react_auditor/rules/react/
no_unnecessary_memo.rs

1use oxc_ast::ast::Program;
2use oxc_ast_visit::Visit;
3use oxc_semantic::Semantic;
4
5use crate::rules::{Rule, RuleFinding, RuleMeta, Severity};
6
7pub struct NoUnnecessaryMemo;
8
9const RULE_META: RuleMeta = RuleMeta {
10    id: "no-unnecessary-memo",
11    default_severity: Severity::Warning,
12    category: "react",
13    description: "Avoid useMemo/useCallback for trivial computations",
14};
15
16impl Rule for NoUnnecessaryMemo {
17    fn meta(&self) -> &RuleMeta {
18        &RULE_META
19    }
20
21    fn run(&self, program: &Program, _semantic: &Semantic, source_text: &str) -> Vec<RuleFinding> {
22        let mut collector = UnnecessaryMemoCollector {
23            findings: Vec::new(),
24            source: source_text,
25        };
26        collector.visit_program(program);
27        collector.findings
28    }
29}
30
31struct UnnecessaryMemoCollector<'a> {
32    findings: Vec<RuleFinding>,
33    source: &'a str,
34}
35
36impl<'a> Visit<'a> for UnnecessaryMemoCollector<'a> {
37    fn visit_call_expression(&mut self, expr: &oxc_ast::ast::CallExpression<'a>) {
38        let name = if let oxc_ast::ast::Expression::Identifier(ident) = &expr.callee {
39            Some(ident.name.as_str())
40        } else if let Some(member) = expr.callee.as_member_expression() {
41            member.static_property_name()
42        } else {
43            None
44        };
45
46        if let Some(name) = name
47            && (name == "useMemo" || name == "useCallback")
48            && expr.arguments.len() >= 2
49            && let Some(last_arg) = expr.arguments.last()
50            && let oxc_ast::ast::Argument::ArrayExpression(arr) = &last_arg
51            && arr.elements.is_empty()
52        {
53            let start = expr.span.start as usize;
54            let line = self.source[..start].lines().count().max(1);
55            let col = start - self.source[..start].rfind('\n').map(|i| i + 1).unwrap_or(0);
56            self.findings.push(RuleFinding {
57                line,
58                column: col + 1,
59                message: format!(
60                    "`{name}` with empty deps array — value will never change, consider removing"
61                ),
62            });
63        }
64    }
65}
react_auditor/rules/react/no_unnecessary_memo.rs

react_auditor/rules/react/
no_unnecessary_memo.rs
