rust-clippy/clippy_lints/src/open_options.rs

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use clippy_utils::diagnostics::span_lint;
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use clippy_utils::paths;
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use clippy_utils::ty::match_type;
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use rustc_ast::ast::LitKind;
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use rustc_hir::{Expr, ExprKind};
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use rustc_lint::{LateContext, LateLintPass};
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use rustc_session::{declare_lint_pass, declare_tool_lint};
use rustc_span::source_map::{Span, Spanned};
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declare_clippy_lint! {
/// **What it does:** Checks for duplicate open options as well as combinations
/// that make no sense.
///
/// **Why is this bad?** In the best case, the code will be harder to read than
/// necessary. I don't know the worst case.
///
/// **Known problems:** None.
///
/// **Example:**
/// ```rust
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/// use std::fs::OpenOptions;
///
/// OpenOptions::new().read(true).truncate(true);
/// ```
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pub NONSENSICAL_OPEN_OPTIONS,
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correctness,
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"nonsensical combination of options for opening a file"
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}
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declare_lint_pass!(OpenOptions => [NONSENSICAL_OPEN_OPTIONS]);
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impl<'tcx> LateLintPass<'tcx> for OpenOptions {
fn check_expr(&mut self, cx: &LateContext<'tcx>, e: &'tcx Expr<'_>) {
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if let ExprKind::MethodCall(ref path, _, ref arguments, _) = e.kind {
let obj_ty = cx.typeck_results().expr_ty(&arguments[0]).peel_refs();
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if path.ident.name == sym!(open) && match_type(cx, obj_ty, &paths::OPEN_OPTIONS) {
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let mut options = Vec::new();
get_open_options(cx, &arguments[0], &mut options);
check_open_options(cx, &options, e.span);
}
}
}
}
#[derive(Debug, PartialEq, Eq, Clone, Copy)]
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enum Argument {
True,
False,
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Unknown,
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}
#[derive(Debug)]
enum OpenOption {
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Write,
Read,
Truncate,
Create,
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Append,
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}
fn get_open_options(cx: &LateContext<'_>, argument: &Expr<'_>, options: &mut Vec<(OpenOption, Argument)>) {
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if let ExprKind::MethodCall(ref path, _, ref arguments, _) = argument.kind {
let obj_ty = cx.typeck_results().expr_ty(&arguments[0]).peel_refs();
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// Only proceed if this is a call on some object of type std::fs::OpenOptions
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if match_type(cx, obj_ty, &paths::OPEN_OPTIONS) && arguments.len() >= 2 {
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let argument_option = match arguments[1].kind {
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ExprKind::Lit(ref span) => {
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if let Spanned {
node: LitKind::Bool(lit),
..
} = *span
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{
if lit { Argument::True } else { Argument::False }
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} else {
// The function is called with a literal which is not a boolean literal.
// This is theoretically possible, but not very likely.
return;
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}
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},
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_ => Argument::Unknown,
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};
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match &*path.ident.as_str() {
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"create" => {
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options.push((OpenOption::Create, argument_option));
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},
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"append" => {
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options.push((OpenOption::Append, argument_option));
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},
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"truncate" => {
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options.push((OpenOption::Truncate, argument_option));
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},
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"read" => {
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options.push((OpenOption::Read, argument_option));
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},
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"write" => {
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options.push((OpenOption::Write, argument_option));
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},
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_ => (),
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}
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get_open_options(cx, &arguments[0], options);
}
}
}
fn check_open_options(cx: &LateContext<'_>, options: &[(OpenOption, Argument)], span: Span) {
let (mut create, mut append, mut truncate, mut read, mut write) = (false, false, false, false, false);
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let (mut create_arg, mut append_arg, mut truncate_arg, mut read_arg, mut write_arg) =
(false, false, false, false, false);
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// This code is almost duplicated (oh, the irony), but I haven't found a way to
// unify it.
for option in options {
match *option {
(OpenOption::Create, arg) => {
if create {
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span_lint(
cx,
NONSENSICAL_OPEN_OPTIONS,
span,
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"the method `create` is called more than once",
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);
} else {
create = true
}
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create_arg = create_arg || (arg == Argument::True);
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},
(OpenOption::Append, arg) => {
if append {
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span_lint(
cx,
NONSENSICAL_OPEN_OPTIONS,
span,
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"the method `append` is called more than once",
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);
} else {
append = true
}
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append_arg = append_arg || (arg == Argument::True);
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},
(OpenOption::Truncate, arg) => {
if truncate {
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span_lint(
cx,
NONSENSICAL_OPEN_OPTIONS,
span,
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"the method `truncate` is called more than once",
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);
} else {
truncate = true
}
truncate_arg = truncate_arg || (arg == Argument::True);
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},
(OpenOption::Read, arg) => {
if read {
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span_lint(
cx,
NONSENSICAL_OPEN_OPTIONS,
span,
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"the method `read` is called more than once",
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);
} else {
read = true
}
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read_arg = read_arg || (arg == Argument::True);
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},
(OpenOption::Write, arg) => {
if write {
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span_lint(
cx,
NONSENSICAL_OPEN_OPTIONS,
span,
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"the method `write` is called more than once",
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);
} else {
write = true
}
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write_arg = write_arg || (arg == Argument::True);
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},
}
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}
if read && truncate && read_arg && truncate_arg && !(write && write_arg) {
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span_lint(
cx,
NONSENSICAL_OPEN_OPTIONS,
span,
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"file opened with `truncate` and `read`",
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);
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}
if append && truncate && append_arg && truncate_arg {
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span_lint(
cx,
NONSENSICAL_OPEN_OPTIONS,
span,
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"file opened with `append` and `truncate`",
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);
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}
}