Merge pull request #308 from rabbitmq/ignore-unknown-props_to_return

khepri_tree: Ignore unknown props to return
rabbitmq · Dec 11, 2024 · 39a97d7 · 39a97d7
2 parents 6f88694 + 257cf32
commit 39a97d7
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Showing 3 changed files with 39 additions and 9 deletions.
diff --git a/src/khepri.erl b/src/khepri.erl
@@ -348,14 +348,8 @@
 %% set, `condition' takes precedence and `favor' is ignored.
 
 -type tree_options() :: #{expect_specific_node => boolean(),
-                          props_to_return => [payload_version |
-                                              child_list_version |
-                                              child_list_length |
-                                              child_names |
-                                              payload |
-                                              has_payload |
-                                              raw_payload |
-                                              delete_reason],
+                          props_to_return => [known_prop_to_return() |
+                                              unknown_prop_to_return()],
                           include_root_props => boolean()}.
 %% Options used during tree traversal.
 %%
@@ -372,6 +366,26 @@
 %% returned as well.</li>
 %% </ul>
 
+-type known_prop_to_return() :: payload_version |
+                                child_list_version |
+                                child_list_length |
+                                child_names |
+                                payload |
+                                has_payload |
+                                raw_payload |
+                                delete_reason.
+%% Name of a known property to return.
+%%
+%% To be used in {@link khepri:tree_options()} `props_to_return' list.
+
+-type unknown_prop_to_return() :: atom().
+%% Name of a property unknown to this version of Khepri.
+%%
+%% This can happen when a query is emitted by a newer version of Khepri that
+%% added new properties to return.
+%%
+%% Can be seen in {@link khepri:tree_options()} `props_to_return' list.
+
 -type put_options() :: #{keep_while => khepri_condition:keep_while()}.
 %% Options specific to updates.
 %%

diff --git a/src/khepri_tree.erl b/src/khepri_tree.erl
@@ -234,7 +234,9 @@ gather_node_props(#node{props = #{payload_version := PVersion,
               end;
           (raw_payload, Acc) ->
               Acc#{raw_payload => Payload};
-          (delete_reason, Acc) ->
+          (_Unknown, Acc) ->
+              %% We ignore props we don't know about. It might be a new one in
+              %% a future version of the machine.
               Acc
       end, #{}, WantedProps);
 gather_node_props(#node{}, _Options) ->

diff --git a/test/queries.erl b/test/queries.erl
@@ -399,3 +399,17 @@ include_child_names_in_query_response_test() ->
                          child_list_version => 2,
                          child_names => [bar, quux]}}},
        Ret).
+
+use_an_unknown_prop_to_return_test() ->
+    Commands = [#put{path = [foo],
+                     payload = khepri_payload:data(value)}],
+    S0 = khepri_machine:init(?MACH_PARAMS(Commands)),
+    Tree = khepri_machine:get_tree(S0),
+    Ret = khepri_tree:find_matching_nodes(
+            Tree, [foo],
+            #{props_to_return => [payload,
+                                  future_prop_name]}),
+
+    ?assertEqual(
+       {ok, #{[foo] => #{data => value}}},
+       Ret).