rule: add union_now_doc_hidden

src/lints/union_now_doc_hidden.ron

@@ -0,0 +1,48 @@
+SemverQuery(
+    id: "union_now_doc_hidden",
+    human_readable_name: "pub union is now #[doc(hidden)]",
+    description: "A pub union is now marked #[doc(hidden)] and is thus no longer part of the public API.",
+    required_update: Major,
+    reference_link: Some("https://doc.rust-lang.org/rustdoc/write-documentation/the-doc-attribute.html#hidden"),
+    query: r#"
+    {
+        CrateDiff {
+            baseline {
+                item {
+                    ... on Union {
+                        visibility_limit @filter(op: "=", value: ["$public"])
+
+                        importable_path {
+                            path @output @tag
+                            public_api @filter(op: "=", value: ["$true"])
+                        }
+                    }
+                }
+            }
+            current {
+                item {
+                    ... on Union {
+                        visibility_limit @filter(op: "=", value: ["$public"])
+                        union_name: name @output
+
+                        importable_path {
+                            path @filter(op: "=", value: ["%path"])
+                            public_api @filter(op: "!=", value: ["$true"])
+                        }
+
+                        span_: span @optional {
+                            filename @output
+                            begin_line @output
+                        }
+                    }
+                }
+            }
+        }
+    }"#,
+    arguments: {
+        "public": "public",
+        "true": true,
+    },
+    error_message: "A pub union is now #[doc(hidden)], removing it from the crate's public API.",
+    per_result_error_template: Some("union {{union_name}} in file {{span_filename}}:{{span_begin_line}}"),
+)

src/query.rs

@@ -531,4 +531,5 @@ add_lints!(
     repr_packed_added,
     repr_packed_removed,
     exported_function_changed_abi,
+    union_now_doc_hidden,
 );

test_crates/union_now_doc_hidden/new/cargo.toml

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

test_crates/union_now_doc_hidden/new/src/lib.rs

@@ -0,0 +1,5 @@
+#[doc(hidden)]
+pub union MyUnion {
+    f1: u32,
+    f2: f32,
+}

test_crates/union_now_doc_hidden/old/cargo.toml

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

test_crates/union_now_doc_hidden/old/src/lib.rs

@@ -0,0 +1,4 @@
+pub union MyUnion {
+    f1: u32,
+    f2: f32,
+}

test_outputs/union_now_doc_hidden.output.ron

@@ -0,0 +1,24 @@
+{
+    "./test_crates/type_hidden_from_public_api/": [
+        {
+            "path": List([
+                String("type_hidden_from_public_api"),
+                String("ExampleUnion"),
+            ]),
+            "span_begin_line": Uint64(19),
+            "span_filename": String("src/lib.rs"),
+            "union_name": String("ExampleUnion"),
+        },
+    ],
+    "./test_crates/union_now_doc_hidden/": [
+        {
+            "path": List([
+                String("union_now_doc_hidden"),
+                String("MyUnion"),
+            ]),
+            "span_begin_line": Uint64(2),
+            "span_filename": String("src/lib.rs"),
+            "union_name": String("MyUnion"),
+        },
+    ],
+}