new lint: redundant_test_prefix basic help, no auto-fix suggestion

Author: farazdagi

CHANGELOG.md

@@ -6115,6 +6115,7 @@ Released 2018-09-13
 [`redundant_pub_crate`]: https://rust-lang.github.io/rust-clippy/master/index.html#redundant_pub_crate
 [`redundant_slicing`]: https://rust-lang.github.io/rust-clippy/master/index.html#redundant_slicing
 [`redundant_static_lifetimes`]: https://rust-lang.github.io/rust-clippy/master/index.html#redundant_static_lifetimes
+[`redundant_test_prefix`]: https://rust-lang.github.io/rust-clippy/master/index.html#redundant_test_prefix
 [`redundant_type_annotations`]: https://rust-lang.github.io/rust-clippy/master/index.html#redundant_type_annotations
 [`ref_as_ptr`]: https://rust-lang.github.io/rust-clippy/master/index.html#ref_as_ptr
 [`ref_binding_to_reference`]: https://rust-lang.github.io/rust-clippy/master/index.html#ref_binding_to_reference
@@ -6459,4 +6460,5 @@ Released 2018-09-13
 [`verbose-bit-mask-threshold`]: https://doc.rust-lang.org/clippy/lint_configuration.html#verbose-bit-mask-threshold
 [`warn-on-all-wildcard-imports`]: https://doc.rust-lang.org/clippy/lint_configuration.html#warn-on-all-wildcard-imports
 [`warn-unsafe-macro-metavars-in-private-macros`]: https://doc.rust-lang.org/clippy/lint_configuration.html#warn-unsafe-macro-metavars-in-private-macros
+[`redundant-test-prefix-in-integration-tests`]: https://doc.rust-lang.org/clippy/lint_configuration.html#redundant-test-prefix-in-integration-tests
 <!-- end autogenerated links to configuration documentation -->

book/src/lint_configuration.md

@@ -1088,3 +1088,13 @@ Whether to also emit warnings for unsafe blocks with metavariable expansions in
 ---
 **Affected lints:**
 * [`macro_metavars_in_unsafe`](https://rust-lang.github.io/rust-clippy/master/index.html#macro_metavars_in_unsafe)
+
+
+## `redundant-test-prefix-in-integration-tests`
+Whether to include integration tests in the linting process or not.
+
+**Default Value:** `false`
+
+---
+**Affected lints:**
+* [`redundant_test_prefix`](https://rust-lang.github.io/rust-clippy/master/index.html#redundant_test_prefix)

clippy_config/src/conf.rs

@@ -846,6 +846,9 @@ define_Conf! {
     /// Whether to also emit warnings for unsafe blocks with metavariable expansions in **private** macros.
     #[lints(macro_metavars_in_unsafe)]
     warn_unsafe_macro_metavars_in_private_macros: bool = false,
+    /// Whether to include integration tests in the linting process or not.
+    #[lints(redundant_test_prefix)]
+    redundant_test_prefix_in_integration_tests: bool = false,
 }
 
 /// Search for the configuration file.

clippy_lints/src/declared_lints.rs

@@ -667,6 +667,7 @@ pub static LINTS: &[&crate::LintInfo] = &[
     crate::redundant_slicing::DEREF_BY_SLICING_INFO,
     crate::redundant_slicing::REDUNDANT_SLICING_INFO,
     crate::redundant_static_lifetimes::REDUNDANT_STATIC_LIFETIMES_INFO,
+    crate::redundant_test_prefix::REDUNDANT_TEST_PREFIX_INFO,
     crate::redundant_type_annotations::REDUNDANT_TYPE_ANNOTATIONS_INFO,
     crate::ref_option_ref::REF_OPTION_REF_INFO,
     crate::ref_patterns::REF_PATTERNS_INFO,

clippy_lints/src/lib.rs

@@ -319,6 +319,7 @@ mod redundant_locals;
 mod redundant_pub_crate;
 mod redundant_slicing;
 mod redundant_static_lifetimes;
+mod redundant_test_prefix;
 mod redundant_type_annotations;
 mod ref_option_ref;
 mod ref_patterns;
@@ -982,5 +983,6 @@ pub fn register_lints(store: &mut rustc_lint::LintStore, conf: &'static Conf) {
     store.register_late_pass(move |_| Box::new(non_std_lazy_statics::NonStdLazyStatic::new(conf)));
     store.register_late_pass(|_| Box::new(manual_option_as_slice::ManualOptionAsSlice::new(conf)));
     store.register_late_pass(|_| Box::new(single_option_map::SingleOptionMap));
+    store.register_late_pass(move |_| Box::new(redundant_test_prefix::RedundantTestPrefix::new(conf)));
     // add lints here, do not remove this comment, it's used in `new_lint`
 }

clippy_lints/src/redundant_test_prefix.rs

@@ -0,0 +1,87 @@
+use clippy_config::Conf;
+use clippy_utils::diagnostics::span_lint_and_help;
+use clippy_utils::{is_in_cfg_test, is_in_test_function};
+use rustc_hir::intravisit::FnKind;
+use rustc_hir::{Body, FnDecl};
+use rustc_lint::{LateContext, LateLintPass};
+use rustc_session::{ impl_lint_pass};
+use rustc_span::Span;
+use rustc_span::def_id::LocalDefId;
+
+declare_clippy_lint! {
+    /// ### What it does
+    /// Checks for test functions (functions annotated with `#[test]`) that prefixed with `test_`
+    /// which is redundant.
+    ///
+    /// ### Why is this bad?
+    /// This is redundant because the test functions are already annotated with `#[test]`.
+    /// Moreover, it clutters the output of `cargo test` as test functions are expanded as
+    /// `module::tests::test_name` in the output.
+    ///
+    /// ### Example
+    /// ```no_run
+    /// #[test]
+    /// fn test_my_use_case() {
+    ///     // test code
+    /// }
+    /// ```
+    /// Use instead:
+    /// ```no_run
+    /// fn my_use_case() {
+    ///    // test code
+    /// }
+    /// ```
+    #[clippy::version = "1.84.0"]
+    pub REDUNDANT_TEST_PREFIX,
+    pedantic,
+    "redundant `test_` prefix in test function name"
+}
+
+pub struct RedundantTestPrefix {
+    in_integration_tests: bool,
+}
+
+impl RedundantTestPrefix {
+    pub fn new(conf: &'static Conf) -> Self {
+        Self {
+            in_integration_tests: conf.redundant_test_prefix_in_integration_tests,
+        }
+    }
+}
+
+impl_lint_pass!(RedundantTestPrefix => [REDUNDANT_TEST_PREFIX]);
+
+impl LateLintPass<'_> for RedundantTestPrefix {
+    fn check_fn(
+        &mut self,
+        cx: &LateContext<'_>,
+        fn_kind: FnKind<'_>,
+        _: &FnDecl<'_>,
+        body: &Body<'_>,
+        span: Span,
+        _: LocalDefId,
+    ) {
+        // Skip the lint if the function is not within a node with `#[cfg(test)]` attribute,
+        // which is true for integration tests. If the lint is enabled for integration tests,
+        // via configuration value, ignore this check.
+        if !(self.in_integration_tests || is_in_cfg_test(cx.tcx, body.id().hir_id)) {
+            return;
+        }
+
+        if is_in_test_function(cx.tcx, body.id().hir_id) && has_redundant_test_prefix(fn_kind) {
+            span_lint_and_help(
+                cx,
+                REDUNDANT_TEST_PREFIX,
+                span,
+                "redundant `test_` prefix in test function name",
+                None,
+                "consider removing the `test_` prefix",
+            );
+        }
+    }
+}
+
+/// Checks if the function has redundant `test_` prefix in its name.
+fn has_redundant_test_prefix(fn_kind: FnKind<'_>) -> bool {
+    matches!(fn_kind, FnKind::ItemFn(ident, ..) if ident.name.as_str().starts_with("test_"))
+}

tests/ui/redundant_test_prefix.rs

@@ -0,0 +1,25 @@
+#![allow(dead_code)]
+#![warn(clippy::redundant_test_prefix)]
+
+fn main() {
+    // test code goes here
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_main() {
+        main();
+    }
+}
+
+mod tests_no_annotations {
+    use super::*;
+
+    #[test]
+    fn test_main() {
+        main();
+    }
+}

tests/ui/redundant_test_prefix.stderr

@@ -0,0 +1,14 @@
+error: redundant `test_` prefix in test function name
+  --> tests/ui/redundant_test_prefix.rs:13:5
+   |
+LL | /     fn test_main() {
+LL | |         main();
+LL | |     }
+   | |_____^
+   |
+   = help: consider removing the `test_` prefix
+   = note: `-D clippy::redundant-test-prefix` implied by `-D warnings`
+   = help: to override `-D warnings` add `#[allow(clippy::redundant_test_prefix)]`
+
+error: aborting due to 1 previous error
+