fix: SET n = map reads n first; label tests in SET values (GQLITE-T-0479)

src/backend/executor/query_dispatch.c

@@ -2069,8 +2069,10 @@ static bool set_values_need_pipeline(cypher_query *query)
             cypher_set_item *it = (cypher_set_item *)items->items[i];
             if (!it || !it->property || it->property->type == AST_NODE_LABEL_EXPR) continue;
             if (!set_value_plain(it->expr)) return true;
-            /* `SET a += {k: a.s}` reads the node it writes */
-            if (it->is_merge && it->expr && it->expr->type == AST_NODE_MAP) {
+            /* `SET a += {k: a.s}` reads the node it writes; `SET a = {k:
+             * a.s}` too, and bulk SET cleared a before it read the value
+             * (GQLITE-T-0479). Bulk SET stores only literal map values. */
+            if (it->expr && it->expr->type == AST_NODE_MAP) {
                 ast_list *a = ((cypher_map *)it->expr)->pairs;
                 for (int k = 0; a && k < a->count; k++) {
                     ast_node *pv = ((cypher_map_pair *)a->items[k])->value;
@@ -5174,6 +5176,8 @@ static bool rw_expr_bound(ast_node *expr, const rw_row *row)
         }
         case AST_NODE_NOT_EXPR: return rw_expr_bound(((cypher_not_expr*)expr)->expr, row);
         case AST_NODE_NULL_CHECK: return rw_expr_bound(((cypher_null_check*)expr)->expr, row);
+        /* `n:A` in a SET value was left to SET, which refused it (GQLITE-T-0479) */
+        case AST_NODE_LABEL_EXPR: return rw_expr_bound(((cypher_label_expr*)expr)->expr, row);
         case AST_NODE_CASE_EXPR: {
             cypher_case_expr *c = (cypher_case_expr*)expr;
             if (!rw_expr_bound(c->operand, row) || !rw_expr_bound(c->else_expr, row)) return false;

tests/functional/109_set_map_case.sql

@@ -0,0 +1,31 @@
+-- ========================================================================
+-- Test 109: SET n = map that reads n, and SET values with label tests
+--           (GQLITE-T-0479)
+-- ========================================================================
+-- PURPOSE: `SET n = {id: n.id}` cleared n and then read n.id, and bulk SET
+--          dropped any map value that was not a literal: n lost id. A SET
+--          value with a label test (`CASE WHEN n:A ...`, `n:A`) was refused
+--          ("SET value must be a literal ...").
+-- NOTE:    Assertions are hard: _assert has CHECK (ok = 1), so under
+--          `sqlite3 -bail` any failed expectation aborts the run.
+-- ========================================================================
+
+.load ./build/graphqlite
+
+SELECT '=== Test 109: SET = map and label tests ===' as test_section;
+
+CREATE TEMP TABLE _assert(name TEXT, ok INTEGER CHECK (ok = 1));
+
+SELECT cypher('CREATE (:A109 {id: 1, v: 5, s: ''x''}), (:B109 {id: 2, v: 6})') as setup;
+
+SELECT cypher('MATCH (n:A109) SET n = {id: n.id, q: n.v + 1, l: [n.s]}') as w1;
+INSERT INTO _assert SELECT 'SET = map reads n before it clears n',
+    json(cypher('MATCH (n:A109) RETURN properties(n) AS p'))
+    = json('[{"p":{"id":1,"q":6,"l":["x"]}}]');
+
+SELECT cypher('MATCH (n) WHERE n:A109 OR n:B109 SET n.k = CASE WHEN n:A109 THEN ''a'' ELSE ''o'' END, n.t = n:B109') as w2;
+INSERT INTO _assert SELECT 'label tests in SET values',
+    json(cypher('MATCH (n) WHERE n:A109 OR n:B109 RETURN n.id AS id, n.k AS k, n.t AS t ORDER BY id'))
+    = json('[{"id":1,"k":"a","t":false},{"id":2,"k":"o","t":true}]');
+
+SELECT 'Test 109 passed: ' || count(*) || ' assertions' AS result FROM _assert;

tests/metamorphic/known.json

@@ -1,6 +1,5 @@
 [
   {"relation": ".", "kind": "error", "error": "invalid JSON result", "task": "GQLITE-T-0484"},
-  {"relation": "set_forms/replace", "kind": "mismatch", "task": "GQLITE-T-0479"},
   {"relation": "^expr_context/call/", "kind": "error", "error": "is not defined", "task": "GQLITE-T-0487"},
   {"relation": "^expr_context/comp/", "kind": "mismatch", "task": "GQLITE-T-0480"},
   {"relation": "^expr_context/(unwind|unwind_var|union)/", "kind": "mismatch", "task": "GQLITE-T-0481"},