trie: more node iterator improvements (#14615)

* ethdb: remove Set

Set deadlocks immediately and isn't part of the Database interface.

* trie: add Err to Iterator

This is useful for testing because the underlying NodeIterator doesn't
need to be kept in a separate variable just to get the error.

* trie: add LeafKey to iterator, panic when not at leaf

LeafKey is useful for callers that can't interpret Path.

* trie: retry failed seek/peek in iterator Next

Instead of failing iteration irrecoverably, make it so Next retries the
pending seek or peek every time.

Smaller changes in this commit make this easier to test:

* The iterator previously returned from Next on encountering a hash
  node. This caused it to visit the same path twice.
* Path returned nibbles with terminator symbol for valueNode attached
  to fullNode, but removed it for valueNode attached to shortNode. Now
  the terminator is always present. This makes Path unique to each node
  and simplifies Leaf.

* trie: add Path to MissingNodeError

The light client trie iterator needs to know the path of the node that's
missing so it can retrieve a proof for it. NodeIterator.Path is not
sufficient because it is updated when the node is resolved and actually
visited by the iterator.

Also remove unused fields. They were added a long time ago before we
knew which fields would be needed for the light client.

trie/trie_test.go

@@ -19,6 +19,7 @@ package trie
 import (
 	"bytes"
 	"encoding/binary"
+	"errors"
 	"fmt"
 	"io/ioutil"
 	"math/rand"
@@ -34,7 +35,7 @@ import (
 
 func init() {
 	spew.Config.Indent = "    "
-	spew.Config.DisableMethods = true
+	spew.Config.DisableMethods = false
 }
 
 // Used for testing
@@ -357,6 +358,7 @@ type randTestStep struct {
 	op    int
 	key   []byte // for opUpdate, opDelete, opGet
 	value []byte // for opUpdate
+	err   error  // for debugging
 }
 
 const (
@@ -406,7 +408,7 @@ func runRandTest(rt randTest) bool {
 	tr, _ := New(common.Hash{}, db)
 	values := make(map[string]string) // tracks content of the trie
 
-	for _, step := range rt {
+	for i, step := range rt {
 		switch step.op {
 		case opUpdate:
 			tr.Update(step.key, step.value)
@@ -418,23 +420,22 @@ func runRandTest(rt randTest) bool {
 			v := tr.Get(step.key)
 			want := values[string(step.key)]
 			if string(v) != want {
-				fmt.Printf("mismatch for key 0x%x, got 0x%x want 0x%x", step.key, v, want)
-				return false
+				rt[i].err = fmt.Errorf("mismatch for key 0x%x, got 0x%x want 0x%x", step.key, v, want)
 			}
 		case opCommit:
-			if _, err := tr.Commit(); err != nil {
-				panic(err)
-			}
+			_, rt[i].err = tr.Commit()
 		case opHash:
 			tr.Hash()
 		case opReset:
 			hash, err := tr.Commit()
 			if err != nil {
-				panic(err)
+				rt[i].err = err
+				return false
 			}
 			newtr, err := New(hash, db)
 			if err != nil {
-				panic(err)
+				rt[i].err = err
+				return false
 			}
 			tr = newtr
 		case opItercheckhash:
@@ -444,17 +445,20 @@ func runRandTest(rt randTest) bool {
 				checktr.Update(it.Key, it.Value)
 			}
 			if tr.Hash() != checktr.Hash() {
-				fmt.Println("hashes not equal")
-				return false
+				rt[i].err = fmt.Errorf("hash mismatch in opItercheckhash")
 			}
 		case opCheckCacheInvariant:
-			return checkCacheInvariant(tr.root, nil, tr.cachegen, false, 0)
+			rt[i].err = checkCacheInvariant(tr.root, nil, tr.cachegen, false, 0)
+		}
+		// Abort the test on error.
+		if rt[i].err != nil {
+			return false
 		}
 	}
 	return true
 }
 
-func checkCacheInvariant(n, parent node, parentCachegen uint16, parentDirty bool, depth int) bool {
+func checkCacheInvariant(n, parent node, parentCachegen uint16, parentDirty bool, depth int) error {
 	var children []node
 	var flag nodeFlag
 	switch n := n.(type) {
@@ -465,33 +469,34 @@ func checkCacheInvariant(n, parent node, parentCachegen uint16, parentDirty bool
 		flag = n.flags
 		children = n.Children[:]
 	default:
-		return true
+		return nil
 	}
 
-	showerror := func() {
-		fmt.Printf("at depth %d node %s", depth, spew.Sdump(n))
-		fmt.Printf("parent: %s", spew.Sdump(parent))
+	errorf := func(format string, args ...interface{}) error {
+		msg := fmt.Sprintf(format, args...)
+		msg += fmt.Sprintf("\nat depth %d node %s", depth, spew.Sdump(n))
+		msg += fmt.Sprintf("parent: %s", spew.Sdump(parent))
+		return errors.New(msg)
 	}
 	if flag.gen > parentCachegen {
-		fmt.Printf("cache invariant violation: %d > %d\n", flag.gen, parentCachegen)
-		showerror()
-		return false
+		return errorf("cache invariant violation: %d > %d\n", flag.gen, parentCachegen)
 	}
 	if depth > 0 && !parentDirty && flag.dirty {
-		fmt.Printf("cache invariant violation: child is dirty but parent isn't\n")
-		showerror()
-		return false
+		return errorf("cache invariant violation: %d > %d\n", flag.gen, parentCachegen)
 	}
 	for _, child := range children {
-		if !checkCacheInvariant(child, n, flag.gen, flag.dirty, depth+1) {
-			return false
+		if err := checkCacheInvariant(child, n, flag.gen, flag.dirty, depth+1); err != nil {
+			return err
 		}
 	}
-	return true
+	return nil
 }
 
 func TestRandom(t *testing.T) {
 	if err := quick.Check(runRandTest, nil); err != nil {
+		if cerr, ok := err.(*quick.CheckError); ok {
+			t.Fatalf("random test iteration %d failed: %s", cerr.Count, spew.Sdump(cerr.In))
+		}
 		t.Fatal(err)
 	}
 }