Add tidy check for list of proc-macro crate transitive dependencies

Author: clubby789

src/tools/tidy/src/deps.rs

@@ -7,6 +7,9 @@ use std::path::Path;
 use build_helper::ci::CiEnv;
 use cargo_metadata::{Metadata, Package, PackageId};
 
+#[path = "../../../bootstrap/src/utils/proc_macro_deps.rs"]
+mod proc_macro_deps;
+
 /// These are licenses that are allowed for all crates, including the runtime,
 /// rustc, tools, etc.
 #[rustfmt::skip]
@@ -567,6 +570,8 @@ const PERMITTED_CRANELIFT_DEPENDENCIES: &[&str] = &[
 pub fn check(root: &Path, cargo: &Path, bad: &mut bool) {
     let mut checked_runtime_licenses = false;
 
+    check_proc_macro_dep_list(root, cargo, bad);
+
     for &(workspace, exceptions, permitted_deps, submodules) in WORKSPACES {
         if has_missing_submodule(root, submodules) {
             continue;
@@ -600,6 +605,37 @@ pub fn check(root: &Path, cargo: &Path, bad: &mut bool) {
     assert!(checked_runtime_licenses);
 }
 
+/// Ensure the list of proc-macro crate transitive dependencies is up to date
+fn check_proc_macro_dep_list(root: &Path, cargo: &Path, bad: &mut bool) {
+    let mut cmd = cargo_metadata::MetadataCommand::new();
+    cmd.cargo_path(cargo)
+        .manifest_path(root.join("Cargo.toml"))
+        .features(cargo_metadata::CargoOpt::AllFeatures)
+        .other_options(vec!["--locked".to_owned()]);
+    let metadata = t!(cmd.exec());
+    let is_proc_macro_pkg =
+        |pkg: &&Package| pkg.dependencies.iter().any(|dep| dep.name.as_str() == "proc-macro2");
+    let mut proc_macro_deps = HashSet::new();
+    for pkg in metadata.packages.iter().filter(is_proc_macro_pkg) {
+        deps_of(&metadata, &pkg.id, &mut proc_macro_deps);
+    }
+    let proc_macro_deps: HashSet<_> =
+        proc_macro_deps.into_iter().map(|dep| metadata[dep].name.clone()).collect();
+    let expected = proc_macro_deps::CRATES.iter().map(|s| s.to_string()).collect::<HashSet<_>>();
+    for missing in proc_macro_deps.difference(&expected) {
+        tidy_error!(
+            bad,
+            "proc-macro crate dependency `{missing}` is not registered in `src/bootstrap/src/utils/proc_macro_deps.rs`",
+        );
+    }
+    for extra in expected.difference(&proc_macro_deps) {
+        tidy_error!(
+            bad,
+            "`{extra}` is not registered in `src/bootstrap/src/utils/proc_macro_deps.rs`, but is not a proc-macro crate dependency",
+        );
+    }
+}
+
 /// Used to skip a check if a submodule is not checked out, and not in a CI environment.
 ///
 /// This helps prevent enforcing developers to fetch submodules for tidy.