cmd, core/state, eth, tests, trie: improve state reader (#27428)

The state availability is checked during the creation of a state reader.

-    In hash-based database, if the specified root node does not exist on disk disk, then
    the state reader won't be created and an error will be returned.

-    In path-based database, if the specified state layer is not available, then the
    state reader won't be created and an error will be returned.

This change also contains a stricter semantics regarding the `Commit` operation: once it has been performed, the trie is no longer usable, and certain operations will return an error.

light/trie.go

@@ -184,8 +184,8 @@ func (t *odrTrie) Hash() common.Hash {
 	return t.trie.Hash()
 }
 
-func (t *odrTrie) NodeIterator(startkey []byte) trie.NodeIterator {
-	return newNodeIterator(t, startkey)
+func (t *odrTrie) NodeIterator(startkey []byte) (trie.NodeIterator, error) {
+	return newNodeIterator(t, startkey), nil
 }
 
 func (t *odrTrie) GetKey(sha []byte) []byte {
@@ -248,7 +248,11 @@ func newNodeIterator(t *odrTrie, startkey []byte) trie.NodeIterator {
 		})
 	}
 	it.do(func() error {
-		it.NodeIterator = it.t.trie.NodeIterator(startkey)
+		var err error
+		it.NodeIterator, err = it.t.trie.NodeIterator(startkey)
+		if err != nil {
+			return err
+		}
 		return it.NodeIterator.Error()
 	})
 	return it

light/trie_test.go

@@ -62,8 +62,16 @@ func TestNodeIterator(t *testing.T) {
 }
 
 func diffTries(t1, t2 state.Trie) error {
-	i1 := trie.NewIterator(t1.NodeIterator(nil))
-	i2 := trie.NewIterator(t2.NodeIterator(nil))
+	trieIt1, err := t1.NodeIterator(nil)
+	if err != nil {
+		return err
+	}
+	trieIt2, err := t2.NodeIterator(nil)
+	if err != nil {
+		return err
+	}
+	i1 := trie.NewIterator(trieIt1)
+	i2 := trie.NewIterator(trieIt2)
 	for i1.Next() && i2.Next() {
 		if !bytes.Equal(i1.Key, i2.Key) {
 			spew.Dump(i2)