Add allow-indexing-slicing-in-tests option (#13854)

Close #13842

changelog: [`indexing_slicing`]: add allow-indexing-slicing-in-tests
option to be able ignore at test

Author: llogiq

CHANGELOG.md

@@ -6214,6 +6214,7 @@ Released 2018-09-13
 [`allow-comparison-to-zero`]: https://doc.rust-lang.org/clippy/lint_configuration.html#allow-comparison-to-zero
 [`allow-dbg-in-tests`]: https://doc.rust-lang.org/clippy/lint_configuration.html#allow-dbg-in-tests
 [`allow-expect-in-tests`]: https://doc.rust-lang.org/clippy/lint_configuration.html#allow-expect-in-tests
+[`allow-indexing-slicing-in-tests`]: https://doc.rust-lang.org/clippy/lint_configuration.html#allow-indexing-slicing-in-tests
 [`allow-mixed-uninlined-format-args`]: https://doc.rust-lang.org/clippy/lint_configuration.html#allow-mixed-uninlined-format-args
 [`allow-one-hash-in-raw-strings`]: https://doc.rust-lang.org/clippy/lint_configuration.html#allow-one-hash-in-raw-strings
 [`allow-panic-in-tests`]: https://doc.rust-lang.org/clippy/lint_configuration.html#allow-panic-in-tests

book/src/lint_configuration.md

@@ -81,6 +81,16 @@ Whether `expect` should be allowed in test functions or `#[cfg(test)]`
 * [`expect_used`](https://rust-lang.github.io/rust-clippy/master/index.html#expect_used)
 
 
+## `allow-indexing-slicing-in-tests`
+Whether `indexing_slicing` should be allowed in test functions or `#[cfg(test)]`
+
+**Default Value:** `false`
+
+---
+**Affected lints:**
+* [`indexing_slicing`](https://rust-lang.github.io/rust-clippy/master/index.html#indexing_slicing)
+
+
 ## `allow-mixed-uninlined-format-args`
 Whether to allow mixed uninlined format args, e.g. `format!("{} {}", a, foo.bar)`
 

clippy_config/src/conf.rs

@@ -291,6 +291,9 @@ define_Conf! {
     /// Whether `expect` should be allowed in test functions or `#[cfg(test)]`
     #[lints(expect_used)]
     allow_expect_in_tests: bool = false,
+    /// Whether `indexing_slicing` should be allowed in test functions or `#[cfg(test)]`
+    #[lints(indexing_slicing)]
+    allow_indexing_slicing_in_tests: bool = false,
     /// Whether to allow mixed uninlined format args, e.g. `format!("{} {}", a, foo.bar)`
     #[lints(uninlined_format_args)]
     allow_mixed_uninlined_format_args: bool = true,

clippy_lints/src/indexing_slicing.rs

@@ -2,7 +2,7 @@ use clippy_config::Conf;
 use clippy_utils::consts::{ConstEvalCtxt, Constant};
 use clippy_utils::diagnostics::{span_lint, span_lint_and_then};
 use clippy_utils::ty::{deref_chain, get_adt_inherent_method};
-use clippy_utils::{higher, is_from_proc_macro};
+use clippy_utils::{higher, is_from_proc_macro, is_in_test};
 use rustc_ast::ast::RangeLimits;
 use rustc_hir::{Expr, ExprKind};
 use rustc_lint::{LateContext, LateLintPass};
@@ -96,12 +96,14 @@ declare_clippy_lint! {
 impl_lint_pass!(IndexingSlicing => [INDEXING_SLICING, OUT_OF_BOUNDS_INDEXING]);
 
 pub struct IndexingSlicing {
+    allow_indexing_slicing_in_tests: bool,
     suppress_restriction_lint_in_const: bool,
 }
 
 impl IndexingSlicing {
     pub fn new(conf: &'static Conf) -> Self {
         Self {
+            allow_indexing_slicing_in_tests: conf.allow_indexing_slicing_in_tests,
             suppress_restriction_lint_in_const: conf.suppress_restriction_lint_in_const,
         }
     }
@@ -122,6 +124,7 @@ impl<'tcx> LateLintPass<'tcx> for IndexingSlicing {
         {
             let note = "the suggestion might not be applicable in constant blocks";
             let ty = cx.typeck_results().expr_ty(array).peel_refs();
+            let allowed_in_tests = self.allow_indexing_slicing_in_tests && is_in_test(cx.tcx, expr.hir_id);
             if let Some(range) = higher::Range::hir(index) {
                 // Ranged indexes, i.e., &x[n..m], &x[n..], &x[..n] and &x[..]
                 if let ty::Array(_, s) = ty.kind() {
@@ -171,6 +174,10 @@ impl<'tcx> LateLintPass<'tcx> for IndexingSlicing {
                     (None, None) => return, // [..] is ok.
                 };
 
+                if allowed_in_tests {
+                    return;
+                }
+
                 span_lint_and_then(cx, INDEXING_SLICING, expr.span, "slicing may panic", |diag| {
                     diag.help(help_msg);
 
@@ -209,6 +216,10 @@ impl<'tcx> LateLintPass<'tcx> for IndexingSlicing {
                     }
                 }
 
+                if allowed_in_tests {
+                    return;
+                }
+
                 span_lint_and_then(cx, INDEXING_SLICING, expr.span, "indexing may panic", |diag| {
                     diag.help("consider using `.get(n)` or `.get_mut(n)` instead");
 

tests/ui-toml/indexing_slicing/clippy.toml

@@ -0,0 +1 @@
+allow-indexing-slicing-in-tests = true

tests/ui-toml/indexing_slicing/indexing_slicing.rs

@@ -0,0 +1,19 @@
+//@compile-flags: --test
+#![warn(clippy::indexing_slicing)]
+#![allow(clippy::no_effect)]
+
+fn main() {
+    let x = [1, 2, 3, 4];
+    let index: usize = 1;
+    &x[index..];
+}
+
+#[cfg(test)]
+mod tests {
+    #[test]
+    fn test_fn() {
+        let x = [1, 2, 3, 4];
+        let index: usize = 1;
+        &x[index..];
+    }
+}

tests/ui-toml/indexing_slicing/indexing_slicing.stderr

@@ -0,0 +1,12 @@
+error: slicing may panic
+  --> tests/ui-toml/indexing_slicing/indexing_slicing.rs:8:6
+   |
+LL |     &x[index..];
+   |      ^^^^^^^^^^
+   |
+   = help: consider using `.get(n..)` or .get_mut(n..)` instead
+   = note: `-D clippy::indexing-slicing` implied by `-D warnings`
+   = help: to override `-D warnings` add `#[allow(clippy::indexing_slicing)]`
+
+error: aborting due to 1 previous error
+

tests/ui-toml/toml_unknown_key/conf_unknown_key.stderr

@@ -6,6 +6,7 @@ error: error reading Clippy's configuration file: unknown field `foobar`, expect
            allow-comparison-to-zero
            allow-dbg-in-tests
            allow-expect-in-tests
+           allow-indexing-slicing-in-tests
            allow-mixed-uninlined-format-args
            allow-one-hash-in-raw-strings
            allow-panic-in-tests
@@ -93,6 +94,7 @@ error: error reading Clippy's configuration file: unknown field `barfoo`, expect
            allow-comparison-to-zero
            allow-dbg-in-tests
            allow-expect-in-tests
+           allow-indexing-slicing-in-tests
            allow-mixed-uninlined-format-args
            allow-one-hash-in-raw-strings
            allow-panic-in-tests
@@ -180,6 +182,7 @@ error: error reading Clippy's configuration file: unknown field `allow_mixed_uni
            allow-comparison-to-zero
            allow-dbg-in-tests
            allow-expect-in-tests
+           allow-indexing-slicing-in-tests
            allow-mixed-uninlined-format-args
            allow-one-hash-in-raw-strings
            allow-panic-in-tests