fix(cypher): reject a non-numeric SKIP/LIMIT operand instead of dropping it

expect() fills p->error and returns NULL when the token after SKIP or LIMIT
is not a number, but both call sites only tested `if (num)` and then fell
through to `*out = r; return 0;`. r->limit kept the -1 "unset" initialiser,
which execution reads as "no LIMIT":

    rb_apply_skip_limit(rb, ret->skip, ret->limit >= 0 ? ret->limit : max_rows);

So `RETURN n.name LIMIT $limit` ran unbounded and answered isError:false with
the whole result set. `SKIP $offset LIMIT 10` lost both clauses at once,
because the orphaned operand also blocked the following match(p, TOK_LIMIT).

Propagate the failure the way the ORDER BY branch directly above already
does. This is the failure mode #1334 banned, reached by a different route.

Fixes #1994

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Signed-off-by: metehanulusoy <ulusoy.metehan03@gmail.com>

Author: metehanulusoy

src/cypher/cypher.c

@@ -1817,20 +1817,27 @@ static int parse_return_or_with(parser_t *p, cbm_return_clause_t **out, bool is_
         }
     }
 
-    /* Optional SKIP */
+    /* Optional SKIP. A non-numeric operand is a loud parse error: expect() has
+     * already filled p->error, and dropping the clause instead would leave
+     * r->skip at its "none" default while the query still reports success. */
     if (match(p, TOK_SKIP)) {
         const cbm_token_t *num = expect(p, TOK_NUMBER);
-        if (num) {
-            r->skip = (int)strtol(num->text, NULL, CBM_DECIMAL_BASE);
+        if (!num) {
+            free_return_clause(r);
+            return CBM_NOT_FOUND;
         }
+        r->skip = (int)strtol(num->text, NULL, CBM_DECIMAL_BASE);
     }
 
-    /* Optional LIMIT */
+    /* Optional LIMIT. Same rule: a dropped LIMIT is the failure mode #1334
+     * banned - the caller would silently receive the whole result set. */
     if (match(p, TOK_LIMIT)) {
         const cbm_token_t *num = expect(p, TOK_NUMBER);
-        if (num) {
-            r->limit = (int)strtol(num->text, NULL, CBM_DECIMAL_BASE);
+        if (!num) {
+            free_return_clause(r);
+            return CBM_NOT_FOUND;
         }
+        r->limit = (int)strtol(num->text, NULL, CBM_DECIMAL_BASE);
     }
 
     *out = r;

tests/test_cypher.c

@@ -420,6 +420,53 @@ TEST(cypher_parse_order_by_over_cap_rejected_issue1334) {
     PASS();
 }
 
+/* #1994: a non-numeric SKIP/LIMIT operand must be a loud parse error too. The old
+ * failure mode was the same one #1334 banned by a different route: expect()
+ * returned NULL, the clause was dropped, and the query still reported success
+ * with limit left at its -1 "no LIMIT" sentinel - so query_graph answered a
+ * bounded query with the entire result set. Cypher parameters ($limit) are the
+ * everyday trigger: they are what a Neo4j-shaped client writes by default. */
+TEST(cypher_parse_nonnumeric_limit_rejected_issue1994) {
+    cbm_query_t *q = NULL;
+    char *err = NULL;
+    int rc = cbm_cypher_parse("MATCH (f:Function) RETURN f.name LIMIT $limit", &q, &err);
+    ASSERT(rc != 0);
+    free(err);
+    PASS();
+}
+
+TEST(cypher_parse_nonnumeric_skip_rejected_issue1994) {
+    cbm_query_t *q = NULL;
+    char *err = NULL;
+    /* The orphaned operand also swallowed the LIMIT that followed it. */
+    int rc = cbm_cypher_parse("MATCH (f:Function) RETURN f.name SKIP $offset LIMIT 10", &q, &err);
+    ASSERT(rc != 0);
+    free(err);
+    PASS();
+}
+
+TEST(cypher_parse_word_limit_operand_rejected_issue1994) {
+    cbm_query_t *q = NULL;
+    char *err = NULL;
+    int rc = cbm_cypher_parse("MATCH (f:Function) RETURN f.name LIMIT abc", &q, &err);
+    ASSERT(rc != 0);
+    free(err);
+    PASS();
+}
+
+/* Control: a well-formed SKIP/LIMIT still parses and still carries its values. */
+TEST(cypher_parse_numeric_skip_limit_still_accepted) {
+    cbm_query_t *q = NULL;
+    char *err = NULL;
+    int rc = cbm_cypher_parse("MATCH (f:Function) RETURN f.name SKIP 2 LIMIT 10", &q, &err);
+    ASSERT_EQ(rc, 0);
+    ASSERT_EQ(q->ret->skip, 2);
+    ASSERT_EQ(q->ret->limit, 10);
+
+    cbm_query_free(q);
+    PASS();
+}
+
 TEST(cypher_parse_return_distinct) {
     cbm_query_t *q = NULL;
     char *err = NULL;
@@ -4116,6 +4163,10 @@ SUITE(cypher) {
     RUN_TEST(cypher_parse_return_order_limit);
     RUN_TEST(cypher_parse_multikey_order_by_issue1334);
     RUN_TEST(cypher_parse_order_by_over_cap_rejected_issue1334);
+    RUN_TEST(cypher_parse_nonnumeric_limit_rejected_issue1994);
+    RUN_TEST(cypher_parse_nonnumeric_skip_rejected_issue1994);
+    RUN_TEST(cypher_parse_word_limit_operand_rejected_issue1994);
+    RUN_TEST(cypher_parse_numeric_skip_limit_still_accepted);
     RUN_TEST(cypher_parse_return_distinct);
     RUN_TEST(cypher_parse_inline_props);
     RUN_TEST(cypher_parse_error);