-
Notifications
You must be signed in to change notification settings - Fork 1.6k
Commit
This commit does not belong to any branch on this repository, and may belong to a fork outside of the repository.
Auto merge of #5998 - deg4uss3r:master, r=yaahc
Add map_err_ignore lint In a large code base a lot of times errors are ignored by using something like: ```rust foo.map_err(|_| Some::Enum)?; ``` This drops the original error in favor of a enum that will not have the original error's context. This lint helps catch throwing away the original error in favor of an enum without its context. --- *Please keep the line below* changelog: Added map_err_ignore lint
- Loading branch information
Showing
8 changed files
with
214 additions
and
18 deletions.
There are no files selected for viewing
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,147 @@ | ||
| use crate::utils::span_lint_and_help; | ||
|
|
||
| use rustc_hir::{CaptureBy, Expr, ExprKind, PatKind}; | ||
| use rustc_lint::{LateContext, LateLintPass}; | ||
| use rustc_session::{declare_lint_pass, declare_tool_lint}; | ||
|
|
||
| declare_clippy_lint! { | ||
| /// **What it does:** Checks for instances of `map_err(|_| Some::Enum)` | ||
| /// | ||
| /// **Why is this bad?** This map_err throws away the original error rather than allowing the enum to contain and report the cause of the error | ||
| /// | ||
| /// **Known problems:** None. | ||
| /// | ||
| /// **Example:** | ||
| /// Before: | ||
| /// ```rust | ||
| /// use std::fmt; | ||
| /// | ||
| /// #[derive(Debug)] | ||
| /// enum Error { | ||
| /// Indivisible, | ||
| /// Remainder(u8), | ||
| /// } | ||
| /// | ||
| /// impl fmt::Display for Error { | ||
| /// fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { | ||
| /// match self { | ||
| /// Error::Indivisible => write!(f, "could not divide input by three"), | ||
| /// Error::Remainder(remainder) => write!( | ||
| /// f, | ||
| /// "input is not divisible by three, remainder = {}", | ||
| /// remainder | ||
| /// ), | ||
| /// } | ||
| /// } | ||
| /// } | ||
| /// | ||
| /// impl std::error::Error for Error {} | ||
| /// | ||
| /// fn divisible_by_3(input: &str) -> Result<(), Error> { | ||
| /// input | ||
| /// .parse::<i32>() | ||
| /// .map_err(|_| Error::Indivisible) | ||
| /// .map(|v| v % 3) | ||
| /// .and_then(|remainder| { | ||
| /// if remainder == 0 { | ||
| /// Ok(()) | ||
| /// } else { | ||
| /// Err(Error::Remainder(remainder as u8)) | ||
| /// } | ||
| /// }) | ||
| /// } | ||
| /// ``` | ||
| /// | ||
| /// After: | ||
| /// ```rust | ||
| /// use std::{fmt, num::ParseIntError}; | ||
| /// | ||
| /// #[derive(Debug)] | ||
| /// enum Error { | ||
| /// Indivisible(ParseIntError), | ||
| /// Remainder(u8), | ||
| /// } | ||
| /// | ||
| /// impl fmt::Display for Error { | ||
| /// fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { | ||
| /// match self { | ||
| /// Error::Indivisible(_) => write!(f, "could not divide input by three"), | ||
| /// Error::Remainder(remainder) => write!( | ||
| /// f, | ||
| /// "input is not divisible by three, remainder = {}", | ||
| /// remainder | ||
| /// ), | ||
| /// } | ||
| /// } | ||
| /// } | ||
| /// | ||
| /// impl std::error::Error for Error { | ||
| /// fn source(&self) -> Option<&(dyn std::error::Error + 'static)> { | ||
| /// match self { | ||
| /// Error::Indivisible(source) => Some(source), | ||
| /// _ => None, | ||
| /// } | ||
| /// } | ||
| /// } | ||
| /// | ||
| /// fn divisible_by_3(input: &str) -> Result<(), Error> { | ||
| /// input | ||
| /// .parse::<i32>() | ||
| /// .map_err(Error::Indivisible) | ||
| /// .map(|v| v % 3) | ||
| /// .and_then(|remainder| { | ||
| /// if remainder == 0 { | ||
| /// Ok(()) | ||
| /// } else { | ||
| /// Err(Error::Remainder(remainder as u8)) | ||
| /// } | ||
| /// }) | ||
| /// } | ||
| /// ``` | ||
| pub MAP_ERR_IGNORE, | ||
| pedantic, | ||
| "`map_err` should not ignore the original error" | ||
| } | ||
|
|
||
| declare_lint_pass!(MapErrIgnore => [MAP_ERR_IGNORE]); | ||
|
|
||
| impl<'tcx> LateLintPass<'tcx> for MapErrIgnore { | ||
| // do not try to lint if this is from a macro or desugaring | ||
| fn check_expr(&mut self, cx: &LateContext<'_>, e: &Expr<'_>) { | ||
| if e.span.from_expansion() { | ||
| return; | ||
| } | ||
|
|
||
| // check if this is a method call (e.g. x.foo()) | ||
| if let ExprKind::MethodCall(ref method, _t_span, ref args, _) = e.kind { | ||
| // only work if the method name is `map_err` and there are only 2 arguments (e.g. x.map_err(|_|[1] | ||
| // Enum::Variant[2])) | ||
| if method.ident.as_str() == "map_err" && args.len() == 2 { | ||
| // make sure the first argument is a closure, and grab the CaptureRef, body_id, and body_span fields | ||
| if let ExprKind::Closure(capture, _, body_id, body_span, _) = args[1].kind { | ||
| // check if this is by Reference (meaning there's no move statement) | ||
| if capture == CaptureBy::Ref { | ||
| // Get the closure body to check the parameters and values | ||
| let closure_body = cx.tcx.hir().body(body_id); | ||
| // make sure there's only one parameter (`|_|`) | ||
| if closure_body.params.len() == 1 { | ||
| // make sure that parameter is the wild token (`_`) | ||
| if let PatKind::Wild = closure_body.params[0].pat.kind { | ||
| // span the area of the closure capture and warn that the | ||
| // original error will be thrown away | ||
| span_lint_and_help( | ||
| cx, | ||
| MAP_ERR_IGNORE, | ||
| body_span, | ||
| "`map_err(|_|...` ignores the original error", | ||
| None, | ||
| "Consider wrapping the error in an enum variant", | ||
| ); | ||
| } | ||
| } | ||
| } | ||
| } | ||
| } | ||
| } | ||
| } | ||
| } |
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,25 @@ | ||
| #![warn(clippy::map_err_ignore)] | ||
| use std::convert::TryFrom; | ||
| use std::error::Error; | ||
| use std::fmt; | ||
|
|
||
| #[derive(Debug)] | ||
| enum Errors { | ||
| Ignored, | ||
| } | ||
|
|
||
| impl Error for Errors {} | ||
|
|
||
| impl fmt::Display for Errors { | ||
| fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { | ||
| write!(f, "Error") | ||
| } | ||
| } | ||
|
|
||
| fn main() -> Result<(), Errors> { | ||
| let x = u32::try_from(-123_i32); | ||
|
|
||
| println!("{:?}", x.map_err(|_| Errors::Ignored)); | ||
|
|
||
| Ok(()) | ||
| } |
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,11 @@ | ||
| error: `map_err(|_|...` ignores the original error | ||
| --> $DIR/map_err.rs:22:32 | ||
| | | ||
| LL | println!("{:?}", x.map_err(|_| Errors::Ignored)); | ||
| | ^^^ | ||
| | | ||
| = note: `-D clippy::map-err-ignore` implied by `-D warnings` | ||
| = help: Consider wrapping the error in an enum variant | ||
|
|
||
| error: aborting due to previous error | ||
|
|