0f5338cd90
The `restriction` group contains many lints which are not about necessarily “bad” things, but style choices — perhaps even style choices which contradict conventional Rust style — or are otherwise very situational. This results in silly wording like “Why is this bad? It isn't, but ...”, which I’ve seen confuse a newcomer at least once. To improve this situation, this commit replaces the “Why is this bad?” section heading with “Why restrict this?”, for most, but not all, restriction lints. I left alone the ones whose placement in the restriction group is more incidental. In order to make this make sense, I had to remove the “It isn't, but” texts from the contents of the sections. Sometimes further changes were needed, or there were obvious fixes to make, and I went ahead and made those changes without attempting to split them into another commit, even though many of them are not strictly necessary for the “Why restrict this?” project.
92 lines
3.6 KiB
Rust
92 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;
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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 restrict this?
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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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