Auto merge of #3803 - felix91gr:master, r=oli-obk

Cognitive Complexity (step 1 out of 3+): name changes

Following up on #3793

**Overall checklist:**

1. **Name changes**
2. MVP of functionality
3. Tests

After this PR, we will start working on the implementation itself.

CHANGELOG.md

@@ -798,11 +798,11 @@ All notable changes to this project will be documented in this file.
 [`cmp_nan`]: https://rust-lang.github.io/rust-clippy/master/index.html#cmp_nan
 [`cmp_null`]: https://rust-lang.github.io/rust-clippy/master/index.html#cmp_null
 [`cmp_owned`]: https://rust-lang.github.io/rust-clippy/master/index.html#cmp_owned
+[`cognitive_complexity`]: https://rust-lang.github.io/rust-clippy/master/index.html#cognitive_complexity
 [`collapsible_if`]: https://rust-lang.github.io/rust-clippy/master/index.html#collapsible_if
 [`const_static_lifetime`]: https://rust-lang.github.io/rust-clippy/master/index.html#const_static_lifetime
 [`copy_iterator`]: https://rust-lang.github.io/rust-clippy/master/index.html#copy_iterator
 [`crosspointer_transmute`]: https://rust-lang.github.io/rust-clippy/master/index.html#crosspointer_transmute
-[`cyclomatic_complexity`]: https://rust-lang.github.io/rust-clippy/master/index.html#cyclomatic_complexity
 [`dbg_macro`]: https://rust-lang.github.io/rust-clippy/master/index.html#dbg_macro
 [`decimal_literal_representation`]: https://rust-lang.github.io/rust-clippy/master/index.html#decimal_literal_representation
 [`declare_interior_mutable_const`]: https://rust-lang.github.io/rust-clippy/master/index.html#declare_interior_mutable_const

README.md

@@ -131,7 +131,7 @@ Some lints can be configured in a TOML file named `clippy.toml` or `.clippy.toml
 
 ```toml
 blacklisted-names = ["toto", "tata", "titi"]
-cyclomatic-complexity-threshold = 30
+cognitive-complexity-threshold = 30
 ```
 
 See the [list of lints](https://rust-lang.github.io/rust-clippy/master/index.html) for more information about which lints can be configured and the

clippy_lints/src/assign_ops.rs

@@ -119,7 +119,7 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for AssignOps {
             },
             hir::ExprKind::Assign(assignee, e) => {
                 if let hir::ExprKind::Binary(op, l, r) = &e.node {
-                    #[allow(clippy::cyclomatic_complexity)]
+                    #[allow(clippy::cognitive_complexity)]
                     let lint = |assignee: &hir::Expr, rhs: &hir::Expr| {
                         let ty = cx.tables.expr_ty(assignee);
                         let rty = cx.tables.expr_ty(rhs);

clippy_lints/src/cyclomatic_complexity.rs → clippy_lints/src/cognitive_complexity.rs

@@ -1,4 +1,4 @@
-//! calculate cyclomatic complexity and warn about overly complex functions
+//! calculate cognitive complexity and warn about overly complex functions
 
 use rustc::cfg::CFG;
 use rustc::hir::intravisit::{walk_expr, NestedVisitorMap, Visitor};
@@ -12,43 +12,43 @@ use syntax::source_map::Span;
 use crate::utils::{in_macro, is_allowed, match_type, paths, span_help_and_lint, LimitStack};
 
 declare_clippy_lint! {
-    /// **What it does:** Checks for methods with high cyclomatic complexity.
+    /// **What it does:** Checks for methods with high cognitive complexity.
     ///
-    /// **Why is this bad?** Methods of high cyclomatic complexity tend to be badly
-    /// readable. Also LLVM will usually optimize small methods better.
+    /// **Why is this bad?** Methods of high cognitive complexity tend to be hard to
+    /// both read and maintain. Also LLVM will tend to optimize small methods better.
     ///
     /// **Known problems:** Sometimes it's hard to find a way to reduce the
     /// complexity.
     ///
     /// **Example:** No. You'll see it when you get the warning.
-    pub CYCLOMATIC_COMPLEXITY,
+    pub COGNITIVE_COMPLEXITY,
     complexity,
     "functions that should be split up into multiple functions"
 }
 
-pub struct CyclomaticComplexity {
+pub struct CognitiveComplexity {
     limit: LimitStack,
 }
 
-impl CyclomaticComplexity {
+impl CognitiveComplexity {
     pub fn new(limit: u64) -> Self {
         Self {
             limit: LimitStack::new(limit),
         }
     }
 }
 
-impl LintPass for CyclomaticComplexity {
+impl LintPass for CognitiveComplexity {
     fn get_lints(&self) -> LintArray {
-        lint_array!(CYCLOMATIC_COMPLEXITY)
+        lint_array!(COGNITIVE_COMPLEXITY)
     }
 
     fn name(&self) -> &'static str {
-        "CyclomaticComplexity"
+        "CognitiveComplexity"
     }
 }
 
-impl CyclomaticComplexity {
+impl CognitiveComplexity {
     fn check<'a, 'tcx: 'a>(&mut self, cx: &'a LateContext<'a, 'tcx>, body: &'tcx Body, span: Span) {
         if in_macro(span) {
             return;
@@ -105,17 +105,17 @@ impl CyclomaticComplexity {
             if rust_cc > self.limit.limit() {
                 span_help_and_lint(
                     cx,
-                    CYCLOMATIC_COMPLEXITY,
+                    COGNITIVE_COMPLEXITY,
                     span,
-                    &format!("the function has a cyclomatic complexity of {}", rust_cc),
+                    &format!("the function has a cognitive complexity of {}", rust_cc),
                     "you could split it up into multiple smaller functions",
                 );
             }
         }
     }
 }
 
-impl<'a, 'tcx> LateLintPass<'a, 'tcx> for CyclomaticComplexity {
+impl<'a, 'tcx> LateLintPass<'a, 'tcx> for CognitiveComplexity {
     fn check_fn(
         &mut self,
         cx: &LateContext<'a, 'tcx>,
@@ -132,10 +132,10 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for CyclomaticComplexity {
     }
 
     fn enter_lint_attrs(&mut self, cx: &LateContext<'a, 'tcx>, attrs: &'tcx [Attribute]) {
-        self.limit.push_attrs(cx.sess(), attrs, "cyclomatic_complexity");
+        self.limit.push_attrs(cx.sess(), attrs, "cognitive_complexity");
     }
     fn exit_lint_attrs(&mut self, cx: &LateContext<'a, 'tcx>, attrs: &'tcx [Attribute]) {
-        self.limit.pop_attrs(cx.sess(), attrs, "cyclomatic_complexity");
+        self.limit.pop_attrs(cx.sess(), attrs, "cognitive_complexity");
     }
 }
 
@@ -201,7 +201,7 @@ fn report_cc_bug(
 ) {
     span_bug!(
         span,
-        "Clippy encountered a bug calculating cyclomatic complexity: cc = {}, arms = {}, \
+        "Clippy encountered a bug calculating cognitive complexity: cc = {}, arms = {}, \
          div = {}, shorts = {}, returns = {}. Please file a bug report.",
         cc,
         narms,
@@ -222,12 +222,12 @@ fn report_cc_bug(
     span: Span,
     id: HirId,
 ) {
-    if !is_allowed(cx, CYCLOMATIC_COMPLEXITY, id) {
+    if !is_allowed(cx, COGNITIVE_COMPLEXITY, id) {
         cx.sess().span_note_without_error(
             span,
             &format!(
-                "Clippy encountered a bug calculating cyclomatic complexity \
-                 (hide this message with `#[allow(cyclomatic_complexity)]`): \
+                "Clippy encountered a bug calculating cognitive complexity \
+                 (hide this message with `#[allow(cognitive_complexity)]`): \
                  cc = {}, arms = {}, div = {}, shorts = {}, returns = {}. \
                  Please file a bug report.",
                 cc, narms, div, shorts, returns

clippy_lints/src/lib.rs

@@ -152,11 +152,11 @@ pub mod block_in_if_condition;
 pub mod booleans;
 pub mod bytecount;
 pub mod cargo_common_metadata;
+pub mod cognitive_complexity;
 pub mod collapsible_if;
 pub mod const_static_lifetime;
 pub mod copies;
 pub mod copy_iterator;
-pub mod cyclomatic_complexity;
 pub mod dbg_macro;
 pub mod default_trait_access;
 pub mod derive;
@@ -478,7 +478,7 @@ pub fn register_plugins(reg: &mut rustc_plugin::Registry<'_>, conf: &Conf) {
     reg.register_late_lint_pass(box temporary_assignment::Pass);
     reg.register_late_lint_pass(box transmute::Transmute);
     reg.register_late_lint_pass(
-        box cyclomatic_complexity::CyclomaticComplexity::new(conf.cyclomatic_complexity_threshold)
+        box cognitive_complexity::CognitiveComplexity::new(conf.cognitive_complexity_threshold)
     );
     reg.register_late_lint_pass(box escape::Pass{too_large_for_stack: conf.too_large_for_stack});
     reg.register_early_lint_pass(box misc_early::MiscEarly);
@@ -666,11 +666,11 @@ pub fn register_plugins(reg: &mut rustc_plugin::Registry<'_>, conf: &Conf) {
         booleans::LOGIC_BUG,
         booleans::NONMINIMAL_BOOL,
         bytecount::NAIVE_BYTECOUNT,
+        cognitive_complexity::COGNITIVE_COMPLEXITY,
         collapsible_if::COLLAPSIBLE_IF,
         const_static_lifetime::CONST_STATIC_LIFETIME,
         copies::IFS_SAME_COND,
         copies::IF_SAME_THEN_ELSE,
-        cyclomatic_complexity::CYCLOMATIC_COMPLEXITY,
         derive::DERIVE_HASH_XOR_EQ,
         double_comparison::DOUBLE_COMPARISONS,
         double_parens::DOUBLE_PARENS,
@@ -962,7 +962,7 @@ pub fn register_plugins(reg: &mut rustc_plugin::Registry<'_>, conf: &Conf) {
         assign_ops::MISREFACTORED_ASSIGN_OP,
         attrs::DEPRECATED_CFG_ATTR,
         booleans::NONMINIMAL_BOOL,
-        cyclomatic_complexity::CYCLOMATIC_COMPLEXITY,
+        cognitive_complexity::COGNITIVE_COMPLEXITY,
         double_comparison::DOUBLE_COMPARISONS,
         double_parens::DOUBLE_PARENS,
         duration_subsec::DURATION_SUBSEC,
@@ -1131,6 +1131,7 @@ pub fn register_plugins(reg: &mut rustc_plugin::Registry<'_>, conf: &Conf) {
 pub fn register_renamed(ls: &mut rustc::lint::LintStore) {
     ls.register_renamed("clippy::stutter", "clippy::module_name_repetitions");
     ls.register_renamed("clippy::new_without_default_derive", "clippy::new_without_default");
+    ls.register_renamed("clippy::cyclomatic_complexity", "clippy::cognitive_complexity");
 }
 
 // only exists to let the dogfood integration test works.

clippy_lints/src/methods/mod.rs

@@ -821,7 +821,7 @@ impl LintPass for Pass {
 }
 
 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Pass {
-    #[allow(clippy::cyclomatic_complexity)]
+    #[allow(clippy::cognitive_complexity)]
     fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx hir::Expr) {
         if in_macro(expr.span) {
             return;

clippy_lints/src/utils/attrs.rs

@@ -15,7 +15,11 @@ pub enum DeprecationStatus {
 
 pub const BUILTIN_ATTRIBUTES: &[(&str, DeprecationStatus)] = &[
     ("author", DeprecationStatus::None),
-    ("cyclomatic_complexity", DeprecationStatus::None),
+    ("cognitive_complexity", DeprecationStatus::None),
+    (
+        "cyclomatic_complexity",
+        DeprecationStatus::Replaced("cognitive_complexity"),
+    ),
     ("dump", DeprecationStatus::None),
 ];
 

clippy_lints/src/utils/conf.rs

@@ -110,8 +110,10 @@ macro_rules! define_Conf {
 define_Conf! {
     /// Lint: BLACKLISTED_NAME. The list of blacklisted names to lint about
     (blacklisted_names, "blacklisted_names", ["foo", "bar", "baz", "quux"] => Vec<String>),
-    /// Lint: CYCLOMATIC_COMPLEXITY. The maximum cyclomatic complexity a function can have
-    (cyclomatic_complexity_threshold, "cyclomatic_complexity_threshold", 25 => u64),
+    /// Lint: COGNITIVE_COMPLEXITY. The maximum cognitive complexity a function can have
+    (cognitive_complexity_threshold, "cognitive_complexity_threshold", 25 => u64),
+    /// DEPRECATED LINT: CYCLOMATIC_COMPLEXITY. Use the Cognitive Complexity lint instead.
+    (cyclomatic_complexity_threshold, "cyclomatic_complexity_threshold", None => Option<u64>),
     /// Lint: DOC_MARKDOWN. The list of words this lint should not consider as identifiers needing ticks
     (doc_valid_idents, "doc_valid_idents", [
         "KiB", "MiB", "GiB", "TiB", "PiB", "EiB",
@@ -227,13 +229,24 @@ pub fn read(path: Option<&path::Path>) -> (Conf, Vec<Error>) {
 
     assert!(ERRORS.lock().expect("no threading -> mutex always safe").is_empty());
     match toml::from_str(&file) {
-        Ok(toml) => (
-            toml,
-            ERRORS.lock().expect("no threading -> mutex always safe").split_off(0),
-        ),
+        Ok(toml) => {
+            let mut errors = ERRORS.lock().expect("no threading -> mutex always safe").split_off(0);
+
+            let toml_ref: &Conf = &toml;
+
+            let cyc_field: Option<u64> = toml_ref.cyclomatic_complexity_threshold;
+
+            if cyc_field.is_some() {
+                let cyc_err = "found deprecated field `cyclomatic-complexity-threshold`. Please use `cognitive-complexity-threshold` instead.".to_string();
+                errors.push(Error::Toml(cyc_err));
+            }
+
+            (toml, errors)
+        },
         Err(e) => {
             let mut errors = ERRORS.lock().expect("no threading -> mutex always safe").split_off(0);
             errors.push(Error::Toml(e.to_string()));
+
             default(errors)
         },
     }

tests/ui-toml/conf_deprecated_key/clippy.toml

@@ -0,0 +1,6 @@
+# that one is an error
+cyclomatic-complexity-threshold = 42
+
+# that one is white-listed
+[third-party]
+clippy-feature = "nightly"

tests/ui-toml/conf_deprecated_key/conf_deprecated_key.rs

@@ -0,0 +1,4 @@
+// error-pattern: error reading Clippy's configuration file: found deprecated field
+// `cyclomatic-complexity-threshold`. Please use `cognitive-complexity-threshold` instead.
+
+fn main() {}

tests/ui-toml/conf_deprecated_key/conf_deprecated_key.stderr

@@ -0,0 +1,4 @@
+error: error reading Clippy's configuration file `$DIR/clippy.toml`: found deprecated field `cyclomatic-complexity-threshold`. Please use `cognitive-complexity-threshold` instead.
+
+error: aborting due to previous error
+

tests/ui-toml/good_toml_no_false_negatives/clippy.toml

@@ -0,0 +1,3 @@
+# that one is white-listed
+[third-party]
+clippy-feature = "nightly"

tests/ui-toml/good_toml_no_false_negatives/conf_no_false_negatives.rs

@@ -0,0 +1,3 @@
+// error-pattern: should give absolutely no error
+
+fn main() {}

tests/ui-toml/toml_unknown_key/conf_unknown_key.stderr

@@ -1,4 +1,4 @@
-error: error reading Clippy's configuration file `$DIR/clippy.toml`: unknown field `foobar`, expected one of `blacklisted-names`, `cyclomatic-complexity-threshold`, `doc-valid-idents`, `too-many-arguments-threshold`, `type-complexity-threshold`, `single-char-binding-names-threshold`, `too-large-for-stack`, `enum-variant-name-threshold`, `enum-variant-size-threshold`, `verbose-bit-mask-threshold`, `literal-representation-threshold`, `trivial-copy-size-limit`, `too-many-lines-threshold`, `third-party`
+error: error reading Clippy's configuration file `$DIR/clippy.toml`: unknown field `foobar`, expected one of `blacklisted-names`, `cognitive-complexity-threshold`, `cyclomatic-complexity-threshold`, `doc-valid-idents`, `too-many-arguments-threshold`, `type-complexity-threshold`, `single-char-binding-names-threshold`, `too-large-for-stack`, `enum-variant-name-threshold`, `enum-variant-size-threshold`, `verbose-bit-mask-threshold`, `literal-representation-threshold`, `trivial-copy-size-limit`, `too-many-lines-threshold`, `third-party`
 
 error: aborting due to previous error