News about name in json

Author: sourcefrog

Cargo.lock

@@ -1,6 +1,6 @@
 [package]
 name = "cargo-mutants"
-version = "26.0.0"
+version = "26.0.1"
 edition = "2021"
 authors = ["Martin Pool"]
 license = "MIT"

Cargo.toml

@@ -1,5 +1,9 @@
 # cargo-mutants changelog
 
+## Unreleased
+
+- New: Added a `name` field in the JSON representation of mutants. Thanks to @0xLoopTheory.
+
 ## 26.0.0 2025-12-07
 
 - Changed: The default is now *not* to shuffle mutants: they run in the deterministic order they are generated in the source tree. This should give somewhat better locality of reference due to consecutively testing changes in each package or module. The previous behavior can be restored with `--shuffle`.

NEWS.md

@@ -49,6 +49,12 @@ pub enum MutationTarget {
 /// A mutation applied to source code.
 #[derive(Clone, Eq, PartialEq, Debug)]
 pub struct Mutant {
+    /// A precomputed human-readable name for this mutant, including the file,
+    /// location, and change description.
+    ///
+    /// This is used in CLI output, filtering, and JSON.
+    pub name: String,
+
     /// Which file is being mutated.
     pub source_file: SourceFile,
 
@@ -103,6 +109,34 @@ pub struct Function {
 }
 
 impl Mutant {
+    /// Construct a mutant discovered while walking source code.
+    ///
+    /// This initializes all fields and precomputes the human-readable `name`
+    /// (including file path, line/column, and change description) for use in
+    /// CLI output, filtering, and JSON.
+    pub(crate) fn new_discovered(
+        source_file: SourceFile,
+        function: Option<Arc<Function>>,
+        span: Span,
+        short_replaced: Option<String>,
+        replacement: String,
+        genre: Genre,
+        target: Option<MutationTarget>,
+    ) -> Self {
+        let mut mutant = Mutant {
+            name: String::new(),
+            source_file,
+            function,
+            span,
+            short_replaced,
+            replacement,
+            genre,
+            target,
+        };
+        mutant.name = mutant.name(true);
+        mutant
+    }
+
     /// Return text of the whole file with the mutation applied.
     pub fn mutated_code(&self) -> String {
         self.span.replace(
@@ -293,6 +327,7 @@ impl Serialize for Mutant {
     {
         // custom serialize to omit inessential info
         let mut ss = serializer.serialize_struct("Mutant", 7)?;
+        ss.serialize_field("name", &self.name)?;
         ss.serialize_field("package", &self.source_file.package.name)?;
         ss.serialize_field("file", &self.source_file.tree_relative_slashes())?;
         ss.serialize_field("function", &self.function.as_ref().map(Arc::as_ref))?;

src/mutant.rs

@@ -44,10 +44,9 @@ pub struct Discovered {
 impl Discovered {
     pub(crate) fn remove_previously_caught(&mut self, previously_caught: &[String]) {
         self.mutants.retain(|m| {
-            let name = m.name(true);
-            let c = previously_caught.contains(&name);
+            let c = previously_caught.contains(&m.name);
             if c {
-                trace!(?name, "skip previously caught mutant");
+                trace!(name = %m.name, "skip previously caught mutant");
             }
             !c
         });
@@ -75,6 +74,7 @@ pub fn walk_tree(
         mutants.append(&mut package_mutants);
         files.append(&mut package_files);
     }
+
     progress.finish();
     Ok(Discovered { mutants, files })
 }
@@ -318,15 +318,16 @@ impl DiscoveryVisitor<'_> {
 
     /// Record that we generated some mutants.
     fn collect_mutant(&mut self, span: Span, replacement: &TokenStream, genre: Genre) {
-        self.mutants.push(Mutant {
-            source_file: self.source_file.clone(),
-            function: self.fn_stack.last().cloned(),
+        let mutant = Mutant::new_discovered(
+            self.source_file.clone(),
+            self.fn_stack.last().cloned(),
             span,
-            short_replaced: None,
-            replacement: replacement.to_pretty_string(),
+            None,
+            replacement.to_pretty_string(),
             genre,
-            target: None,
-        });
+            None,
+        );
+        self.mutants.push(mutant);
     }
 
     fn collect_fn_mutants(&mut self, sig: &Signature, block: &Block) {
@@ -656,15 +657,15 @@ impl<'ast> Visit<'ast> for DiscoveryVisitor<'_> {
                     continue;
                 }
                 let short_replaced = Some(arm.pat.to_pretty_string());
-                let mutant = Mutant {
-                    source_file: self.source_file.clone(),
-                    function: self.fn_stack.last().cloned(),
-                    span: arm.span().into(),
+                let mutant = Mutant::new_discovered(
+                    self.source_file.clone(),
+                    self.fn_stack.last().cloned(),
+                    arm.span().into(),
                     short_replaced,
-                    replacement: String::new(),
-                    genre: Genre::MatchArm,
-                    target: None,
-                };
+                    String::new(),
+                    Genre::MatchArm,
+                    None,
+                );
                 self.mutants.push(mutant);
             }
         } else {
@@ -722,18 +723,18 @@ impl<'ast> Visit<'ast> for DiscoveryVisitor<'_> {
                         // No comma, just the field
                         field.span().into()
                     };
-                    let mutant = Mutant {
-                        source_file: self.source_file.clone(),
-                        function: self.fn_stack.last().cloned(),
+                    let mutant = Mutant::new_discovered(
+                        self.source_file.clone(),
+                        self.fn_stack.last().cloned(),
                         span,
-                        short_replaced: None,
-                        replacement: String::new(),
-                        genre: Genre::StructField,
-                        target: Some(MutationTarget::StructLiteralField {
+                        None,
+                        String::new(),
+                        Genre::StructField,
+                        Some(MutationTarget::StructLiteralField {
                             field_name: field_name_str,
                             struct_name: struct_name.clone(),
                         }),
-                    };
+                    );
                     self.mutants.push(mutant);
                 }
             }

src/visit.rs

@@ -4,6 +4,7 @@ expression: mutants_json
 ---
 [
   {
+    "name": "src/bin/factorial.rs:2:5: replace main with ()",
     "package": "cargo-mutants-testdata-factorial",
     "file": "src/bin/factorial.rs",
     "function": {
@@ -34,6 +35,7 @@ expression: mutants_json
     "genre": "FnValue"
   },
   {
+    "name": "src/bin/factorial.rs:8:5: replace factorial -> u32 with 0",
     "package": "cargo-mutants-testdata-factorial",
     "file": "src/bin/factorial.rs",
     "function": {
@@ -64,6 +66,7 @@ expression: mutants_json
     "genre": "FnValue"
   },
   {
+    "name": "src/bin/factorial.rs:8:5: replace factorial -> u32 with 1",
     "package": "cargo-mutants-testdata-factorial",
     "file": "src/bin/factorial.rs",
     "function": {
@@ -94,6 +97,7 @@ expression: mutants_json
     "genre": "FnValue"
   },
   {
+    "name": "src/bin/factorial.rs:10:11: replace *= with += in factorial",
     "package": "cargo-mutants-testdata-factorial",
     "file": "src/bin/factorial.rs",
     "function": {
@@ -124,6 +128,7 @@ expression: mutants_json
     "genre": "BinaryOperator"
   },
   {
+    "name": "src/bin/factorial.rs:10:11: replace *= with /= in factorial",
     "package": "cargo-mutants-testdata-factorial",
     "file": "src/bin/factorial.rs",
     "function": {

tests/snapshots/main__mutants.json.snap

@@ -20,6 +20,7 @@ expression: "String::from_utf8_lossy(&output.stdout)"
       }
     },
     "genre": "FnValue",
+    "name": "src/lib.rs:18:5: replace double -> usize with 0",
     "package": "cargo-mutants-testdata-cfg-attr-test-skip",
     "replacement": "0",
     "span": {
@@ -50,6 +51,7 @@ expression: "String::from_utf8_lossy(&output.stdout)"
       }
     },
     "genre": "FnValue",
+    "name": "src/lib.rs:18:5: replace double -> usize with 1",
     "package": "cargo-mutants-testdata-cfg-attr-test-skip",
     "replacement": "1",
     "span": {
@@ -80,6 +82,7 @@ expression: "String::from_utf8_lossy(&output.stdout)"
       }
     },
     "genre": "BinaryOperator",
+    "name": "src/lib.rs:18:7: replace * with + in double",
     "package": "cargo-mutants-testdata-cfg-attr-test-skip",
     "replacement": "+",
     "span": {
@@ -110,6 +113,7 @@ expression: "String::from_utf8_lossy(&output.stdout)"
       }
     },
     "genre": "BinaryOperator",
+    "name": "src/lib.rs:18:7: replace * with / in double",
     "package": "cargo-mutants-testdata-cfg-attr-test-skip",
     "replacement": "/",
     "span": {

tests/util/snapshots/main__util__list_mutants_in_cfg_attr_test_skip_json.snap

@@ -20,6 +20,7 @@ expression: "String::from_utf8_lossy(&output.stdout)"
       }
     },
     "genre": "FnValue",
+    "name": "src/bin/factorial.rs:2:5: replace main with ()",
     "package": "cargo-mutants-testdata-factorial",
     "replacement": "()",
     "span": {
@@ -50,6 +51,7 @@ expression: "String::from_utf8_lossy(&output.stdout)"
       }
     },
     "genre": "FnValue",
+    "name": "src/bin/factorial.rs:8:5: replace factorial -> u32 with 0",
     "package": "cargo-mutants-testdata-factorial",
     "replacement": "0",
     "span": {
@@ -80,6 +82,7 @@ expression: "String::from_utf8_lossy(&output.stdout)"
       }
     },
     "genre": "FnValue",
+    "name": "src/bin/factorial.rs:8:5: replace factorial -> u32 with 1",
     "package": "cargo-mutants-testdata-factorial",
     "replacement": "1",
     "span": {
@@ -110,6 +113,7 @@ expression: "String::from_utf8_lossy(&output.stdout)"
       }
     },
     "genre": "BinaryOperator",
+    "name": "src/bin/factorial.rs:10:11: replace *= with += in factorial",
     "package": "cargo-mutants-testdata-factorial",
     "replacement": "+=",
     "span": {
@@ -140,6 +144,7 @@ expression: "String::from_utf8_lossy(&output.stdout)"
       }
     },
     "genre": "BinaryOperator",
+    "name": "src/bin/factorial.rs:10:11: replace *= with /= in factorial",
     "package": "cargo-mutants-testdata-factorial",
     "replacement": "/=",
     "span": {