From 489e6d3e3fc25663c18d22a033b7864019b0f912 Mon Sep 17 00:00:00 2001
From: Mitsuo Heijo <mitsuo.heijo@gmail.com>
Date: Fri, 13 Nov 2020 01:50:21 +0900
Subject: [PATCH 01/15] Add io/fs#FS Driver #471

---
 source/iofs/README.md                  | 38 ++++++++++++++++++++++++++
 source/iofs/iofs.go                    | 36 ++++++++++++++++++++++++
 source/iofs/iofs_test.go               | 31 +++++++++++++++++++++
 source/iofs/testdata/1_foobar.down.sql |  1 +
 source/iofs/testdata/1_foobar.up.sql   |  1 +
 source/iofs/testdata/3_foobar.up.sql   |  1 +
 source/iofs/testdata/4_foobar.down.sql |  1 +
 source/iofs/testdata/4_foobar.up.sql   |  1 +
 source/iofs/testdata/5_foobar.down.sql |  1 +
 source/iofs/testdata/7_foobar.down.sql |  1 +
 source/iofs/testdata/7_foobar.up.sql   |  1 +
 11 files changed, 113 insertions(+)
 create mode 100644 source/iofs/README.md
 create mode 100644 source/iofs/iofs.go
 create mode 100644 source/iofs/iofs_test.go
 create mode 100644 source/iofs/testdata/1_foobar.down.sql
 create mode 100644 source/iofs/testdata/1_foobar.up.sql
 create mode 100644 source/iofs/testdata/3_foobar.up.sql
 create mode 100644 source/iofs/testdata/4_foobar.down.sql
 create mode 100644 source/iofs/testdata/4_foobar.up.sql
 create mode 100644 source/iofs/testdata/5_foobar.down.sql
 create mode 100644 source/iofs/testdata/7_foobar.down.sql
 create mode 100644 source/iofs/testdata/7_foobar.up.sql

diff --git a/source/iofs/README.md b/source/iofs/README.md
new file mode 100644
index 000000000..4a72504bf
--- /dev/null
+++ b/source/iofs/README.md
@@ -0,0 +1,38 @@
+# iofs
+
+Driver with file system interface (`io/fs#FS`) supported from Go 1.16.
+
+This Driver cannot be used with versions below Go 1.15.
+
+## Usage
+
+Directory embedding example
+
+```go
+package main
+
+import (
+	"embed"
+	"log"
+
+	"github.com/golang-migrate/migrate/v4"
+	_ "github.com/golang-migrate/migrate/v4/database/postgres"
+	"github.com/golang-migrate/migrate/v4/source/iofs"
+)
+
+//go:embed migrations
+var fs embed.FS
+
+func main() {
+	d, err := iofs.WithInstance(fs, "migrations")
+	if err != nil {
+		log.Fatal(err)
+	}
+	m, err := migrate.NewWithSourceInstance("iofs", d, "postgres://postgres@localhost/postgres?sslmode=disable")
+	if err != nil {
+		log.Fatal(err)
+	}
+	err = m.Up()
+	// ...
+}
+```
diff --git a/source/iofs/iofs.go b/source/iofs/iofs.go
new file mode 100644
index 000000000..43f820e9c
--- /dev/null
+++ b/source/iofs/iofs.go
@@ -0,0 +1,36 @@
+// +build go1.16
+
+package iofs
+
+import (
+	"errors"
+	"fmt"
+	"io/fs"
+	"net/http"
+
+	"github.com/golang-migrate/migrate/v4/source"
+	"github.com/golang-migrate/migrate/v4/source/httpfs"
+)
+
+func init() {
+	source.Register("iofs", &Iofs{})
+}
+
+// Iofs is a source driver for io/fs#FS.
+type Iofs struct {
+	httpfs.PartialDriver
+}
+
+// Open by url does not supported with Iofs.
+func (i *Iofs) Open(url string) (source.Driver, error) {
+	return nil, errors.New("iofs driver does not support open by url")
+}
+
+// WithInstance wraps io/fs#FS as source.Driver.
+func WithInstance(fsys fs.FS, path string) (source.Driver, error) {
+	var i Iofs
+	if err := i.Init(http.FS(fsys), path); err != nil {
+		return nil, fmt.Errorf("failed to init driver with path %s: %w", path, err)
+	}
+	return &i, nil
+}
diff --git a/source/iofs/iofs_test.go b/source/iofs/iofs_test.go
new file mode 100644
index 000000000..e2bfba2d8
--- /dev/null
+++ b/source/iofs/iofs_test.go
@@ -0,0 +1,31 @@
+// +build go1.16
+
+package iofs_test
+
+import (
+	"embed"
+	"testing"
+
+	"github.com/golang-migrate/migrate/v4/source/iofs"
+	st "github.com/golang-migrate/migrate/v4/source/testing"
+)
+
+//go:embed testdata
+var fs embed.FS
+
+func Test(t *testing.T) {
+	d, err := iofs.WithInstance(fs, "testdata")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	st.Test(t, d)
+}
+
+func TestOpen(t *testing.T) {
+	i := new(iofs.Iofs)
+	_, err := i.Open("")
+	if err == nil {
+		t.Fatal("iofs driver does not support open by url")
+	}
+}
diff --git a/source/iofs/testdata/1_foobar.down.sql b/source/iofs/testdata/1_foobar.down.sql
new file mode 100644
index 000000000..4267951a5
--- /dev/null
+++ b/source/iofs/testdata/1_foobar.down.sql
@@ -0,0 +1 @@
+1 down
diff --git a/source/iofs/testdata/1_foobar.up.sql b/source/iofs/testdata/1_foobar.up.sql
new file mode 100644
index 000000000..046fd5a5d
--- /dev/null
+++ b/source/iofs/testdata/1_foobar.up.sql
@@ -0,0 +1 @@
+1 up
diff --git a/source/iofs/testdata/3_foobar.up.sql b/source/iofs/testdata/3_foobar.up.sql
new file mode 100644
index 000000000..77c1b77dc
--- /dev/null
+++ b/source/iofs/testdata/3_foobar.up.sql
@@ -0,0 +1 @@
+3 up
diff --git a/source/iofs/testdata/4_foobar.down.sql b/source/iofs/testdata/4_foobar.down.sql
new file mode 100644
index 000000000..b405d8bd0
--- /dev/null
+++ b/source/iofs/testdata/4_foobar.down.sql
@@ -0,0 +1 @@
+4 down
diff --git a/source/iofs/testdata/4_foobar.up.sql b/source/iofs/testdata/4_foobar.up.sql
new file mode 100644
index 000000000..eba61bb94
--- /dev/null
+++ b/source/iofs/testdata/4_foobar.up.sql
@@ -0,0 +1 @@
+4 up
diff --git a/source/iofs/testdata/5_foobar.down.sql b/source/iofs/testdata/5_foobar.down.sql
new file mode 100644
index 000000000..6dc96e206
--- /dev/null
+++ b/source/iofs/testdata/5_foobar.down.sql
@@ -0,0 +1 @@
+5 down
diff --git a/source/iofs/testdata/7_foobar.down.sql b/source/iofs/testdata/7_foobar.down.sql
new file mode 100644
index 000000000..46636016b
--- /dev/null
+++ b/source/iofs/testdata/7_foobar.down.sql
@@ -0,0 +1 @@
+7 down
diff --git a/source/iofs/testdata/7_foobar.up.sql b/source/iofs/testdata/7_foobar.up.sql
new file mode 100644
index 000000000..cdbc410ee
--- /dev/null
+++ b/source/iofs/testdata/7_foobar.up.sql
@@ -0,0 +1 @@
+7 up

From 65cbb0ffc3d0d963277d58b592d8a37e77b67576 Mon Sep 17 00:00:00 2001
From: Mitsuo Heijo <mitsuo.heijo@gmail.com>
Date: Fri, 13 Nov 2020 18:05:24 +0900
Subject: [PATCH 02/15] Refactor iofs.Iofs to be independent of httpfs

---
 Makefile                   |   2 +-
 internal/cli/build_iofs.go |   8 +++
 source/errors.go           |   9 ++-
 source/iofs/README.md      |   2 +-
 source/iofs/iofs.go        | 134 +++++++++++++++++++++++++++++++++++--
 5 files changed, 145 insertions(+), 10 deletions(-)
 create mode 100644 internal/cli/build_iofs.go

diff --git a/Makefile b/Makefile
index 152cdb7bd..ddf03bead 100644
--- a/Makefile
+++ b/Makefile
@@ -1,4 +1,4 @@
-SOURCE ?= file go_bindata github github_ee bitbucket aws_s3 google_cloud_storage godoc_vfs gitlab
+SOURCE ?= file go_bindata github github_ee bitbucket aws_s3 google_cloud_storage godoc_vfs gitlab iofs
 DATABASE ?= postgres mysql redshift cassandra spanner cockroachdb clickhouse mongodb sqlserver firebird neo4j
 DATABASE_TEST ?= $(DATABASE) sqlite sqlcipher
 VERSION ?= $(shell git describe --tags 2>/dev/null | cut -c 2-)
diff --git a/internal/cli/build_iofs.go b/internal/cli/build_iofs.go
new file mode 100644
index 000000000..2a1346029
--- /dev/null
+++ b/internal/cli/build_iofs.go
@@ -0,0 +1,8 @@
+// +build go1.16
+// +build iofs
+
+package cli
+
+import (
+	_ "github.com/golang-migrate/migrate/v4/source/iofs"
+)
diff --git a/source/errors.go b/source/errors.go
index 93d66e0d4..50203d934 100644
--- a/source/errors.go
+++ b/source/errors.go
@@ -1,15 +1,18 @@
 package source
 
-import "os"
-
 // ErrDuplicateMigration is an error type for reporting duplicate migration
 // files.
 type ErrDuplicateMigration struct {
 	Migration
-	os.FileInfo
+	FileInfo
 }
 
 // Error implements error interface.
 func (e ErrDuplicateMigration) Error() string {
 	return "duplicate migration file: " + e.Name()
 }
+
+// FileInfo is the interface that extracts the minimum required function from os.FileInfo by ErrDuplicateMigration.
+type FileInfo interface {
+	Name() string
+}
diff --git a/source/iofs/README.md b/source/iofs/README.md
index 4a72504bf..c24745694 100644
--- a/source/iofs/README.md
+++ b/source/iofs/README.md
@@ -2,7 +2,7 @@
 
 Driver with file system interface (`io/fs#FS`) supported from Go 1.16.
 
-This Driver cannot be used with versions below Go 1.15.
+This Driver cannot be used with Go versions 1.15 and below.
 
 ## Usage
 
diff --git a/source/iofs/iofs.go b/source/iofs/iofs.go
index 43f820e9c..f889997ed 100644
--- a/source/iofs/iofs.go
+++ b/source/iofs/iofs.go
@@ -5,11 +5,12 @@ package iofs
 import (
 	"errors"
 	"fmt"
+	"io"
 	"io/fs"
-	"net/http"
+	"path"
+	"strconv"
 
 	"github.com/golang-migrate/migrate/v4/source"
-	"github.com/golang-migrate/migrate/v4/source/httpfs"
 )
 
 func init() {
@@ -18,7 +19,9 @@ func init() {
 
 // Iofs is a source driver for io/fs#FS.
 type Iofs struct {
-	httpfs.PartialDriver
+	migrations *source.Migrations
+	fsys       fs.ReadDirFS
+	path       string
 }
 
 // Open by url does not supported with Iofs.
@@ -27,10 +30,131 @@ func (i *Iofs) Open(url string) (source.Driver, error) {
 }
 
 // WithInstance wraps io/fs#FS as source.Driver.
-func WithInstance(fsys fs.FS, path string) (source.Driver, error) {
+func WithInstance(fsys fs.ReadDirFS, path string) (source.Driver, error) {
 	var i Iofs
-	if err := i.Init(http.FS(fsys), path); err != nil {
+	if err := i.Init(fsys, path); err != nil {
 		return nil, fmt.Errorf("failed to init driver with path %s: %w", path, err)
 	}
 	return &i, nil
 }
+
+// Init prepares not initialized Iofs instance to read migrations from a
+// fs.ReadDirFS instance and a relative path.
+func (p *Iofs) Init(fsys fs.ReadDirFS, path string) error {
+	entries, err := fsys.ReadDir(path)
+	if err != nil {
+		return err
+	}
+
+	ms := source.NewMigrations()
+	for _, e := range entries {
+		if e.IsDir() {
+			continue
+		}
+		m, err := source.DefaultParse(e.Name())
+		if err != nil {
+			continue
+		}
+		if !ms.Append(m) {
+			return source.ErrDuplicateMigration{
+				Migration: *m,
+				FileInfo:  e,
+			}
+		}
+	}
+
+	p.fsys = fsys
+	p.path = path
+	p.migrations = ms
+	return nil
+}
+
+// Close is part of source.Driver interface implementation. This is a no-op.
+func (p *Iofs) Close() error {
+	return nil
+}
+
+// First is part of source.Driver interface implementation.
+func (p *Iofs) First() (version uint, err error) {
+	if version, ok := p.migrations.First(); ok {
+		return version, nil
+	}
+	return 0, &fs.PathError{
+		Op:   "first",
+		Path: p.path,
+		Err:  fs.ErrNotExist,
+	}
+}
+
+// Prev is part of source.Driver interface implementation.
+func (p *Iofs) Prev(version uint) (prevVersion uint, err error) {
+	if version, ok := p.migrations.Prev(version); ok {
+		return version, nil
+	}
+	return 0, &fs.PathError{
+		Op:   "prev for version " + strconv.FormatUint(uint64(version), 10),
+		Path: p.path,
+		Err:  fs.ErrNotExist,
+	}
+}
+
+// Next is part of source.Driver interface implementation.
+func (p *Iofs) Next(version uint) (nextVersion uint, err error) {
+	if version, ok := p.migrations.Next(version); ok {
+		return version, nil
+	}
+	return 0, &fs.PathError{
+		Op:   "next for version " + strconv.FormatUint(uint64(version), 10),
+		Path: p.path,
+		Err:  fs.ErrNotExist,
+	}
+}
+
+// ReadUp is part of source.Driver interface implementation.
+func (p *Iofs) ReadUp(version uint) (r io.ReadCloser, identifier string, err error) {
+	if m, ok := p.migrations.Up(version); ok {
+		body, err := p.open(path.Join(p.path, m.Raw))
+		if err != nil {
+			return nil, "", err
+		}
+		return body, m.Identifier, nil
+	}
+	return nil, "", &fs.PathError{
+		Op:   "read up for version " + strconv.FormatUint(uint64(version), 10),
+		Path: p.path,
+		Err:  fs.ErrNotExist,
+	}
+}
+
+// ReadDown is part of source.Driver interface implementation.
+func (p *Iofs) ReadDown(version uint) (r io.ReadCloser, identifier string, err error) {
+	if m, ok := p.migrations.Down(version); ok {
+		body, err := p.open(path.Join(p.path, m.Raw))
+		if err != nil {
+			return nil, "", err
+		}
+		return body, m.Identifier, nil
+	}
+	return nil, "", &fs.PathError{
+		Op:   "read down for version " + strconv.FormatUint(uint64(version), 10),
+		Path: p.path,
+		Err:  fs.ErrNotExist,
+	}
+}
+
+func (p *Iofs) open(path string) (fs.File, error) {
+	f, err := p.fsys.Open(path)
+	if err == nil {
+		return f, nil
+	}
+	// Some non-standard file systems may return errors that don't include the path, that
+	// makes debugging harder.
+	if !errors.As(err, new(*fs.PathError)) {
+		err = &fs.PathError{
+			Op:   "open",
+			Path: path,
+			Err:  err,
+		}
+	}
+	return nil, err
+}

From e18e378b2065bfc93302652a75a0ef31d3486c12 Mon Sep 17 00:00:00 2001
From: Mitsuo Heijo <mitsuo.heijo@gmail.com>
Date: Sat, 14 Nov 2020 21:56:20 +0900
Subject: [PATCH 03/15] Rename Iofs to IoFS, accepts fs.FS and use
 fs.DirEntry.Info() to undo the changes in ErrDuplicateMigration

---
 source/errors.go         |  9 +++-----
 source/iofs/iofs.go      | 44 ++++++++++++++++++++++------------------
 source/iofs/iofs_test.go |  2 +-
 3 files changed, 28 insertions(+), 27 deletions(-)

diff --git a/source/errors.go b/source/errors.go
index 50203d934..93d66e0d4 100644
--- a/source/errors.go
+++ b/source/errors.go
@@ -1,18 +1,15 @@
 package source
 
+import "os"
+
 // ErrDuplicateMigration is an error type for reporting duplicate migration
 // files.
 type ErrDuplicateMigration struct {
 	Migration
-	FileInfo
+	os.FileInfo
 }
 
 // Error implements error interface.
 func (e ErrDuplicateMigration) Error() string {
 	return "duplicate migration file: " + e.Name()
 }
-
-// FileInfo is the interface that extracts the minimum required function from os.FileInfo by ErrDuplicateMigration.
-type FileInfo interface {
-	Name() string
-}
diff --git a/source/iofs/iofs.go b/source/iofs/iofs.go
index f889997ed..ca79ba29f 100644
--- a/source/iofs/iofs.go
+++ b/source/iofs/iofs.go
@@ -14,34 +14,34 @@ import (
 )
 
 func init() {
-	source.Register("iofs", &Iofs{})
+	source.Register("iofs", &IoFS{})
 }
 
-// Iofs is a source driver for io/fs#FS.
-type Iofs struct {
+// IoFS is a source driver for io/fs#FS.
+type IoFS struct {
 	migrations *source.Migrations
-	fsys       fs.ReadDirFS
+	fsys       fs.FS
 	path       string
 }
 
-// Open by url does not supported with Iofs.
-func (i *Iofs) Open(url string) (source.Driver, error) {
+// Open by url does not supported with IoFS.
+func (i *IoFS) Open(url string) (source.Driver, error) {
 	return nil, errors.New("iofs driver does not support open by url")
 }
 
 // WithInstance wraps io/fs#FS as source.Driver.
-func WithInstance(fsys fs.ReadDirFS, path string) (source.Driver, error) {
-	var i Iofs
+func WithInstance(fsys fs.FS, path string) (source.Driver, error) {
+	var i IoFS
 	if err := i.Init(fsys, path); err != nil {
 		return nil, fmt.Errorf("failed to init driver with path %s: %w", path, err)
 	}
 	return &i, nil
 }
 
-// Init prepares not initialized Iofs instance to read migrations from a
-// fs.ReadDirFS instance and a relative path.
-func (p *Iofs) Init(fsys fs.ReadDirFS, path string) error {
-	entries, err := fsys.ReadDir(path)
+// Init prepares not initialized IoFS instance to read migrations from a
+// fs.FS instance and a relative path.
+func (p *IoFS) Init(fsys fs.FS, path string) error {
+	entries, err := fs.ReadDir(fsys, path)
 	if err != nil {
 		return err
 	}
@@ -55,10 +55,14 @@ func (p *Iofs) Init(fsys fs.ReadDirFS, path string) error {
 		if err != nil {
 			continue
 		}
+		file, err := e.Info()
+		if err != nil {
+			continue
+		}
 		if !ms.Append(m) {
 			return source.ErrDuplicateMigration{
 				Migration: *m,
-				FileInfo:  e,
+				FileInfo:  file,
 			}
 		}
 	}
@@ -70,12 +74,12 @@ func (p *Iofs) Init(fsys fs.ReadDirFS, path string) error {
 }
 
 // Close is part of source.Driver interface implementation. This is a no-op.
-func (p *Iofs) Close() error {
+func (p *IoFS) Close() error {
 	return nil
 }
 
 // First is part of source.Driver interface implementation.
-func (p *Iofs) First() (version uint, err error) {
+func (p *IoFS) First() (version uint, err error) {
 	if version, ok := p.migrations.First(); ok {
 		return version, nil
 	}
@@ -87,7 +91,7 @@ func (p *Iofs) First() (version uint, err error) {
 }
 
 // Prev is part of source.Driver interface implementation.
-func (p *Iofs) Prev(version uint) (prevVersion uint, err error) {
+func (p *IoFS) Prev(version uint) (prevVersion uint, err error) {
 	if version, ok := p.migrations.Prev(version); ok {
 		return version, nil
 	}
@@ -99,7 +103,7 @@ func (p *Iofs) Prev(version uint) (prevVersion uint, err error) {
 }
 
 // Next is part of source.Driver interface implementation.
-func (p *Iofs) Next(version uint) (nextVersion uint, err error) {
+func (p *IoFS) Next(version uint) (nextVersion uint, err error) {
 	if version, ok := p.migrations.Next(version); ok {
 		return version, nil
 	}
@@ -111,7 +115,7 @@ func (p *Iofs) Next(version uint) (nextVersion uint, err error) {
 }
 
 // ReadUp is part of source.Driver interface implementation.
-func (p *Iofs) ReadUp(version uint) (r io.ReadCloser, identifier string, err error) {
+func (p *IoFS) ReadUp(version uint) (r io.ReadCloser, identifier string, err error) {
 	if m, ok := p.migrations.Up(version); ok {
 		body, err := p.open(path.Join(p.path, m.Raw))
 		if err != nil {
@@ -127,7 +131,7 @@ func (p *Iofs) ReadUp(version uint) (r io.ReadCloser, identifier string, err err
 }
 
 // ReadDown is part of source.Driver interface implementation.
-func (p *Iofs) ReadDown(version uint) (r io.ReadCloser, identifier string, err error) {
+func (p *IoFS) ReadDown(version uint) (r io.ReadCloser, identifier string, err error) {
 	if m, ok := p.migrations.Down(version); ok {
 		body, err := p.open(path.Join(p.path, m.Raw))
 		if err != nil {
@@ -142,7 +146,7 @@ func (p *Iofs) ReadDown(version uint) (r io.ReadCloser, identifier string, err e
 	}
 }
 
-func (p *Iofs) open(path string) (fs.File, error) {
+func (p *IoFS) open(path string) (fs.File, error) {
 	f, err := p.fsys.Open(path)
 	if err == nil {
 		return f, nil
diff --git a/source/iofs/iofs_test.go b/source/iofs/iofs_test.go
index e2bfba2d8..6f1185f39 100644
--- a/source/iofs/iofs_test.go
+++ b/source/iofs/iofs_test.go
@@ -23,7 +23,7 @@ func Test(t *testing.T) {
 }
 
 func TestOpen(t *testing.T) {
-	i := new(iofs.Iofs)
+	i := new(iofs.IoFS)
 	_, err := i.Open("")
 	if err == nil {
 		t.Fatal("iofs driver does not support open by url")

From e9ae08da0c5abc15d567294012205073e92e35d5 Mon Sep 17 00:00:00 2001
From: Mitsuo Heijo <mitsuo.heijo@gmail.com>
Date: Sun, 15 Nov 2020 13:38:32 +0900
Subject: [PATCH 04/15] fix documents and migration directory for testing

---
 source/iofs/README.md                         | 37 +------------------
 source/iofs/doc.go                            | 10 +++++
 source/iofs/example_test.go                   | 28 ++++++++++++++
 source/iofs/iofs_test.go                      |  7 ++--
 .../{ => migrations}/1_foobar.down.sql        |  0
 .../testdata/{ => migrations}/1_foobar.up.sql |  0
 .../testdata/{ => migrations}/3_foobar.up.sql |  0
 .../{ => migrations}/4_foobar.down.sql        |  0
 .../testdata/{ => migrations}/4_foobar.up.sql |  0
 .../{ => migrations}/5_foobar.down.sql        |  0
 .../{ => migrations}/7_foobar.down.sql        |  0
 .../testdata/{ => migrations}/7_foobar.up.sql |  0
 12 files changed, 42 insertions(+), 40 deletions(-)
 create mode 100644 source/iofs/doc.go
 create mode 100644 source/iofs/example_test.go
 rename source/iofs/testdata/{ => migrations}/1_foobar.down.sql (100%)
 rename source/iofs/testdata/{ => migrations}/1_foobar.up.sql (100%)
 rename source/iofs/testdata/{ => migrations}/3_foobar.up.sql (100%)
 rename source/iofs/testdata/{ => migrations}/4_foobar.down.sql (100%)
 rename source/iofs/testdata/{ => migrations}/4_foobar.up.sql (100%)
 rename source/iofs/testdata/{ => migrations}/5_foobar.down.sql (100%)
 rename source/iofs/testdata/{ => migrations}/7_foobar.down.sql (100%)
 rename source/iofs/testdata/{ => migrations}/7_foobar.up.sql (100%)

diff --git a/source/iofs/README.md b/source/iofs/README.md
index c24745694..d75b328b9 100644
--- a/source/iofs/README.md
+++ b/source/iofs/README.md
@@ -1,38 +1,3 @@
 # iofs
 
-Driver with file system interface (`io/fs#FS`) supported from Go 1.16.
-
-This Driver cannot be used with Go versions 1.15 and below.
-
-## Usage
-
-Directory embedding example
-
-```go
-package main
-
-import (
-	"embed"
-	"log"
-
-	"github.com/golang-migrate/migrate/v4"
-	_ "github.com/golang-migrate/migrate/v4/database/postgres"
-	"github.com/golang-migrate/migrate/v4/source/iofs"
-)
-
-//go:embed migrations
-var fs embed.FS
-
-func main() {
-	d, err := iofs.WithInstance(fs, "migrations")
-	if err != nil {
-		log.Fatal(err)
-	}
-	m, err := migrate.NewWithSourceInstance("iofs", d, "postgres://postgres@localhost/postgres?sslmode=disable")
-	if err != nil {
-		log.Fatal(err)
-	}
-	err = m.Up()
-	// ...
-}
-```
+https://pkg.go.dev/github.com/golang-migrate/migrate/v4/source/iofs
diff --git a/source/iofs/doc.go b/source/iofs/doc.go
new file mode 100644
index 000000000..6b2c862e0
--- /dev/null
+++ b/source/iofs/doc.go
@@ -0,0 +1,10 @@
+/*
+Package iofs provides the Go 1.16+ io/fs#FS driver.
+
+It can accept various file systems (like embed.FS, archive/zip#Reader) implementing io/fs#FS.
+
+This driver cannot be used with Go versions 1.15 and below.
+
+Also, Opening with a URL scheme is not supported.
+*/
+package iofs
diff --git a/source/iofs/example_test.go b/source/iofs/example_test.go
new file mode 100644
index 000000000..f8d1e7571
--- /dev/null
+++ b/source/iofs/example_test.go
@@ -0,0 +1,28 @@
+// +build go1.16
+
+package iofs_test
+
+import (
+	"embed"
+	"log"
+
+	"github.com/golang-migrate/migrate/v4"
+	_ "github.com/golang-migrate/migrate/v4/database/postgres"
+	"github.com/golang-migrate/migrate/v4/source/iofs"
+)
+
+//go:embed testdata/migrations/*.sql
+var fs embed.FS
+
+func Example() {
+	d, err := iofs.WithInstance(fs, "testdata/migrations")
+	if err != nil {
+		log.Fatal(err)
+	}
+	m, err := migrate.NewWithSourceInstance("iofs", d, "postgres://postgres@localhost/postgres?sslmode=disable")
+	if err != nil {
+		log.Fatal(err)
+	}
+	err = m.Up()
+	// ...
+}
diff --git a/source/iofs/iofs_test.go b/source/iofs/iofs_test.go
index 6f1185f39..16f2055e6 100644
--- a/source/iofs/iofs_test.go
+++ b/source/iofs/iofs_test.go
@@ -10,11 +10,10 @@ import (
 	st "github.com/golang-migrate/migrate/v4/source/testing"
 )
 
-//go:embed testdata
-var fs embed.FS
-
 func Test(t *testing.T) {
-	d, err := iofs.WithInstance(fs, "testdata")
+	//go:embed testdata/migrations/*.sql
+	var fs embed.FS
+	d, err := iofs.WithInstance(fs, "testdata/migrations")
 	if err != nil {
 		t.Fatal(err)
 	}
diff --git a/source/iofs/testdata/1_foobar.down.sql b/source/iofs/testdata/migrations/1_foobar.down.sql
similarity index 100%
rename from source/iofs/testdata/1_foobar.down.sql
rename to source/iofs/testdata/migrations/1_foobar.down.sql
diff --git a/source/iofs/testdata/1_foobar.up.sql b/source/iofs/testdata/migrations/1_foobar.up.sql
similarity index 100%
rename from source/iofs/testdata/1_foobar.up.sql
rename to source/iofs/testdata/migrations/1_foobar.up.sql
diff --git a/source/iofs/testdata/3_foobar.up.sql b/source/iofs/testdata/migrations/3_foobar.up.sql
similarity index 100%
rename from source/iofs/testdata/3_foobar.up.sql
rename to source/iofs/testdata/migrations/3_foobar.up.sql
diff --git a/source/iofs/testdata/4_foobar.down.sql b/source/iofs/testdata/migrations/4_foobar.down.sql
similarity index 100%
rename from source/iofs/testdata/4_foobar.down.sql
rename to source/iofs/testdata/migrations/4_foobar.down.sql
diff --git a/source/iofs/testdata/4_foobar.up.sql b/source/iofs/testdata/migrations/4_foobar.up.sql
similarity index 100%
rename from source/iofs/testdata/4_foobar.up.sql
rename to source/iofs/testdata/migrations/4_foobar.up.sql
diff --git a/source/iofs/testdata/5_foobar.down.sql b/source/iofs/testdata/migrations/5_foobar.down.sql
similarity index 100%
rename from source/iofs/testdata/5_foobar.down.sql
rename to source/iofs/testdata/migrations/5_foobar.down.sql
diff --git a/source/iofs/testdata/7_foobar.down.sql b/source/iofs/testdata/migrations/7_foobar.down.sql
similarity index 100%
rename from source/iofs/testdata/7_foobar.down.sql
rename to source/iofs/testdata/migrations/7_foobar.down.sql
diff --git a/source/iofs/testdata/7_foobar.up.sql b/source/iofs/testdata/migrations/7_foobar.up.sql
similarity index 100%
rename from source/iofs/testdata/7_foobar.up.sql
rename to source/iofs/testdata/migrations/7_foobar.up.sql

From 416f878661f8409d2e111b267b0a14d66a1540a4 Mon Sep 17 00:00:00 2001
From: Mitsuo Heijo <mitsuo.heijo@gmail.com>
Date: Sun, 15 Nov 2020 17:48:53 +0900
Subject: [PATCH 05/15] Fix iofs.Driver so that it can be used by embedding it
 like httpfs.PartialDriver

---
 source/iofs/example_test.go |  2 +-
 source/iofs/iofs.go         | 75 ++++++++++++++++++-------------------
 source/iofs/iofs_test.go    | 10 +----
 3 files changed, 38 insertions(+), 49 deletions(-)

diff --git a/source/iofs/example_test.go b/source/iofs/example_test.go
index f8d1e7571..6b55f5e6e 100644
--- a/source/iofs/example_test.go
+++ b/source/iofs/example_test.go
@@ -15,7 +15,7 @@ import (
 var fs embed.FS
 
 func Example() {
-	d, err := iofs.WithInstance(fs, "testdata/migrations")
+	d, err := iofs.NewDriver(fs, "testdata/migrations")
 	if err != nil {
 		log.Fatal(err)
 	}
diff --git a/source/iofs/iofs.go b/source/iofs/iofs.go
index ca79ba29f..b90c008f1 100644
--- a/source/iofs/iofs.go
+++ b/source/iofs/iofs.go
@@ -13,34 +13,31 @@ import (
 	"github.com/golang-migrate/migrate/v4/source"
 )
 
-func init() {
-	source.Register("iofs", &IoFS{})
-}
-
-// IoFS is a source driver for io/fs#FS.
-type IoFS struct {
+// Driver is a source driver that wraps io/fs#FS.
+type Driver struct {
 	migrations *source.Migrations
 	fsys       fs.FS
 	path       string
 }
 
-// Open by url does not supported with IoFS.
-func (i *IoFS) Open(url string) (source.Driver, error) {
-	return nil, errors.New("iofs driver does not support open by url")
-}
-
-// WithInstance wraps io/fs#FS as source.Driver.
-func WithInstance(fsys fs.FS, path string) (source.Driver, error) {
-	var i IoFS
+// NewDriver returns a new Driver from io/fs#FS and a relative path.
+func NewDriver(fsys fs.FS, path string) (source.Driver, error) {
+	var i Driver
 	if err := i.Init(fsys, path); err != nil {
 		return nil, fmt.Errorf("failed to init driver with path %s: %w", path, err)
 	}
 	return &i, nil
 }
 
+// Open is part of source.Driver interface implementation.
+// Open panics when called directly.
+func (i *Driver) Open(url string) (source.Driver, error) {
+	panic("iofs: Driver does not support open with url")
+}
+
 // Init prepares not initialized IoFS instance to read migrations from a
-// fs.FS instance and a relative path.
-func (p *IoFS) Init(fsys fs.FS, path string) error {
+// io/fs#FS instance and a relative path.
+func (i *Driver) Init(fsys fs.FS, path string) error {
 	entries, err := fs.ReadDir(fsys, path)
 	if err != nil {
 		return err
@@ -67,57 +64,57 @@ func (p *IoFS) Init(fsys fs.FS, path string) error {
 		}
 	}
 
-	p.fsys = fsys
-	p.path = path
-	p.migrations = ms
+	i.fsys = fsys
+	i.path = path
+	i.migrations = ms
 	return nil
 }
 
 // Close is part of source.Driver interface implementation. This is a no-op.
-func (p *IoFS) Close() error {
+func (i *Driver) Close() error {
 	return nil
 }
 
 // First is part of source.Driver interface implementation.
-func (p *IoFS) First() (version uint, err error) {
-	if version, ok := p.migrations.First(); ok {
+func (i *Driver) First() (version uint, err error) {
+	if version, ok := i.migrations.First(); ok {
 		return version, nil
 	}
 	return 0, &fs.PathError{
 		Op:   "first",
-		Path: p.path,
+		Path: i.path,
 		Err:  fs.ErrNotExist,
 	}
 }
 
 // Prev is part of source.Driver interface implementation.
-func (p *IoFS) Prev(version uint) (prevVersion uint, err error) {
-	if version, ok := p.migrations.Prev(version); ok {
+func (i *Driver) Prev(version uint) (prevVersion uint, err error) {
+	if version, ok := i.migrations.Prev(version); ok {
 		return version, nil
 	}
 	return 0, &fs.PathError{
 		Op:   "prev for version " + strconv.FormatUint(uint64(version), 10),
-		Path: p.path,
+		Path: i.path,
 		Err:  fs.ErrNotExist,
 	}
 }
 
 // Next is part of source.Driver interface implementation.
-func (p *IoFS) Next(version uint) (nextVersion uint, err error) {
-	if version, ok := p.migrations.Next(version); ok {
+func (i *Driver) Next(version uint) (nextVersion uint, err error) {
+	if version, ok := i.migrations.Next(version); ok {
 		return version, nil
 	}
 	return 0, &fs.PathError{
 		Op:   "next for version " + strconv.FormatUint(uint64(version), 10),
-		Path: p.path,
+		Path: i.path,
 		Err:  fs.ErrNotExist,
 	}
 }
 
 // ReadUp is part of source.Driver interface implementation.
-func (p *IoFS) ReadUp(version uint) (r io.ReadCloser, identifier string, err error) {
-	if m, ok := p.migrations.Up(version); ok {
-		body, err := p.open(path.Join(p.path, m.Raw))
+func (i *Driver) ReadUp(version uint) (r io.ReadCloser, identifier string, err error) {
+	if m, ok := i.migrations.Up(version); ok {
+		body, err := i.open(path.Join(i.path, m.Raw))
 		if err != nil {
 			return nil, "", err
 		}
@@ -125,15 +122,15 @@ func (p *IoFS) ReadUp(version uint) (r io.ReadCloser, identifier string, err err
 	}
 	return nil, "", &fs.PathError{
 		Op:   "read up for version " + strconv.FormatUint(uint64(version), 10),
-		Path: p.path,
+		Path: i.path,
 		Err:  fs.ErrNotExist,
 	}
 }
 
 // ReadDown is part of source.Driver interface implementation.
-func (p *IoFS) ReadDown(version uint) (r io.ReadCloser, identifier string, err error) {
-	if m, ok := p.migrations.Down(version); ok {
-		body, err := p.open(path.Join(p.path, m.Raw))
+func (i *Driver) ReadDown(version uint) (r io.ReadCloser, identifier string, err error) {
+	if m, ok := i.migrations.Down(version); ok {
+		body, err := i.open(path.Join(i.path, m.Raw))
 		if err != nil {
 			return nil, "", err
 		}
@@ -141,13 +138,13 @@ func (p *IoFS) ReadDown(version uint) (r io.ReadCloser, identifier string, err e
 	}
 	return nil, "", &fs.PathError{
 		Op:   "read down for version " + strconv.FormatUint(uint64(version), 10),
-		Path: p.path,
+		Path: i.path,
 		Err:  fs.ErrNotExist,
 	}
 }
 
-func (p *IoFS) open(path string) (fs.File, error) {
-	f, err := p.fsys.Open(path)
+func (i *Driver) open(path string) (fs.File, error) {
+	f, err := i.fsys.Open(path)
 	if err == nil {
 		return f, nil
 	}
diff --git a/source/iofs/iofs_test.go b/source/iofs/iofs_test.go
index 16f2055e6..1a440d8ce 100644
--- a/source/iofs/iofs_test.go
+++ b/source/iofs/iofs_test.go
@@ -13,18 +13,10 @@ import (
 func Test(t *testing.T) {
 	//go:embed testdata/migrations/*.sql
 	var fs embed.FS
-	d, err := iofs.WithInstance(fs, "testdata/migrations")
+	d, err := iofs.NewDriver(fs, "testdata/migrations")
 	if err != nil {
 		t.Fatal(err)
 	}
 
 	st.Test(t, d)
 }
-
-func TestOpen(t *testing.T) {
-	i := new(iofs.IoFS)
-	_, err := i.Open("")
-	if err == nil {
-		t.Fatal("iofs driver does not support open by url")
-	}
-}

From 45ec3dc77310866e7119079620a8a3c1f078c340 Mon Sep 17 00:00:00 2001
From: Mitsuo Heijo <mitsuo.heijo@gmail.com>
Date: Sun, 15 Nov 2020 18:58:51 +0900
Subject: [PATCH 06/15] iofs.Driver closes the file system if possible

---
 source/iofs/iofs.go | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/source/iofs/iofs.go b/source/iofs/iofs.go
index b90c008f1..b95e757d4 100644
--- a/source/iofs/iofs.go
+++ b/source/iofs/iofs.go
@@ -70,9 +70,14 @@ func (i *Driver) Init(fsys fs.FS, path string) error {
 	return nil
 }
 
-// Close is part of source.Driver interface implementation. This is a no-op.
-func (i *Driver) Close() error {
-	return nil
+// Close is part of source.Driver interface implementation.
+// Closes the file system if possible.
+func (d *Driver) Close() error {
+	c, ok := d.fsys.(io.Closer)
+	if !ok {
+		return nil
+	}
+	return c.Close()
 }
 
 // First is part of source.Driver interface implementation.

From 3af8acfc6c7f2bf11557a4f7b32a9b3301202a0b Mon Sep 17 00:00:00 2001
From: Mitsuo Heijo <mitsuo.heijo@gmail.com>
Date: Sun, 15 Nov 2020 18:59:23 +0900
Subject: [PATCH 07/15] Rename receiver

---
 source/iofs/iofs.go | 48 ++++++++++++++++++++++-----------------------
 1 file changed, 24 insertions(+), 24 deletions(-)

diff --git a/source/iofs/iofs.go b/source/iofs/iofs.go
index b95e757d4..63a2330ba 100644
--- a/source/iofs/iofs.go
+++ b/source/iofs/iofs.go
@@ -31,13 +31,13 @@ func NewDriver(fsys fs.FS, path string) (source.Driver, error) {
 
 // Open is part of source.Driver interface implementation.
 // Open panics when called directly.
-func (i *Driver) Open(url string) (source.Driver, error) {
+func (d *Driver) Open(url string) (source.Driver, error) {
 	panic("iofs: Driver does not support open with url")
 }
 
 // Init prepares not initialized IoFS instance to read migrations from a
 // io/fs#FS instance and a relative path.
-func (i *Driver) Init(fsys fs.FS, path string) error {
+func (d *Driver) Init(fsys fs.FS, path string) error {
 	entries, err := fs.ReadDir(fsys, path)
 	if err != nil {
 		return err
@@ -64,9 +64,9 @@ func (i *Driver) Init(fsys fs.FS, path string) error {
 		}
 	}
 
-	i.fsys = fsys
-	i.path = path
-	i.migrations = ms
+	d.fsys = fsys
+	d.path = path
+	d.migrations = ms
 	return nil
 }
 
@@ -81,45 +81,45 @@ func (d *Driver) Close() error {
 }
 
 // First is part of source.Driver interface implementation.
-func (i *Driver) First() (version uint, err error) {
-	if version, ok := i.migrations.First(); ok {
+func (d *Driver) First() (version uint, err error) {
+	if version, ok := d.migrations.First(); ok {
 		return version, nil
 	}
 	return 0, &fs.PathError{
 		Op:   "first",
-		Path: i.path,
+		Path: d.path,
 		Err:  fs.ErrNotExist,
 	}
 }
 
 // Prev is part of source.Driver interface implementation.
-func (i *Driver) Prev(version uint) (prevVersion uint, err error) {
-	if version, ok := i.migrations.Prev(version); ok {
+func (d *Driver) Prev(version uint) (prevVersion uint, err error) {
+	if version, ok := d.migrations.Prev(version); ok {
 		return version, nil
 	}
 	return 0, &fs.PathError{
 		Op:   "prev for version " + strconv.FormatUint(uint64(version), 10),
-		Path: i.path,
+		Path: d.path,
 		Err:  fs.ErrNotExist,
 	}
 }
 
 // Next is part of source.Driver interface implementation.
-func (i *Driver) Next(version uint) (nextVersion uint, err error) {
-	if version, ok := i.migrations.Next(version); ok {
+func (d *Driver) Next(version uint) (nextVersion uint, err error) {
+	if version, ok := d.migrations.Next(version); ok {
 		return version, nil
 	}
 	return 0, &fs.PathError{
 		Op:   "next for version " + strconv.FormatUint(uint64(version), 10),
-		Path: i.path,
+		Path: d.path,
 		Err:  fs.ErrNotExist,
 	}
 }
 
 // ReadUp is part of source.Driver interface implementation.
-func (i *Driver) ReadUp(version uint) (r io.ReadCloser, identifier string, err error) {
-	if m, ok := i.migrations.Up(version); ok {
-		body, err := i.open(path.Join(i.path, m.Raw))
+func (d *Driver) ReadUp(version uint) (r io.ReadCloser, identifier string, err error) {
+	if m, ok := d.migrations.Up(version); ok {
+		body, err := d.open(path.Join(d.path, m.Raw))
 		if err != nil {
 			return nil, "", err
 		}
@@ -127,15 +127,15 @@ func (i *Driver) ReadUp(version uint) (r io.ReadCloser, identifier string, err e
 	}
 	return nil, "", &fs.PathError{
 		Op:   "read up for version " + strconv.FormatUint(uint64(version), 10),
-		Path: i.path,
+		Path: d.path,
 		Err:  fs.ErrNotExist,
 	}
 }
 
 // ReadDown is part of source.Driver interface implementation.
-func (i *Driver) ReadDown(version uint) (r io.ReadCloser, identifier string, err error) {
-	if m, ok := i.migrations.Down(version); ok {
-		body, err := i.open(path.Join(i.path, m.Raw))
+func (d *Driver) ReadDown(version uint) (r io.ReadCloser, identifier string, err error) {
+	if m, ok := d.migrations.Down(version); ok {
+		body, err := d.open(path.Join(d.path, m.Raw))
 		if err != nil {
 			return nil, "", err
 		}
@@ -143,13 +143,13 @@ func (i *Driver) ReadDown(version uint) (r io.ReadCloser, identifier string, err
 	}
 	return nil, "", &fs.PathError{
 		Op:   "read down for version " + strconv.FormatUint(uint64(version), 10),
-		Path: i.path,
+		Path: d.path,
 		Err:  fs.ErrNotExist,
 	}
 }
 
-func (i *Driver) open(path string) (fs.File, error) {
-	f, err := i.fsys.Open(path)
+func (d *Driver) open(path string) (fs.File, error) {
+	f, err := d.fsys.Open(path)
 	if err == nil {
 		return f, nil
 	}

From 0e9937b5de9c146d3038db4310dc1fe86472cc6a Mon Sep 17 00:00:00 2001
From: Mitsuo Heijo <mitsuo.heijo@gmail.com>
Date: Sun, 15 Nov 2020 19:04:40 +0900
Subject: [PATCH 08/15] Refactor file driver to use iofs.Driver

---
 source/file/file.go       | 27 ++++++---------------------
 source/file/file_go115.go | 32 ++++++++++++++++++++++++++++++++
 source/file/file_go116.go | 31 +++++++++++++++++++++++++++++++
 3 files changed, 69 insertions(+), 21 deletions(-)
 create mode 100644 source/file/file_go115.go
 create mode 100644 source/file/file_go116.go

diff --git a/source/file/file.go b/source/file/file.go
index ee10d08d1..b56e5ddbd 100644
--- a/source/file/file.go
+++ b/source/file/file.go
@@ -1,31 +1,24 @@
 package file
 
 import (
-	"net/http"
 	nurl "net/url"
 	"os"
 	"path/filepath"
 
 	"github.com/golang-migrate/migrate/v4/source"
-	"github.com/golang-migrate/migrate/v4/source/httpfs"
 )
 
 func init() {
 	source.Register("file", &File{})
 }
 
-type File struct {
-	httpfs.PartialDriver
-	url  string
-	path string
-}
+type File = file
 
-func (f *File) Open(url string) (source.Driver, error) {
+func parseURL(url string) (string, error) {
 	u, err := nurl.Parse(url)
 	if err != nil {
-		return nil, err
+		return "", err
 	}
-
 	// concat host and path to restore full path
 	// host might be `.`
 	p := u.Opaque
@@ -37,7 +30,7 @@ func (f *File) Open(url string) (source.Driver, error) {
 		// default to current directory if no path
 		wd, err := os.Getwd()
 		if err != nil {
-			return nil, err
+			return "", err
 		}
 		p = wd
 
@@ -45,17 +38,9 @@ func (f *File) Open(url string) (source.Driver, error) {
 		// make path absolute if relative
 		abs, err := filepath.Abs(p)
 		if err != nil {
-			return nil, err
+			return "", err
 		}
 		p = abs
 	}
-
-	nf := &File{
-		url:  url,
-		path: p,
-	}
-	if err := nf.Init(http.Dir(p), ""); err != nil {
-		return nil, err
-	}
-	return nf, nil
+	return p, nil
 }
diff --git a/source/file/file_go115.go b/source/file/file_go115.go
new file mode 100644
index 000000000..6fd502277
--- /dev/null
+++ b/source/file/file_go115.go
@@ -0,0 +1,32 @@
+// +build !go1.16
+
+package file
+
+import (
+	"net/http"
+
+	"github.com/golang-migrate/migrate/v4/source"
+	"github.com/golang-migrate/migrate/v4/source/httpfs"
+)
+
+type file struct {
+	httpfs.PartialDriver
+	url  string
+	path string
+}
+
+func (f *file) Open(url string) (source.Driver, error) {
+	p, err := parseURL(url)
+	if err != nil {
+		return nil, err
+	}
+
+	nf := &File{
+		url:  url,
+		path: p,
+	}
+	if err := nf.Init(http.Dir(p), ""); err != nil {
+		return nil, err
+	}
+	return nf, nil
+}
diff --git a/source/file/file_go116.go b/source/file/file_go116.go
new file mode 100644
index 000000000..eca1b1394
--- /dev/null
+++ b/source/file/file_go116.go
@@ -0,0 +1,31 @@
+// +build go1.16
+
+package file
+
+import (
+	"os"
+
+	"github.com/golang-migrate/migrate/v4/source"
+	"github.com/golang-migrate/migrate/v4/source/iofs"
+)
+
+type file struct {
+	iofs.Driver
+	url  string
+	path string
+}
+
+func (f *file) Open(url string) (source.Driver, error) {
+	p, err := parseURL(url)
+	if err != nil {
+		return nil, err
+	}
+	nf := &file{
+		url:  url,
+		path: p,
+	}
+	if err := nf.Init(os.DirFS(p), "."); err != nil {
+		return nil, err
+	}
+	return nf, nil
+}

From 7fb518d4d79380415b737130d9fa38e9b2b5562a Mon Sep 17 00:00:00 2001
From: Mitsuo Heijo <mitsuo.heijo@gmail.com>
Date: Sun, 15 Nov 2020 19:04:54 +0900
Subject: [PATCH 09/15] iofs build constraint is not needed so remove it

---
 Makefile                   | 2 +-
 internal/cli/build_iofs.go | 8 --------
 2 files changed, 1 insertion(+), 9 deletions(-)
 delete mode 100644 internal/cli/build_iofs.go

diff --git a/Makefile b/Makefile
index ddf03bead..152cdb7bd 100644
--- a/Makefile
+++ b/Makefile
@@ -1,4 +1,4 @@
-SOURCE ?= file go_bindata github github_ee bitbucket aws_s3 google_cloud_storage godoc_vfs gitlab iofs
+SOURCE ?= file go_bindata github github_ee bitbucket aws_s3 google_cloud_storage godoc_vfs gitlab
 DATABASE ?= postgres mysql redshift cassandra spanner cockroachdb clickhouse mongodb sqlserver firebird neo4j
 DATABASE_TEST ?= $(DATABASE) sqlite sqlcipher
 VERSION ?= $(shell git describe --tags 2>/dev/null | cut -c 2-)
diff --git a/internal/cli/build_iofs.go b/internal/cli/build_iofs.go
deleted file mode 100644
index 2a1346029..000000000
--- a/internal/cli/build_iofs.go
+++ /dev/null
@@ -1,8 +0,0 @@
-// +build go1.16
-// +build iofs
-
-package cli
-
-import (
-	_ "github.com/golang-migrate/migrate/v4/source/iofs"
-)

From 3c0290b8815f2dd7e00ff34358e15d700eab2314 Mon Sep 17 00:00:00 2001
From: Mitsuo Heijo <mitsuo.heijo@gmail.com>
Date: Sun, 15 Nov 2020 19:08:13 +0900
Subject: [PATCH 10/15] Properly return an error in a corner case

---
 source/iofs/iofs.go | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/source/iofs/iofs.go b/source/iofs/iofs.go
index 63a2330ba..048b75bcb 100644
--- a/source/iofs/iofs.go
+++ b/source/iofs/iofs.go
@@ -50,11 +50,11 @@ func (d *Driver) Init(fsys fs.FS, path string) error {
 		}
 		m, err := source.DefaultParse(e.Name())
 		if err != nil {
-			continue
+			return err
 		}
 		file, err := e.Info()
 		if err != nil {
-			continue
+			return err
 		}
 		if !ms.Append(m) {
 			return source.ErrDuplicateMigration{

From 2cd12a63b50b7ac48d12dd0adc1ec4f4b49c3b93 Mon Sep 17 00:00:00 2001
From: Mitsuo Heijo <mitsuo.heijo@gmail.com>
Date: Sun, 15 Nov 2020 21:54:00 +0900
Subject: [PATCH 11/15] Increase golangci-lint timeout

---
 .golangci.yml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/.golangci.yml b/.golangci.yml
index f447ee1ce..916eb75c7 100644
--- a/.golangci.yml
+++ b/.golangci.yml
@@ -1,6 +1,6 @@
 run:
   # timeout for analysis, e.g. 30s, 5m, default is 1m
-  timeout: 2m
+  timeout: 5m
 linters:
   enable:
     #- golint

From ca6628d88ee8b51143861a9bb7f5b49c2fc6895d Mon Sep 17 00:00:00 2001
From: Mitsuo Heijo <mitsuo.heijo@gmail.com>
Date: Sun, 15 Nov 2020 21:54:35 +0900
Subject: [PATCH 12/15] Fix example code

---
 source/iofs/example_test.go | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/source/iofs/example_test.go b/source/iofs/example_test.go
index 6b55f5e6e..957710cbf 100644
--- a/source/iofs/example_test.go
+++ b/source/iofs/example_test.go
@@ -24,5 +24,8 @@ func Example() {
 		log.Fatal(err)
 	}
 	err = m.Up()
+	if err != nil {
+		// ...
+	}
 	// ...
 }

From 58e98376671528d02bab9efa82a8fd50b3348cf5 Mon Sep 17 00:00:00 2001
From: Mitsuo Heijo <mitsuo.heijo@gmail.com>
Date: Tue, 17 Nov 2020 19:57:37 +0900
Subject: [PATCH 13/15] Revert "Increase golangci-lint timeout"

This reverts commit 2cd12a63b50b7ac48d12dd0adc1ec4f4b49c3b93.
---
 .golangci.yml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/.golangci.yml b/.golangci.yml
index 916eb75c7..f447ee1ce 100644
--- a/.golangci.yml
+++ b/.golangci.yml
@@ -1,6 +1,6 @@
 run:
   # timeout for analysis, e.g. 30s, 5m, default is 1m
-  timeout: 5m
+  timeout: 2m
 linters:
   enable:
     #- golint

From 321662e41ab5f2a8b55d35098f60f45fe5093c27 Mon Sep 17 00:00:00 2001
From: Mitsuo Heijo <mitsuo.heijo@gmail.com>
Date: Tue, 17 Nov 2020 20:15:14 +0900
Subject: [PATCH 14/15] unexport driver, add iofs.PartialDriver, remove type
 alias from file driver

---
 source/file/file.go         |  2 --
 source/file/file_go115.go   |  4 ++--
 source/file/file_go116.go   |  8 +++----
 source/iofs/example_test.go |  2 +-
 source/iofs/iofs.go         | 47 ++++++++++++++++++++++---------------
 source/iofs/iofs_test.go    |  2 +-
 6 files changed, 36 insertions(+), 29 deletions(-)

diff --git a/source/file/file.go b/source/file/file.go
index b56e5ddbd..82408b99a 100644
--- a/source/file/file.go
+++ b/source/file/file.go
@@ -12,8 +12,6 @@ func init() {
 	source.Register("file", &File{})
 }
 
-type File = file
-
 func parseURL(url string) (string, error) {
 	u, err := nurl.Parse(url)
 	if err != nil {
diff --git a/source/file/file_go115.go b/source/file/file_go115.go
index 6fd502277..e2857b364 100644
--- a/source/file/file_go115.go
+++ b/source/file/file_go115.go
@@ -9,13 +9,13 @@ import (
 	"github.com/golang-migrate/migrate/v4/source/httpfs"
 )
 
-type file struct {
+type File struct {
 	httpfs.PartialDriver
 	url  string
 	path string
 }
 
-func (f *file) Open(url string) (source.Driver, error) {
+func (f *File) Open(url string) (source.Driver, error) {
 	p, err := parseURL(url)
 	if err != nil {
 		return nil, err
diff --git a/source/file/file_go116.go b/source/file/file_go116.go
index eca1b1394..5203b4bdb 100644
--- a/source/file/file_go116.go
+++ b/source/file/file_go116.go
@@ -9,18 +9,18 @@ import (
 	"github.com/golang-migrate/migrate/v4/source/iofs"
 )
 
-type file struct {
-	iofs.Driver
+type File struct {
+	iofs.PartialDriver
 	url  string
 	path string
 }
 
-func (f *file) Open(url string) (source.Driver, error) {
+func (f *File) Open(url string) (source.Driver, error) {
 	p, err := parseURL(url)
 	if err != nil {
 		return nil, err
 	}
-	nf := &file{
+	nf := &File{
 		url:  url,
 		path: p,
 	}
diff --git a/source/iofs/example_test.go b/source/iofs/example_test.go
index 957710cbf..87d4e568b 100644
--- a/source/iofs/example_test.go
+++ b/source/iofs/example_test.go
@@ -15,7 +15,7 @@ import (
 var fs embed.FS
 
 func Example() {
-	d, err := iofs.NewDriver(fs, "testdata/migrations")
+	d, err := iofs.New(fs, "testdata/migrations")
 	if err != nil {
 		log.Fatal(err)
 	}
diff --git a/source/iofs/iofs.go b/source/iofs/iofs.go
index 048b75bcb..b558e79fe 100644
--- a/source/iofs/iofs.go
+++ b/source/iofs/iofs.go
@@ -13,16 +13,13 @@ import (
 	"github.com/golang-migrate/migrate/v4/source"
 )
 
-// Driver is a source driver that wraps io/fs#FS.
-type Driver struct {
-	migrations *source.Migrations
-	fsys       fs.FS
-	path       string
+type driver struct {
+	PartialDriver
 }
 
-// NewDriver returns a new Driver from io/fs#FS and a relative path.
-func NewDriver(fsys fs.FS, path string) (source.Driver, error) {
-	var i Driver
+// New returns a new Driver from io/fs#FS and a relative path.
+func New(fsys fs.FS, path string) (source.Driver, error) {
+	var i driver
 	if err := i.Init(fsys, path); err != nil {
 		return nil, fmt.Errorf("failed to init driver with path %s: %w", path, err)
 	}
@@ -31,13 +28,25 @@ func NewDriver(fsys fs.FS, path string) (source.Driver, error) {
 
 // Open is part of source.Driver interface implementation.
 // Open panics when called directly.
-func (d *Driver) Open(url string) (source.Driver, error) {
-	panic("iofs: Driver does not support open with url")
+func (d *driver) Open(url string) (source.Driver, error) {
+	panic("iofs: driver does not support open with url")
+}
+
+// PartialDriver is a helper service for creating new source drivers working with
+// io/fs.FS instances. It implements all source.Driver interface methods
+// except for Open(). New driver could embed this struct and add missing Open()
+// method.
+//
+// To prepare PartialDriver for use Init() function.
+type PartialDriver struct {
+	migrations *source.Migrations
+	fsys       fs.FS
+	path       string
 }
 
 // Init prepares not initialized IoFS instance to read migrations from a
 // io/fs#FS instance and a relative path.
-func (d *Driver) Init(fsys fs.FS, path string) error {
+func (d *PartialDriver) Init(fsys fs.FS, path string) error {
 	entries, err := fs.ReadDir(fsys, path)
 	if err != nil {
 		return err
@@ -50,7 +59,7 @@ func (d *Driver) Init(fsys fs.FS, path string) error {
 		}
 		m, err := source.DefaultParse(e.Name())
 		if err != nil {
-			return err
+			continue
 		}
 		file, err := e.Info()
 		if err != nil {
@@ -72,7 +81,7 @@ func (d *Driver) Init(fsys fs.FS, path string) error {
 
 // Close is part of source.Driver interface implementation.
 // Closes the file system if possible.
-func (d *Driver) Close() error {
+func (d *PartialDriver) Close() error {
 	c, ok := d.fsys.(io.Closer)
 	if !ok {
 		return nil
@@ -81,7 +90,7 @@ func (d *Driver) Close() error {
 }
 
 // First is part of source.Driver interface implementation.
-func (d *Driver) First() (version uint, err error) {
+func (d *PartialDriver) First() (version uint, err error) {
 	if version, ok := d.migrations.First(); ok {
 		return version, nil
 	}
@@ -93,7 +102,7 @@ func (d *Driver) First() (version uint, err error) {
 }
 
 // Prev is part of source.Driver interface implementation.
-func (d *Driver) Prev(version uint) (prevVersion uint, err error) {
+func (d *PartialDriver) Prev(version uint) (prevVersion uint, err error) {
 	if version, ok := d.migrations.Prev(version); ok {
 		return version, nil
 	}
@@ -105,7 +114,7 @@ func (d *Driver) Prev(version uint) (prevVersion uint, err error) {
 }
 
 // Next is part of source.Driver interface implementation.
-func (d *Driver) Next(version uint) (nextVersion uint, err error) {
+func (d *PartialDriver) Next(version uint) (nextVersion uint, err error) {
 	if version, ok := d.migrations.Next(version); ok {
 		return version, nil
 	}
@@ -117,7 +126,7 @@ func (d *Driver) Next(version uint) (nextVersion uint, err error) {
 }
 
 // ReadUp is part of source.Driver interface implementation.
-func (d *Driver) ReadUp(version uint) (r io.ReadCloser, identifier string, err error) {
+func (d *PartialDriver) ReadUp(version uint) (r io.ReadCloser, identifier string, err error) {
 	if m, ok := d.migrations.Up(version); ok {
 		body, err := d.open(path.Join(d.path, m.Raw))
 		if err != nil {
@@ -133,7 +142,7 @@ func (d *Driver) ReadUp(version uint) (r io.ReadCloser, identifier string, err e
 }
 
 // ReadDown is part of source.Driver interface implementation.
-func (d *Driver) ReadDown(version uint) (r io.ReadCloser, identifier string, err error) {
+func (d *PartialDriver) ReadDown(version uint) (r io.ReadCloser, identifier string, err error) {
 	if m, ok := d.migrations.Down(version); ok {
 		body, err := d.open(path.Join(d.path, m.Raw))
 		if err != nil {
@@ -148,7 +157,7 @@ func (d *Driver) ReadDown(version uint) (r io.ReadCloser, identifier string, err
 	}
 }
 
-func (d *Driver) open(path string) (fs.File, error) {
+func (d *PartialDriver) open(path string) (fs.File, error) {
 	f, err := d.fsys.Open(path)
 	if err == nil {
 		return f, nil
diff --git a/source/iofs/iofs_test.go b/source/iofs/iofs_test.go
index 1a440d8ce..2e0def2c7 100644
--- a/source/iofs/iofs_test.go
+++ b/source/iofs/iofs_test.go
@@ -13,7 +13,7 @@ import (
 func Test(t *testing.T) {
 	//go:embed testdata/migrations/*.sql
 	var fs embed.FS
-	d, err := iofs.NewDriver(fs, "testdata/migrations")
+	d, err := iofs.New(fs, "testdata/migrations")
 	if err != nil {
 		t.Fatal(err)
 	}

From 02da3b65068d842fe0da714547ff7a66fe966854 Mon Sep 17 00:00:00 2001
From: Mitsuo Heijo <mitsuo.heijo@gmail.com>
Date: Wed, 18 Nov 2020 18:54:47 +0900
Subject: [PATCH 15/15] do not panic in Open, return error

---
 source/iofs/iofs.go | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/source/iofs/iofs.go b/source/iofs/iofs.go
index b558e79fe..f76e44387 100644
--- a/source/iofs/iofs.go
+++ b/source/iofs/iofs.go
@@ -27,9 +27,9 @@ func New(fsys fs.FS, path string) (source.Driver, error) {
 }
 
 // Open is part of source.Driver interface implementation.
-// Open panics when called directly.
+// Open cannot be called on the iofs passthrough driver.
 func (d *driver) Open(url string) (source.Driver, error) {
-	panic("iofs: driver does not support open with url")
+	return nil, errors.New("Open() cannot be called on the iofs passthrough driver")
 }
 
 // PartialDriver is a helper service for creating new source drivers working with