From 2a8e7a0e76301e4fca04d86cb296dfff1928034c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Jean-S=C3=A9bastien=20P=C3=A9dron?=
 <jean-sebastien.pedron@dumbbell.fr>
Date: Wed, 5 Nov 2025 21:38:28 +0100
Subject: [PATCH] khepri_tree: Ignore `keep_while` conditions on children on
 node creation

[Why]
If a parent has a `keep_while` condition on a child node, the child node
can't possibly exist when the parent is created. Therefore, ignore this
condition when the parent is created because it will always be false.

[How]
Drop `keep_while` conditions on nodes that have the created node as
prefix.

While here, move this logic to its own function.
---
 src/khepri_tree.erl            | 26 ++++++++++++++++++++++----
 test/keep_while_conditions.erl | 23 +++++++++++++++++++++++
 2 files changed, 45 insertions(+), 4 deletions(-)

diff --git a/src/khepri_tree.erl b/src/khepri_tree.erl
index d4bb6e89..01b37bd6 100644
--- a/src/khepri_tree.erl
+++ b/src/khepri_tree.erl
@@ -655,11 +655,13 @@ insert_or_update_node(
                           Path, Node, Payload, TreeOptions, Result),
                   case Ret of
                       {ok, Node1, Result1} when Result1 =/= #{} ->
-                          AbsKeepWhile = to_absolute_keep_while(
-                                           Path, KeepWhile),
-                          KeepWhileOnOthers = maps:remove(Path, AbsKeepWhile),
+                          AbsKeepWhile0 = to_absolute_keep_while(
+                                            Path, KeepWhile),
+                          AbsKeepWhile1 = (
+                            filter_out_irrelevant_keep_while_conds(
+                              Path, Node, AbsKeepWhile0)),
                           KWMet = are_keep_while_conditions_met(
-                                    Tree, KeepWhileOnOthers),
+                                    Tree, AbsKeepWhile1),
                           case KWMet of
                               true ->
                                   {ok, Node1, {updated, Path, Result1}};
@@ -739,6 +741,22 @@ insert_or_update_node_cb(_, {interrupted, Reason, Info}, _, _, _) ->
     Reason1 = ?khepri_error(Reason, Info),
     {error, Reason1}.
 
+filter_out_irrelevant_keep_while_conds(
+  Path, {interrupted, node_not_found, #{node_is_target := true}}, KeepWhile) ->
+    %% A `keep_while' condition on self is irrelevant if the node does not
+    %% exist yet.
+    KeepWhile1 = maps:remove(Path, KeepWhile),
+    %% Likewise for `keep_while' conditions that apply to children of the
+    %% node.
+    KeepWhile2 = maps:filter(
+                   fun(KWPath, _) ->
+                           not lists:prefix(Path, KWPath)
+                   end, KeepWhile1),
+    KeepWhile2;
+filter_out_irrelevant_keep_while_conds(
+  _Path, _Node, KeepWhile) ->
+    KeepWhile.
+
 gather_node_props_from_old_and_new_nodes(OldNode, NewNode, TreeOptions) ->
     OldNodeProps = case OldNode of
                        undefined ->
diff --git a/test/keep_while_conditions.erl b/test/keep_while_conditions.erl
index 15847ca1..ba656680 100644
--- a/test/keep_while_conditions.erl
+++ b/test/keep_while_conditions.erl
@@ -188,6 +188,29 @@ insert_when_keep_while_false_on_self_test() ->
     ?assertEqual({ok, #{[foo] => #{}}}, Ret),
     ?assertEqual([{aux, trigger_delayed_aux_queries_eval}], SE).
 
+insert_when_keep_while_false_on_child_test() ->
+    S0 = khepri_machine:init(?MACH_PARAMS()),
+    KeepWhile = #{[?THIS_KHEPRI_NODE, bar] => #if_has_data{}},
+    Command = #put{path = [foo],
+                   payload = khepri_payload:data(foo_value),
+                   options = #{keep_while => KeepWhile}},
+    {S1, Ret, SE} = khepri_machine:apply(?META, Command, S0),
+    Root = khepri_machine:get_root(S1),
+
+    ?assertEqual(
+       #node{
+          props =
+          #{payload_version => 1,
+            child_list_version => 2},
+          child_nodes =
+          #{foo =>
+            #node{
+               props = ?INIT_NODE_PROPS,
+               payload = khepri_payload:data(foo_value)}}},
+       Root),
+    ?assertEqual({ok, #{[foo] => #{}}}, Ret),
+    ?assertEqual([{aux, trigger_delayed_aux_queries_eval}], SE).
+
 keep_while_still_true_after_command_test() ->
     KeepWhile = #{[foo] => #if_child_list_length{count = 0}},
     Commands = [#put{path = [foo],