fiddle: Don't overwrite existing fiddle names unintentionally.

fiddle/go/named/named.go

Index: fiddle/go/named/named.go
diff --git a/fiddle/go/named/named.go b/fiddle/go/named/named.go
index a8c8074dcb240387c7a52ab9fc8ef73f70e0137e..5dab096c8e0e91b582c8e64eb3849c46858ab3b2 100644
--- a/fiddle/go/named/named.go
+++ b/fiddle/go/named/named.go
@@ -2,6 +2,7 @@
 package named
 
 import (
+	"errors"
 	"fmt"
 	"path/filepath"
 	"regexp"
@@ -13,6 +14,8 @@ import (
 )
 
 var (
+	DuplicateNameErr = errors.New("Name already exists.")
+
 	// fiddleHashRe is used to validate fiddle hashes.
 	fiddleHashRe = regexp.MustCompile("^[0-9a-zA-Z]{32}$")
 
@@ -57,10 +60,11 @@ func New(st NameStore) *Named {
 
 // Add a named fiddle.
 //
-//   name - The name of the fidde, w/o the @ prefix.
-//   hash - The fiddle hash.
-//   user - The email of the user that created the name.
-func (n *Named) Add(name, hash, user string) error {
+//   name      - The name of the fidde, w/o the @ prefix.
+//   hash      - The fiddle hash.
+//   user      - The email of the user that created the name.
+//   overwrite - True if the write should proceed if the name already exists.
+func (n *Named) Add(name, hash, user string, overwrite bool) error {
 	if !fiddleNameRe.MatchString(name) {
 		return fmt.Errorf("Not a valid fiddle name %q", name)
 	}
@@ -69,6 +73,10 @@ func (n *Named) Add(name, hash, user string) error {
 	}
 	oldHash, err := n.DereferenceID("@" + name)
 	if err == nil {

[rmistry, 2016/04/25 12:59:18]

I had to look at this a few times to see what it was doing. Looks like line 74
returns an err if the name does not exist yet. If there is no error means that a
name already exists. Either way its ok to write has long as overwrite is True.

+		// This name exists already.
+		if !overwrite {
+			return DuplicateNameErr
+		}
 		if oldHash == hash {
 			// Don't bother writing if the hash is already correct.
 			return nil