Handle recursive aux builds without deadlock

CHANGELOG.md

@@ -11,8 +11,12 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Fixed
 
+* aux builds don't hang anymore if they are recursively depending on themselves
+
 ### Changed
 
+* Basic tests now work even without the `rustc` cargo feature
+
 ### Removed
 
 ## [0.26.0] - 2024-09-07

src/build_manager.rs

@@ -1,6 +1,7 @@
 //! Auxiliary and dependency builder. Extendable to custom builds.
 
 use std::{
+    cell::RefCell,
     collections::{hash_map::Entry, HashMap},
     ffi::OsString,
     sync::{Arc, OnceLock, RwLock},
@@ -84,6 +85,39 @@ impl BuildManager {
             });
         }
         let mut lock = self.cache.write().unwrap();
+
+        thread_local! {
+            static STACK: RefCell<Vec<String>> = RefCell::new(vec![]);
+        }
+        STACK.with_borrow_mut(|stack| {
+            if stack.contains(&description) {
+                Err(Errored {
+                    command: format!("{description:?}"),
+                    errors: vec![],
+                    stderr: b"recursive build".to_vec(),
+                    stdout: vec![],
+                })
+            } else {
+                stack.push(description.clone());
+                Ok(())
+            }
+        })?;
+        struct Handle(Arc<OnceLock<Result<Vec<OsString>, ()>>>, String);
+
+        impl std::ops::Deref for Handle {
+            type Target = OnceLock<Result<Vec<OsString>, ()>>;
+
+            fn deref(&self) -> &Self::Target {
+                &self.0
+            }
+        }
+
+        impl Drop for Handle {
+            fn drop(&mut self) {
+                STACK.with_borrow_mut(|stack| assert_eq!(stack.pop().unwrap(), self.1))
+            }
+        }
+
         let once = match lock.entry(description) {
             Entry::Occupied(entry) => {
                 if let Some(res) = entry.get().get() {
@@ -94,12 +128,14 @@ impl BuildManager {
                         stdout: vec![],
                     });
                 }
-                entry.get().clone()
+
+                Handle(entry.get().clone(), entry.key().clone())
             }
             Entry::Vacant(entry) => {
                 let once = Arc::new(OnceLock::new());
-                entry.insert(once.clone());
-                once
+                let handle = Handle(once.clone(), entry.key().clone());
+                entry.insert(once);
+                handle
             }
         };
         drop(lock);

tests/integrations/basic-fail/Cargo.stdout

@@ -475,6 +475,8 @@ tests/actual_tests_bless/no_test.rs ... FAILED
 tests/actual_tests_bless/non_top_level_configs.rs ... FAILED
 tests/actual_tests_bless/pass.rs ... ok
 tests/actual_tests_bless/pass_with_annotation.rs ... FAILED
+Building aux file tests/actual_tests_bless/auxiliary/recursive.rs ... FAILED
+tests/actual_tests_bless/recursive_aux_build.rs ... FAILED
 tests/actual_tests_bless/revised_revision.rs ... FAILED
 tests/actual_tests_bless/revisioned_executable.rs (revision `run`) ... ok
 tests/actual_tests_bless/revisioned_executable.rs (revision `panic`) ... ok
@@ -767,6 +769,29 @@ full stdout:
 
 
 
+FAILED TEST: tests/actual_tests_bless/recursive_aux_build.rs
+command: "$CMD"
+
+error: aux build failed
+ --> tests/actual_tests_bless/recursive_aux_build.rs:1:16
+  |
+1 | //@ aux-build: recursive.rs
+  |                ^^^^^^^^^^^^ tests/actual_tests_bless/recursive_aux_build.rs
+  |
+error: aux build failed
+ --> tests/actual_tests_bless/auxiliary/recursive.rs:1:16
+  |
+1 | //@ aux-build: recursive.rs
+  |                ^^^^^^^^^^^^ tests/actual_tests_bless/auxiliary/recursive.rs
+  |
+
+
+full stderr:
+recursive build
+full stdout:
+
+
+
 FAILED TEST: tests/actual_tests_bless/revised_revision.rs
 command: parse comments
 
@@ -1066,6 +1091,7 @@ FAILURES:
     tests/actual_tests_bless/no_test.rs
     tests/actual_tests_bless/non_top_level_configs.rs
     tests/actual_tests_bless/pass_with_annotation.rs
+    tests/actual_tests_bless/recursive_aux_build.rs
     tests/actual_tests_bless/revised_revision.rs
     tests/actual_tests_bless/revisioned_executable.rs (revision panic.run)
     tests/actual_tests_bless/revisioned_executable_panic.rs (revision run.run)
@@ -1078,7 +1104,7 @@ FAILURES:
     tests/actual_tests_bless/unknown_revision2.rs
     tests/actual_tests_bless/wrong_diagnostic_code.rs
 
-test result: FAIL. 23 failed; 24 passed; 3 ignored
+test result: FAIL. 24 failed; 24 passed; 3 ignored
 
 Building dependencies ... ok
 tests/actual_tests_bless_yolo/revisions_bad.rs (revision `foo`) ... ok

tests/integrations/basic-fail/tests/actual_tests_bless/auxiliary/recursive.rs

@@ -0,0 +1 @@
+//@ aux-build: recursive.rs

tests/integrations/basic-fail/tests/actual_tests_bless/recursive_aux_build.rs

@@ -0,0 +1 @@
+//@ aux-build: recursive.rs