4 files changed, 49 insertions, 7 deletions

diff --git a/include/libcamera/internal/yaml_parser.h b/include/libcamera/internal/yaml_parser.h
index 16708e48..6211ff4a 100644
--- a/include/libcamera/internal/yaml_parser.h
+++ b/include/libcamera/internal/yaml_parser.h
@@ -159,6 +159,14 @@ public:
 	{
 		return type_ == Type::Dictionary;
 	}
+	bool isEmpty() const
+	{
+		return type_ == Type::Empty;
+	}
+	explicit operator bool() const
+	{
+		return type_ != Type::Empty;
+	}
 
 	std::size_t size() const;
 
@@ -212,6 +220,7 @@ private:
 		Dictionary,
 		List,
 		Value,
+		Empty,
 	};
 
 	template<typename T>
diff --git a/src/libcamera/yaml_parser.cpp b/src/libcamera/yaml_parser.cpp
index 8b6a4038..4784f2dc 100644
--- a/src/libcamera/yaml_parser.cpp
+++ b/src/libcamera/yaml_parser.cpp
@@ -38,12 +38,12 @@ static const YamlObject empty;
  * \brief A class representing the tree structure of the YAML content
  *
  * The YamlObject class represents the tree structure of YAML content. A
- * YamlObject can be a dictionary or list of YamlObjects or a value if a tree
- * leaf.
+ * YamlObject can be empty, a dictionary or list of YamlObjects, or a value if a
+ * tree leaf.
  */
 
 YamlObject::YamlObject()
-	: type_(Type::Value)
+	: type_(Type::Empty)
 {
 }
 
@@ -71,6 +71,20 @@ YamlObject::~YamlObject() = default;
  */
 
 /**
+ * \fn YamlObject::isEmpty()
+ * \brief Return whether the YamlObject is an empty
+ *
+ * \return True if the YamlObject is empty, false otherwise
+ */
+
+/**
+ * \fn YamlObject::operator bool()
+ * \brief Return whether the YamlObject is a non-empty
+ *
+ * \return False if the YamlObject is empty, true otherwise
+ */
+
+/**
  * \fn YamlObject::size()
  * \brief Retrieve the number of elements in a dictionary or list YamlObject
  *
@@ -443,7 +457,8 @@ template std::optional<std::vector<Size>> YamlObject::getList<Size>() const;
  *
  * This function retrieves an element of the YamlObject. Only YamlObject
  * instances of List type associate elements with index, calling this function
- * on other types of instances is invalid and results in undefined behaviour.
+ * on other types of instances or with an invalid index results in an empty
+ * object.
  *
  * \return The YamlObject as an element of the list
  */
@@ -480,8 +495,8 @@ bool YamlObject::contains(const std::string &key) const
  *
  * This function retrieve a member of a YamlObject by name. Only YamlObject
  * instances of Dictionary type associate elements with names, calling this
- * function on other types of instances is invalid and results in undefined
- * behaviour.
+ * function on other types of instances or with a nonexistent key results in an
+ * empty object.
  *
  * \return The YamlObject corresponding to the \a key member
  */
diff --git a/test/meson.build b/test/meson.build
index dcd169a8..5ed052ed 100644
--- a/test/meson.build
+++ b/test/meson.build
@@ -73,7 +73,7 @@ internal_tests = [
     {'name': 'timer-thread', 'sources': ['timer-thread.cpp']},
     {'name': 'unique-fd', 'sources': ['unique-fd.cpp']},
     {'name': 'utils', 'sources': ['utils.cpp']},
-    {'name': 'yaml-parser', 'sources': ['yaml-parser.cpp'], 'should_fail': true},
+    {'name': 'yaml-parser', 'sources': ['yaml-parser.cpp']},
 ]
 
 internal_non_parallel_tests = [
diff --git a/test/yaml-parser.cpp b/test/yaml-parser.cpp
index 4cc77e26..1b22c87b 100644
--- a/test/yaml-parser.cpp
+++ b/test/yaml-parser.cpp
@@ -542,6 +542,24 @@ protected:
 			return TestFail;
 		}
 
+		/* Test nonexistent object has value type empty. */
+		if (!dictObj["nonexistent"].isEmpty()) {
+			cerr << "Accessing nonexistent object returns non-empty object" << std::endl;
+			return TestFail;
+		}
+
+		/* Test explicit cast to bool on an empty object returns true. */
+		if (!!dictObj["empty"] != true) {
+			cerr << "Casting empty entry to bool returns false" << std::endl;
+			return TestFail;
+		}
+
+		/* Test explicit cast to bool on nonexistent object returns false. */
+		if (!!dictObj["nonexistent"] != false) {
+			cerr << "Casting nonexistent dict entry to bool returns true" << std::endl;
+			return TestFail;
+		}
+
 		/* Make sure utils::map_keys() works on the adapter. */
 		(void)utils::map_keys(dictObj.asDict());