Add union_missing lint

src/lints/union_missing.ron

@@ -0,0 +1,51 @@
+SemverQuery(
+    id: "union_missing",
+    human_readable_name: "pub union removed or renamed",
+    description: "A union can no longer be imported by its prior path.",
+    required_update: Major,
+    reference_link: Some("https://doc.rust-lang.org/cargo/reference/semver.html#item-remove"),
+    query: r#"
+    {
+        CrateDiff {
+            baseline {
+                item {
+                    ... on Union {
+                        visibility_limit @filter(op: "=", value: ["$public"]) @output
+                        name @output
+
+                        importable_path {
+                            path @output @tag
+                            public_api @filter(op: "=", value: ["$true"])
+                        }
+
+                        span_: span @optional {
+                            filename @output
+                            begin_line @output
+                        }
+                    }
+                }
+            }
+            current @fold @transform(op: "count") @filter(op: "=", value: ["$zero"]) {
+                item {
+                    # We coerce to `ImplOwner` here, not `Union`, because it's sometimes possible
+                    # to change a union into an enum or struct without causing a breaking change.
+                    # More info: https://github.com/obi1kenobi/cargo-semver-checks/issues/297
+                    ... on ImplOwner {
+                        visibility_limit @filter(op: "=", value: ["$public"])
+
+                        importable_path {
+                            path @filter(op: "=", value: ["%path"])
+                        }
+                    }
+                }
+            }
+        }
+    }"#,
+    arguments: {
+        "public": "public",
+        "zero": 0,
+        "true": true,
+    },
+    error_message: "A publicly-visible union cannot be imported by its prior path. A `pub use` may have been removed, or the union itself may have been renamed or removed entirely.",
+    per_result_error_template: Some("union {{join \"::\" path}}, previously in file {{span_filename}}:{{span_begin_line}}"),
+)

src/query.rs

@@ -476,6 +476,7 @@ macro_rules! add_lints {
 }
 
 add_lints!(
+    union_missing,
     function_export_name_changed,
     union_field_missing,
     pub_static_now_doc_hidden,

test_crates/union_field_missing/new/src/lib.rs

@@ -3,20 +3,24 @@ union PrivateUnion {
     f3: f32,
 }
 
-
 // pub union with private fields shouldn't cause any breaking changes
 pub union PubUnionPrivateField {
     f3: f32,
 }
 
-
 // pub union with pub fields renamed should cause breaking changes
-pub union PubUnionPubFieldRenamed{
+pub union PubUnionPubFieldRenamed {
     pub f1: u32,
     pub f3: f32,
 }
 
 // pub union with pub fields removed should cause breaking changes
-pub union PubUnionPubFieldRemoved{
+pub union PubUnionPubFieldRemoved {
+    pub f1: u32,
+}
+
+// this should only trigger the union_missing lint, not union_field_missing
+union PubUnionBecomesPrivateAndPubFieldRemoved {
     pub f1: u32,
+    f2: f32,
 }

test_crates/union_field_missing/old/src/lib.rs

@@ -4,22 +4,26 @@ union PrivateUnion {
     f2: f32,
 }
 
-
 // pub union with private fields shouldn't cause any breaking changes
 pub union PubUnionPrivateField {
     f1: u32,
     f2: f32,
 }
 
-
 // pub union with pub fields renamed should cause breaking changes
-pub union PubUnionPubFieldRenamed{
+pub union PubUnionPubFieldRenamed {
     pub f1: u32,
     pub f2: f32,
 }
 
 // pub union with pub fields renamed should cause breaking changes
-pub union PubUnionPubFieldRemoved{
+pub union PubUnionPubFieldRemoved {
+    pub f1: u32,
+    pub f2: f32,
+}
+
+// this should only trigger the union_missing lint, not union_field_missing
+pub union PubUnionBecomesPrivateAndPubFieldRemoved {
     pub f1: u32,
     pub f2: f32,
 }

test_crates/union_missing/new/Cargo.toml

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

test_crates/union_missing/new/src/lib.rs

@@ -0,0 +1,14 @@
+union PubUnionBecomesPrivate {
+    f1: i32,
+}
+
+pub mod public_mod {
+    pub union PubUnion {
+        f1: i32,
+    }
+}
+
+// should not trigger union_missing so long as path remains importable
+pub struct PubUnionBecomesStruct {
+    f1: i32,
+}

test_crates/union_missing/old/Cargo.toml

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

test_crates/union_missing/old/src/lib.rs

@@ -0,0 +1,36 @@
+pub union PubUnionRemoved {
+    f1: i32,
+}
+
+pub union PubUnionBecomesPrivate {
+    f1: i32,
+}
+
+pub mod public_mod {
+    pub union PubUnion {
+        f1: i32,
+    }
+}
+
+pub use public_mod::PubUnion as PubUseUnionRemoved;
+
+// should not trigger union_missing so long as path remains importable
+pub union PubUnionBecomesStruct {
+    f1: i32,
+}
+
+// the following unions should not trigger lints when removed
+union PrivateUnion {
+    f1: i32,
+}
+
+mod private_mod {
+    pub union PrivatePathPubUnion {
+        f1: i32,
+    }
+}
+
+#[doc(hidden)]
+pub union DocHiddenUnion {
+    f1: i32,
+}

test_outputs/union_field_missing.output.ron

@@ -6,7 +6,7 @@
                 String("union_field_missing"),
                 String("PubUnionPubFieldRenamed"),
             ]),
-            "span_begin_line": Uint64(18),
+            "span_begin_line": Uint64(16),
             "span_filename": String("src/lib.rs"),
             "union_name": String("PubUnionPubFieldRenamed"),
         },
@@ -16,7 +16,7 @@
                 String("union_field_missing"),
                 String("PubUnionPubFieldRemoved"),
             ]),
-            "span_begin_line": Uint64(24),
+            "span_begin_line": Uint64(22),
             "span_filename": String("src/lib.rs"),
             "union_name": String("PubUnionPubFieldRemoved"),
         },       

test_outputs/union_missing.output.ron

@@ -0,0 +1,68 @@
+{
+    "./test_crates/repr_packed_added_removed/": [
+        {
+            "name": String("UnionBecomesPackedAndPrivate"),
+            "path": List([
+                String("repr_packed_added_removed"),
+                String("UnionBecomesPackedAndPrivate"),
+            ]),
+            "span_begin_line": Uint64(41),
+            "span_filename": String("src/lib.rs"),
+            "visibility_limit": String("public"),
+        },
+        {
+            "name": String("UnionBecomesUnpackedAndPrivate"),
+            "path": List([
+                String("repr_packed_added_removed"),
+                String("UnionBecomesUnpackedAndPrivate"),
+            ]),
+            "span_begin_line": Uint64(47),
+            "span_filename": String("src/lib.rs"),
+            "visibility_limit": String("public"),
+        },
+    ],
+    "./test_crates/union_field_missing/": [
+        {
+            "name": String("PubUnionBecomesPrivateAndPubFieldRemoved"),
+            "path": List([
+                String("union_field_missing"),
+                String("PubUnionBecomesPrivateAndPubFieldRemoved"),
+            ]),
+            "span_begin_line": Uint64(26),
+            "span_filename": String("src/lib.rs"),
+            "visibility_limit": String("public"),
+        },
+    ],
+    "./test_crates/union_missing/": [
+        {
+            "name": String("PubUnionRemoved"),
+            "path": List([
+                String("union_missing"),
+                String("PubUnionRemoved"),
+            ]),
+            "span_begin_line": Uint64(1),
+            "span_filename": String("src/lib.rs"),
+            "visibility_limit": String("public"),
+        },
+        {
+            "name": String("PubUnionBecomesPrivate"),
+            "path": List([
+                String("union_missing"),
+                String("PubUnionBecomesPrivate"),
+            ]),
+            "span_begin_line": Uint64(5),
+            "span_filename": String("src/lib.rs"),
+            "visibility_limit": String("public"),
+        },
+        {
+            "name": String("PubUnion"),
+            "path": List([
+                String("union_missing"),
+                String("PubUseUnionRemoved"),
+            ]),
+            "span_begin_line": Uint64(10),
+            "span_filename": String("src/lib.rs"),
+            "visibility_limit": String("public"),
+        },
+    ],
+}