Error refactoring.

Fixed up a few error issues and refactored out the Error type.

bucket.go

@@ -2,6 +2,40 @@ package bolt
 
 import (
 	"bytes"
+	"errors"
+)
+
+var (
+	// ErrBucketNotFound is returned when trying to access a bucket that has
+	// not been created yet.
+	ErrBucketNotFound = errors.New("bucket not found")
+
+	// ErrBucketExists is returned when creating a bucket that already exists.
+	ErrBucketExists = errors.New("bucket already exists")
+
+	// ErrBucketNameRequired is returned when creating a bucket with a blank name.
+	ErrBucketNameRequired = errors.New("bucket name required")
+
+	// ErrBucketNameTooLarge is returned when creating a bucket with a name
+	// that is longer than MaxBucketNameSize.
+	ErrBucketNameTooLarge = errors.New("bucket name too large")
+
+	// ErrBucketNotWritable is returned when changing data on a bucket
+	// reference that was created from a read-only transaction.
+	ErrBucketNotWritable = errors.New("bucket not writable")
+
+	// ErrKeyRequired is returned when inserting a zero-length key.
+	ErrKeyRequired = errors.New("key required")
+
+	// ErrKeyTooLarge is returned when inserting a key that is larger than MaxKeySize.
+	ErrKeyTooLarge = errors.New("key too large")
+
+	// ErrValueTooLarge is returned when inserting a value that is larger than MaxValueSize.
+	ErrValueTooLarge = errors.New("value too large")
+
+	// ErrSequenceOverflow is returned when the next sequence number will be
+	// larger than the maximum integer size.
+	ErrSequenceOverflow = errors.New("sequence overflow")
 )
 
 // Bucket represents a collection of key/value pairs inside the database.

bucket_test.go

@@ -2,6 +2,7 @@ package bolt
 
 import (
 	"bytes"
+	"errors"
 	"fmt"
 	"os"
 	"strconv"
@@ -203,12 +204,12 @@ func TestBucketForEachShortCircuit(t *testing.T) {
 			err := tx.Bucket("widgets").ForEach(func(k, v []byte) error {
 				index++
 				if bytes.Equal(k, []byte("baz")) {
-					return &Error{"marker", nil}
+					return errors.New("marker")
 				}
 				return nil
 			})
-			assert.Equal(t, err, &Error{"marker", nil})
+			assert.Equal(t, errors.New("marker"), err)
-			assert.Equal(t, index, 2)
+			assert.Equal(t, 2, index)
 			return nil
 		})
 	})

db.go

@@ -1,6 +1,7 @@
 package bolt
 
 import (
+	"errors"
 	"fmt"
 	"io"
 	"os"
@@ -15,6 +16,16 @@ const minMmapSize = 1 << 22 // 4MB
 // The largest step that can be taken when remapping the mmap.
 const maxMmapStep = 1 << 30 // 1GB
 
+var (
+	// ErrDatabaseNotOpen is returned when a DB instance is accessed before it
+	// is opened or after it is closed.
+	ErrDatabaseNotOpen = errors.New("database not open")
+
+	// ErrDatabaseOpen is returned when opening a database that is
+	// already open.
+	ErrDatabaseOpen = errors.New("database already open")
+)
+
 // DB represents a collection of buckets persisted to a file on disk.
 // All data access is performed through transactions which can be obtained through the DB.
 // All the functions on DB will return a ErrDatabaseNotOpen if accessed before Open() is called.
@@ -89,7 +100,7 @@ func (db *DB) Open(path string, mode os.FileMode) error {
 
 	// Initialize the database if it doesn't exist.
 	if info, err := db.file.Stat(); err != nil {
-		return &Error{"stat error", err}
+		return fmt.Errorf("stat error: %s", err)
 	} else if info.Size() == 0 {
 		// Initialize new files with meta pages.
 		if err := db.init(); err != nil {
@@ -101,7 +112,7 @@ func (db *DB) Open(path string, mode os.FileMode) error {
 		if _, err := db.file.ReadAt(buf[:], 0); err == nil {
 			m := db.pageInBuffer(buf[:], 0).meta()
 			if err := m.validate(); err != nil {
-				return &Error{"meta error", err}
+				return fmt.Errorf("meta error: %s", err)
 			}
 			db.pageSize = int(m.pageSize)
 		}
@@ -140,9 +151,9 @@ func (db *DB) mmap(minsz int) error {
 
 	info, err := db.file.Stat()
 	if err != nil {
-		return &Error{"mmap stat error", err}
+		return fmt.Errorf("mmap stat error: %s", err)
 	} else if int(info.Size()) < db.pageSize*2 {
-		return &Error{"file size too small", err}
+		return fmt.Errorf("file size too small")
 	}
 
 	// Ensure the size is at least the minimum size.
@@ -163,10 +174,10 @@ func (db *DB) mmap(minsz int) error {
 
 	// Validate the meta pages.
 	if err := db.meta0.validate(); err != nil {
-		return &Error{"meta0 error", err}
+		return fmt.Errorf("meta0 error: %s", err)
 	}
 	if err := db.meta1.validate(); err != nil {
-		return &Error{"meta1 error", err}
+		return fmt.Errorf("meta1 error: %s", err)
 	}
 
 	return nil
@@ -529,7 +540,7 @@ func (db *DB) allocate(count int) (*page, error) {
 	var minsz = int((p.id+pgid(count))+1) * db.pageSize
 	if minsz >= len(db.data) {
 		if err := db.mmap(minsz); err != nil {
-			return nil, &Error{"mmap allocate error", err}
+			return nil, fmt.Errorf("mmap allocate error: %s", err)
 		}
 	}
 

db_test.go

@@ -1,6 +1,7 @@
 package bolt
 
 import (
+	"errors"
 	"io"
 	"io/ioutil"
 	"math/rand"
@@ -8,6 +9,7 @@ import (
 	"strconv"
 	"strings"
 	"testing"
+	"unsafe"
 
 	"github.com/stretchr/testify/assert"
 )
@@ -53,14 +55,12 @@ func TestDBReopen(t *testing.T) {
 
 // Ensure that the database returns an error if the file handle cannot be open.
 func TestDBOpenFileError(t *testing.T) {
-	withDBFile(func(db *DB, path string) {
+	withDB(func(db *DB, path string) {
-		exp := &os.PathError{
-			Op:   "open",
-			Path: path + "/youre-not-my-real-parent",
-			Err:  syscall.ENOTDIR,
-		}
 		err := db.Open(path+"/youre-not-my-real-parent", 0666)
-		assert.Equal(t, err, exp)
+		if err, _ := err.(*os.PathError); assert.Error(t, err) {
+			assert.Equal(t, path+"/youre-not-my-real-parent", err.Path)
+			assert.Equal(t, "open", err.Op)
+		}
 	})
 }
 
@@ -78,13 +78,14 @@ func TestDBMetaInitWriteError(t *testing.T) {
 
 // Ensure that a database that is too small returns an error.
 func TestDBFileTooSmall(t *testing.T) {
-	withDBFile(func(db *DB, path string) {
+	withOpenDB(func(db *DB, path string) {
-		// corrupt the database
+		db.Close()
-		err := os.Truncate(path, int64(os.Getpagesize()))
-		assert.NoError(t, err)
 
-		err = db.Open(path, 0666)
+		// corrupt the database
-		assert.Equal(t, err, &Error{"file size too small", nil})
+		assert.NoError(t, os.Truncate(path, int64(os.Getpagesize())))
+
+		err := db.Open(path, 0666)
+		assert.Equal(t, errors.New("file size too small"), err)
 	})
 }
 
@@ -108,7 +109,7 @@ func TestDBCorruptMeta0(t *testing.T) {
 
 		// Open the database.
 		err = db.Open(path, 0666)
-		assert.Equal(t, err, &Error{"meta error", ErrInvalid})
+		assert.Equal(t, err, errors.New("meta error: invalid database"))
 	})
 }
 

error.go

@@ -1,71 +0,0 @@
-package bolt
-
-var (
-	// ErrInvalid is returned when a data file is not a Bolt-formatted database.
-	ErrInvalid = &Error{"Invalid database", nil}
-
-	// ErrVersionMismatch is returned when the data file was created with a
-	// different version of Bolt.
-	ErrVersionMismatch = &Error{"version mismatch", nil}
-
-	// ErrDatabaseNotOpen is returned when a DB instance is accessed before it
-	// is opened or after it is closed.
-	ErrDatabaseNotOpen = &Error{"database not open", nil}
-
-	// ErrDatabaseOpen is returned when opening a database that is
-	// already open.
-	ErrDatabaseOpen = &Error{"database already open", nil}
-
-	// ErrTxNotWritable is returned when performing a write operation on a
-	// read-only transaction.
-	ErrTxNotWritable = &Error{"tx not writable", nil}
-
-	// ErrTxClosed is returned when committing or rolling back a transaction
-	// that has already been committed or rolled back.
-	ErrTxClosed = &Error{"tx closed", nil}
-
-	// ErrBucketNotFound is returned when trying to access a bucket that has
-	// not been created yet.
-	ErrBucketNotFound = &Error{"bucket not found", nil}
-
-	// ErrBucketExists is returned when creating a bucket that already exists.
-	ErrBucketExists = &Error{"bucket already exists", nil}
-
-	// ErrBucketNameRequired is returned when creating a bucket with a blank name.
-	ErrBucketNameRequired = &Error{"bucket name required", nil}
-
-	// ErrBucketNameTooLarge is returned when creating a bucket with a name
-	// that is longer than MaxBucketNameSize.
-	ErrBucketNameTooLarge = &Error{"bucket name too large", nil}
-
-	// ErrBucketNotWritable is returned when changing data on a bucket
-	// reference that was created from a read-only transaction.
-	ErrBucketNotWritable = &Error{"bucket not writable", nil}
-
-	// ErrKeyRequired is returned when inserting a zero-length key.
-	ErrKeyRequired = &Error{"key required", nil}
-
-	// ErrKeyTooLarge is returned when inserting a key that is larger than MaxKeySize.
-	ErrKeyTooLarge = &Error{"key too large", nil}
-
-	// ErrValueTooLarge is returned when inserting a value that is larger than MaxValueSize.
-	ErrValueTooLarge = &Error{"value too large", nil}
-
-	// ErrSequenceOverflow is returned when the next sequence number will be
-	// larger than the maximum integer size.
-	ErrSequenceOverflow = &Error{"sequence overflow", nil}
-)
-
-// Error represents an error condition caused by Bolt.
-type Error struct {
-	message string
-	cause   error
-}
-
-// Error returns a string representation of the error.
-func (e *Error) Error() string {
-	if e.cause != nil {
-		return e.message + ": " + e.cause.Error()
-	}
-	return e.message
-}

error_test.go

@@ -1,12 +0,0 @@
-package bolt
-
-import (
-	"github.com/stretchr/testify/assert"
-	"testing"
-)
-
-// Ensure that nested errors are appropriately formatted.
-func TestError(t *testing.T) {
-	e := &Error{"one error", &Error{"two error", nil}}
-	assert.Equal(t, e.Error(), "one error: two error")
-}

meta.go

@@ -1,7 +1,20 @@
 package bolt
 
+import (
+	"errors"
+)
+
 const magic uint32 = 0xED0CDAED
 
+var (
+	// ErrInvalid is returned when a data file is not a Bolt-formatted database.
+	ErrInvalid = errors.New("invalid database")
+
+	// ErrVersionMismatch is returned when the data file was created with a
+	// different version of Bolt.
+	ErrVersionMismatch = errors.New("version mismatch")
+)
+
 type meta struct {
 	magic    uint32
 	version  uint32

tx.go

@@ -1,10 +1,21 @@
 package bolt
 
 import (
+	"errors"
 	"sort"
 	"unsafe"
 )
 
+var (
+	// ErrTxNotWritable is returned when performing a write operation on a
+	// read-only transaction.
+	ErrTxNotWritable = errors.New("tx not writable")
+
+	// ErrTxClosed is returned when committing or rolling back a transaction
+	// that has already been committed or rolled back.
+	ErrTxClosed = errors.New("tx closed")
+)
+
 // txid represents the internal transaction identifier.
 type txid uint64