From 898b6a0e072c4f8ba741e83bd7fd12a4c2ccb1a2 Mon Sep 17 00:00:00 2001 From: Jason Newcomb Date: Sun, 30 May 2021 09:35:06 -0400 Subject: [PATCH] Add lint `suspicious_splitn` --- CHANGELOG.md | 1 + clippy_lints/src/lib.rs | 3 + clippy_lints/src/methods/mod.rs | 36 ++++++++++- clippy_lints/src/methods/suspicious_splitn.rs | 52 ++++++++++++++++ tests/ui/single_char_pattern.fixed | 4 +- tests/ui/single_char_pattern.rs | 4 +- tests/ui/single_char_pattern.stderr | 4 +- tests/ui/suspicious_splitn.rs | 16 +++++ tests/ui/suspicious_splitn.stderr | 59 +++++++++++++++++++ 9 files changed, 172 insertions(+), 7 deletions(-) create mode 100644 clippy_lints/src/methods/suspicious_splitn.rs create mode 100644 tests/ui/suspicious_splitn.rs create mode 100644 tests/ui/suspicious_splitn.stderr diff --git a/CHANGELOG.md b/CHANGELOG.md index abfe7f91f4b..59daa074282 100644 --- a/CHANGELOG.md +++ b/CHANGELOG.md @@ -2671,6 +2671,7 @@ Released 2018-09-13 [`suspicious_map`]: https://rust-lang.github.io/rust-clippy/master/index.html#suspicious_map [`suspicious_op_assign_impl`]: https://rust-lang.github.io/rust-clippy/master/index.html#suspicious_op_assign_impl [`suspicious_operation_groupings`]: https://rust-lang.github.io/rust-clippy/master/index.html#suspicious_operation_groupings +[`suspicious_splitn`]: https://rust-lang.github.io/rust-clippy/master/index.html#suspicious_splitn [`suspicious_unary_op_formatting`]: https://rust-lang.github.io/rust-clippy/master/index.html#suspicious_unary_op_formatting [`tabs_in_doc_comments`]: https://rust-lang.github.io/rust-clippy/master/index.html#tabs_in_doc_comments [`temporary_assignment`]: https://rust-lang.github.io/rust-clippy/master/index.html#temporary_assignment diff --git a/clippy_lints/src/lib.rs b/clippy_lints/src/lib.rs index 4c9c44f55d1..0e815be9bd5 100644 --- a/clippy_lints/src/lib.rs +++ b/clippy_lints/src/lib.rs @@ -779,6 +779,7 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf: methods::SKIP_WHILE_NEXT, methods::STRING_EXTEND_CHARS, methods::SUSPICIOUS_MAP, + methods::SUSPICIOUS_SPLITN, methods::UNINIT_ASSUMED_INIT, methods::UNNECESSARY_FILTER_MAP, methods::UNNECESSARY_FOLD, @@ -1312,6 +1313,7 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf: LintId::of(methods::SKIP_WHILE_NEXT), LintId::of(methods::STRING_EXTEND_CHARS), LintId::of(methods::SUSPICIOUS_MAP), + LintId::of(methods::SUSPICIOUS_SPLITN), LintId::of(methods::UNINIT_ASSUMED_INIT), LintId::of(methods::UNNECESSARY_FILTER_MAP), LintId::of(methods::UNNECESSARY_FOLD), @@ -1688,6 +1690,7 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf: LintId::of(mem_replace::MEM_REPLACE_WITH_UNINIT), LintId::of(methods::CLONE_DOUBLE_REF), LintId::of(methods::ITERATOR_STEP_BY_ZERO), + LintId::of(methods::SUSPICIOUS_SPLITN), LintId::of(methods::UNINIT_ASSUMED_INIT), LintId::of(methods::ZST_OFFSET), LintId::of(minmax::MIN_MAX), diff --git a/clippy_lints/src/methods/mod.rs b/clippy_lints/src/methods/mod.rs index 0b998dbf86c..3904572c627 100644 --- a/clippy_lints/src/methods/mod.rs +++ b/clippy_lints/src/methods/mod.rs @@ -48,6 +48,7 @@ mod skip_while_next; mod string_extend_chars; mod suspicious_map; +mod suspicious_splitn; mod uninit_assumed_init; mod unnecessary_filter_map; mod unnecessary_fold; @@ -1633,6 +1634,35 @@ "replace `.iter().count()` with `.len()`" } +declare_clippy_lint! { + /// **What it does:** Checks for calls to `splitn` and related functions with + /// either zero or one splits. + /// + /// **Why is this bad?** These calls don't actually split the value and are + /// likely to be intended as a different number. + /// + /// **Known problems:** None. + /// + /// **Example:** + /// + /// ```rust + /// // Bad + /// let s = ""; + /// for x in s.splitn(1, ":") { + /// // use x + /// } + /// + /// // Good + /// let s = ""; + /// for x in s.splitn(2, ":") { + /// // use x + /// } + /// ``` + pub SUSPICIOUS_SPLITN, + correctness, + "checks for `.splitn(0, ..)` and `.splitn(1, ..)`" +} + pub struct Methods { avoid_breaking_exported_api: bool, msrv: Option, @@ -1705,7 +1735,8 @@ pub fn new(avoid_breaking_exported_api: bool, msrv: Option) -> Sel MAP_COLLECT_RESULT_UNIT, FROM_ITER_INSTEAD_OF_COLLECT, INSPECT_FOR_EACH, - IMPLICIT_CLONE + IMPLICIT_CLONE, + SUSPICIOUS_SPLITN ]); /// Extracts a method call name, args, and `Span` of the method name. @@ -2024,6 +2055,9 @@ fn check_methods<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>, msrv: Optio unnecessary_lazy_eval::check(cx, expr, recv, arg, "or"); } }, + ("splitn" | "splitn_mut" | "rsplitn" | "rsplitn_mut", [count_arg, _]) => { + suspicious_splitn::check(cx, name, expr, recv, count_arg); + }, ("step_by", [arg]) => iterator_step_by_zero::check(cx, expr, arg), ("to_os_string" | "to_owned" | "to_path_buf" | "to_vec", []) => { implicit_clone::check(cx, name, expr, recv, span); diff --git a/clippy_lints/src/methods/suspicious_splitn.rs b/clippy_lints/src/methods/suspicious_splitn.rs new file mode 100644 index 00000000000..43affe20dc5 --- /dev/null +++ b/clippy_lints/src/methods/suspicious_splitn.rs @@ -0,0 +1,52 @@ +use clippy_utils::diagnostics::span_lint_and_note; +use if_chain::if_chain; +use rustc_ast::LitKind; +use rustc_hir::{Expr, ExprKind}; +use rustc_lint::LateContext; +use rustc_span::source_map::Spanned; + +use super::SUSPICIOUS_SPLITN; + +pub(super) fn check( + cx: &LateContext<'_>, + method_name: &str, + expr: &Expr<'_>, + self_arg: &Expr<'_>, + count_arg: &Expr<'_>, +) { + if_chain! { + // Ignore empty slice literal + if !matches!(self_arg.kind, ExprKind::Array([])); + // Ignore empty string literal + if !matches!(self_arg.kind, ExprKind::Lit(Spanned { node: LitKind::Str(s, _), .. }) if s.is_empty()); + if let ExprKind::Lit(count_lit) = &count_arg.kind; + if let LitKind::Int(count, _) = count_lit.node; + if count <= 1; + if let Some(call_id) = cx.typeck_results().type_dependent_def_id(expr.hir_id); + if let Some(impl_id) = cx.tcx.impl_of_method(call_id); + let lang_items = cx.tcx.lang_items(); + if lang_items.slice_impl() == Some(impl_id) || lang_items.str_impl() == Some(impl_id); + then { + let (msg, note_msg) = if count == 0 { + (format!("`{}` called with `0` splits", method_name), + "the resulting iterator will always return `None`") + } else { + (format!("`{}` called with `1` split", method_name), + if lang_items.slice_impl() == Some(impl_id) { + "the resulting iterator will always return the entire slice followed by `None`" + } else { + "the resulting iterator will always return the entire string followed by `None`" + }) + }; + + span_lint_and_note( + cx, + SUSPICIOUS_SPLITN, + expr.span, + &msg, + None, + note_msg, + ); + } + } +} diff --git a/tests/ui/single_char_pattern.fixed b/tests/ui/single_char_pattern.fixed index fcbe9af9f56..1abd2b7883d 100644 --- a/tests/ui/single_char_pattern.fixed +++ b/tests/ui/single_char_pattern.fixed @@ -25,8 +25,8 @@ fn main() { x.rsplit('x'); x.split_terminator('x'); x.rsplit_terminator('x'); - x.splitn(0, 'x'); - x.rsplitn(0, 'x'); + x.splitn(2, 'x'); + x.rsplitn(2, 'x'); x.matches('x'); x.rmatches('x'); x.match_indices('x'); diff --git a/tests/ui/single_char_pattern.rs b/tests/ui/single_char_pattern.rs index b8bc20f4070..e662bf34be2 100644 --- a/tests/ui/single_char_pattern.rs +++ b/tests/ui/single_char_pattern.rs @@ -25,8 +25,8 @@ fn main() { x.rsplit("x"); x.split_terminator("x"); x.rsplit_terminator("x"); - x.splitn(0, "x"); - x.rsplitn(0, "x"); + x.splitn(2, "x"); + x.rsplitn(2, "x"); x.matches("x"); x.rmatches("x"); x.match_indices("x"); diff --git a/tests/ui/single_char_pattern.stderr b/tests/ui/single_char_pattern.stderr index 6d94d8a34e3..22d4b2d460f 100644 --- a/tests/ui/single_char_pattern.stderr +++ b/tests/ui/single_char_pattern.stderr @@ -75,13 +75,13 @@ LL | x.rsplit_terminator("x"); error: single-character string constant used as pattern --> $DIR/single_char_pattern.rs:28:17 | -LL | x.splitn(0, "x"); +LL | x.splitn(2, "x"); | ^^^ help: try using a `char` instead: `'x'` error: single-character string constant used as pattern --> $DIR/single_char_pattern.rs:29:18 | -LL | x.rsplitn(0, "x"); +LL | x.rsplitn(2, "x"); | ^^^ help: try using a `char` instead: `'x'` error: single-character string constant used as pattern diff --git a/tests/ui/suspicious_splitn.rs b/tests/ui/suspicious_splitn.rs new file mode 100644 index 00000000000..a944aa79cfe --- /dev/null +++ b/tests/ui/suspicious_splitn.rs @@ -0,0 +1,16 @@ +#![warn(clippy::suspicious_splitn)] + +fn main() { + let _ = "a,b,c".splitn(3, ','); + let _ = [0, 1, 2, 1, 3].splitn(3, |&x| x == 1); + let _ = "".splitn(0, ','); + let _ = [].splitn(0, |&x: &u32| x == 1); + + let _ = "a,b".splitn(0, ','); + let _ = "a,b".rsplitn(0, ','); + let _ = "a,b".splitn(1, ','); + let _ = [0, 1, 2].splitn(0, |&x| x == 1); + let _ = [0, 1, 2].splitn_mut(0, |&x| x == 1); + let _ = [0, 1, 2].splitn(1, |&x| x == 1); + let _ = [0, 1, 2].rsplitn_mut(1, |&x| x == 1); +} diff --git a/tests/ui/suspicious_splitn.stderr b/tests/ui/suspicious_splitn.stderr new file mode 100644 index 00000000000..2e4bfe93b94 --- /dev/null +++ b/tests/ui/suspicious_splitn.stderr @@ -0,0 +1,59 @@ +error: `splitn` called with `0` splits + --> $DIR/suspicious_splitn.rs:9:13 + | +LL | let _ = "a,b".splitn(0, ','); + | ^^^^^^^^^^^^^^^^^^^^ + | + = note: `-D clippy::suspicious-splitn` implied by `-D warnings` + = note: the resulting iterator will always return `None` + +error: `rsplitn` called with `0` splits + --> $DIR/suspicious_splitn.rs:10:13 + | +LL | let _ = "a,b".rsplitn(0, ','); + | ^^^^^^^^^^^^^^^^^^^^^ + | + = note: the resulting iterator will always return `None` + +error: `splitn` called with `1` split + --> $DIR/suspicious_splitn.rs:11:13 + | +LL | let _ = "a,b".splitn(1, ','); + | ^^^^^^^^^^^^^^^^^^^^ + | + = note: the resulting iterator will always return the entire string followed by `None` + +error: `splitn` called with `0` splits + --> $DIR/suspicious_splitn.rs:12:13 + | +LL | let _ = [0, 1, 2].splitn(0, |&x| x == 1); + | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + | + = note: the resulting iterator will always return `None` + +error: `splitn_mut` called with `0` splits + --> $DIR/suspicious_splitn.rs:13:13 + | +LL | let _ = [0, 1, 2].splitn_mut(0, |&x| x == 1); + | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + | + = note: the resulting iterator will always return `None` + +error: `splitn` called with `1` split + --> $DIR/suspicious_splitn.rs:14:13 + | +LL | let _ = [0, 1, 2].splitn(1, |&x| x == 1); + | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + | + = note: the resulting iterator will always return the entire slice followed by `None` + +error: `rsplitn_mut` called with `1` split + --> $DIR/suspicious_splitn.rs:15:13 + | +LL | let _ = [0, 1, 2].rsplitn_mut(1, |&x| x == 1); + | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + | + = note: the resulting iterator will always return the entire slice followed by `None` + +error: aborting due to 7 previous errors + -- 2.44.0