {
 	// added to the client.
 	driverPriority map[string]int
 
+	// ignoreNoReferentialDriverWarning toggles whether we warn the user
+	// when there is no registered driver that supports referential data when
+	// they call AddData()
+	ignoreNoReferentialDriverWarning bool
+
 	// drivers contains the drivers for policy engines understood
 	// by the constraint framework client.
 	// Does not require mutex locking as Driver is threadsafe
@@ -547,6 +552,8 @@ func (c *Client) AddData(ctx context.Context, data interface{}) (*types.Response
 				}
 				continue
 			}
+		} else if !c.ignoreNoReferentialDriverWarning {
+			errMap[name] = ErrNoReferentialDriver
 		}
 
 		resp.Handled[name] = true
@@ -586,6 +593,8 @@ func (c *Client) RemoveData(ctx context.Context, data interface{}) (*types.Respo
 				errMap[target] = err
 				continue
 			}
+		} else if !c.ignoreNoReferentialDriverWarning {
+			errMap[target] = ErrNoReferentialDriver
 		}
 
 		resp.Handled[target] = true

constraint/pkg/client/client_opts.go

@@ -65,3 +65,10 @@ func Driver(d drivers.Driver) Opt {
 		return nil
 	}
 }
+
+func IgnoreNoReferentialDriverWarning(ignore bool) Opt {
+	return func(client *Client) error {
+		client.ignoreNoReferentialDriverWarning = ignore
+		return nil
+	}
+}

constraint/pkg/client/drivers/interface.go

@@ -33,10 +33,12 @@ type Driver interface {
 	RemoveConstraint(ctx context.Context, constraint *unstructured.Unstructured) error
 
 	// AddData caches data to be used for referential Constraints. Replaces data
-	// if it already exists at the specified path.
+	// if it already exists at the specified path. This is a deprecated method that
+	// will only be called for the "Rego" driver.
 	AddData(ctx context.Context, target string, path storage.Path, data interface{}) error
 	// RemoveData removes cached data, so the data at the specified path can no
-	// longer be used in referential Constraints.
+	// longer be used in referential Constraints. This is a deprecated method that
+	// will only be called for the "Rego" driver.
 	RemoveData(ctx context.Context, target string, path storage.Path) error
 
 	// Query runs the passed target's Constraints against review.

constraint/pkg/client/errors.go

@@ -7,6 +7,7 @@ import (
 var (
 	ErrCreatingBackend           = errors.New("unable to create backend")
 	ErrNoDriverName              = errors.New("driver has no name")
+	ErrNoReferentialDriver       = errors.New("no driver that supports referential constraints added")
 	ErrDuplicateDriver           = errors.New("duplicate drivers of the same name")
 	ErrCreatingClient            = errors.New("unable to create client")
 	ErrMissingConstraint         = errors.New("missing Constraint")