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|
//! Unnecessary Manual RenderResult Creation
//!
//! ## Summary
//!
//! Detects `#[renderer]` functions that manually create a `RenderResult` and
//! manage it via `r_println!(r, ...)` style calls, when they could be simplified
//! to `#[renderer(buffer)]` which handles the buffer automatically.
//!
//! This lint will not trigger if `r` is used outside of `r_println!`,
//! `r_eprintln!`, `r_print`, `r_eprint`, or `r_append`.
//!
//! ## Metadata
//!
//! Author: `Weicao-CatilGrass`
//! Default: `warn`
use crate::linter::mlint_report::{MlintLevel, MlintReport};
pub fn linter(ast: syn::ItemFn, source: &str) -> Vec<MlintReport> {
if !has_renderer_attr(&ast) {
return vec![];
}
let stmts = &ast.block.stmts;
if stmts.len() < 2 {
return vec![];
}
let (r_ident, let_idx) = match find_render_result_new(stmts) {
Some(pair) => pair,
None => return vec![],
};
let r_name = r_ident.to_string();
let mut only_print_and_return = true;
let mut print_count = 0;
for stmt in &stmts[let_idx + 1..] {
if !check_stmt_usage(stmt, &r_name, &mut print_count) {
only_print_and_return = false;
break;
}
}
if only_print_and_return && print_count > 0 {
let span = MlintReport::span_from_syn(&ast.sig, source);
vec![MlintReport {
source_code: source.to_string(),
level: MlintLevel::Warning,
lint_code: "unnecessary_render_result_creation".into(),
message: format!(
"unnecessary manual `RenderResult` creation in `{}`: use `#[renderer(buffer)]` instead",
ast.sig.ident,
),
spans: vec![span],
attached_reports: vec![MlintReport {
level: MlintLevel::Help,
message: format!(
"change to `#[renderer(buffer)]` and use `r_println!(...)` without the `{}` parameter",
r_name,
),
..Default::default()
}],
..Default::default()
}]
} else {
vec![]
}
}
fn has_renderer_attr(func: &syn::ItemFn) -> bool {
func.attrs.iter().any(|a| {
if !a.path().is_ident("renderer") {
return false;
}
if let Ok(list) = a.meta.require_list() {
let tokens = list.tokens.to_string();
if tokens.contains("buffer") {
return false;
}
}
true
})
}
fn find_render_result_new(stmts: &[syn::Stmt]) -> Option<(proc_macro2::Ident, usize)> {
for (i, stmt) in stmts.iter().enumerate() {
if let syn::Stmt::Local(local) = stmt
&& let Some(init) = &local.init
&& let syn::Pat::Ident(pat_id) = &local.pat
&& pat_id.mutability.is_some()
&& let syn::Expr::Call(call) = &*init.expr
&& let syn::Expr::Path(expr_path) = call.func.as_ref()
{
let segs = &expr_path.path.segments;
let matches = match segs.len() {
2 => {
segs[0].ident == "RenderResult"
&& (segs[1].ident == "new" || segs[1].ident == "default")
}
3 => {
segs[0].ident == "mingling"
&& segs[1].ident == "RenderResult"
&& (segs[2].ident == "new" || segs[2].ident == "default")
}
_ => false,
};
if matches {
return Some((pat_id.ident.clone(), i));
}
}
// Also handle `RenderResult::from(...)` and `mingling::RenderResult::from(...)`
if let syn::Stmt::Local(local) = stmt
&& let Some(init) = &local.init
&& let syn::Pat::Ident(pat_id) = &local.pat
&& pat_id.mutability.is_some()
&& let syn::Expr::Call(call) = &*init.expr
&& let syn::Expr::Path(expr_path) = call.func.as_ref()
{
let segs = &expr_path.path.segments;
let matches = match segs.len() {
2 => segs[0].ident == "RenderResult" && segs[1].ident == "from",
3 => {
segs[0].ident == "mingling"
&& segs[1].ident == "RenderResult"
&& segs[2].ident == "from"
}
_ => false,
};
if matches {
return Some((pat_id.ident.clone(), i));
}
}
}
None
}
fn check_stmt_usage(stmt: &syn::Stmt, r_name: &str, print_count: &mut usize) -> bool {
// return r; → allowed
if let syn::Stmt::Expr(expr, _) = stmt
&& let syn::Expr::Return(ret) = expr
&& let Some(ret_expr) = &ret.expr
&& let syn::Expr::Path(p) = ret_expr.as_ref()
&& p.path.is_ident(r_name)
{
return true;
}
// r_println!(r, ...) → allowed
if let syn::Stmt::Macro(stmt_mac) = stmt {
let macro_name = stmt_mac
.mac
.path
.segments
.last()
.map(|s| s.ident.to_string())
.unwrap_or_default();
let is_r_macro = matches!(
macro_name.as_str(),
"r_println" | "r_eprintln" | "r_print" | "r_eprint" | "r_append"
);
if is_r_macro
&& let Some(first_arg) = stmt_mac.mac.tokens.clone().into_iter().next()
&& first_arg.to_string() == *r_name
{
*print_count += 1;
return true;
}
}
let s = format!("{stmt:#?}");
!s.contains(&format!("\"{r_name}\""))
}
|
