Auto merge of #12803 - wutchzone:panic-in-tests, r=y21

Add configuration option for ignoring `panic!()` in tests

```
changelog: [`panic`]: Now can be disabled in tests with the `allow-panic-in-tests` option
```

I often find myself using `panic!(…)` in tests a lot, where I often do something like:

```rust
match enam {
  Enam::A => …,
  Enam::B => …,
  _ => panic!("This should not happen at all."),
}
```
I think this patch should go nicely with already existing `allow-unwrap-in-tests` and `allow-expect-in-tests`.

CHANGELOG.md

@@ -5942,6 +5942,7 @@ Released 2018-09-13
 [`allow-expect-in-tests`]: https://doc.rust-lang.org/clippy/lint_configuration.html#allow-expect-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
 [`allow-print-in-tests`]: https://doc.rust-lang.org/clippy/lint_configuration.html#allow-print-in-tests
 [`allow-private-module-inception`]: https://doc.rust-lang.org/clippy/lint_configuration.html#allow-private-module-inception
 [`allow-renamed-params-for`]: https://doc.rust-lang.org/clippy/lint_configuration.html#allow-renamed-params-for

book/src/lint_configuration.md

@@ -101,6 +101,16 @@ Whether to allow `r#""#` when `r""` can be used
 * [`unnecessary_raw_string_hashes`](https://rust-lang.github.io/rust-clippy/master/index.html#unnecessary_raw_string_hashes)
 
 
+## `allow-panic-in-tests`
+Whether `panic` should be allowed in test functions or `#[cfg(test)]`
+
+**Default Value:** `false`
+
+---
+**Affected lints:**
+* [`panic`](https://rust-lang.github.io/rust-clippy/master/index.html#panic)
+
+
 ## `allow-print-in-tests`
 Whether print macros (ex. `println!`) should be allowed in test functions or `#[cfg(test)]`
 

clippy_config/src/conf.rs

@@ -457,6 +457,10 @@ define_Conf! {
     ///
     /// Whether `unwrap` should be allowed in test functions or `#[cfg(test)]`
     (allow_unwrap_in_tests: bool = false),
+    /// Lint: PANIC.
+    ///
+    /// Whether `panic` should be allowed in test functions or `#[cfg(test)]`
+    (allow_panic_in_tests: bool = false),
     /// Lint: DBG_MACRO.
     ///
     /// Whether `dbg!` should be allowed in test functions or `#[cfg(test)]`

clippy_lints/src/lib.rs

@@ -532,6 +532,7 @@ pub fn register_lints(store: &mut rustc_lint::LintStore, conf: &'static Conf) {
         allow_expect_in_tests,
         allow_mixed_uninlined_format_args,
         allow_one_hash_in_raw_strings,
+        allow_panic_in_tests,
         allow_print_in_tests,
         allow_private_module_inception,
         allow_unwrap_in_tests,
@@ -769,7 +770,7 @@ pub fn register_lints(store: &mut rustc_lint::LintStore, conf: &'static Conf) {
             allow_in_test: allow_useless_vec_in_tests,
         })
     });
-    store.register_late_pass(|_| Box::new(panic_unimplemented::PanicUnimplemented));
+    store.register_late_pass(move |_| Box::new(panic_unimplemented::PanicUnimplemented { allow_panic_in_tests }));
     store.register_late_pass(|_| Box::new(strings::StringLitAsBytes));
     store.register_late_pass(|_| Box::new(derive::Derive));
     store.register_late_pass(move |_| Box::new(derivable_impls::DerivableImpls::new(msrv())));

clippy_lints/src/panic_unimplemented.rs

@@ -1,8 +1,14 @@
 use clippy_utils::diagnostics::span_lint;
+use clippy_utils::is_in_test;
 use clippy_utils::macros::{is_panic, root_macro_call_first_node};
 use rustc_hir::Expr;
 use rustc_lint::{LateContext, LateLintPass};
-use rustc_session::declare_lint_pass;
+use rustc_session::impl_lint_pass;
+
+#[derive(Clone)]
+pub struct PanicUnimplemented {
+    pub allow_panic_in_tests: bool,
+}
 
 declare_clippy_lint! {
     /// ### What it does
@@ -77,7 +83,7 @@ declare_clippy_lint! {
     "usage of the `unreachable!` macro"
 }
 
-declare_lint_pass!(PanicUnimplemented => [UNIMPLEMENTED, UNREACHABLE, TODO, PANIC]);
+impl_lint_pass!(PanicUnimplemented => [UNIMPLEMENTED, UNREACHABLE, TODO, PANIC]);
 
 impl<'tcx> LateLintPass<'tcx> for PanicUnimplemented {
     fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
@@ -85,7 +91,9 @@ impl<'tcx> LateLintPass<'tcx> for PanicUnimplemented {
             return;
         };
         if is_panic(cx, macro_call.def_id) {
-            if cx.tcx.hir().is_inside_const_context(expr.hir_id) {
+            if cx.tcx.hir().is_inside_const_context(expr.hir_id)
+                || self.allow_panic_in_tests && is_in_test(cx.tcx, expr.hir_id)
+            {
                 return;
             }
 

tests/ui-toml/panic/clippy.toml

@@ -0,0 +1 @@
+allow-panic-in-tests = true

tests/ui-toml/panic/panic.rs

@@ -0,0 +1,54 @@
+//@compile-flags: --test
+#![warn(clippy::panic)]
+
+fn main() {
+    enum Enam {
+        A,
+    }
+    let a = Enam::A;
+    match a {
+        Enam::A => {},
+        _ => panic!(""),
+    }
+}
+
+#[test]
+fn lonely_test() {
+    enum Enam {
+        A,
+    }
+    let a = Enam::A;
+    match a {
+        Enam::A => {},
+        _ => panic!(""),
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    // should not lint in `#[cfg(test)]` modules
+    #[test]
+    fn test_fn() {
+        enum Enam {
+            A,
+        }
+        let a = Enam::A;
+        match a {
+            Enam::A => {},
+            _ => panic!(""),
+        }
+
+        bar();
+    }
+
+    fn bar() {
+        enum Enam {
+            A,
+        }
+        let a = Enam::A;
+        match a {
+            Enam::A => {},
+            _ => panic!(""),
+        }
+    }
+}

tests/ui-toml/panic/panic.stderr

@@ -0,0 +1,11 @@
+error: `panic` should not be present in production code
+  --> tests/ui-toml/panic/panic.rs:11:14
+   |
+LL |         _ => panic!(""),
+   |              ^^^^^^^^^^
+   |
+   = note: `-D clippy::panic` implied by `-D warnings`
+   = help: to override `-D warnings` add `#[allow(clippy::panic)]`
+
+error: aborting due to 1 previous error
+

tests/ui-toml/toml_unknown_key/conf_unknown_key.stderr

@@ -8,6 +8,7 @@ error: error reading Clippy's configuration file: unknown field `foobar`, expect
            allow-expect-in-tests
            allow-mixed-uninlined-format-args
            allow-one-hash-in-raw-strings
+           allow-panic-in-tests
            allow-print-in-tests
            allow-private-module-inception
            allow-renamed-params-for
@@ -91,6 +92,7 @@ error: error reading Clippy's configuration file: unknown field `barfoo`, expect
            allow-expect-in-tests
            allow-mixed-uninlined-format-args
            allow-one-hash-in-raw-strings
+           allow-panic-in-tests
            allow-print-in-tests
            allow-private-module-inception
            allow-renamed-params-for
@@ -174,6 +176,7 @@ error: error reading Clippy's configuration file: unknown field `allow_mixed_uni
            allow-expect-in-tests
            allow-mixed-uninlined-format-args
            allow-one-hash-in-raw-strings
+           allow-panic-in-tests
            allow-print-in-tests
            allow-private-module-inception
            allow-renamed-params-for