mirror of
https://github.com/rust-lang/rust-clippy
synced 2024-12-24 03:53:20 +00:00
162 lines
5.1 KiB
Rust
162 lines
5.1 KiB
Rust
//! calculate cognitive complexity and warn about overly complex functions
|
|
|
|
use rustc_ast::ast::Attribute;
|
|
use rustc_hir::intravisit::{walk_expr, FnKind, NestedVisitorMap, Visitor};
|
|
use rustc_hir::{Body, Expr, ExprKind, FnDecl, HirId};
|
|
use rustc_lint::{LateContext, LateLintPass, LintContext};
|
|
use rustc_middle::hir::map::Map;
|
|
use rustc_session::{declare_tool_lint, impl_lint_pass};
|
|
use rustc_span::source_map::Span;
|
|
use rustc_span::BytePos;
|
|
|
|
use crate::utils::{match_type, paths, snippet_opt, span_lint_and_help, LimitStack};
|
|
|
|
declare_clippy_lint! {
|
|
/// **What it does:** Checks for methods with high cognitive complexity.
|
|
///
|
|
/// **Why is this bad?** Methods of high cognitive complexity tend to be hard to
|
|
/// both read and maintain. Also LLVM will tend to optimize small methods better.
|
|
///
|
|
/// **Known problems:** Sometimes it's hard to find a way to reduce the
|
|
/// complexity.
|
|
///
|
|
/// **Example:** No. You'll see it when you get the warning.
|
|
pub COGNITIVE_COMPLEXITY,
|
|
nursery,
|
|
"functions that should be split up into multiple functions"
|
|
}
|
|
|
|
pub struct CognitiveComplexity {
|
|
limit: LimitStack,
|
|
}
|
|
|
|
impl CognitiveComplexity {
|
|
#[must_use]
|
|
pub fn new(limit: u64) -> Self {
|
|
Self {
|
|
limit: LimitStack::new(limit),
|
|
}
|
|
}
|
|
}
|
|
|
|
impl_lint_pass!(CognitiveComplexity => [COGNITIVE_COMPLEXITY]);
|
|
|
|
impl CognitiveComplexity {
|
|
#[allow(clippy::cast_possible_truncation)]
|
|
fn check<'a, 'tcx>(
|
|
&mut self,
|
|
cx: &'a LateContext<'a, 'tcx>,
|
|
kind: FnKind<'tcx>,
|
|
decl: &'tcx FnDecl<'_>,
|
|
body: &'tcx Body<'_>,
|
|
body_span: Span,
|
|
) {
|
|
if body_span.from_expansion() {
|
|
return;
|
|
}
|
|
|
|
let expr = &body.value;
|
|
|
|
let mut helper = CCHelper { cc: 1, returns: 0 };
|
|
helper.visit_expr(expr);
|
|
let CCHelper { cc, returns } = helper;
|
|
let ret_ty = cx.tables.node_type(expr.hir_id);
|
|
let ret_adjust = if match_type(cx, ret_ty, &paths::RESULT) {
|
|
returns
|
|
} else {
|
|
#[allow(clippy::integer_division)]
|
|
(returns / 2)
|
|
};
|
|
|
|
let mut rust_cc = cc;
|
|
// prevent degenerate cases where unreachable code contains `return` statements
|
|
if rust_cc >= ret_adjust {
|
|
rust_cc -= ret_adjust;
|
|
}
|
|
|
|
if rust_cc > self.limit.limit() {
|
|
let fn_span = match kind {
|
|
FnKind::ItemFn(ident, _, _, _, _) | FnKind::Method(ident, _, _, _) => ident.span,
|
|
FnKind::Closure(_) => {
|
|
let header_span = body_span.with_hi(decl.output.span().lo());
|
|
let pos = snippet_opt(cx, header_span).and_then(|snip| {
|
|
let low_offset = snip.find('|')?;
|
|
let high_offset = 1 + snip.get(low_offset + 1..)?.find('|')?;
|
|
let low = header_span.lo() + BytePos(low_offset as u32);
|
|
let high = low + BytePos(high_offset as u32 + 1);
|
|
|
|
Some((low, high))
|
|
});
|
|
|
|
if let Some((low, high)) = pos {
|
|
Span::new(low, high, header_span.ctxt())
|
|
} else {
|
|
return;
|
|
}
|
|
},
|
|
};
|
|
|
|
span_lint_and_help(
|
|
cx,
|
|
COGNITIVE_COMPLEXITY,
|
|
fn_span,
|
|
&format!(
|
|
"the function has a cognitive complexity of ({}/{})",
|
|
rust_cc,
|
|
self.limit.limit()
|
|
),
|
|
"you could split it up into multiple smaller functions",
|
|
);
|
|
}
|
|
}
|
|
}
|
|
|
|
impl<'a, 'tcx> LateLintPass<'a, 'tcx> for CognitiveComplexity {
|
|
fn check_fn(
|
|
&mut self,
|
|
cx: &LateContext<'a, 'tcx>,
|
|
kind: FnKind<'tcx>,
|
|
decl: &'tcx FnDecl<'_>,
|
|
body: &'tcx Body<'_>,
|
|
span: Span,
|
|
hir_id: HirId,
|
|
) {
|
|
let def_id = cx.tcx.hir().local_def_id(hir_id);
|
|
if !cx.tcx.has_attr(def_id, sym!(test)) {
|
|
self.check(cx, kind, decl, body, span);
|
|
}
|
|
}
|
|
|
|
fn enter_lint_attrs(&mut self, cx: &LateContext<'a, 'tcx>, attrs: &'tcx [Attribute]) {
|
|
self.limit.push_attrs(cx.sess(), attrs, "cognitive_complexity");
|
|
}
|
|
fn exit_lint_attrs(&mut self, cx: &LateContext<'a, 'tcx>, attrs: &'tcx [Attribute]) {
|
|
self.limit.pop_attrs(cx.sess(), attrs, "cognitive_complexity");
|
|
}
|
|
}
|
|
|
|
struct CCHelper {
|
|
cc: u64,
|
|
returns: u64,
|
|
}
|
|
|
|
impl<'tcx> Visitor<'tcx> for CCHelper {
|
|
type Map = Map<'tcx>;
|
|
|
|
fn visit_expr(&mut self, e: &'tcx Expr<'_>) {
|
|
walk_expr(self, e);
|
|
match e.kind {
|
|
ExprKind::Match(_, ref arms, _) => {
|
|
if arms.len() > 1 {
|
|
self.cc += 1;
|
|
}
|
|
self.cc += arms.iter().filter(|arm| arm.guard.is_some()).count() as u64;
|
|
},
|
|
ExprKind::Ret(_) => self.returns += 1,
|
|
_ => {},
|
|
}
|
|
}
|
|
fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> {
|
|
NestedVisitorMap::None
|
|
}
|
|
}
|