new lint: trait_method_marked_deprecated

src/lints/trait_method_marked_deprecated.ron

@@ -0,0 +1,61 @@
+SemverQuery(
+    id: "trait_method_marked_deprecated",
+    human_readable_name: "trait method #[deprecated] added",
+    description: "A trait method has been newly marked with #[deprecated].",
+    required_update: Minor,
+    lint_level: Deny,
+    reference_link: Some("https://doc.rust-lang.org/reference/attributes/diagnostics.html#the-deprecated-attribute"),
+    query: r#"
+    {
+        CrateDiff {
+            current {
+                item {
+                    ... on Trait {
+                        visibility_limit @filter(op: "=", value: ["$public"])
+                        name @output
+
+                        importable_path {
+                            path @tag @output
+                            public_api @filter(op: "=", value: ["$true"])
+                        }
+
+                        method {
+                            method_name: name @output @tag
+                            public_api_eligible @filter(op: "=", value: ["$true"])
+                            deprecated @filter(op: "=", value: ["$true"])
+                        }
+
+                        span_: span @optional {
+                            filename @output
+                            begin_line @output
+                        }
+                    }
+                }
+            }
+            baseline {
+                item {
+                    ... on Trait {
+                        visibility_limit @filter(op: "=", value: ["$public"]) @output
+
+                        importable_path {
+                            path @filter(op: "=", value: ["%path"])
+                            public_api @filter(op: "=", value: ["$true"])
+                        }
+
+                        method {
+                            name @filter(op: "=", value: ["%method_name"])
+                            public_api_eligible @filter(op: "=", value: ["$true"])
+                            deprecated @filter(op: "!=", value: ["$true"])
+                        }
+                    }
+                }
+            }
+        }
+    }"#,
+    arguments: {
+        "public": "public",
+        "true": true,
+    },
+    error_message: "A trait method is now #[deprecated]. Downstream crates will get a compiler warning when using this method.",
+    per_result_error_template: Some("method {{method_name}} in trait {{join \"::\" path}} in {{span_filename}}:{{span_begin_line}}"),
+)

src/query.rs

@@ -1220,6 +1220,7 @@ add_lints!(
     trait_marked_deprecated,
     trait_method_added,
     trait_method_default_impl_removed,
+    trait_method_marked_deprecated,
     trait_method_missing,
     trait_method_now_doc_hidden,
     trait_method_parameter_count_changed,

test_crates/trait_method_marked_deprecated/new/Cargo.toml

@@ -0,0 +1,7 @@
+[package]
+publish = false
+name = "trait_method_marked_deprecated"
+version = "0.1.0"
+edition = "2021"
+
+[dependencies]

test_crates/trait_method_marked_deprecated/new/src/lib.rs

@@ -0,0 +1,51 @@
+pub trait TraitWithMethodToBeDeprecated {
+    // These methods are now deprecated and should be reported
+    #[deprecated]
+    fn method_to_deprecated(&self) -> i32;
+
+    #[deprecated = "This method is deprecated"]
+    fn method_to_deprecated_message(&self, input: &str) -> String;
+
+    // These methods should not trigger the lint
+    fn method_stays_normal(&self);
+
+    #[deprecated]
+    fn method_already_deprecated(&self);
+
+    #[deprecated = "New message"]
+    fn method_message_changes(&self);
+}
+
+// Changes to private trait methods should not be reported
+trait PrivateTrait {
+    #[deprecated]
+    fn private_method_to_deprecated(&self);
+}
+
+#[deprecated]
+pub trait DeprecatedTrait {
+    // Adding deprecated to a method in an already deprecated trait should not be reported
+    #[deprecated]
+    fn method_in_deprecated_trait(&self);
+}
+
+// This trait was added in the new version with deprecated methods.
+// It should NOT be reported by this rule to avoid duplicate lints.
+pub trait NewTraitWithDeprecatedMethod {
+    #[deprecated]
+    fn new_deprecated_method(&self);
+}
+
+// Hidden trait - changes to its methods should not be reported
+#[doc(hidden)]
+pub trait HiddenTrait {
+    #[deprecated]
+    fn method_becomes_deprecated(&self);
+}
+
+// Public trait with hidden method should not be reported
+pub trait PublicTraitWithHiddenMethod {
+    #[doc(hidden)]
+    #[deprecated]
+    fn hidden_method_becomes_deprecated(&self);
+}

test_crates/trait_method_marked_deprecated/old/Cargo.toml

@@ -0,0 +1,7 @@
+[package]
+publish = false
+name = "trait_method_marked_deprecated"
+version = "0.1.0"
+edition = "2021"
+
+[dependencies]

test_crates/trait_method_marked_deprecated/old/src/lib.rs

@@ -0,0 +1,39 @@
+pub trait TraitWithMethodToBeDeprecated {
+    // This method will be marked deprecated
+    fn method_to_deprecated(&self) -> i32;
+
+    // This method will be marked deprecated with a message
+    fn method_to_deprecated_message(&self, input: &str) -> String;
+
+    // These methods should not trigger the lint
+    fn method_stays_normal(&self);
+
+    #[deprecated]
+    fn method_already_deprecated(&self);
+
+    #[deprecated = "Old message"]
+    fn method_message_changes(&self);
+}
+
+// Changes to private trait methods should not be reported
+trait PrivateTrait {
+    fn private_method_to_deprecated(&self);
+}
+
+#[deprecated]
+pub trait DeprecatedTrait {
+    // Adding deprecated to a method in an already deprecated trait should not be reported
+    fn method_in_deprecated_trait(&self);
+}
+
+// Hidden trait - changes to its methods should not be reported
+#[doc(hidden)]
+pub trait HiddenTrait {
+    fn method_becomes_deprecated(&self);
+}
+
+// Public trait with hidden method should not be reported
+pub trait PublicTraitWithHiddenMethod {
+    #[doc(hidden)]
+    fn hidden_method_becomes_deprecated(&self);
+}

test_outputs/query_execution/trait_method_marked_deprecated.snap

@@ -0,0 +1,54 @@
+---
+source: src/query.rs
+expression: "&query_execution_results"
+---
+{
+  "./test_crates/trait_marked_deprecated/": [
+    {
+      "method_name": String("method"),
+      "name": String("TraitToDeprecatedTrait"),
+      "path": List([
+        String("trait_marked_deprecated"),
+        String("TraitToDeprecatedTrait"),
+      ]),
+      "span_begin_line": Uint64(5),
+      "span_filename": String("src/lib.rs"),
+      "visibility_limit": String("public"),
+    },
+    {
+      "method_name": String("method"),
+      "name": String("TraitToDeprecatedMessageTrait"),
+      "path": List([
+        String("trait_marked_deprecated"),
+        String("TraitToDeprecatedMessageTrait"),
+      ]),
+      "span_begin_line": Uint64(10),
+      "span_filename": String("src/lib.rs"),
+      "visibility_limit": String("public"),
+    },
+  ],
+  "./test_crates/trait_method_marked_deprecated/": [
+    {
+      "method_name": String("method_to_deprecated"),
+      "name": String("TraitWithMethodToBeDeprecated"),
+      "path": List([
+        String("trait_method_marked_deprecated"),
+        String("TraitWithMethodToBeDeprecated"),
+      ]),
+      "span_begin_line": Uint64(1),
+      "span_filename": String("src/lib.rs"),
+      "visibility_limit": String("public"),
+    },
+    {
+      "method_name": String("method_to_deprecated_message"),
+      "name": String("TraitWithMethodToBeDeprecated"),
+      "path": List([
+        String("trait_method_marked_deprecated"),
+        String("TraitWithMethodToBeDeprecated"),
+      ]),
+      "span_begin_line": Uint64(1),
+      "span_filename": String("src/lib.rs"),
+      "visibility_limit": String("public"),
+    },
+  ],
+}