doc/features: add dynamic values support (#3436)

dialect/sql/builder.go

@@ -2217,7 +2217,7 @@ func (s *Selector) AppendSelect(columns ...string) *Selector {
 // AppendSelectAs appends additional column to the SELECT statement with the given alias.
 func (s *Selector) AppendSelectAs(column, as string) *Selector {
 	s.selection = append(s.selection, ExprFunc(func(b *Builder) {
-		if b.isIdent(column) {
+		if b.isIdent(column) || isFunc(column) || isModifier(column) {
 			b.WriteString(column)
 		} else {
 			b.WriteString(s.C(column))

dialect/sql/scan_test.go

@@ -353,6 +353,12 @@ func TestInterface(t *testing.T) {
 	require.Equal(t, []driver.Value{int64(10), int64(20)}, values)
 }
 
+func TestScanTypeOf(t *testing.T) {
+	mock := &Rows{ColumnScanner: toRows(sqlmock.NewRows([]string{"age"}).AddRow(10))}
+	tv := ScanTypeOf(mock, 0)
+	require.IsType(t, (*any)(nil), tv)
+}
+
 func toRows(mrows *sqlmock.Rows) *sql.Rows {
 	db, mock, _ := sqlmock.New()
 	mock.ExpectQuery("").WillReturnRows(mrows)

doc/md/features.md

@@ -144,6 +144,30 @@ The above code will produce the following SQL query:
 SELECT SUM(LENGTH(name)) FROM `pet`
 ```
 
+#### Select and Scan Dynamic Values
+
+If you work with SQL modifiers and need to scan dynamic values not present in your Ent schema definition, such as
+aggregation or custom ordering, you can apply `AppendSelect`/`AppendSelectAs` to the `sql.Selector`. You can later
+access their values using the `Value` method defined on each entity:
+
+```go {6,11}
+const as = "name_length"
+
+// Query the entity with the dynamic value.
+p := client.Pet.Query().
+	Modify(func(s *sql.Selector) {
+		s.AppendSelectAs("LENGTH(name)", as)
+	}).
+	FirstX(ctx)
+
+// Read the value from the entity.
+n, err := p.Value(as)
+if err != nil {
+    log.Fatal(err)
+}
+fmt.Println("Name length: %d == %d", n, len(p.Name))
+```
+
 #### Modify Example 2
 
 ```go

entc/integration/integration_test.go

@@ -24,8 +24,6 @@ import (
 	"testing"
 	"time"
 
-	"entgo.io/ent/entc/integration/ent/exvaluescan"
-
 	"entgo.io/ent/dialect"
 	"entgo.io/ent/dialect/sql"
 	sqlschema "entgo.io/ent/dialect/sql/schema"
@@ -33,6 +31,7 @@ import (
 	"entgo.io/ent/entc/integration/ent"
 	"entgo.io/ent/entc/integration/ent/card"
 	"entgo.io/ent/entc/integration/ent/enttest"
+	"entgo.io/ent/entc/integration/ent/exvaluescan"
 	"entgo.io/ent/entc/integration/ent/file"
 	"entgo.io/ent/entc/integration/ent/filetype"
 	"entgo.io/ent/entc/integration/ent/group"
@@ -779,6 +778,19 @@ func Select(t *testing.T, client *ent.Client) {
 		}).
 		ExecX(ctx)
 	require.True(allUpper(), "at names must be upper-cased")
+
+	// Select and scan dynamic values.
+	const as = "name_length"
+	pets = client.Pet.Query().
+		Modify(func(s *sql.Selector) {
+			s.AppendSelectAs("LENGTH(name)", as)
+		}).
+		AllX(ctx)
+	for _, p := range pets {
+		n, err := p.Value(as)
+		require.NoError(err)
+		require.EqualValues(len(p.Name), n)
+	}
 }
 
 func Aggregate(t *testing.T, client *ent.Client) {