fix: change property of ErrNotFound - s/Key/Cid

ABI compatible with github.com/ipfs/go-ipld-format#ErrNotFound for smoother
upgrade path

Author: rvagg

storage/memstore/memstore.go

@@ -57,7 +57,7 @@ func (store *Store) Get(ctx context.Context, key string) ([]byte, error) {
 	store.beInitialized()
 	content, exists := store.Bag[key]
 	if !exists {
-		return nil, storage.ErrNotFound{Key: key}
+		return nil, storage.NewErrNotFoundForKey(key)
 	}
 	cpy := make([]byte, len(content))
 	copy(cpy, content)
@@ -83,7 +83,7 @@ func (store *Store) Put(ctx context.Context, key string, content []byte) error {
 func (store *Store) GetStream(ctx context.Context, key string) (io.ReadCloser, error) {
 	content, exists := store.Bag[key]
 	if !exists {
-		return nil, storage.ErrNotFound{Key: key}
+		return nil, storage.NewErrNotFoundForKey(key)
 	}
 	return noopCloser{bytes.NewReader(content)}, nil
 }
@@ -92,7 +92,7 @@ func (store *Store) GetStream(ctx context.Context, key string) (io.ReadCloser, e
 func (store *Store) Peek(ctx context.Context, key string) ([]byte, io.Closer, error) {
 	content, exists := store.Bag[key]
 	if !exists {
-		return nil, nil, storage.ErrNotFound{Key: key}
+		return nil, nil, storage.NewErrNotFoundForKey(key)
 	}
 	return content, noopCloser{nil}, nil
 }

storage/notfound.go

@@ -7,8 +7,9 @@ import (
 )
 
 // ErrNotFound is a 404, but for block storage systems. It is returned when
-// a block is not found. The Key is typically the binary form of a CID
-// (CID#KeyString()).
+// a block is not found. The Cid property may be cid.Undef if the NotFound error
+// was not created with a specific CID (e.g. when using a non-CID key in a
+// storage Get operation).
 //
 // ErrNotFound implements `interface{NotFound() bool}`, which makes it roughly
 // compatible with the legacy github.com/ipfs/go-ipld-format#ErrNotFound.
@@ -23,20 +24,30 @@ import (
 // matching function that should be able to determine whether an ErrNotFound,
 // either new or legacy, exists within a wrapped error chain.
 type ErrNotFound struct {
-	Key string
+	Cid cid.Cid
 }
 
 // NewErrNotFound is a convenience factory that creates a new ErrNotFound error
 // from a CID.
 func NewErrNotFound(c cid.Cid) ErrNotFound {
-	return ErrNotFound{Key: c.KeyString()}
+	return ErrNotFound{Cid: c}
+}
+
+// NewErrNotFound is a convenience factory that creates a new ErrNotFound error
+// from a key. If the key is a CID#KeyString(), then it will be cast to a CID,
+// otherwise the Cid of the ErrNotFound will be cid.Undef.
+func NewErrNotFoundForKey(key string) ErrNotFound {
+	if c, err := cid.Cast([]byte(key)); err == nil {
+		return ErrNotFound{Cid: c}
+	}
+	return ErrNotFound{Cid: cid.Undef}
 }
 
 func (e ErrNotFound) Error() string {
-	if c, err := cid.Cast([]byte(e.Key)); err == nil && c != cid.Undef {
-		return "ipld: could not find " + c.String()
+	if e.Cid == cid.Undef {
+		return "ipld: could not find node"
 	}
-	return "ipld: could not find " + e.Key
+	return "ipld: could not find " + e.Cid.String()
 }
 
 // NotFound always returns true, and is used to feature-test for ErrNotFound

storage/notfound_test.go

@@ -10,14 +10,14 @@ import (
 )
 
 func TestNotFound(t *testing.T) {
-	nf := storage.ErrNotFound{Key: "foo"}
+	nf := storage.ErrNotFound{}
 	if !storage.IsNotFound(nf) {
 		t.Fatal("expected ErrNotFound to be a NotFound error")
 	}
 	if !errors.Is(nf, storage.ErrNotFound{}) {
 		t.Fatal("expected ErrNotFound to be a NotFound error")
 	}
-	if nf.Error() != "ipld: could not find foo" {
+	if nf.Error() != "ipld: could not find node" {
 		t.Fatal("unexpected error message")
 	}