entc/gen: add <E>Loaded for <T>Edges (#319)

This helps to determine if the edge was loaded (or requested) in
eager-loading even if it's empty.

examples/start/ent/car.go

@@ -13,6 +13,7 @@ import (
 
 	"github.com/facebookincubator/ent/dialect/sql"
 	"github.com/facebookincubator/ent/examples/start/ent/car"
+	"github.com/facebookincubator/ent/examples/start/ent/user"
 )
 
 // Car is the model entity for the Car schema.
@@ -34,6 +35,23 @@ type Car struct {
 type CarEdges struct {
 	// Owner holds the value of the owner edge.
 	Owner *User
+	// loadedTypes holds the information for reporting if a
+	// type was loaded (or requested) in eager-loading or not.
+	loadedTypes [1]bool
+}
+
+// OwnerWithError returns the Owner value or an error if the edge
+// was not loaded in eager-loading, or loaded but was not found.
+func (e CarEdges) OwnerWithError() (*User, error) {
+	if e.loadedTypes[0] {
+		if e.Owner == nil {
+			// The edge owner was loaded in eager-loading,
+			// but was not found.
+			return nil, &NotFoundError{label: user.Label}
+		}
+		return e.Owner, nil
+	}
+	return nil, &NotLoadedError{edge: "owner"}
 }
 
 // scanValues returns the types for scanning values from sql.Rows.

examples/start/ent/car_query.go

@@ -294,9 +294,12 @@ func (cq *CarQuery) Select(field string, fields ...string) *CarSelect {
 
 func (cq *CarQuery) sqlAll(ctx context.Context) ([]*Car, error) {
 	var (
-		nodes   []*Car = []*Car{}
-		withFKs        = cq.withFKs
-		_spec          = cq.querySpec()
+		nodes       = []*Car{}
+		withFKs     = cq.withFKs
+		_spec       = cq.querySpec()
+		loadedTypes = [1]bool{
+			cq.withOwner != nil,
+		}
 	)
 	if cq.withOwner != nil {
 		withFKs = true
@@ -318,6 +321,7 @@ func (cq *CarQuery) sqlAll(ctx context.Context) ([]*Car, error) {
 			return fmt.Errorf("ent: Assign called without calling ScanValues")
 		}
 		node := nodes[len(nodes)-1]
+		node.Edges.loadedTypes = loadedTypes
 		return node.assignValues(values...)
 	}
 	if err := sqlgraph.QueryNodes(ctx, cq.driver, _spec); err != nil {

examples/start/ent/ent.go

@@ -129,12 +129,12 @@ func IsNotSingular(err error) bool {
 
 // NotLoadedError returns when trying to get a node that was not loaded by the query.
 type NotLoadedError struct {
-	label string
+	edge string
 }
 
 // Error implements the error interface.
 func (e *NotLoadedError) Error() string {
-	return fmt.Sprintf("ent: %s not loaded", e.label)
+	return fmt.Sprintf("ent: %s edge was not loaded", e.edge)
 }
 
 // IsNotLoaded returns a boolean indicating whether the error is a not loaded error.

examples/start/ent/group.go

@@ -30,6 +30,18 @@ type Group struct {
 type GroupEdges struct {
 	// Users holds the value of the users edge.
 	Users []*User
+	// loadedTypes holds the information for reporting if a
+	// type was loaded (or requested) in eager-loading or not.
+	loadedTypes [1]bool
+}
+
+// UsersWithError returns the Users value or an error if the edge
+// was not loaded in eager-loading.
+func (e GroupEdges) UsersWithError() ([]*User, error) {
+	if e.loadedTypes[0] {
+		return e.Users, nil
+	}
+	return nil, &NotLoadedError{edge: "users"}
 }
 
 // scanValues returns the types for scanning values from sql.Rows.

examples/start/ent/group_query.go

@@ -294,8 +294,11 @@ func (gq *GroupQuery) Select(field string, fields ...string) *GroupSelect {
 
 func (gq *GroupQuery) sqlAll(ctx context.Context) ([]*Group, error) {
 	var (
-		nodes []*Group = []*Group{}
-		_spec          = gq.querySpec()
+		nodes       = []*Group{}
+		_spec       = gq.querySpec()
+		loadedTypes = [1]bool{
+			gq.withUsers != nil,
+		}
 	)
 	_spec.ScanValues = func() []interface{} {
 		node := &Group{config: gq.config}
@@ -308,6 +311,7 @@ func (gq *GroupQuery) sqlAll(ctx context.Context) ([]*Group, error) {
 			return fmt.Errorf("ent: Assign called without calling ScanValues")
 		}
 		node := nodes[len(nodes)-1]
+		node.Edges.loadedTypes = loadedTypes
 		return node.assignValues(values...)
 	}
 	if err := sqlgraph.QueryNodes(ctx, gq.driver, _spec); err != nil {

examples/start/ent/user.go

@@ -34,6 +34,27 @@ type UserEdges struct {
 	Cars []*Car
 	// Groups holds the value of the groups edge.
 	Groups []*Group
+	// loadedTypes holds the information for reporting if a
+	// type was loaded (or requested) in eager-loading or not.
+	loadedTypes [2]bool
+}
+
+// CarsWithError returns the Cars value or an error if the edge
+// was not loaded in eager-loading.
+func (e UserEdges) CarsWithError() ([]*Car, error) {
+	if e.loadedTypes[0] {
+		return e.Cars, nil
+	}
+	return nil, &NotLoadedError{edge: "cars"}
+}
+
+// GroupsWithError returns the Groups value or an error if the edge
+// was not loaded in eager-loading.
+func (e UserEdges) GroupsWithError() ([]*Group, error) {
+	if e.loadedTypes[1] {
+		return e.Groups, nil
+	}
+	return nil, &NotLoadedError{edge: "groups"}
 }
 
 // scanValues returns the types for scanning values from sql.Rows.

examples/start/ent/user_query.go

@@ -319,8 +319,12 @@ func (uq *UserQuery) Select(field string, fields ...string) *UserSelect {
 
 func (uq *UserQuery) sqlAll(ctx context.Context) ([]*User, error) {
 	var (
-		nodes []*User = []*User{}
-		_spec         = uq.querySpec()
+		nodes       = []*User{}
+		_spec       = uq.querySpec()
+		loadedTypes = [2]bool{
+			uq.withCars != nil,
+			uq.withGroups != nil,
+		}
 	)
 	_spec.ScanValues = func() []interface{} {
 		node := &User{config: uq.config}
@@ -333,6 +337,7 @@ func (uq *UserQuery) sqlAll(ctx context.Context) ([]*User, error) {
 			return fmt.Errorf("ent: Assign called without calling ScanValues")
 		}
 		node := nodes[len(nodes)-1]
+		node.Edges.loadedTypes = loadedTypes
 		return node.assignValues(values...)
 	}
 	if err := sqlgraph.QueryNodes(ctx, uq.driver, _spec); err != nil {