Type specs: maybe/1 => option/1

so that we don't have to think about quoting.
'maybe' is a keyword in Erlang 25+ and as of 26,
it is an always-on language feature.

Closes #401

src/ra.hrl

@@ -4,7 +4,7 @@
 %%
 %% Copyright (c) 2017-2022 VMware, Inc. or its affiliates.  All rights reserved.
 %%
--type 'maybe'(T) :: undefined | T.
+-type option(T) :: undefined | T.
 
 %%
 %% Most of the records here are covered on Figure 2

src/ra_directory.erl

@@ -63,7 +63,7 @@ deinit(#{directory := Name,
     _ = dets:close(NameRev),
     ok.
 
--spec register_name(ra_system:names() | atom(), ra_uid(), pid(), 'maybe'(pid()), atom(),
+-spec register_name(ra_system:names() | atom(), ra_uid(), pid(), option(pid()), atom(),
                     ra_cluster_name()) -> ok.
 register_name(System, UId, Pid, ParentPid, ServerName, ClusterName)
   when is_atom(System) ->
@@ -135,7 +135,7 @@ where_is_parent(#{directory := Dir}, UId) when is_binary(UId) ->
         [] -> undefined
     end.
 
--spec name_of(atom() | ra_system:names(), ra_uid()) -> 'maybe'(atom()).
+-spec name_of(atom() | ra_system:names(), ra_uid()) -> option(atom()).
 name_of(SystemOrNames, UId) ->
     Tbl = get_name(SystemOrNames),
     case ets:lookup(Tbl, UId) of
@@ -144,7 +144,7 @@ name_of(SystemOrNames, UId) ->
     end.
 
 -spec cluster_name_of(ra_system:names() | atom(), ra_uid()) ->
-    'maybe'(ra_cluster_name()).
+    option(ra_cluster_name()).
 cluster_name_of(SystemOrNames, UId) ->
     Tbl = get_name(SystemOrNames),
     case ets:lookup(Tbl, UId) of
@@ -153,7 +153,7 @@ cluster_name_of(SystemOrNames, UId) ->
     end.
 
 
--spec pid_of(atom() | ra_system:names(), ra_uid()) -> 'maybe'(pid()).
+-spec pid_of(atom() | ra_system:names(), ra_uid()) -> option(pid()).
 pid_of(SystemOrNames, UId) ->
     case ets:lookup(get_name(SystemOrNames), UId) of
         [{_, Pid, _, _, _}] -> Pid;

src/ra_log.erl

@@ -100,7 +100,7 @@
          % if this is set a snapshot write is in progress for the
          % index specified
          cache = ra_log_cache:init() :: ra_log_cache:state(),
-         last_resend_time :: 'maybe'(integer()),
+         last_resend_time :: option(integer()),
          reader :: ra_log_reader:state(),
          readers = [] :: [pid()]
         }).
@@ -546,7 +546,7 @@ next_index(#?MODULE{last_index = LastIdx}) ->
     LastIdx + 1.
 
 -spec fetch(ra_index(), state()) ->
-    {maybe(log_entry()), state()}.
+    {option(log_entry()), state()}.
 fetch(Idx, State0) ->
     case fold(Idx, Idx, fun(E, Acc) -> [E | Acc] end, [], State0) of
         {[], State} ->
@@ -556,7 +556,7 @@ fetch(Idx, State0) ->
     end.
 
 -spec fetch_term(ra_index(), state()) ->
-    {'maybe'(ra_term()), state()}.
+    {option(ra_term()), state()}.
 fetch_term(Idx, #?MODULE{last_index = LastIdx,
                          first_index = FirstIdx} = State0)
   when Idx < FirstIdx orelse Idx > LastIdx ->
@@ -598,7 +598,7 @@ install_snapshot({SnapIdx, _} = IdxTerm, SnapState,
      Effs}.
 
 -spec recover_snapshot(State :: state()) ->
-    'maybe'({ra_snapshot:meta(), term()}).
+    option({ra_snapshot:meta(), term()}).
 recover_snapshot(#?MODULE{snapshot_state = SnapState}) ->
     case ra_snapshot:recover(SnapState) of
         {ok, Meta, MacState} ->
@@ -607,7 +607,7 @@ recover_snapshot(#?MODULE{snapshot_state = SnapState}) ->
             undefined
     end.
 
--spec snapshot_index_term(State :: state()) -> 'maybe'(ra_idxterm()).
+-spec snapshot_index_term(State :: state()) -> option(ra_idxterm()).
 snapshot_index_term(#?MODULE{snapshot_state = SS}) ->
     ra_snapshot:current(SS).
 

src/ra_log_segment.erl

@@ -46,7 +46,7 @@
               max_count = ?SEGMENT_MAX_ENTRIES :: non_neg_integer(),
               max_pending = ?SEGMENT_MAX_PENDING :: non_neg_integer(),
               filename :: file:filename_all(),
-              fd :: 'maybe'(file:io_device()),
+              fd :: option(file:io_device()),
               index_size :: pos_integer(),
               access_pattern :: sequential | random,
               mode = append :: read | append,
@@ -59,8 +59,8 @@
          data_start :: pos_integer(),
          data_offset :: pos_integer(),
          data_write_offset :: pos_integer(),
-         index = undefined :: maybe(ra_segment_index()),
-         range :: 'maybe'({ra_index(), ra_index()}),
+         index = undefined :: option(ra_segment_index()),
+         range :: option({ra_index(), ra_index()}),
          pending_data = [] :: iodata(),
          pending_index = [] :: iodata(),
          pending_count = 0 :: non_neg_integer(),
@@ -331,7 +331,7 @@ map_get_(Key, Map) when is_map_key(Key, Map) ->
 map_get_(Key, _Map) ->
     exit({missing_key, Key}).
 
--spec term_query(state(), Idx :: ra_index()) -> 'maybe'(ra_term()).
+-spec term_query(state(), Idx :: ra_index()) -> option(ra_term()).
 term_query(#state{index = Index}, Idx) ->
     case Index of
         #{Idx := {Term, _, _, _}} ->
@@ -367,7 +367,7 @@ fold0(Cfg, Cache0, Idx, FinalIdx, Index, Fun, AccFun, Acc0) ->
                   Cfg#cfg.filename})
     end.
 
--spec range(state()) -> maybe({ra_index(), ra_index()}).
+-spec range(state()) -> option({ra_index(), ra_index()}).
 range(#state{range = Range}) ->
     Range.
 
@@ -379,7 +379,7 @@ max_count(#state{cfg = #cfg{max_count = Max}}) ->
 filename(#state{cfg = #cfg{filename = Fn}}) ->
     Fn.
 
--spec segref(state()) -> 'maybe'(ra_log:segment_ref()).
+-spec segref(state()) -> option(ra_log:segment_ref()).
 segref(#state{range = undefined}) ->
     undefined;
 segref(#state{range = {Start, End},

src/ra_log_wal.erl

@@ -94,8 +94,8 @@
                compress_mem_tables = false :: boolean()
               }).
 
--record(wal, {fd :: 'maybe'(file:io_device()),
-              filename :: 'maybe'(file:filename()),
+-record(wal, {fd :: option(file:io_device()),
+              filename :: option(file:filename()),
               writer_name_cache = {0, #{}} :: writer_name_cache(),
               max_size :: non_neg_integer(),
               entry_count = 0 :: non_neg_integer()
@@ -117,7 +117,7 @@
                 % and the last index seen
                 writers = #{} :: #{ra_uid() =>
                                    {in_seq | out_of_seq, ra_index()}},
-                batch :: 'maybe'(#batch{})
+                batch :: option(#batch{})
                }).
 
 -type state() :: #state{}.

src/ra_server.erl

@@ -64,14 +64,14 @@
 
 -type ra_server_state() ::
     #{cfg := #cfg{},
-      leader_id => 'maybe'(ra_server_id()),
+      leader_id => option(ra_server_id()),
       cluster := ra_cluster(),
       cluster_change_permitted := boolean(),
       cluster_index_term := ra_idxterm(),
       previous_cluster => {ra_index(), ra_term(), ra_cluster()},
       current_term := ra_term(),
       log := term(),
-      voted_for => 'maybe'(ra_server_id()), % persistent
+      voted_for => option(ra_server_id()), % persistent
       votes => non_neg_integer(),
       membership => ra_membership(),
       commit_index := ra_index(),
@@ -87,7 +87,7 @@
       query_index := non_neg_integer(),
       queries_waiting_heartbeats := queue:queue({non_neg_integer(), consistent_query_ref()}),
       pending_consistent_queries := [consistent_query_ref()],
-      commit_latency => 'maybe'(non_neg_integer())
+      commit_latency => option(non_neg_integer())
      }.
 
 -type ra_state() :: leader | follower | candidate
@@ -1498,15 +1498,15 @@ uid(#{cfg := #cfg{uid = UId}}) -> UId.
 -spec system_config(ra_server_state()) -> ra_system:config().
 system_config(#{cfg := #cfg{system_config = SC}}) -> SC.
 
--spec leader_id(ra_server_state()) -> 'maybe'(ra_server_id()).
+-spec leader_id(ra_server_state()) -> option(ra_server_id()).
 leader_id(State) ->
     maps:get(leader_id, State, undefined).
 
 -spec clear_leader_id(ra_server_state()) -> ra_server_state().
 clear_leader_id(State) ->
     State#{leader_id => undefined}.
 
--spec current_term(ra_server_state()) -> 'maybe'(ra_term()).
+-spec current_term(ra_server_state()) -> option(ra_term()).
 current_term(State) ->
     maps:get(current_term, State).
 

src/ra_server_proc.erl

@@ -85,7 +85,7 @@
 -type gen_statem_start_ret() :: {ok, pid()} | ignore | {error, term()}.
 
 %% ra_event types
--type ra_event_reject_detail() :: {not_leader, Leader :: 'maybe'(ra_server_id()),
+-type ra_event_reject_detail() :: {not_leader, Leader :: option(ra_server_id()),
                                    ra_server:command_correlation()}.
 
 -type ra_event_body() ::

src/ra_snapshot.erl

@@ -60,9 +60,9 @@
          %% snapshot subdirs are store below
          %% this as <data_dir>/snapshots/Term_Index
          directory :: file:filename(),
-         pending :: 'maybe'({pid(), ra_idxterm()}),
-         accepting :: 'maybe'(#accept{}),
-         current :: 'maybe'(ra_idxterm())}).
+         pending :: option({pid(), ra_idxterm()}),
+         accepting :: option(#accept{}),
+         current :: option(ra_idxterm())}).
 
 -define(ETSTBL, ra_log_snapshot_state).
 
@@ -197,14 +197,14 @@ init_ets() ->
     _ = ets:new(?ETSTBL, TableFlags),
     ok.
 
--spec current(state()) -> 'maybe'(ra_idxterm()).
+-spec current(state()) -> option(ra_idxterm()).
 current(#?MODULE{current = Current}) -> Current.
 
--spec pending(state()) -> 'maybe'({pid(), ra_idxterm()}).
+-spec pending(state()) -> option({pid(), ra_idxterm()}).
 pending(#?MODULE{pending = Pending}) ->
     Pending.
 
--spec accepting(state()) -> 'maybe'(ra_idxterm()).
+-spec accepting(state()) -> option(ra_idxterm()).
 accepting(#?MODULE{accepting = undefined}) ->
     undefined;
 accepting(#?MODULE{accepting = #accept{idxterm = Accepting}}) ->
@@ -213,7 +213,7 @@ accepting(#?MODULE{accepting = #accept{idxterm = Accepting}}) ->
 -spec directory(state()) -> file:filename().
 directory(#?MODULE{directory = Dir}) -> Dir.
 
--spec last_index_for(ra_uid()) -> 'maybe'(ra_index()).
+-spec last_index_for(ra_uid()) -> option(ra_index()).
 last_index_for(UId) ->
     case ets:lookup(?ETSTBL, UId) of
         [] -> undefined;
@@ -400,7 +400,7 @@ read_meta(Module, Location) ->
     Module:read_meta(Location).
 
 -spec current_snapshot_dir(state()) ->
-    'maybe'(file:filename()).
+    option(file:filename()).
 current_snapshot_dir(#?MODULE{directory = Dir,
                               current = {Idx, Term}}) ->
     make_snapshot_dir(Dir, Idx, Term);

test/ra_fifo.erl

@@ -89,7 +89,7 @@
                          cancel.
 
 -type protocol() ::
-    {enqueue, Sender :: 'maybe'(pid()), MsgSeq :: 'maybe'(msg_seqno()),
+    {enqueue, Sender :: option(pid()), MsgSeq :: option(msg_seqno()),
      Msg :: raw_msg()} |
     {checkout, Spec :: checkout_spec(), Customer :: customer_id()} |
     {settle, MsgIds :: [msg_id()], Customer :: customer_id()} |
@@ -160,10 +160,10 @@
          % customers that require further service are queued here
          % needs to be part of snapshot
          service_queue = queue:new() :: queue:queue(customer_id()),
-         dead_letter_handler :: 'maybe'(applied_mfa()),
-         cancel_customer_handler :: 'maybe'(applied_mfa()),
-         become_leader_handler :: 'maybe'(applied_mfa()),
-         metrics_handler :: 'maybe'(applied_mfa()),
+         dead_letter_handler :: option(applied_mfa()),
+         cancel_customer_handler :: option(applied_mfa()),
+         become_leader_handler :: option(applied_mfa()),
+         metrics_handler :: option(applied_mfa()),
          prefix_msg_count = 0 :: non_neg_integer()
         }).
 

test/ra_fifo_client.erl

@@ -30,17 +30,17 @@
 
 -record(state, {cluster_name :: ra_cluster_name(),
                 servers = [] :: [ra_server_id()],
-                leader :: 'maybe'(ra_server_id()),
+                leader :: option(ra_server_id()),
                 next_seq = 0 :: seq(),
-                last_applied :: 'maybe'(seq()),
+                last_applied :: option(seq()),
                 next_enqueue_seq = 1 :: seq(),
                 %% indicates that we've exceeded the soft limit
                 slow = false :: boolean(),
                 unsent_commands = #{} :: #{ra_fifo:customer_id() =>
                                            {[seq()], [seq()], [seq()]}},
                 soft_limit = ?SOFT_LIMIT :: non_neg_integer(),
                 pending = #{} :: #{seq() =>
-                                   {'maybe'(term()), ra_fifo:command()}},
+                                   {option(term()), ra_fifo:command()}},
                 customer_deliveries = #{} :: #{ra_fifo:customer_tag() =>
                                                seq()},
                 priority = normal :: normal | low,

test/ra_log_memory.erl

@@ -46,7 +46,7 @@
                 last_written = {0, 0} :: ra_idxterm(), % only here to fake the async api of the file based one
                 entries = #{0 => {0, undefined}} :: #{ra_term() => {ra_index(), term()}},
                 meta = #{} :: ra_log_memory_meta(),
-                snapshot :: 'maybe'(snapshot())}).
+                snapshot :: option(snapshot())}).
 
 -type ra_log_memory_state() :: #state{} | ra_log:state().
 
@@ -127,7 +127,7 @@ sparse_take(Idx, Log, Num, Max, Res) ->
     end.
 
 
--spec last_index_term(ra_log_memory_state()) -> 'maybe'(ra_idxterm()).
+-spec last_index_term(ra_log_memory_state()) -> option(ra_idxterm()).
 last_index_term(#state{last_index = LastIdx,
                        entries = Log,
                        snapshot = Snapshot}) ->
@@ -184,7 +184,7 @@ next_index(#state{last_index = LastIdx}) ->
     LastIdx + 1.
 
 -spec fetch(ra_index(), ra_log_memory_state()) ->
-    {'maybe'(log_entry()), ra_log_memory_state()}.
+    {option(log_entry()), ra_log_memory_state()}.
 fetch(Idx, #state{entries = Log} = State) ->
     case Log of
         #{Idx := {T, D}} ->
@@ -193,7 +193,7 @@ fetch(Idx, #state{entries = Log} = State) ->
     end.
 
 -spec fetch_term(ra_index(), ra_log_memory_state()) ->
-    {'maybe'(ra_term()), ra_log_memory_state()}.
+    {option(ra_term()), ra_log_memory_state()}.
 fetch_term(Idx, #state{entries = Log} = State) ->
     case Log of
         #{Idx := {T, _}} ->
@@ -229,7 +229,7 @@ recover_snapshot(#state{snapshot = {Meta, Data}}) ->
 
 
 -spec read_meta(Key :: ra_log:ra_meta_key(), State :: ra_log_memory_state()) ->
-    'maybe'(term()).
+    option(term()).
 read_meta(Key, #state{meta = Meta}) ->
     maps:get(Key, Meta, undefined).