Correctly seek in raft's ListPage when after=.

When a non-empty path is given that ends in a slash and after=., the
resulting seek prefix from joining the path and the period has the
slash trimmed off. This results in no list results, because this seek
prefix lacks the trailing slash and is thus not prefixed by the expected
prefix. E.g., for foo/ and after=., we end up with seekPrefix=foo, which
doesn't start with our prefix (foo/).

Correctly handle this edge case. This was caught by randomized testing
across multiple storage backends.

Signed-off-by: Alexander Scheel <[email protected]>

changelog/294.txt

@@ -0,0 +1,3 @@
+```release-note:bug
+physical/raft: fix ListPage calls when after=. resulting in an empty list
+```

physical/raft/fsm.go

@@ -543,6 +543,12 @@ func (f *FSM) ListPage(ctx context.Context, prefix string, after string, limit i
  seekPrefix := []byte(filepath.Join(prefix, after))
  if after == "" {
  seekPrefix = prefixBytes
+ } else if !bytes.HasPrefix(seekPrefix, prefixBytes) {
+ // filepath.Join has the very unfortunate behavior of trimming the
+ // trailing slash when after=".". When e.g., prefix=foo/, this gives
+ // us seekPrefix=foo, which fails the initial HasPrefix check,
+ // skipping all results.
+ seekPrefix = prefixBytes
  }
 
  var keys []string

sdk/physical/testing.go

@@ -31,6 +31,10 @@ func testListAndPage(t testing.TB, b Backend, prefix string, expected []string)
  require.NoError(t, err, "initial list page failed")
  sortaEqualSlice(t, expected, page, "expected list page to match")
 
+ page, err = b.ListPage(context.Background(), prefix, ".", -100)
+ require.NoError(t, err, "initial list page failed")
+ sortaEqualSlice(t, expected, page, "expected list page with after=. to match bare list")
+
  page, err = b.ListPage(context.Background(), prefix, "", -1)
  require.NoError(t, err, "initial list page failed")
  sortaEqualSlice(t, expected, page, "expected list page to match")