Add max-ident-chars-length to config and is set to 100 by default.

Author: JurrianFahner

CHANGELOG.md

@@ -6109,6 +6109,7 @@ Released 2018-09-13
 [`match_str_case_mismatch`]: https://rust-lang.github.io/rust-clippy/master/index.html#match_str_case_mismatch
 [`match_wild_err_arm`]: https://rust-lang.github.io/rust-clippy/master/index.html#match_wild_err_arm
 [`match_wildcard_for_single_variants`]: https://rust-lang.github.io/rust-clippy/master/index.html#match_wildcard_for_single_variants
+[`max_ident_chars`]: https://rust-lang.github.io/rust-clippy/master/index.html#max_ident_chars
 [`maybe_infinite_iter`]: https://rust-lang.github.io/rust-clippy/master/index.html#maybe_infinite_iter
 [`maybe_misused_cfg`]: https://rust-lang.github.io/rust-clippy/master/index.html#maybe_misused_cfg
 [`mem_discriminant_non_enum`]: https://rust-lang.github.io/rust-clippy/master/index.html#mem_discriminant_non_enum
@@ -6626,6 +6627,7 @@ Released 2018-09-13
 [`literal-representation-threshold`]: https://doc.rust-lang.org/clippy/lint_configuration.html#literal-representation-threshold
 [`matches-for-let-else`]: https://doc.rust-lang.org/clippy/lint_configuration.html#matches-for-let-else
 [`max-fn-params-bools`]: https://doc.rust-lang.org/clippy/lint_configuration.html#max-fn-params-bools
+[`max-ident-chars-length`]: https://doc.rust-lang.org/clippy/lint_configuration.html#max-ident-chars-length
 [`max-include-file-size`]: https://doc.rust-lang.org/clippy/lint_configuration.html#max-include-file-size
 [`max-struct-bools`]: https://doc.rust-lang.org/clippy/lint_configuration.html#max-struct-bools
 [`max-suggested-slice-pattern-length`]: https://doc.rust-lang.org/clippy/lint_configuration.html#max-suggested-slice-pattern-length

book/src/lint_configuration.md

@@ -714,6 +714,16 @@ The maximum number of bool parameters a function can have
 * [`fn_params_excessive_bools`](https://rust-lang.github.io/rust-clippy/master/index.html#fn_params_excessive_bools)
 
 
+## `max-ident-chars-length`
+The maximum length of an identifier
+
+**Default Value:** `100`
+
+---
+**Affected lints:**
+* [`ident_chars`](https://rust-lang.github.io/rust-clippy/master/index.html#ident_chars)
+
+
 ## `max-include-file-size`
 The maximum size of a file included via `include_bytes!()` or `include_str!()`, in bytes
 
@@ -763,7 +773,7 @@ Minimum chars an ident can have, anything below or equal to this will be linted.
 
 ---
 **Affected lints:**
-* [`min_ident_chars`](https://rust-lang.github.io/rust-clippy/master/index.html#min_ident_chars)
+* [`ident_chars`](https://rust-lang.github.io/rust-clippy/master/index.html#ident_chars)
 
 
 ## `missing-docs-allow-unused`

clippy_config/src/conf.rs

@@ -682,6 +682,9 @@ define_Conf! {
     /// The maximum number of bool parameters a function can have
     #[lints(fn_params_excessive_bools)]
     max_fn_params_bools: u64 = 3,
+    /// The maximum length of an identifier
+    #[lints(ident_chars)]
+    max_ident_chars_length: u32 = 100,
     /// The maximum size of a file included via `include_bytes!()` or `include_str!()`, in bytes
     #[lints(large_include_file)]
     max_include_file_size: u64 = 1_000_000,
@@ -697,7 +700,7 @@ define_Conf! {
     #[lints(type_repetition_in_bounds)]
     max_trait_bounds: u64 = 3,
     /// Minimum chars an ident can have, anything below or equal to this will be linted.
-    #[lints(min_ident_chars)]
+    #[lints(ident_chars)]
     min_ident_chars_threshold: u64 = 1,
     /// Whether to allow fields starting with an underscore to skip documentation requirements
     #[lints(missing_docs_in_private_items)]

clippy_lints/src/declared_lints.rs

@@ -198,6 +198,8 @@ pub static LINTS: &[&::declare_clippy_lint::LintInfo] = &[
     crate::functions::TOO_MANY_ARGUMENTS_INFO,
     crate::functions::TOO_MANY_LINES_INFO,
     crate::future_not_send::FUTURE_NOT_SEND_INFO,
+    crate::ident_chars::MAX_IDENT_CHARS_INFO,
+    crate::ident_chars::MIN_IDENT_CHARS_INFO,
     crate::if_let_mutex::IF_LET_MUTEX_INFO,
     crate::if_not_else::IF_NOT_ELSE_INFO,
     crate::if_then_some_else_none::IF_THEN_SOME_ELSE_NONE_INFO,
@@ -497,7 +499,6 @@ pub static LINTS: &[&::declare_clippy_lint::LintInfo] = &[
     crate::methods::WAKER_CLONE_WAKE_INFO,
     crate::methods::WRONG_SELF_CONVENTION_INFO,
     crate::methods::ZST_OFFSET_INFO,
-    crate::min_ident_chars::MIN_IDENT_CHARS_INFO,
     crate::minmax::MIN_MAX_INFO,
     crate::misc::SHORT_CIRCUIT_STATEMENT_INFO,
     crate::misc::TOPLEVEL_REF_ARG_INFO,

clippy_lints/src/min_ident_chars.rs renamed to clippy_lints/src/ident_chars.rs

@@ -45,18 +45,54 @@ declare_clippy_lint! {
     restriction,
     "disallows idents that are too short"
 }
-impl_lint_pass!(MinIdentChars => [MIN_IDENT_CHARS]);
 
+declare_clippy_lint! {
+    /// ### What it does
+    /// Checks for identifiers which are too long (higher than the configured threshold).
+    /// Note: This lint can be very noisy when enabled; it may be desirable to only enable it
+    /// temporarily.
+    ///
+    /// ### Why restrict this?
+    /// To improve readability of code and make it possible to enforce this lint to align a code
+    /// style on this subject within a team.
+    ///
+    /// ### Example of long identifiers
+    /// ```rust,ignore
+    /// for from_a_long_list_of_movies_which_might_contain_ferris_or_not_you_never_know in movies {
+    ///     let title = from_a_long_list_of_movies_which_might_contain_ferris_or_not_you_never_know.title;
+    /// }
+    /// ```
+    /// Use instead:
+    /// ```rust,ignore
+    /// for movie in movies {
+    ///     let title = movie.title;
+    /// }
+    /// ```
+    ///
+    /// ### Limitations
+    /// Trait implementations which use the same function or parameter name as the trait declaration will
+    /// not be warned about, even if the name is longer than the configured limit.
+    #[clippy::version = "1.90.0"]
+    pub MAX_IDENT_CHARS,
+    restriction,
+    "disallows idents which exceeding the max ident length"
+}
+
+impl_lint_pass!(MinIdentChars => [MIN_IDENT_CHARS, MAX_IDENT_CHARS]);
+
+#[allow(clippy::struct_field_names)]
 pub struct MinIdentChars {
     allowed_idents_below_min_chars: FxHashSet<String>,
     min_ident_chars_threshold: u64,
+    max_variable_name_length: u32,
 }
 
 impl MinIdentChars {
     pub fn new(conf: &'static Conf) -> Self {
         Self {
             allowed_idents_below_min_chars: conf.allowed_idents_below_min_chars.iter().cloned().collect(),
             min_ident_chars_threshold: conf.min_ident_chars_threshold,
+            max_variable_name_length: conf.max_ident_chars_length,
         }
     }
 
@@ -68,6 +104,10 @@ impl MinIdentChars {
             && !str.is_empty()
             && !self.allowed_idents_below_min_chars.contains(str)
     }
+
+    fn is_ident_too_long(&self, cx: &LateContext<'_>, str: &str, span: Span) -> bool {
+        !span.in_external_macro(cx.sess().source_map()) && str.len() > self.max_variable_name_length as usize
+    }
 }
 
 impl LateLintPass<'_> for MinIdentChars {
@@ -108,6 +148,13 @@ impl LateLintPass<'_> for MinIdentChars {
         {
             emit_min_ident_chars(self, cx, str, ident.span);
         }
+
+        if let PatKind::Binding(_, _, ident, ..) = pat.kind
+            && let str = ident.as_str()
+            && self.is_ident_too_long(cx, str, ident.span)
+        {
+            emit_max_ident_chars(self, cx, str, ident.span);
+        }
     }
 }
 
@@ -199,6 +246,34 @@ impl Visitor<'_> for IdentVisitor<'_, '_> {
 
             emit_min_ident_chars(conf, cx, str, ident.span);
         }
+
+        if conf.is_ident_too_long(cx, str, ident.span) {
+            // Check whether the node is part of a `use` statement. We don't want to emit a warning if the user
+            // has no control over the type.
+            let usenode = opt_as_use_node(node).or_else(|| {
+                cx.tcx
+                    .hir_parent_iter(hir_id)
+                    .find_map(|(_, node)| opt_as_use_node(node))
+            });
+
+            // If the name of the identifier is the same as the one of the imported item, this means that we
+            // found a `use foo::bar`. We can early-return to not emit the warning.
+            // If however the identifier is different, this means it is an alias (`use foo::bar as baz`). In
+            // this case, we need to emit the warning for `baz`.
+            if let Some(imported_item_path) = usenode
+                // use `present_items` because it could be in any of type_ns, value_ns, macro_ns
+                && let Some(Res::Def(_, imported_item_defid)) = imported_item_path.res.value_ns
+                && cx.tcx.item_name(imported_item_defid).as_str() == str
+            {
+                return;
+            }
+
+            if is_from_proc_macro(cx, &ident) {
+                return;
+            }
+
+            emit_min_ident_chars(conf, cx, str, ident.span);
+        }
     }
 }
 
@@ -215,6 +290,15 @@ fn emit_min_ident_chars(conf: &MinIdentChars, cx: &impl LintContext, ident: &str
     span_lint(cx, MIN_IDENT_CHARS, span, help);
 }
 
+fn emit_max_ident_chars(conf: &MinIdentChars, cx: &impl LintContext, ident: &str, span: Span) {
+    let help = Cow::Owned(format!(
+        "this ident is too long ({} > {})",
+        ident.len(),
+        conf.max_variable_name_length,
+    ));
+    span_lint(cx, MAX_IDENT_CHARS, span, help);
+}
+
 /// Attempt to convert the node to an [`ItemKind::Use`] node.
 ///
 /// If it is, return the [`UsePath`] contained within.

clippy_lints/src/lib.rs

@@ -155,6 +155,7 @@ mod from_raw_with_void_ptr;
 mod from_str_radix_10;
 mod functions;
 mod future_not_send;
+mod ident_chars;
 mod if_let_mutex;
 mod if_not_else;
 mod if_then_some_else_none;
@@ -232,7 +233,6 @@ mod match_result_ok;
 mod matches;
 mod mem_replace;
 mod methods;
-mod min_ident_chars;
 mod minmax;
 mod misc;
 mod misc_early;
@@ -761,7 +761,7 @@ pub fn register_lint_passes(store: &mut rustc_lint::LintStore, conf: &'static Co
     store.register_late_pass(|_| Box::new(redundant_type_annotations::RedundantTypeAnnotations));
     store.register_late_pass(|_| Box::new(arc_with_non_send_sync::ArcWithNonSendSync));
     store.register_late_pass(|_| Box::new(needless_if::NeedlessIf));
-    store.register_late_pass(move |_| Box::new(min_ident_chars::MinIdentChars::new(conf)));
+    store.register_late_pass(move |_| Box::new(ident_chars::MinIdentChars::new(conf)));
     store.register_late_pass(move |_| Box::new(large_stack_frames::LargeStackFrames::new(conf)));
     store.register_late_pass(|_| Box::new(single_range_in_vec_init::SingleRangeInVecInit));
     store.register_late_pass(move |_| Box::new(needless_pass_by_ref_mut::NeedlessPassByRefMut::new(conf)));

tests/ui-toml/min_ident_chars/auxiliary/extern_types.rs renamed to tests/ui-toml/ident_chars/auxiliary/extern_types.rs

@@ -1,2 +1,5 @@
 allowed-idents-below-min-chars = ["Owo", "Uwu", "wha", "t_e", "lse", "_do", "_i_", "put", "her", "_e"]
 min-ident-chars-threshold = 3
+
+# override the default length of variables to test the configuration
+max-ident-chars-length = 50

tests/ui-toml/min_ident_chars/clippy.toml renamed to tests/ui-toml/ident_chars/clippy.toml

@@ -0,0 +1,15 @@
+#![warn(clippy::max_ident_chars)]
+
+fn a_function(ferris_singlehandedly_refactored_the_monolith_while_juggling_crates_and_lifetimes: &str) {
+    //~^ max_ident_chars
+}
+
+fn another_function(just_a_short_name: &str) {
+    // should not cause a problem
+}
+
+fn main() {
+    // `ferris_singlehandedly_refactored_the_monolith_while_juggling_crates_and_lifetimes` is too long
+    let ferris_singlehandedly_refactored_the_monolith_while_juggling_crates_and_lifetimes = "very long indeed";
+    //~^ max_ident_chars
+}

tests/ui-toml/ident_chars/max_ident_chars.rs

@@ -0,0 +1,17 @@
+error: this ident is too long (81 > 50)
+  --> tests/ui-toml/ident_chars/max_ident_chars.rs:3:15
+   |
+LL | fn a_function(ferris_singlehandedly_refactored_the_monolith_while_juggling_crates_and_lifetimes: &str) {
+   |               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: `-D clippy::max-ident-chars` implied by `-D warnings`
+   = help: to override `-D warnings` add `#[allow(clippy::max_ident_chars)]`
+
+error: this ident is too long (81 > 50)
+  --> tests/ui-toml/ident_chars/max_ident_chars.rs:13:9
+   |
+LL |     let ferris_singlehandedly_refactored_the_monolith_while_juggling_crates_and_lifetimes = "very long indeed";
+   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: aborting due to 2 previous errors
+