add comments for source

database/testing/testing.go

@@ -1,3 +1,6 @@
+// Package testing has the database tests.
+// All database drivers must pass the Test function.
+// This lives in it's own package so it stays a test dependency.
 package testing
 
 import (
@@ -8,6 +11,7 @@ import (
 	"github.com/mattes/migrate/database"
 )
 
+// Test runs tests against database implementations.
 func Test(t *testing.T, d database.Driver, migration []byte) {
 	if migration == nil {
 		panic("test must provide migration reader")

source/driver.go

@@ -1,3 +1,7 @@
+// Package source provides the Source interface.
+// All source drivers must implement this interface, register themselves,
+// optionally provide a `WithInstance` function and pass the tests
+// in package source/testing.
 package source
 
 import (
@@ -10,22 +14,51 @@ import (
 var driversMu sync.RWMutex
 var drivers = make(map[string]Driver)
 
+// Driver is an interface every driver must implement.
+// The driver implementation must pass the `Test` in source/testing.
+// Optionally provide a `WithInstance` function, so users can bypass `Open`
+// and use an existing source instance.
 type Driver interface {
+	// Open returns a a new driver instance configured with parameters
+	// coming from the URL string. Migrate will call this function
+	// only once per instance.
 	Open(url string) (Driver, error)
 
+	// Close closes the underlying source instance managed by the driver.
+	// Migrate will call this function only once per instance.
 	Close() error
 
+	// First returns the very first migration version available to the driver.
+	// Migrate will call this function multiple times.
+	// If there is no version available, it must return os.ErrNotExist.
 	First() (version uint, err error)
 
+	// Prev returns the previous version for a given version available to the driver.
+	// Migrate will call this function multiple times.
+	// If there is no previous version available, it must return os.ErrNotExist.
 	Prev(version uint) (prevVersion uint, err error)
 
+	// Next returns the next version for a given version available to the driver.
+	// Migrate will call this function multiple times.
+	// If there is no next version available, it must return os.ErrNotExist.
 	Next(version uint) (nextVersion uint, err error)
 
+	// ReadUp returns the UP migration body and an identifier that helps
+	// finding this migration in the source for a given version.
+	// If there is no up migration available for this version,
+	// it must return os.ErrNotExist.
+	// Do not start reading, just return the ReadCloser!
 	ReadUp(version uint) (r io.ReadCloser, identifier string, err error)
 
+	// ReadDown returns the DOWN migration body and an identifier that helps
+	// finding this migration in the source for a given version.
+	// If there is no down migration available for this version,
+	// it must return os.ErrNotExist.
+	// Do not start reading, just return the ReadCloser!
 	ReadDown(version uint) (r io.ReadCloser, identifier string, err error)
 }
 
+// Open returns a new driver instance.
 func Open(url string) (Driver, error) {
 	u, err := nurl.Parse(url)
 	if err != nil {
@@ -46,6 +79,7 @@ func Open(url string) (Driver, error) {
 	return d.Open(url)
 }
 
+// Register globally registers a driver.
 func Register(name string, driver Driver) {
 	driversMu.Lock()
 	defer driversMu.Unlock()

source/driver_test.go

@@ -0,0 +1,8 @@
+package source
+
+func ExampleDriver() {
+	// see source/stub for an example
+
+	// source/stub/stub.go has the driver implementation
+	// source/stub/stub_test.go runs source/testing/test.go:Test
+}

source/migration.go

@@ -4,6 +4,7 @@ import (
 	"sort"
 )
 
+// Direction is either up or down.
 type Direction string
 
 const (
@@ -11,13 +12,27 @@ const (
 	Up             = "up"
 )
 
+// Migration is a helper struct for source drivers that need to
+// build the full directory tree in memory.
+// Migration is fully independent from migrate.Migration.
 type Migration struct {
-	Version    uint
+	// Version is the version of this migration.
+	Version uint
+
+	// Identifier can be any string that helps identifying
+	// this migration in the source.
 	Identifier string
-	Direction  Direction
-	Raw        string
+
+	// Direction is either Up or Down.
+	Direction Direction
+
+	// Raw holds the raw location path to this migration in source.
+	// ReadUp and ReadDown will use this.
+	Raw string
 }
 
+// Migrations wraps Migration and has an internal index
+// to keep track of Migration order.
 type Migrations struct {
 	index      uintSlice
 	migrations map[uint]map[Direction]*Migration

source/migration_test.go

@@ -0,0 +1,33 @@
+package source
+
+import (
+	"testing"
+)
+
+func TestNewMigrations(t *testing.T) {
+	// TODO
+}
+
+func TestAppend(t *testing.T) {
+	// TODO
+}
+
+func TestBuildIndex(t *testing.T) {
+	// TODO
+}
+
+func TestFirst(t *testing.T) {
+	// TODO
+}
+
+func TestPrev(t *testing.T) {
+	// TODO
+}
+
+func TestUp(t *testing.T) {
+	// TODO
+}
+
+func TestDown(t *testing.T) {
+	// TODO
+}

source/parse.go

@@ -6,16 +6,21 @@ import (
 	"strconv"
 )
 
-var ErrParse = fmt.Errorf("no match")
+var (
+	ErrParse = fmt.Errorf("no match")
+)
 
-var DefaultParse = Parse
+var (
+	DefaultParse = Parse
+	DefaultRegex = Regex
+)
 
-var DefaultRegex = Regex
-
-// filename example: `123_name.up.ext`
-// filename example: `123_name.down.ext`
+// Regex matches the following pattern:
+//  123_name.up.ext
+//  123_name.down.ext
 var Regex = regexp.MustCompile(`^([0-9]+)_(.*)\.(` + string(Down) + `|` + string(Up) + `)\.(.*)$`)
 
+// Parse returns Migration for matching Regex pattern.
 func Parse(raw string) (*Migration, error) {
 	m := Regex.FindStringSubmatch(raw)
 	if len(m) == 5 {

source/testing/testing.go

@@ -1,3 +1,6 @@
+// Package testing has the source tests.
+// All source drivers must pass the Test function.
+// This lives in it's own package so it stays a test dependency.
 package testing
 
 import (
@@ -7,13 +10,14 @@ import (
 	"github.com/mattes/migrate/source"
 )
 
-// Test tests a driver implementation
-// It assumes the following migration "files"
-//
-// u = up file, d = down file, n = version
+// Test runs tests against source implementations.
+// It assumes that the driver tests has access to the following migrations:
 //
+// u = up migration, d = down migration, n = version
 //  |  1  |  -  |  3  |  4  |  5  |  -  |  7  |
 //  | u d |  -  | u   | u d |   d |  -  | u d |
+//
+// See source/stub/stub_test.go or source/file/file_test.go for an example.
 func Test(t *testing.T, d source.Driver) {
 	TestFirst(t, d)
 	TestPrev(t, d)