Function parse_exists_predicate

src/cypher/cypher.c:1041–1073

Parse a bounded EXISTS predicate: EXISTS { (anchor)-[:TYPE]->() } — a * single-hop, edge-type-specific existence check anchored on a bound variable * (e.g. WHERE NOT EXISTS { (f)<-[:CALLS]-() } finds functions with no callers). * Multi-hop / nested-WHERE EXISTS is intentionally unsupported. */

 * (e.g. WHERE NOT EXISTS { (f)<-[:CALLS]-() } finds functions with no callers).
 * Multi-hop / nested-WHERE EXISTS is intentionally unsupported. */
static cbm_expr_t *parse_exists_predicate(parser_t *p, bool negated) {
    advance(p); /* EXISTS */
    if (!match(p, TOK_LBRACE)) {
        snprintf(p->error, sizeof(p->error), "expected '{' after EXISTS at pos %d", peek(p)->pos);
        return NULL;
    }
    cbm_node_pattern_t anchor = {0};
    cbm_rel_pattern_t rel = {0};
    cbm_node_pattern_t far_node = {0};
    if (parse_node(p, &anchor) < 0 || parse_rel(p, &rel) < 0 || parse_node(p, &far_node) < 0) {
        free_one_node_pattern(&anchor);
        free_one_rel_pattern(&rel);
        free_one_node_pattern(&far_node);
        snprintf(p->error, sizeof(p->error),
                 "unsupported EXISTS pattern — only the single-hop form "
                 "'(var)-[:TYPE]->()' is supported");
        return NULL;
    }
    expect(p, TOK_RBRACE);

    cbm_condition_t c = {0};
    c.negated = negated;
    c.op = heap_strdup("EXISTS");
    c.variable = heap_strdup(anchor.variable ? anchor.variable : "");
    c.value = (rel.type_count > 0 && rel.types[0]) ? heap_strdup(rel.types[0]) : NULL;
    c.exists_dir = (rel.direction && strcmp(rel.direction, "inbound") == 0) ? 1
                   : (rel.direction && strcmp(rel.direction, "any") == 0)   ? 2
                                                                            : 0;
    free_one_node_pattern(&anchor);
    free_one_rel_pattern(&rel);
    free_one_node_pattern(&far_node);
    return expr_leaf(c);
}

/* Parse the operator + value tail shared by every condition subject
 * (var[.prop] and multi-arg functions like coalesce(...)): IS [NOT] NULL,