add to tests and configuration

clippy_lints/src/min_ident_chars.rs

@@ -8,6 +8,7 @@ use rustc_hir::{
 use rustc_lint::{LateContext, LateLintPass, LintContext};
 use rustc_middle::lint::in_external_macro;
 use rustc_session::{declare_tool_lint, impl_lint_pass};
+use rustc_span::Span;
 use std::borrow::Cow;
 
 declare_clippy_lint! {
@@ -56,26 +57,18 @@ impl LateLintPass<'_> for MinIdentChars {
         walk_item(&mut IdentVisitor { conf: self, cx }, item);
     }
 
-    // This is necessary as bindings are not visited in `visit_id`. :/
+    // This is necessary as `Node::Pat`s are not visited in `visit_id`. :/
     #[expect(clippy::cast_possible_truncation)]
     fn check_pat(&mut self, cx: &LateContext<'_>, pat: &Pat<'_>) {
         if let PatKind::Binding(_, _, ident, ..) = pat.kind
             && let str = ident.as_str()
             && !in_external_macro(cx.sess(), ident.span)
             && str.len() <= self.min_ident_chars_threshold as usize
+            && !str.starts_with('_')
             && !str.is_empty()
             && self.allowed_idents_below_min_chars.get(&str.to_owned()).is_none()
         {
-            let help = if self.min_ident_chars_threshold == 1 {
-                Cow::Borrowed("this ident consists of a single char")
-            } else {
-                Cow::Owned(format!(
-                    "this ident is too short ({} <= {})",
-                    str.len(),
-                    self.min_ident_chars_threshold,
-                ))
-            };
-            span_lint(cx, MIN_IDENT_CHARS, ident.span, &help);
+            emit_min_ident_chars(self, cx, str, ident.span);
         }
     }
 }
@@ -112,6 +105,7 @@ impl Visitor<'_> for IdentVisitor<'_, '_> {
         let str = ident.as_str();
         if !in_external_macro(cx.sess(), ident.span)
             && str.len() <= conf.min_ident_chars_threshold as usize
+            && !str.starts_with('_')
             && !str.is_empty()
             && conf.allowed_idents_below_min_chars.get(&str.to_owned()).is_none()
         {
@@ -141,16 +135,20 @@ impl Visitor<'_> for IdentVisitor<'_, '_> {
                 return;
             }
 
-            let help = if conf.min_ident_chars_threshold == 1 {
-                Cow::Borrowed("this ident consists of a single char")
-            } else {
-                Cow::Owned(format!(
-                    "this ident is too short ({} <= {})",
-                    str.len(),
-                    conf.min_ident_chars_threshold,
-                ))
-            };
-            span_lint(cx, MIN_IDENT_CHARS, ident.span, &help);
+            emit_min_ident_chars(conf, cx, str, ident.span);
         }
     }
 }
+
+fn emit_min_ident_chars(conf: &MinIdentChars, cx: &impl LintContext, ident: &str, span: Span) {
+    let help = if conf.min_ident_chars_threshold == 1 {
+        Cow::Borrowed("this ident consists of a single char")
+    } else {
+        Cow::Owned(format!(
+            "this ident is too short ({} <= {})",
+            ident.len(),
+            conf.min_ident_chars_threshold,
+        ))
+    };
+    span_lint(cx, MIN_IDENT_CHARS, span, &help);
+}

clippy_lints/src/utils/conf.rs

@@ -525,7 +525,9 @@ define_Conf! {
     (allow_private_module_inception: bool = false),
     /// Lint: MIN_IDENT_CHARS.
     ///
-    /// Allowed names below the minimum allowed characters.
+    /// Allowed names below the minimum allowed characters. The value `".."` can be used as part of
+    /// the list to indicate, that the configured values should be appended to the default
+    /// configuration of Clippy. By default, any configuration will replace the default value.
     (allowed_idents_below_min_chars: rustc_data_structures::fx::FxHashSet<String> =
         super::DEFAULT_ALLOWED_IDENTS_BELOW_MIN_CHARS.iter().map(ToString::to_string).collect()),
     /// Lint: MIN_IDENT_CHARS.
@@ -599,6 +601,12 @@ pub fn read(sess: &Session, path: &Path) -> TryConf {
         Ok(mut conf) => {
             extend_vec_if_indicator_present(&mut conf.conf.doc_valid_idents, DEFAULT_DOC_VALID_IDENTS);
             extend_vec_if_indicator_present(&mut conf.conf.disallowed_names, DEFAULT_DISALLOWED_NAMES);
+            // TODO: THIS SHOULD BE TESTED, this comment will be gone soon
+            if conf.conf.allowed_idents_below_min_chars.contains(&"..".to_owned()) {
+                conf.conf
+                    .allowed_idents_below_min_chars
+                    .extend(DEFAULT_ALLOWED_IDENTS_BELOW_MIN_CHARS.iter().map(ToString::to_string));
+            }
 
             conf
         },

tests/ui/min_ident_chars.rs

@@ -67,6 +67,7 @@ fn main() {
     let o = O { o };
 
     for j in 0..1000 {}
+    for _ in 0..10 {}
 
     // Do not lint code from external macros
     external! { for j in 0..1000 {} }
@@ -78,4 +79,6 @@ fn main() {
 }
 
 fn b() {}
-fn owo() {}
+fn wrong_pythagoras(a: f32, b: f32) -> f32 {
+    a * a + a * b
+}

tests/ui/min_ident_chars.stderr

@@ -157,10 +157,22 @@ LL |     let o = O { o };
    |         ^
 
 error: this ident consists of a single char
-  --> $DIR/min_ident_chars.rs:80:4
+  --> $DIR/min_ident_chars.rs:81:4
    |
 LL | fn b() {}
    |    ^
 
-error: aborting due to 27 previous errors
+error: this ident consists of a single char
+  --> $DIR/min_ident_chars.rs:82:21
+   |
+LL | fn wrong_pythagoras(a: f32, b: f32) -> f32 {
+   |                     ^
+
+error: this ident consists of a single char
+  --> $DIR/min_ident_chars.rs:82:29
+   |
+LL | fn wrong_pythagoras(a: f32, b: f32) -> f32 {
+   |                             ^
+
+error: aborting due to 29 previous errors