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Auto merge of #5272 - jmeyers35:file_read_lint, r=flip1995
add lint on File::read_to_string and File::read_to_end Adds lint `verbose_file_reads` which checks for use of File::read_to_end and File::read_to_string. Closes rust-lang/rust-clippy#4916 changelog: add lint on File::{read_to_end, read_to_string}
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,83 @@ | ||
| use crate::utils::{match_type, paths, span_lint_and_help}; | ||
| use if_chain::if_chain; | ||
| use rustc_hir::{Expr, ExprKind, QPath}; | ||
| use rustc_lint::{LateContext, LateLintPass}; | ||
| use rustc_session::{declare_lint_pass, declare_tool_lint}; | ||
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||
| declare_clippy_lint! { | ||
| /// **What it does:** Checks for use of File::read_to_end and File::read_to_string. | ||
| /// | ||
| /// **Why is this bad?** `fs::{read, read_to_string}` provide the same functionality when `buf` is empty with fewer imports and no intermediate values. | ||
| /// 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) | ||
| /// **Known problems:** None. | ||
| /// | ||
| /// **Example:** | ||
| /// | ||
| /// ```rust,no_run | ||
| /// # use std::io::Read; | ||
| /// # use std::fs::File; | ||
| /// let mut f = File::open("foo.txt").unwrap(); | ||
| /// let mut bytes = Vec::new(); | ||
| /// f.read_to_end(&mut bytes).unwrap(); | ||
| /// ``` | ||
| /// Can be written more concisely as | ||
| /// ```rust,no_run | ||
| /// # use std::fs; | ||
| /// let mut bytes = fs::read("foo.txt").unwrap(); | ||
| /// ``` | ||
| pub VERBOSE_FILE_READS, | ||
| complexity, | ||
| "use of `File::read_to_end` or `File::read_to_string`" | ||
| } | ||
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| declare_lint_pass!(VerboseFileReads => [VERBOSE_FILE_READS]); | ||
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| impl<'a, 'tcx> LateLintPass<'a, 'tcx> for VerboseFileReads { | ||
| fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr<'tcx>) { | ||
| if is_file_read_to_end(cx, expr) { | ||
| span_lint_and_help( | ||
| cx, | ||
| VERBOSE_FILE_READS, | ||
| expr.span, | ||
| "use of `File::read_to_end`", | ||
| "consider using `fs::read` instead", | ||
| ); | ||
| } else if is_file_read_to_string(cx, expr) { | ||
| span_lint_and_help( | ||
| cx, | ||
| VERBOSE_FILE_READS, | ||
| expr.span, | ||
| "use of `File::read_to_string`", | ||
| "consider using `fs::read_to_string` instead", | ||
| ) | ||
| } | ||
| } | ||
| } | ||
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| fn is_file_read_to_end<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr<'tcx>) -> bool { | ||
| if_chain! { | ||
| if let ExprKind::MethodCall(method_name, _, exprs) = expr.kind; | ||
| if method_name.ident.as_str() == "read_to_end"; | ||
| if let ExprKind::Path(QPath::Resolved(None, _)) = &exprs[0].kind; | ||
| let ty = cx.tables.expr_ty(&exprs[0]); | ||
| if match_type(cx, ty, &paths::FILE); | ||
| then { | ||
| return true | ||
| } | ||
| } | ||
| false | ||
| } | ||
|
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||
| fn is_file_read_to_string<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr<'tcx>) -> bool { | ||
| if_chain! { | ||
| if let ExprKind::MethodCall(method_name, _, exprs) = expr.kind; | ||
| if method_name.ident.as_str() == "read_to_string"; | ||
| if let ExprKind::Path(QPath::Resolved(None, _)) = &exprs[0].kind; | ||
| let ty = cx.tables.expr_ty(&exprs[0]); | ||
| if match_type(cx, ty, &paths::FILE); | ||
| then { | ||
| return true | ||
| } | ||
| } | ||
| false | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,28 @@ | ||
| #![warn(clippy::verbose_file_reads)] | ||
| use std::env::temp_dir; | ||
| use std::fs::File; | ||
| use std::io::Read; | ||
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| struct Struct; | ||
| // To make sure we only warn on File::{read_to_end, read_to_string} calls | ||
| impl Struct { | ||
| pub fn read_to_end(&self) {} | ||
|
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| pub fn read_to_string(&self) {} | ||
| } | ||
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| fn main() -> std::io::Result<()> { | ||
| let path = "foo.txt"; | ||
| // Lint shouldn't catch this | ||
| let s = Struct; | ||
| s.read_to_end(); | ||
| s.read_to_string(); | ||
| // Should catch this | ||
| let mut f = File::open(&path)?; | ||
| let mut buffer = Vec::new(); | ||
| f.read_to_end(&mut buffer)?; | ||
| // ...and this | ||
| let mut string_buffer = String::new(); | ||
| f.read_to_string(&mut string_buffer)?; | ||
| Ok(()) | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,19 @@ | ||
| error: use of `File::read_to_end` | ||
| --> $DIR/verbose_file_reads.rs:23:5 | ||
| | | ||
| LL | f.read_to_end(&mut buffer)?; | ||
| | ^^^^^^^^^^^^^^^^^^^^^^^^^^ | ||
| | | ||
| = note: `-D clippy::verbose-file-reads` implied by `-D warnings` | ||
| = help: consider using `fs::read` instead | ||
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| error: use of `File::read_to_string` | ||
| --> $DIR/verbose_file_reads.rs:26:5 | ||
| | | ||
| LL | f.read_to_string(&mut string_buffer)?; | ||
| | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ | ||
| | | ||
| = help: consider using `fs::read_to_string` instead | ||
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| error: aborting due to 2 previous errors | ||
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