Add CreateBucketIfNotExists().

db.go

@@ -389,6 +389,14 @@ func (db *DB) CreateBucket(name string) error {
 	})
 }
 
+// CreateBucketIfNotExists creates a new bucket with the given name if it doesn't already exist.
+// This function can return an error if the name is blank, or the bucket name is too long.
+func (db *DB) CreateBucketIfNotExists(name string) error {
+	return db.Do(func(t *RWTransaction) error {
+		return t.CreateBucketIfNotExists(name)
+	})
+}
+
 // DeleteBucket removes a bucket from the database.
 // Returns an error if the bucket does not exist.
 func (db *DB) DeleteBucket(name string) error {

rwtransaction.go

@@ -49,6 +49,16 @@ func (t *RWTransaction) CreateBucket(name string) error {
 	return nil
 }
 
+// CreateBucketIfNotExists creates a new bucket if it doesn't already exist.
+// Returns an error if the bucket name is blank, or if the bucket name is too long.
+func (t *RWTransaction) CreateBucketIfNotExists(name string) error {
+	err := t.CreateBucket(name)
+	if err != nil && err != ErrBucketExists {
+		return err
+	}
+	return nil
+}
+
 // DeleteBucket deletes a bucket.
 // Returns an error if the bucket cannot be found.
 func (t *RWTransaction) DeleteBucket(name string) error {

rwtransaction_test.go

@@ -44,6 +44,19 @@ func TestRWTransactionCreateBucket(t *testing.T) {
 	})
 }
 
+// Ensure that a bucket can be created if it doesn't already exist.
+func TestRWTransactionCreateBucketIfNotExists(t *testing.T) {
+	withOpenDB(func(db *DB, path string) {
+		assert.NoError(t, db.CreateBucketIfNotExists("widgets"))
+		assert.NoError(t, db.CreateBucketIfNotExists("widgets"))
+
+		// Read the bucket through a separate transaction.
+		b, err := db.Bucket("widgets")
+		assert.NotNil(t, b)
+		assert.NoError(t, err)
+	})
+}
+
 // Ensure that a bucket cannot be created twice.
 func TestRWTransactionRecreateBucket(t *testing.T) {
 	withOpenDB(func(db *DB, path string) {