Better report mutation in trait default fns (#172)

src/mutate.rs

@@ -118,26 +118,26 @@ impl Mutant {
         }
         let mut v: Vec<StyledObject<String>> = Vec::new();
         v.push(s("replace "));
-        if self.genre != Genre::FnValue {
+        if self.genre == Genre::FnValue {
+            let function = self
+                .function
+                .as_ref()
+                .expect("FnValue mutant should have a function");
+            v.push(s(&function.function_name).bright().magenta());
+            if !function.return_type.is_empty() {
+                v.push(s(" "));
+                v.push(s(&function.return_type).magenta());
+            }
+            v.push(s(" with "));
+            v.push(s(self.replacement_text()).yellow());
+        } else {
             v.push(s(self.original_text()).yellow());
             v.push(s(" with "));
             v.push(s(&self.replacement).bright().yellow());
-            v.push(s(" in "));
-        }
-        if let Some(function) = &self.function {
-            v.push(s(&function.function_name).bright().magenta());
-        } else {
-            v.push(s("module"));
-        }
-        if self.genre == Genre::FnValue {
             if let Some(function) = &self.function {
-                if !function.return_type.is_empty() {
-                    v.push(s(" "));
-                    v.push(s(&function.return_type).magenta());
-                }
+                v.push(s(" in "));
+                v.push(s(&function.function_name).bright().magenta());
             }
-            v.push(s(" with "));
-            v.push(s(self.replacement_text()).yellow());
         }
         v
     }

src/snapshots/cargo_mutants__visit__test__expected_mutants_for_own_source_tree.snap

@@ -230,7 +230,6 @@ src/mutate.rs: replace Mutant::styled_parts::s -> StyledObject<String> with Styl
 src/mutate.rs: replace Mutant::styled_parts::s -> StyledObject<String> with StyledObject::from_iter(["xyzzy".into()])
 src/mutate.rs: replace Mutant::styled_parts::s -> StyledObject<String> with StyledObject::new("xyzzy".into())
 src/mutate.rs: replace Mutant::styled_parts::s -> StyledObject<String> with StyledObject::from("xyzzy".into())
-src/mutate.rs: replace != with == in Mutant::styled_parts
 src/mutate.rs: replace == with != in Mutant::styled_parts
 src/mutate.rs: replace Mutant::original_text -> String with String::new()
 src/mutate.rs: replace Mutant::original_text -> String with "xyzzy".into()
@@ -401,8 +400,11 @@ src/visit.rs: replace DiscoveryVisitor<'o>::in_namespace -> T with Default::defa
 src/visit.rs: replace <impl Visit for DiscoveryVisitor<'_>>::visit_item_fn with ()
 src/visit.rs: replace <impl Visit for DiscoveryVisitor<'_>>::visit_impl_item_fn with ()
 src/visit.rs: replace == with != in <impl Visit for DiscoveryVisitor<'_>>::visit_impl_item_fn
+src/visit.rs: replace <impl Visit for DiscoveryVisitor<'_>>::visit_trait_item_fn with ()
+src/visit.rs: replace == with != in <impl Visit for DiscoveryVisitor<'_>>::visit_trait_item_fn
 src/visit.rs: replace <impl Visit for DiscoveryVisitor<'_>>::visit_item_impl with ()
 src/visit.rs: replace == with != in <impl Visit for DiscoveryVisitor<'_>>::visit_item_impl
+src/visit.rs: replace <impl Visit for DiscoveryVisitor<'_>>::visit_item_trait with ()
 src/visit.rs: replace <impl Visit for DiscoveryVisitor<'_>>::visit_item_mod with ()
 src/visit.rs: replace <impl Visit for DiscoveryVisitor<'_>>::visit_expr_binary with ()
 src/visit.rs: replace function_body_span -> Option<Span> with None

src/visit.rs

@@ -226,6 +226,7 @@ impl<'ast> Visit<'ast> for DiscoveryVisitor<'_> {
             name = function_name
         )
         .entered();
+        trace!("visit fn");
         if fn_sig_excluded(&i.sig) || attrs_excluded(&i.attrs) || block_is_empty(&i.block) {
             return;
         }
@@ -259,6 +260,29 @@ impl<'ast> Visit<'ast> for DiscoveryVisitor<'_> {
         self.leave_function(function);
     }
 
+    /// Visit `fn foo() { ... }` within a trait, i.e. a default implementation of a function.
+    fn visit_trait_item_fn(&mut self, i: &'ast syn::TraitItemFn) {
+        let function_name = i.sig.ident.to_pretty_string();
+        let _span = trace_span!(
+            "fn",
+            line = i.sig.fn_token.span.start().line,
+            name = function_name
+        )
+        .entered();
+        if fn_sig_excluded(&i.sig) || attrs_excluded(&i.attrs) || i.sig.ident == "new" {
+            return;
+        }
+        if let Some(block) = &i.default {
+            if block_is_empty(block) {
+                return;
+            }
+            let function = self.enter_function(&i.sig.ident, &i.sig.output, i.span());
+            self.collect_fn_mutants(&i.sig, block);
+            syn::visit::visit_trait_item_fn(self, i);
+            self.leave_function(function);
+        }
+    }
+
     /// Visit `impl Foo { ...}` or `impl Debug for Foo { ... }`.
     fn visit_item_impl(&mut self, i: &'ast syn::ItemImpl) {
         if attrs_excluded(&i.attrs) {
@@ -278,6 +302,16 @@ impl<'ast> Visit<'ast> for DiscoveryVisitor<'_> {
         self.in_namespace(&name, |v| syn::visit::visit_item_impl(v, i));
     }
 
+    /// Visit `trait Foo { ... }`
+    fn visit_item_trait(&mut self, i: &'ast syn::ItemTrait) {
+        let name = i.ident.to_pretty_string();
+        let _span = trace_span!("trait", line = i.span().start().line, name).entered();
+        if attrs_excluded(&i.attrs) {
+            return;
+        }
+        self.in_namespace(&name, |v| syn::visit::visit_item_trait(v, i));
+    }
+
     /// Visit `mod foo { ... }` or `mod foo;`.
     fn visit_item_mod(&mut self, node: &'ast syn::ItemMod) {
         let mod_name = &node.ident.unraw().to_string();
@@ -298,6 +332,7 @@ impl<'ast> Visit<'ast> for DiscoveryVisitor<'_> {
     /// Visit `a op b` expressions.
     fn visit_expr_binary(&mut self, i: &'ast syn::ExprBinary) {
         let _span = trace_span!("binary", line = i.op.span().start().line).entered();
+        trace!("visit binary operator");
         if attrs_excluded(&i.attrs) {
             return;
         }

testdata/well_tested/src/lib.rs

@@ -21,3 +21,4 @@ pub mod simple_fns;
 mod slices;
 mod static_item;
 mod struct_with_lifetime;
+mod traits;

testdata/well_tested/src/traits.rs

@@ -0,0 +1,22 @@
+//! Test mutation of a default fn in a trait.
+
+trait Something {
+    fn is_three(&self, a: usize) -> bool {
+        a == 3
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+
+    struct Three;
+
+    impl Something for Three {}
+
+    #[test]
+    fn test_is_three() {
+        assert!(Three.is_three(3));
+        assert!(!Three.is_three(4));
+    }
+}

tests/cli/config.rs

@@ -148,6 +148,7 @@ fn exclude_file_argument_overrides_config() {
             src/empty_fns.rs
             src/methods.rs
             src/result.rs
+            src/traits.rs
         " }));
 }
 

tests/cli/main.rs

@@ -568,8 +568,8 @@ fn well_tested_tree_quiet() {
         fs::read_to_string(tmp_src_dir.path().join("mutants.out/outcomes.json")).unwrap();
     println!("outcomes.json:\n{outcomes_json}");
     let outcomes: serde_json::Value = outcomes_json.parse().unwrap();
-    assert_eq!(outcomes["total_mutants"], 43);
-    assert_eq!(outcomes["caught"], 43);
+    assert_eq!(outcomes["total_mutants"], 46);
+    assert_eq!(outcomes["caught"], 46);
     assert_eq!(outcomes["unviable"], 0);
     assert_eq!(outcomes["missed"], 0);
 }

tests/cli/snapshots/cli__list_files_json_well_tested.snap

@@ -58,6 +58,10 @@ expression: "String::from_utf8_lossy(&output.stdout)"
   {
     "package": "cargo-mutants-testdata-well-tested",
     "path": "src/struct_with_lifetime.rs"
+  },
+  {
+    "package": "cargo-mutants-testdata-well-tested",
+    "path": "src/traits.rs"
   }
 ]
 

tests/cli/snapshots/cli__list_files_text_well_tested.snap

@@ -16,4 +16,5 @@ src/simple_fns.rs
 src/slices.rs
 src/static_item.rs
 src/struct_with_lifetime.rs
+src/traits.rs
 

tests/cli/snapshots/cli__list_mutants_in_all_trees_as_json.snap

@@ -3789,6 +3789,96 @@ expression: buf
         "line": 15
       }
     }
+  },
+  {
+    "file": "src/traits.rs",
+    "function": {
+      "function_name": "Something::is_three",
+      "return_type": "-> bool",
+      "span": {
+        "end": {
+          "column": 6,
+          "line": 6
+        },
+        "start": {
+          "column": 5,
+          "line": 4
+        }
+      }
+    },
+    "genre": "FnValue",
+    "package": "cargo-mutants-testdata-well-tested",
+    "replacement": "true",
+    "span": {
+      "end": {
+        "column": 15,
+        "line": 5
+      },
+      "start": {
+        "column": 9,
+        "line": 5
+      }
+    }
+  },
+  {
+    "file": "src/traits.rs",
+    "function": {
+      "function_name": "Something::is_three",
+      "return_type": "-> bool",
+      "span": {
+        "end": {
+          "column": 6,
+          "line": 6
+        },
+        "start": {
+          "column": 5,
+          "line": 4
+        }
+      }
+    },
+    "genre": "FnValue",
+    "package": "cargo-mutants-testdata-well-tested",
+    "replacement": "false",
+    "span": {
+      "end": {
+        "column": 15,
+        "line": 5
+      },
+      "start": {
+        "column": 9,
+        "line": 5
+      }
+    }
+  },
+  {
+    "file": "src/traits.rs",
+    "function": {
+      "function_name": "Something::is_three",
+      "return_type": "-> bool",
+      "span": {
+        "end": {
+          "column": 6,
+          "line": 6
+        },
+        "start": {
+          "column": 5,
+          "line": 4
+        }
+      }
+    },
+    "genre": "BinaryOperator",
+    "package": "cargo-mutants-testdata-well-tested",
+    "replacement": "!=",
+    "span": {
+      "end": {
+        "column": 13,
+        "line": 5
+      },
+      "start": {
+        "column": 11,
+        "line": 5
+      }
+    }
   }
 ]
 ```

tests/cli/snapshots/cli__list_mutants_in_all_trees_as_text.snap

@@ -286,9 +286,12 @@ src/slices.rs:4:5: replace pad -> &'a[Cow<'static, str>] with Vec::leak(vec![Cow
 src/slices.rs:13:5: replace return_mut_slice -> &mut[usize] with Vec::leak(Vec::new())
 src/slices.rs:13:5: replace return_mut_slice -> &mut[usize] with Vec::leak(vec![0])
 src/slices.rs:13:5: replace return_mut_slice -> &mut[usize] with Vec::leak(vec![1])
-src/static_item.rs:1:33: replace == with != in module
+src/static_item.rs:1:33: replace == with !=
 src/struct_with_lifetime.rs:15:9: replace Lex<'buf>::buf_len -> usize with 0
 src/struct_with_lifetime.rs:15:9: replace Lex<'buf>::buf_len -> usize with 1
+src/traits.rs:5:9: replace Something::is_three -> bool with true
+src/traits.rs:5:9: replace Something::is_three -> bool with false
+src/traits.rs:5:11: replace == with != in Something::is_three
 ```
 
 ## testdata/with_child_directories

tests/cli/snapshots/cli__list_mutants_json_well_tested.snap

@@ -1279,5 +1279,95 @@ expression: "String::from_utf8_lossy(&output.stdout)"
         "line": 15
       }
     }
+  },
+  {
+    "file": "src/traits.rs",
+    "function": {
+      "function_name": "Something::is_three",
+      "return_type": "-> bool",
+      "span": {
+        "end": {
+          "column": 6,
+          "line": 6
+        },
+        "start": {
+          "column": 5,
+          "line": 4
+        }
+      }
+    },
+    "genre": "FnValue",
+    "package": "cargo-mutants-testdata-well-tested",
+    "replacement": "true",
+    "span": {
+      "end": {
+        "column": 15,
+        "line": 5
+      },
+      "start": {
+        "column": 9,
+        "line": 5
+      }
+    }
+  },
+  {
+    "file": "src/traits.rs",
+    "function": {
+      "function_name": "Something::is_three",
+      "return_type": "-> bool",
+      "span": {
+        "end": {
+          "column": 6,
+          "line": 6
+        },
+        "start": {
+          "column": 5,
+          "line": 4
+        }
+      }
+    },
+    "genre": "FnValue",
+    "package": "cargo-mutants-testdata-well-tested",
+    "replacement": "false",
+    "span": {
+      "end": {
+        "column": 15,
+        "line": 5
+      },
+      "start": {
+        "column": 9,
+        "line": 5
+      }
+    }
+  },
+  {
+    "file": "src/traits.rs",
+    "function": {
+      "function_name": "Something::is_three",
+      "return_type": "-> bool",
+      "span": {
+        "end": {
+          "column": 6,
+          "line": 6
+        },
+        "start": {
+          "column": 5,
+          "line": 4
+        }
+      }
+    },
+    "genre": "BinaryOperator",
+    "package": "cargo-mutants-testdata-well-tested",
+    "replacement": "!=",
+    "span": {
+      "end": {
+        "column": 13,
+        "line": 5
+      },
+      "start": {
+        "column": 11,
+        "line": 5
+      }
+    }
   }
 ]