From 444e5b857a68ff8bb6485c3246702c7f9a5bac8e Mon Sep 17 00:00:00 2001
From: Lucas Molas <schomatis@gmail.com>
Date: Tue, 29 Jun 2021 16:39:14 -0300
Subject: [PATCH] docs

---
 hamt/util.go         |  9 ++++++++-
 io/directory_test.go | 13 +++++++++----
 2 files changed, 17 insertions(+), 5 deletions(-)

diff --git a/hamt/util.go b/hamt/util.go
index e4f6876dc..ce37ecfed 100644
--- a/hamt/util.go
+++ b/hamt/util.go
@@ -126,10 +126,17 @@ func CreateFullShard(ds ipld.DAGService, treeHeight int) (rootNode ipld.Node, er
 	for i := 0; i < totalChildren; i++ {
 		var hashbuf [8]byte
 		binary.LittleEndian.PutUint64(hashbuf[:], uint64(i))
-		_, err = root.SetAndPrevious(context.Background(), string(hashbuf[:treeHeight]), unixfs.EmptyFileNode())
+		var previous *ipld.Link
+		previous, err = root.SetAndPrevious(context.Background(), string(hashbuf[:treeHeight]), unixfs.EmptyFileNode())
 		if err != nil {
 			return
 		}
+		if previous != nil {
+			// We shouldn't be overwriting any value, otherwise the tree
+			// won't be full.
+			return nil, fmt.Errorf("we have overwritten entry %s",
+				previous.Cid)
+		}
 	}
 
 	rootNode, err = root.Node()
diff --git a/io/directory_test.go b/io/directory_test.go
index 70e0f201f..5ad8ca8ee 100644
--- a/io/directory_test.go
+++ b/io/directory_test.go
@@ -264,6 +264,9 @@ func TestHAMTEnumerationWhenComputingSize(t *testing.T) {
 	//oldShardWidth := DefaultShardWidth
 	//defer func() { DefaultShardWidth = oldShardWidth }()
 	//DefaultShardWidth = 8
+	// FIXME: We should be able to use a smaller DefaultShardWidth to have
+	//  a deeper tree and cheaper tests once the import cycle is resolved
+	//  in hamt.CreateFullShard.
 
 	treeHeight := 2
 	thresholdToWidthRatio := 4
@@ -285,9 +288,7 @@ func TestHAMTEnumerationWhenComputingSize(t *testing.T) {
 	assert.NoError(t, err)
 
 	sequentialDagService.ResetCounter()
-	// FIXME: Revert to const timeout after debugging.
-	below, timeoutExceeded := hamtDir.sizeBelowThreshold(1, func(ctx context.Context, _ *ipld.Link) {
-	})
+	below, timeoutExceeded := hamtDir.sizeBelowThreshold(EvaluateHAMTTransitionTimeout, nil)
 	assert.False(t, below)
 	assert.False(t, timeoutExceeded)
 	assert.Equal(t, nodesToFetch, sequentialDagService.UniqueCidsFetched())
@@ -433,10 +434,14 @@ func TestDirBuilder(t *testing.T) {
 }
 
 // serialFetchDag is a DAG service that keeps track of requested nodes
-// and serves them in FIFO order to keep tight control on requests.
+// and serves them in FIFO order to keep tight control on requests. (We
+// don't use GetMany.)
+// FIXME: We still depend on the walk function to be sequential. The name
+//  here might be misleading.
 type serialFetchDag struct {
 	ipld.DAGService
 
+	// FIXME: Remove if we won't be using it for now.
 	nextNode    <-chan struct{}
 	cidsFetched map[cid.Cid]struct{}
 	mapLock     sync.Mutex