93 lines
3.6 KiB
Rust
93 lines
3.6 KiB
Rust
use clippy_utils::diagnostics::span_lint_and_help;
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use clippy_utils::macros::{find_assert_args, find_assert_eq_args, root_macro_call_first_node, PanicExpn};
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use clippy_utils::{is_in_cfg_test, is_in_test_function};
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use rustc_hir::Expr;
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use rustc_lint::{LateContext, LateLintPass};
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use rustc_session::{declare_lint_pass, declare_tool_lint};
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use rustc_span::sym;
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declare_clippy_lint! {
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/// ### What it does
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/// Checks assertions without a custom panic message.
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///
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/// ### Why is this bad?
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/// Without a good custom message, it'd be hard to understand what went wrong when the assertion fails.
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/// A good custom message should be more about why the failure of the assertion is problematic
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/// and not what is failed because the assertion already conveys that.
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///
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/// Although the same reasoning applies to testing functions, this lint ignores them as they would be too noisy.
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/// Also, in most cases understanding the test failure would be easier
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/// compared to understanding a complex invariant distributed around the codebase.
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///
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/// ### Known problems
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/// This lint cannot check the quality of the custom panic messages.
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/// Hence, you can suppress this lint simply by adding placeholder messages
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/// like "assertion failed". However, we recommend coming up with good messages
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/// that provide useful information instead of placeholder messages that
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/// don't provide any extra information.
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///
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/// ### Example
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/// ```no_run
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/// # struct Service { ready: bool }
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/// fn call(service: Service) {
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/// assert!(service.ready);
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/// }
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/// ```
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/// Use instead:
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/// ```no_run
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/// # struct Service { ready: bool }
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/// fn call(service: Service) {
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/// assert!(service.ready, "`service.poll_ready()` must be called first to ensure that service is ready to receive requests");
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/// }
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/// ```
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#[clippy::version = "1.70.0"]
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pub MISSING_ASSERT_MESSAGE,
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restriction,
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"checks assertions without a custom panic message"
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}
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declare_lint_pass!(MissingAssertMessage => [MISSING_ASSERT_MESSAGE]);
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impl<'tcx> LateLintPass<'tcx> for MissingAssertMessage {
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fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
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let Some(macro_call) = root_macro_call_first_node(cx, expr) else {
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return;
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};
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let single_argument = match cx.tcx.get_diagnostic_name(macro_call.def_id) {
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Some(sym::assert_macro | sym::debug_assert_macro) => true,
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Some(
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sym::assert_eq_macro | sym::assert_ne_macro | sym::debug_assert_eq_macro | sym::debug_assert_ne_macro,
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) => false,
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_ => return,
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};
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// This lint would be very noisy in tests, so just ignore if we're in test context
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if is_in_test_function(cx.tcx, expr.hir_id) || is_in_cfg_test(cx.tcx, expr.hir_id) {
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return;
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}
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let panic_expn = if single_argument {
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let Some((_, panic_expn)) = find_assert_args(cx, expr, macro_call.expn) else {
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return;
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};
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panic_expn
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} else {
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let Some((_, _, panic_expn)) = find_assert_eq_args(cx, expr, macro_call.expn) else {
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return;
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};
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panic_expn
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};
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if let PanicExpn::Empty = panic_expn {
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span_lint_and_help(
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cx,
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MISSING_ASSERT_MESSAGE,
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macro_call.span,
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"assert without any message",
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None,
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"consider describing why the failing assert is problematic",
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);
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}
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}
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}
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