Attempt to resolve type confusion

Dialyzer doesn't see the fold_option as being a valid Options entry in fold/4, as only the read_options are expected by the iterator functions.  The first_key option will be ignored by the iterator, but may be passed in - so this change reflects this in the spec

Make options explicit

Otherwise issue with detecting option combinations

Update eleveldb.erl

Add first_key to iterator options

The iterator will ignore first_key, but first_key may be present on the options

Update eleveldb.erl

.gitignore

@@ -12,3 +12,4 @@ c_src/system
 .local_dialyzer_plt
 .rebar
 _build
+.DS_Store

src/eleveldb.erl

@@ -132,14 +132,14 @@ init() ->
                          {whole_file_expiry, boolean()}
                         ].
 
--type read_option() :: {verify_checksums, boolean()} |
-                       {fill_cache, boolean()} |
-                       {iterator_refresh, boolean()}.
+-type read_options() :: [{verify_checksums, boolean()} |
+                        {fill_cache, boolean()} |
+                        {iterator_refresh, boolean()}].
 
--type read_options() :: [read_option()].
-
--type fold_option()  :: {first_key, Key::binary()}.
--type fold_options() :: [read_option() | fold_option()].
+-type fold_options() :: [{verify_checksums, boolean()} |
+                        {fill_cache, boolean()} |
+                        {iterator_refresh, boolean()} |
+                        {first_key, binary()}].
 
 -type write_options() :: [{sync, boolean()}].
 
@@ -205,21 +205,25 @@ async_put(Ref, Context, Key, Value, Opts) ->
 async_write(_CallerRef, _Ref, _Updates, _Opts) ->
     erlang:nif_error({error, not_loaded}).
 
--spec async_iterator(reference(), db_ref(), read_options()) -> ok.
+-spec async_iterator(reference(), db_ref(), fold_options()) -> ok.
 async_iterator(_CallerRef, _Ref, _Opts) ->
     erlang:nif_error({error, not_loaded}).
 
--spec async_iterator(reference(), db_ref(), read_options(), keys_only) -> ok.
+-spec async_iterator(reference(), db_ref(), fold_options(), keys_only) -> ok.
 async_iterator(_CallerRef, _Ref, _Opts, keys_only) ->
     erlang:nif_error({error, not_loaded}).
 
--spec iterator(db_ref(), read_options()) -> {ok, itr_ref()}.
+-spec iterator(db_ref(), fold_options()) -> {ok, itr_ref()}.
+%% Note that only read_options may influence the iterator, if the first_key
+%% is to be set, it must be done through explicitly calling iterator_move 
 iterator(Ref, Opts) ->
     CallerRef = make_ref(),
     async_iterator(CallerRef, Ref, Opts),
     ?WAIT_FOR_REPLY(CallerRef).
 
--spec iterator(db_ref(), read_options(), keys_only) -> {ok, itr_ref()}.
+-spec iterator(db_ref(), fold_options(), keys_only) -> {ok, itr_ref()}.
+%% Note that only read_options may influence the iterator, if the first_key
+%% is to be set, it must be done through explicitly calling iterator_move
 iterator(Ref, Opts, keys_only) ->
     CallerRef = make_ref(),
     async_iterator(CallerRef, Ref, Opts, keys_only),
@@ -270,7 +274,7 @@ fold(Ref, Fun, Acc0, Opts) ->
 
 %% Fold over the keys in the database
 %% will throw an exception if the database is closed while the fold runs
--spec fold_keys(db_ref(), fold_keys_fun(), any(), read_options()) -> any().
+-spec fold_keys(db_ref(), fold_keys_fun(), any(), fold_options()) -> any().
 fold_keys(Ref, Fun, Acc0, Opts) ->
     {ok, Itr} = iterator(Ref, Opts, keys_only),
     do_fold(Itr, Fun, Acc0, Opts).