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use clippy_utils::diagnostics::{span_lint, span_lint_and_help};
use clippy_utils::{is_trait_method, is_try, match_trait_method, paths};
use rustc_hir as hir;
use rustc_lint::{LateContext, LateLintPass};
use rustc_session::{declare_lint_pass, declare_tool_lint};
use rustc_span::sym;
declare_clippy_lint! {
/// ### What it does
/// Checks for unused written/read amount.
///
/// ### Why is this bad?
/// `io::Write::write(_vectored)` and
/// `io::Read::read(_vectored)` are not guaranteed to
/// process the entire buffer. They return how many bytes were processed, which
/// might be smaller
/// than a given buffer's length. If you don't need to deal with
/// partial-write/read, use
/// `write_all`/`read_exact` instead.
///
/// When working with asynchronous code (either with the `futures`
/// crate or with `tokio`), a similar issue exists for
/// `AsyncWriteExt::write()` and `AsyncReadExt::read()` : these
/// functions are also not guaranteed to process the entire
/// buffer. Your code should either handle partial-writes/reads, or
/// call the `write_all`/`read_exact` methods on those traits instead.
///
/// ### Known problems
/// Detects only common patterns.
///
/// ### Examples
/// ```rust,ignore
/// use std::io;
/// fn foo<W: io::Write>(w: &mut W) -> io::Result<()> {
/// // must be `w.write_all(b"foo")?;`
/// w.write(b"foo")?;
/// Ok(())
/// }
/// ```
#[clippy::version = "pre 1.29.0"]
pub UNUSED_IO_AMOUNT,
correctness,
"unused written/read amount"
}
declare_lint_pass!(UnusedIoAmount => [UNUSED_IO_AMOUNT]);
impl<'tcx> LateLintPass<'tcx> for UnusedIoAmount {
fn check_stmt(&mut self, cx: &LateContext<'_>, s: &hir::Stmt<'_>) {
let (hir::StmtKind::Semi(expr) | hir::StmtKind::Expr(expr)) = s.kind else {
return
};
match expr.kind {
hir::ExprKind::Match(res, _, _) if is_try(cx, expr).is_some() => {
if let hir::ExprKind::Call(func, [ref arg_0, ..]) = res.kind {
if matches!(
func.kind,
hir::ExprKind::Path(hir::QPath::LangItem(hir::LangItem::TryTraitBranch, ..))
) {
check_map_error(cx, arg_0, expr);
}
} else {
check_map_error(cx, res, expr);
}
},
hir::ExprKind::MethodCall(path, arg_0, ..) => match path.ident.as_str() {
"expect" | "unwrap" | "unwrap_or" | "unwrap_or_else" | "is_ok" | "is_err" => {
check_map_error(cx, arg_0, expr);
},
_ => (),
},
_ => (),
}
}
}
/// If `expr` is an (e).await, return the inner expression "e" that's being
/// waited on. Otherwise return None.
fn try_remove_await<'a>(expr: &'a hir::Expr<'a>) -> Option<&hir::Expr<'a>> {
if let hir::ExprKind::Match(expr, _, hir::MatchSource::AwaitDesugar) = expr.kind {
if let hir::ExprKind::Call(func, [ref arg_0, ..]) = expr.kind {
if matches!(
func.kind,
hir::ExprKind::Path(hir::QPath::LangItem(hir::LangItem::IntoFutureIntoFuture, ..))
) {
return Some(arg_0);
}
}
}
None
}
fn check_map_error(cx: &LateContext<'_>, call: &hir::Expr<'_>, expr: &hir::Expr<'_>) {
let mut call = call;
while let hir::ExprKind::MethodCall(path, receiver, ..) = call.kind {
if matches!(path.ident.as_str(), "or" | "or_else" | "ok") {
call = receiver;
} else {
break;
}
}
if let Some(call) = try_remove_await(call) {
check_method_call(cx, call, expr, true);
} else {
check_method_call(cx, call, expr, false);
}
}
fn check_method_call(cx: &LateContext<'_>, call: &hir::Expr<'_>, expr: &hir::Expr<'_>, is_await: bool) {
if let hir::ExprKind::MethodCall(path, ..) = call.kind {
let symbol = path.ident.as_str();
let read_trait = if is_await {
match_trait_method(cx, call, &paths::FUTURES_IO_ASYNCREADEXT)
|| match_trait_method(cx, call, &paths::TOKIO_IO_ASYNCREADEXT)
} else {
is_trait_method(cx, call, sym::IoRead)
};
let write_trait = if is_await {
match_trait_method(cx, call, &paths::FUTURES_IO_ASYNCWRITEEXT)
|| match_trait_method(cx, call, &paths::TOKIO_IO_ASYNCWRITEEXT)
} else {
is_trait_method(cx, call, sym::IoWrite)
};
match (read_trait, write_trait, symbol, is_await) {
(true, _, "read", false) => span_lint_and_help(
cx,
UNUSED_IO_AMOUNT,
expr.span,
"read amount is not handled",
None,
"use `Read::read_exact` instead, or handle partial reads",
),
(true, _, "read", true) => span_lint_and_help(
cx,
UNUSED_IO_AMOUNT,
expr.span,
"read amount is not handled",
None,
"use `AsyncReadExt::read_exact` instead, or handle partial reads",
),
(true, _, "read_vectored", _) => {
span_lint(cx, UNUSED_IO_AMOUNT, expr.span, "read amount is not handled");
},
(_, true, "write", false) => span_lint_and_help(
cx,
UNUSED_IO_AMOUNT,
expr.span,
"written amount is not handled",
None,
"use `Write::write_all` instead, or handle partial writes",
),
(_, true, "write", true) => span_lint_and_help(
cx,
UNUSED_IO_AMOUNT,
expr.span,
"written amount is not handled",
None,
"use `AsyncWriteExt::write_all` instead, or handle partial writes",
),
(_, true, "write_vectored", _) => {
span_lint(cx, UNUSED_IO_AMOUNT, expr.span, "written amount is not handled");
},
_ => (),
}
}
}
|
