Merge pull request #30 from moznion/sql_interface

Implements database/sql/driver.Valuer and database/sql.Scanner on Option type

README.md

@@ -168,6 +168,40 @@ if err != nil {
 fmt.Printf("%s\n", marshal) // => {}
 ```
 
+### SQL Driver Support
+
+`Option[T]` satisfies [sql/driver.Valuer](https://pkg.go.dev/database/sql/driver#Valuer) and [sql.Scanner](https://pkg.go.dev/database/sql#Scanner), so this type can be used by SQL interface on Golang.
+
+example of the primitive usage:
+
+```go
+sqlStmt := "CREATE TABLE tbl (id INTEGER NOT NULL PRIMARY KEY, name VARCHAR(32));"
+db.Exec(sqlStmt)
+
+tx, _ := db.Begin()
+func() {
+    stmt, _ := tx.Prepare("INSERT INTO tbl(id, name) values(?, ?)")
+    defer stmt.Close()
+    stmt.Exec(1, "foo")
+}()
+func() {
+    stmt, _ := tx.Prepare("INSERT INTO tbl(id) values(?)")
+    defer stmt.Close()
+    stmt.Exec(2) // name is NULL
+}()
+tx.Commit()
+
+var maybeName Option[string]
+
+row := db.QueryRow("SELECT name FROM tbl WHERE id = 1")
+row.Scan(&maybeName)
+fmt.Println(maybeName) // Some[foo]
+
+row := db.QueryRow("SELECT name FROM tbl WHERE id = 2")
+row.Scan(&maybeName)
+fmt.Println(maybeName) // None[]
+```
+
 ## Known Issues
 
 The runtime raises a compile error like "methods cannot have type parameters", so `Map()`, `MapOr()`, `MapWithError()`, `MapOrWithError()`, `Zip()`, `ZipWith()`, `Unzip()` and `UnzipWith()` have been providing as functions. Basically, it would be better to provide them as the methods, but currently, it compromises with the limitation.

go.mod

@@ -2,7 +2,10 @@ module github.com/moznion/go-optional
 
 go 1.19
 
-require github.com/stretchr/testify v1.8.4
+require (
+	github.com/mattn/go-sqlite3 v1.14.17
+	github.com/stretchr/testify v1.8.4
+)
 
 require (
 	github.com/davecgh/go-spew v1.1.1 // indirect

go.sum

@@ -1,29 +1,12 @@
-github.com/davecgh/go-spew v1.1.0 h1:ZDRjVQ15GmhC3fiQ8ni8+OwkZQO4DARzQgrnXU1Liz8=
-github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
 github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/mattn/go-sqlite3 v1.14.17 h1:mCRHCLDUBXgpKAqIKsaAaAsrAlbkeomtRFKXh2L6YIM=
+github.com/mattn/go-sqlite3 v1.14.17/go.mod h1:2eHXhiwb8IkHr+BDWZGa96P6+rkvnG63S2DGjv9HUNg=
 github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
 github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
-github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
-github.com/stretchr/objx v0.4.0/go.mod h1:YvHI0jy2hoMjB+UWwv71VJQ9isScKT/TqJzVSSt89Yw=
-github.com/stretchr/objx v0.5.0/go.mod h1:Yh+to48EsGEfYuaHDzXPcE3xhTkx73EhmCGUpEOglKo=
-github.com/stretchr/testify v1.7.1 h1:5TQK59W5E3v0r2duFAb7P95B6hEeOyEnHRa8MjYSMTY=
-github.com/stretchr/testify v1.7.1/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=
-github.com/stretchr/testify v1.7.2 h1:4jaiDzPyXQvSd7D0EjG45355tLlV3VOECpq10pLC+8s=
-github.com/stretchr/testify v1.7.2/go.mod h1:R6va5+xMeoiuVRoj+gSkQ7d3FALtqAAGI1FQKckRals=
-github.com/stretchr/testify v1.8.0 h1:pSgiaMZlXftHpm5L7V1+rVB+AZJydKsMxsQBIJw4PKk=
-github.com/stretchr/testify v1.8.0/go.mod h1:yNjHg4UonilssWZ8iaSj1OCr/vHnekPRkoO+kdMU+MU=
-github.com/stretchr/testify v1.8.1 h1:w7B6lhMri9wdJUVmEZPGGhZzrYTPvgJArz7wNPgYKsk=
-github.com/stretchr/testify v1.8.1/go.mod h1:w2LPCIKwWwSfY2zedu0+kehJoqGctiVI29o6fzry7u4=
-github.com/stretchr/testify v1.8.2 h1:+h33VjcLVPDHtOdpUCuF+7gSuG3yGIftsP1YvFihtJ8=
-github.com/stretchr/testify v1.8.2/go.mod h1:w2LPCIKwWwSfY2zedu0+kehJoqGctiVI29o6fzry7u4=
-github.com/stretchr/testify v1.8.3 h1:RP3t2pwF7cMEbC1dqtB6poj3niw/9gnV4Cjg5oW5gtY=
-github.com/stretchr/testify v1.8.3/go.mod h1:sz/lmYIOXD/1dqDmKjjqLyZ2RngseejIcXlSw2iwfAo=
 github.com/stretchr/testify v1.8.4 h1:CcVxjf3Q8PM0mHUKJCdn+eZZtm5yQwehR5yeSVQQcUk=
 github.com/stretchr/testify v1.8.4/go.mod h1:sz/lmYIOXD/1dqDmKjjqLyZ2RngseejIcXlSw2iwfAo=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405 h1:yhCVgyC4o1eVCa2tZl7eS0r+SDo693bJlVdllGtEeKM=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
-gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c h1:dUUwHk2QECo/6vqA44rthZ8ie2QXMNeKRTHCNY2nXvo=
-gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
 gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
 gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=

option.go

@@ -13,6 +13,7 @@ var (
 )
 
 // Option is a data type that must be Some (i.e. having a value) or None (i.e. doesn't have a value).
+// This type implements database/sql/driver.Valuer and database/sql.Scanner.
 type Option[T any] []T
 
 const (

sql_driver.go

@@ -0,0 +1,46 @@
+package optional
+
+import (
+	"database/sql/driver"
+	"errors"
+	"time"
+)
+
+var (
+	ErrSQLScannerIncompatibleDataType      = errors.New("incompatible data type for SQL scanner on Option[T]")
+	ErrSQLDriverValuerIncompatibleDataType = errors.New("incompatible data type for SQL driver Valuer on Option[T]")
+)
+
+// Scan assigns a value from a database driver.
+// This method is required from database/sql.Scanner interface.
+func (o *Option[T]) Scan(src any) error {
+	if src == nil {
+		*o = None[T]()
+		return nil
+	}
+
+	switch src.(type) {
+	case string, []byte, int64, float64, bool, time.Time:
+		*o = Some[T](src.(T))
+	default:
+		return ErrSQLScannerIncompatibleDataType
+	}
+
+	return nil
+}
+
+// Value returns a driver Value.
+// This method is required from database/sql/driver.Valuer interface.
+func (o Option[T]) Value() (driver.Value, error) {
+	if o.IsNone() {
+		return nil, nil
+	}
+
+	v := o.Unwrap()
+	switch (interface{})(v).(type) {
+	case string, []byte, int64, float64, bool, time.Time:
+		return v, nil
+	default:
+		return nil, ErrSQLDriverValuerIncompatibleDataType
+	}
+}

sql_driver_test.go

@@ -0,0 +1,176 @@
+package optional
+
+import (
+	"database/sql"
+	"database/sql/driver"
+	"os"
+	"testing"
+	"time"
+
+	_ "github.com/mattn/go-sqlite3"
+	"github.com/stretchr/testify/assert"
+)
+
+func TestOption_Scan(t *testing.T) {
+	o := Some[any](nil)
+
+	err := o.Scan("bar")
+	assert.NoError(t, err)
+	assert.EqualValues(t, "bar", o.Unwrap())
+
+	err = o.Scan([]byte("buz"))
+	assert.NoError(t, err)
+	assert.EqualValues(t, []byte("buz"), o.Unwrap())
+
+	err = o.Scan(int64(42))
+	assert.NoError(t, err)
+	assert.EqualValues(t, 42, o.Unwrap())
+
+	err = o.Scan(float64(123.456))
+	assert.NoError(t, err)
+	assert.EqualValues(t, 123.456, o.Unwrap())
+
+	err = o.Scan(true)
+	assert.NoError(t, err)
+	assert.EqualValues(t, true, o.Unwrap())
+
+	now := time.Now()
+	err = o.Scan(now)
+	assert.NoError(t, err)
+	assert.EqualValues(t, now, o.Unwrap())
+}
+
+func TestOption_Scan_None(t *testing.T) {
+	o := Some[any](nil)
+
+	err := o.Scan(nil)
+	assert.NoError(t, err)
+	assert.True(t, o.IsNone())
+}
+
+func TestOption_Scan_UnsupportedTypes(t *testing.T) {
+	o := Some[any](nil)
+
+	err := o.Scan(int32(42))
+	assert.ErrorIs(t, err, ErrSQLScannerIncompatibleDataType)
+}
+
+func TestOption_Scan_ScannerInterfaceSatisfaction(t *testing.T) {
+	o := Some[any]("string")
+	var s sql.Scanner = &o
+	assert.NotNil(t, s)
+}
+
+func TestOption_Value(t *testing.T) {
+	{
+		o := Some[string]("foo")
+		v, err := o.Value()
+		assert.NoError(t, err)
+		assert.EqualValues(t, "foo", v)
+	}
+
+	{
+		o := Some[[]byte]([]byte("bar"))
+		v, err := o.Value()
+		assert.NoError(t, err)
+		assert.EqualValues(t, []byte("bar"), v)
+	}
+
+	{
+		o := Some[int64](42)
+		v, err := o.Value()
+		assert.NoError(t, err)
+		assert.EqualValues(t, 42, v)
+	}
+
+	{
+		o := Some[float64](123.456)
+		v, err := o.Value()
+		assert.NoError(t, err)
+		assert.EqualValues(t, 123.456, v)
+	}
+
+	{
+		o := Some[bool](true)
+		v, err := o.Value()
+		assert.NoError(t, err)
+		assert.EqualValues(t, true, v)
+	}
+
+	{
+		now := time.Now()
+		o := Some[time.Time](now)
+		v, err := o.Value()
+		assert.NoError(t, err)
+		assert.EqualValues(t, now, v)
+	}
+}
+
+func TestOption_Value_None(t *testing.T) {
+	o := None[string]()
+	v, err := o.Value()
+	assert.NoError(t, err)
+	assert.Nil(t, v)
+}
+
+func TestOption_Value_UnsupportedTypes(t *testing.T) {
+	o := Some[int32](0)
+	_, err := o.Value()
+	assert.ErrorIs(t, err, ErrSQLDriverValuerIncompatibleDataType)
+}
+
+func TestOption_Value_ValuerInterfaceSatisfaction(t *testing.T) {
+	o := Some[any]("string")
+	var s driver.Valuer = &o
+	assert.NotNil(t, s)
+}
+
+func TestOption_SQLScan(t *testing.T) {
+	tmpfile, err := os.CreateTemp(os.TempDir(), "testdb")
+	assert.NoError(t, err)
+
+	db, err := sql.Open("sqlite3", tmpfile.Name())
+	assert.NoError(t, err)
+	defer func() {
+		_ = db.Close()
+	}()
+
+	sqlStmt := "CREATE TABLE test_table (id INTEGER NOT NULL PRIMARY KEY, name VARCHAR(32));"
+	_, err = db.Exec(sqlStmt)
+	assert.NoError(t, err)
+
+	tx, err := db.Begin()
+	assert.NoError(t, err)
+	func() {
+		stmt, err := tx.Prepare("INSERT INTO test_table(id, name) values(?, ?)")
+		assert.NoError(t, err)
+		defer func() {
+			_ = stmt.Close()
+		}()
+		_, err = stmt.Exec(1, "foo")
+		assert.NoError(t, err)
+	}()
+	func() {
+		stmt, err := tx.Prepare("INSERT INTO test_table(id) values(?)")
+		assert.NoError(t, err)
+		defer func() {
+			_ = stmt.Close()
+		}()
+		_, err = stmt.Exec(2)
+		assert.NoError(t, err)
+	}()
+	err = tx.Commit()
+	assert.NoError(t, err)
+
+	var maybeName Option[string]
+
+	row := db.QueryRow("SELECT name FROM test_table WHERE id = 1")
+	err = row.Scan(&maybeName)
+	assert.NoError(t, err)
+	assert.Equal(t, "foo", maybeName.Unwrap())
+
+	row = db.QueryRow("SELECT name FROM test_table WHERE id = 2")
+	err = row.Scan(&maybeName)
+	assert.NoError(t, err)
+	assert.True(t, maybeName.IsNone())
+}