diff options
Diffstat (limited to 'src/tools/clippy/clippy_lints/src/open_options.rs')
| -rw-r--r-- | src/tools/clippy/clippy_lints/src/open_options.rs | 202 |
1 files changed, 202 insertions, 0 deletions
diff --git a/src/tools/clippy/clippy_lints/src/open_options.rs b/src/tools/clippy/clippy_lints/src/open_options.rs new file mode 100644 index 000000000..5a0b50420 --- /dev/null +++ b/src/tools/clippy/clippy_lints/src/open_options.rs @@ -0,0 +1,202 @@ +use clippy_utils::diagnostics::span_lint; +use clippy_utils::paths; +use clippy_utils::ty::match_type; +use rustc_ast::ast::LitKind; +use rustc_hir::{Expr, ExprKind}; +use rustc_lint::{LateContext, LateLintPass}; +use rustc_session::{declare_lint_pass, declare_tool_lint}; +use rustc_span::source_map::{Span, Spanned}; + +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. + /// + /// ### Example + /// ```rust + /// use std::fs::OpenOptions; + /// + /// OpenOptions::new().read(true).truncate(true); + /// ``` + #[clippy::version = "pre 1.29.0"] + pub NONSENSICAL_OPEN_OPTIONS, + correctness, + "nonsensical combination of options for opening a file" +} + +declare_lint_pass!(OpenOptions => [NONSENSICAL_OPEN_OPTIONS]); + +impl<'tcx> LateLintPass<'tcx> for OpenOptions { + fn check_expr(&mut self, cx: &LateContext<'tcx>, e: &'tcx Expr<'_>) { + if let ExprKind::MethodCall(path, [self_arg, ..], _) = &e.kind { + let obj_ty = cx.typeck_results().expr_ty(self_arg).peel_refs(); + if path.ident.name == sym!(open) && match_type(cx, obj_ty, &paths::OPEN_OPTIONS) { + let mut options = Vec::new(); + get_open_options(cx, self_arg, &mut options); + check_open_options(cx, &options, e.span); + } + } + } +} + +#[derive(Debug, PartialEq, Eq, Clone, Copy)] +enum Argument { + True, + False, + Unknown, +} + +#[derive(Debug)] +enum OpenOption { + Write, + Read, + Truncate, + Create, + Append, +} + +fn get_open_options(cx: &LateContext<'_>, argument: &Expr<'_>, options: &mut Vec<(OpenOption, Argument)>) { + if let ExprKind::MethodCall(path, arguments, _) = argument.kind { + let obj_ty = cx.typeck_results().expr_ty(&arguments[0]).peel_refs(); + + // Only proceed if this is a call on some object of type std::fs::OpenOptions + if match_type(cx, obj_ty, &paths::OPEN_OPTIONS) && arguments.len() >= 2 { + let argument_option = match arguments[1].kind { + ExprKind::Lit(ref span) => { + if let Spanned { + node: LitKind::Bool(lit), + .. + } = *span + { + if lit { Argument::True } else { Argument::False } + } else { + // The function is called with a literal which is not a boolean literal. + // This is theoretically possible, but not very likely. + return; + } + }, + _ => Argument::Unknown, + }; + + match path.ident.as_str() { + "create" => { + options.push((OpenOption::Create, argument_option)); + }, + "append" => { + options.push((OpenOption::Append, argument_option)); + }, + "truncate" => { + options.push((OpenOption::Truncate, argument_option)); + }, + "read" => { + options.push((OpenOption::Read, argument_option)); + }, + "write" => { + options.push((OpenOption::Write, argument_option)); + }, + _ => (), + } + + 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); + let (mut create_arg, mut append_arg, mut truncate_arg, mut read_arg, mut write_arg) = + (false, false, false, false, false); + // 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 { + span_lint( + cx, + NONSENSICAL_OPEN_OPTIONS, + span, + "the method `create` is called more than once", + ); + } else { + create = true; + } + create_arg = create_arg || (arg == Argument::True); + }, + (OpenOption::Append, arg) => { + if append { + span_lint( + cx, + NONSENSICAL_OPEN_OPTIONS, + span, + "the method `append` is called more than once", + ); + } else { + append = true; + } + append_arg = append_arg || (arg == Argument::True); + }, + (OpenOption::Truncate, arg) => { + if truncate { + span_lint( + cx, + NONSENSICAL_OPEN_OPTIONS, + span, + "the method `truncate` is called more than once", + ); + } else { + truncate = true; + } + truncate_arg = truncate_arg || (arg == Argument::True); + }, + (OpenOption::Read, arg) => { + if read { + span_lint( + cx, + NONSENSICAL_OPEN_OPTIONS, + span, + "the method `read` is called more than once", + ); + } else { + read = true; + } + read_arg = read_arg || (arg == Argument::True); + }, + (OpenOption::Write, arg) => { + if write { + span_lint( + cx, + NONSENSICAL_OPEN_OPTIONS, + span, + "the method `write` is called more than once", + ); + } else { + write = true; + } + write_arg = write_arg || (arg == Argument::True); + }, + } + } + + if read && truncate && read_arg && truncate_arg && !(write && write_arg) { + span_lint( + cx, + NONSENSICAL_OPEN_OPTIONS, + span, + "file opened with `truncate` and `read`", + ); + } + if append && truncate && append_arg && truncate_arg { + span_lint( + cx, + NONSENSICAL_OPEN_OPTIONS, + span, + "file opened with `append` and `truncate`", + ); + } +} |