dialect/sql/schema: support setting default value expressions on id fields (#3089)

dialect/sql/schema/atlas.go

@@ -11,6 +11,7 @@ import (
 	"errors"
 	"fmt"
 	"net/url"
+	"reflect"
 	"sort"
 	"strings"
 
@@ -1102,3 +1103,16 @@ func (a *Atlas) legacyMigrate() (*Migrate, error) {
 	}
 	return m, nil
 }
+
+// removeAttr is a temporary patch due to compiler errors we get by using the generic
+// schema.RemoveAttr function (<autogenerated>:1: internal compiler error: panic: ...).
+// Can be removed in Go 1.20. See: https://github.com/golang/go/issues/54302.
+func removeAttr(attrs []schema.Attr, t reflect.Type) []schema.Attr {
+	f := make([]schema.Attr, 0, len(attrs))
+	for _, a := range attrs {
+		if reflect.TypeOf(a) != t {
+			f = append(f, a)
+		}
+	}
+	return f
+}

dialect/sql/schema/mysql.go

@@ -8,6 +8,7 @@ import (
 	"context"
 	"fmt"
 	"math"
+	"reflect"
 	"strconv"
 	"strings"
 
@@ -932,8 +933,12 @@ func (d *MySQL) atUniqueC(t1 *Table, c1 *Column, t2 *schema.Table, c2 *schema.Co
 	t2.AddIndexes(schema.NewUniqueIndex(c1.Name).AddColumns(c2))
 }
 
-func (d *MySQL) atIncrementC(_ *schema.Table, c *schema.Column) {
-	c.AddAttrs(&mysql.AutoIncrement{})
+func (d *MySQL) atIncrementC(t *schema.Table, c *schema.Column) {
+	if c.Default != nil {
+		t.Attrs = removeAttr(t.Attrs, reflect.TypeOf(&mysql.AutoIncrement{}))
+	} else {
+		c.AddAttrs(&mysql.AutoIncrement{})
+	}
 }
 
 func (d *MySQL) atIncrementT(t *schema.Table, v int64) {

dialect/sql/schema/postgres.go

@@ -7,6 +7,7 @@ package schema
 import (
 	"context"
 	"fmt"
+	"reflect"
 	"strconv"
 	"strings"
 	"unicode"
@@ -769,7 +770,10 @@ func (d *Postgres) atImplicitIndexName(idx *Index, t1 *Table, c1 *Column) bool {
 }
 
 func (d *Postgres) atIncrementC(t *schema.Table, c *schema.Column) {
-	if _, ok := c.Type.Type.(*postgres.SerialType); ok {
+	// Skip marking this column as an identity in case it is
+	// serial type or a default was already defined for it.
+	if _, ok := c.Type.Type.(*postgres.SerialType); ok || c.Default != nil {
+		t.Attrs = removeAttr(t.Attrs, reflect.TypeOf(&postgres.Identity{}))
 		return
 	}
 	id := &postgres.Identity{}

dialect/sql/schema/sqlite.go

@@ -8,6 +8,7 @@ import (
 	"context"
 	stdsql "database/sql"
 	"fmt"
+	"reflect"
 	"strconv"
 	"strings"
 
@@ -473,8 +474,12 @@ func (d *SQLite) atImplicitIndexName(idx *Index, t1 *Table, c1 *Column) bool {
 	return err == nil && i > 0
 }
 
-func (d *SQLite) atIncrementC(_ *schema.Table, c *schema.Column) {
-	c.AddAttrs(&sqlite.AutoIncrement{})
+func (d *SQLite) atIncrementC(t *schema.Table, c *schema.Column) {
+	if c.Default != nil {
+		t.Attrs = removeAttr(t.Attrs, reflect.TypeOf(&sqlite.AutoIncrement{}))
+	} else {
+		c.AddAttrs(&sqlite.AutoIncrement{})
+	}
 }
 
 func (d *SQLite) atIncrementT(t *schema.Table, v int64) {