89 lines
3.0 KiB
Rust
89 lines
3.0 KiB
Rust
use clippy_utils::diagnostics::span_lint_and_help;
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use clippy_utils::paths;
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use clippy_utils::ty::match_type;
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use if_chain::if_chain;
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use rustc_hir::{Expr, ExprKind, QPath};
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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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declare_clippy_lint! {
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/// ### What it does
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/// Checks for use of File::read_to_end and File::read_to_string.
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///
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/// ### Why is this bad?
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/// `fs::{read, read_to_string}` provide the same functionality when `buf` is empty with fewer imports and no intermediate values.
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/// See also: [fs::read docs](https://doc.rust-lang.org/std/fs/fn.read.html), [fs::read_to_string docs](https://doc.rust-lang.org/std/fs/fn.read_to_string.html)
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///
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/// ### Example
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/// ```rust,no_run
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/// # use std::io::Read;
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/// # use std::fs::File;
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/// let mut f = File::open("foo.txt").unwrap();
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/// let mut bytes = Vec::new();
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/// f.read_to_end(&mut bytes).unwrap();
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/// ```
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/// Can be written more concisely as
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/// ```rust,no_run
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/// # use std::fs;
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/// let mut bytes = fs::read("foo.txt").unwrap();
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/// ```
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#[clippy::version = "1.44.0"]
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pub VERBOSE_FILE_READS,
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restriction,
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"use of `File::read_to_end` or `File::read_to_string`"
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}
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declare_lint_pass!(VerboseFileReads => [VERBOSE_FILE_READS]);
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impl<'tcx> LateLintPass<'tcx> for VerboseFileReads {
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fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'tcx>) {
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if is_file_read_to_end(cx, expr) {
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span_lint_and_help(
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cx,
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VERBOSE_FILE_READS,
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expr.span,
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"use of `File::read_to_end`",
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None,
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"consider using `fs::read` instead",
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);
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} else if is_file_read_to_string(cx, expr) {
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span_lint_and_help(
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cx,
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VERBOSE_FILE_READS,
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expr.span,
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"use of `File::read_to_string`",
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None,
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"consider using `fs::read_to_string` instead",
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);
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}
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}
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}
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fn is_file_read_to_end<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'tcx>) -> bool {
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if_chain! {
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if let ExprKind::MethodCall(method_name, exprs, _) = expr.kind;
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if method_name.ident.as_str() == "read_to_end";
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if let ExprKind::Path(QPath::Resolved(None, _)) = &exprs[0].kind;
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let ty = cx.typeck_results().expr_ty(&exprs[0]);
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if match_type(cx, ty, &paths::FILE);
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then {
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return true
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}
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}
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false
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}
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fn is_file_read_to_string<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'tcx>) -> bool {
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if_chain! {
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if let ExprKind::MethodCall(method_name, exprs, _) = expr.kind;
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if method_name.ident.as_str() == "read_to_string";
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if let ExprKind::Path(QPath::Resolved(None, _)) = &exprs[0].kind;
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let ty = cx.typeck_results().expr_ty(&exprs[0]);
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if match_type(cx, ty, &paths::FILE);
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then {
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return true
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}
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}
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false
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}
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