InputCommon: Return error, if any, from ControlReference::SetExpression().

2 files changed, 5 insertions, 2 deletions

diff --git a/Source/Core/InputCommon/ControlReference/ControlReference.cpp b/Source/Core/InputCommon/ControlReference/ControlReference.cpp
index b1dd5deee3..671f2f3379 100644
--- a/Source/Core/InputCommon/ControlReference/ControlReference.cpp
+++ b/Source/Core/InputCommon/ControlReference/ControlReference.cpp
@@ -50,12 +50,13 @@ std::string ControlReference::GetExpression() const
   return m_expression;
 }
 
-void ControlReference::SetExpression(std::string expr)
+std::optional<std::string> ControlReference::SetExpression(std::string expr)
 {
   m_expression = std::move(expr);
   auto parse_result = ParseExpression(m_expression);
   m_parse_status = parse_result.status;
   m_parsed_expression = std::move(parse_result.expr);
+  return parse_result.description;
 }
 
 ControlReference::ControlReference() : range(1), m_parsed_expression(nullptr)
diff --git a/Source/Core/InputCommon/ControlReference/ControlReference.h b/Source/Core/InputCommon/ControlReference/ControlReference.h
index de289ba265..fb4b5cc1df 100644
--- a/Source/Core/InputCommon/ControlReference/ControlReference.h
+++ b/Source/Core/InputCommon/ControlReference/ControlReference.h
@@ -38,7 +38,9 @@ public:
   ciface::ExpressionParser::ParseStatus GetParseStatus() const;
   void UpdateReference(ciface::ExpressionParser::ControlEnvironment& env);
   std::string GetExpression() const;
-  void SetExpression(std::string expr);
+
+  // Returns a human-readable error description when the given expression is invalid.
+  std::optional<std::string> SetExpression(std::string expr);
 
   ControlState range;