Add lint unflagged_test_modules

CHANGELOG.md

@@ -4964,6 +4964,7 @@ Released 2018-09-13
 [`unchecked_duration_subtraction`]: https://rust-lang.github.io/rust-clippy/master/index.html#unchecked_duration_subtraction
 [`undocumented_unsafe_blocks`]: https://rust-lang.github.io/rust-clippy/master/index.html#undocumented_unsafe_blocks
 [`undropped_manually_drops`]: https://rust-lang.github.io/rust-clippy/master/index.html#undropped_manually_drops
+[`unflagged_test_modules`]: https://rust-lang.github.io/rust-clippy/master/index.html#unflagged_test_modules
 [`unicode_not_nfc`]: https://rust-lang.github.io/rust-clippy/master/index.html#unicode_not_nfc
 [`unimplemented`]: https://rust-lang.github.io/rust-clippy/master/index.html#unimplemented
 [`uninit_assumed_init`]: https://rust-lang.github.io/rust-clippy/master/index.html#uninit_assumed_init

clippy_lints/src/declared_lints.rs

@@ -606,6 +606,7 @@ pub(crate) static LINTS: &[&crate::LintInfo] = &[
     crate::types::VEC_BOX_INFO,
     crate::undocumented_unsafe_blocks::UNDOCUMENTED_UNSAFE_BLOCKS_INFO,
     crate::undocumented_unsafe_blocks::UNNECESSARY_SAFETY_COMMENT_INFO,
+    crate::unflagged_test_modules::UNFLAGGED_TEST_MODULES_INFO,
     crate::unicode::INVISIBLE_CHARACTERS_INFO,
     crate::unicode::NON_ASCII_LITERAL_INFO,
     crate::unicode::UNICODE_NOT_NFC_INFO,

clippy_lints/src/lib.rs

@@ -295,6 +295,7 @@ mod trait_bounds;
 mod transmute;
 mod types;
 mod undocumented_unsafe_blocks;
+mod unflagged_test_modules;
 mod unicode;
 mod uninit_vec;
 mod unit_return_expecting_ord;
@@ -938,6 +939,7 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
     store.register_late_pass(|_| Box::new(let_with_type_underscore::UnderscoreTyped));
     store.register_late_pass(|_| Box::new(allow_attributes::AllowAttribute));
     store.register_late_pass(move |_| Box::new(manual_main_separator_str::ManualMainSeparatorStr::new(msrv())));
+    store.register_late_pass(|_| Box::new(unflagged_test_modules::UnflaggedTestModules));
     // add lints here, do not remove this comment, it's used in `new_lint`
 }
 

clippy_lints/src/unflagged_test_modules.rs

@@ -0,0 +1,73 @@
+use clippy_utils::diagnostics::span_lint_and_sugg;
+use rustc_hir::*;
+use rustc_lint::{LateContext, LateLintPass};
+use rustc_session::{declare_lint_pass, declare_tool_lint};
+use rustc_span::{symbol::sym, BytePos};
+
+declare_clippy_lint! {
+    /// ### What it does
+    ///
+    /// Triggers when a testing module (that contains "test" or "tests" in its name) isn't flagged with the `#[cfg(test)]` attribute.
+    ///
+    /// ### Why is this bad?
+    ///
+    /// The attribute `#[cfg(test)]` is used to tell Rust to compile and run the test code only when you run `cargo test` and not when you run `cargo  build`. This saves compile time and space in the resulting compiled artifact because tests are not included. So not using `#[cfg(test)]` for tests is both a waste of time and space.
+    ///
+    /// ### Example
+    /// ```rust
+    /// mod my_cool_tests {
+    /// 	// [...]
+    /// }
+    /// ```
+    /// Use instead:
+    /// ```rust
+    /// #[cfg(test)]
+    /// mod my_cool_tests {
+    /// 	// [...]
+    /// }
+    /// ```
+    #[clippy::version = "1.70.0"]
+    pub UNFLAGGED_TEST_MODULES,
+    pedantic,
+    "the testing module `my_cool_tests` wasn't marked with `#[cfg(test)]`"
+}
+declare_lint_pass!(UnflaggedTestModules => [UNFLAGGED_TEST_MODULES]);
+
+impl LateLintPass<'_> for UnflaggedTestModules {
+    fn check_item_post(&mut self, cx: &LateContext<'_>, item: &rustc_hir::Item<'_>) {
+        if let ItemKind::Mod(_) = item.kind {
+            // If module name contains *test* or *tests*.
+            if item
+                .ident
+                .name
+                .to_ident_string()
+                .split('_')
+                .any(|seg| seg == "test" || seg == "tests")
+            {
+                for attr in cx.tcx.get_attrs(item.owner_id.to_def_id(), sym::cfg) {
+                    if_chain! {
+                        if attr.has_name(sym::cfg);
+                        if let Some(items) = attr.meta_item_list();
+                        if let [item] = &*items;
+                        if item.has_name(sym::test);
+                        then {
+                            return;
+                        }
+                    }
+                }
+                // If no #[cfg(test)] is found
+                span_lint_and_sugg(
+                    cx,
+                    UNFLAGGED_TEST_MODULES,
+                    item.ident.span.with_lo(
+                        item.ident.span.lo() - BytePos(4), // Add `mod` keyword
+                    ),
+                    "this testing module isn't flagged with #[cfg(test)]",
+                    "add the attribute",
+                    format!("#[cfg(test)]\nmod {}", item.ident.as_str()),
+                    rustc_errors::Applicability::MachineApplicable,
+                );
+            }
+        }
+    }
+}

tests/ui/unflagged_test_modules.fixed

@@ -0,0 +1,18 @@
+// run-rustfix
+// compile-flags: --test
+#![allow(unused)]
+#![warn(clippy::unflagged_test_modules)]
+
+fn main() {
+    // test code goes here
+}
+
+#[cfg(test)]
+mod tests {
+    fn my_test() {}
+}
+
+#[cfg(test)]
+mod test {
+    fn my_other_test() {}
+}

tests/ui/unflagged_test_modules.rs

@@ -0,0 +1,17 @@
+// run-rustfix
+// compile-flags: --test
+#![allow(unused)]
+#![warn(clippy::unflagged_test_modules)]
+
+fn main() {
+    // test code goes here
+}
+
+#[cfg(test)]
+mod tests {
+    fn my_test() {}
+}
+
+mod test {
+    fn my_other_test() {}
+}

tests/ui/unflagged_test_modules.stderr

@@ -0,0 +1,15 @@
+error: this testing module isn't flagged with #[cfg(test)]
+  --> $DIR/unflagged_test_modules.rs:15:1
+   |
+LL | mod test {
+   | ^^^^^^^^
+   |
+   = note: `-D clippy::unflagged-test-modules` implied by `-D warnings`
+help: add the attribute
+   |
+LL + #[cfg(test)]
+LL ~ mod test {
+   |
+
+error: aborting due to previous error
+