Ignore functions annotated with #[test]

book/src/lint_configuration.md

@@ -94,6 +94,7 @@ Suppress lints whenever the suggested change would cause breakage for other crat
 * [`linkedlist`](https://rust-lang.github.io/rust-clippy/master/index.html#linkedlist)
 * [`rc_mutex`](https://rust-lang.github.io/rust-clippy/master/index.html#rc_mutex)
 * [`unnecessary_box_returns`](https://rust-lang.github.io/rust-clippy/master/index.html#unnecessary_box_returns)
+* [`single_call_fn`](https://rust-lang.github.io/rust-clippy/master/index.html#single_call_fn)
 
 
 ## `msrv`

clippy_lints/src/single_call_fn.rs

@@ -1,5 +1,5 @@
 use clippy_utils::diagnostics::span_lint_and_help;
-use clippy_utils::is_from_proc_macro;
+use clippy_utils::{is_from_proc_macro, is_in_test_function};
 use rustc_data_structures::fx::FxHashMap;
 use rustc_hir::def_id::LocalDefId;
 use rustc_hir::intravisit::{walk_expr, Visitor};
@@ -12,7 +12,7 @@ use rustc_span::Span;
 
 declare_clippy_lint! {
     /// ### What it does
-    /// Checks for functions that are only used once.
+    /// Checks for functions that are only used once. Does not lint tests.
     ///
     /// ### Why is this bad?
     /// It's usually not, splitting a function into multiple parts often improves readability and in
@@ -73,6 +73,7 @@ impl<'tcx> LateLintPass<'tcx> for SingleCallFn {
         if self.avoid_breaking_exported_api && cx.effective_visibilities.is_exported(def_id)
             || in_external_macro(cx.sess(), span)
             || is_from_proc_macro(cx, &(&kind, body, cx.tcx.local_def_id_to_hir_id(def_id), span))
+            || is_in_test_function(cx.tcx, body.value.hir_id)
         {
             return;
         }

tests/ui/single_call_fn.rs

@@ -1,4 +1,5 @@
 //@aux-build:proc_macros.rs
+//@compile-flags: --test
 #![allow(clippy::redundant_closure_call, unused)]
 #![warn(clippy::single_call_fn)]
 #![no_main]
@@ -64,3 +65,11 @@ fn e() {
     b();
     b();
 }
+
+#[test]
+fn k() {}
+
+#[test]
+fn l() {
+    k();
+}

tests/ui/single_call_fn.stderr

@@ -1,5 +1,5 @@
 error: this function is only used once
-  --> $DIR/single_call_fn.rs:33:1
+  --> $DIR/single_call_fn.rs:34:1
    |
 LL | / fn c() {
 LL | |     println!("really");
@@ -9,44 +9,44 @@ LL | | }
    | |_^
    |
 help: used here
-  --> $DIR/single_call_fn.rs:40:5
+  --> $DIR/single_call_fn.rs:41:5
    |
 LL |     c();
    |     ^
    = note: `-D clippy::single-call-fn` implied by `-D warnings`
 
 error: this function is only used once
-  --> $DIR/single_call_fn.rs:12:1
+  --> $DIR/single_call_fn.rs:13:1
    |
 LL | fn i() {}
    | ^^^^^^^^^
    |
 help: used here
-  --> $DIR/single_call_fn.rs:17:13
+  --> $DIR/single_call_fn.rs:18:13
    |
 LL |     let a = i;
    |             ^
 
 error: this function is only used once
-  --> $DIR/single_call_fn.rs:43:1
+  --> $DIR/single_call_fn.rs:44:1
    |
 LL | fn a() {}
    | ^^^^^^^^^
    |
 help: used here
-  --> $DIR/single_call_fn.rs:46:5
+  --> $DIR/single_call_fn.rs:47:5
    |
 LL |     a();
    |     ^
 
 error: this function is only used once
-  --> $DIR/single_call_fn.rs:13:1
+  --> $DIR/single_call_fn.rs:14:1
    |
 LL | fn j() {}
    | ^^^^^^^^^
    |
 help: used here
-  --> $DIR/single_call_fn.rs:24:9
+  --> $DIR/single_call_fn.rs:25:9
    |
 LL |         j();
    |         ^