Flakiness: Introduce a lock to serialise check_type test

Summary:
Tests using this function are occasionally failing in CI.
I suspect it is because of running more than one erlang_service instance at the same time.
Protect the function with a lock to check the hypothesis.
It may not help, because other tests using the erlang_service have a static connection.
Dealing with that will be step 2 if this does not help.

Differential Revision: D54631248

fbshipit-source-id: 842f601c815524bfa84957f959a7ac2cc36452bf

crates/ide/src/codemod_helpers.rs

@@ -476,13 +476,16 @@ pub(crate) fn find_call_in_function<T, U>(
 #[cfg(test)]
 mod tests {
 
+    use std::sync::Mutex;
+
     use elp_ide_db::elp_base_db::FileId;
     use elp_ide_db::elp_base_db::SourceDatabase;
     use elp_syntax::algo::find_node_at_offset;
     use elp_syntax::ast;
     use hir::FunctionDef;
     use hir::InFile;
     use hir::Semantic;
+    use lazy_static::lazy_static;
 
     use super::find_call_in_function;
     use super::FunctionMatch;
@@ -760,6 +763,15 @@ mod tests {
 
     #[track_caller]
     fn check_type(fixture: &str) {
+        // We are seeing flaky tests in CI related to this test
+        // function. T181455753.
+        // It is potentially a race condition, where the erlang
+        // service is not fully re-entrant. Protect against this with a lock, for now
+        lazy_static! {
+            static ref CHECK_TYPE_GLOBAL_LOCK: Mutex<()> = Mutex::new(());
+        }
+        let _guard = CHECK_TYPE_GLOBAL_LOCK.lock();
+
         let (db, position, _diagnostics_enabled, expected) = fixture::db_annotations(fixture);
         let host = AnalysisHost { db };
         let sema = Semantic::new(&host.db);