Add -Wmixed-oneway

Warns if an interface has both oneway and non-oneway methods.

Do not mix oneway with non-oneway methods, because it makes
understanding the threading model complicated for clients and servers.
Specifically, when reading client code of a particular interface, you
need to look up for each method if that method will block or not.

Bug: 168028537
Test: aidl_unittests
Change-Id: If3b4eca0c33532becf7ff90af0d3c6379b7f6821

1 files changed, 14 insertions, 0 deletions

diff --git a/diagnostics.cpp b/diagnostics.cpp
index bf50cc2e..4af90331 100644
--- a/diagnostics.cpp
+++ b/diagnostics.cpp
@@ -211,6 +211,19 @@ struct DiagnoseExplicitDefault : DiagnosticsVisitor {
   }
 };
 
+struct DiagnoseMixedOneway : DiagnosticsVisitor {
+  DiagnoseMixedOneway(DiagnosticsContext& diag) : DiagnosticsVisitor(diag) {}
+  void Visit(const AidlInterface& i) override {
+    const auto& methods = i.GetMethods();
+    if (std::adjacent_find(begin(methods), end(methods), [](const auto& a, const auto& b) {
+          return a->IsOneway() != b->IsOneway();
+        }) != end(methods)) {
+      diag.Report(i.GetLocation(), DiagnosticID::mixed_oneway)
+          << "The interface '" << i.GetName() << "' has both one-way and two-way methods.";
+    }
+  }
+};
+
 bool Diagnose(const AidlDocument& doc, const DiagnosticMapping& mapping) {
   DiagnosticsContext diag(mapping);
 
@@ -219,6 +232,7 @@ bool Diagnose(const AidlDocument& doc, const DiagnosticMapping& mapping) {
   DiagnoseInoutParameter{diag}.Check(doc);
   DiagnoseConstName{diag}.Check(doc);
   DiagnoseExplicitDefault{diag}.Check(doc);
+  DiagnoseMixedOneway{diag}.Check(doc);
 
   return diag.ErrorCount() == 0;
 }