Add Module::child(), Module::childrenDfs() and Module::immediateChildren()

Those functions are implemented in the same manner as in `SchemaNode`
and allows to walk through modules children. This is counterpart to
already implemented `Module::childInstantiables()` that returns
instantiables schema nodes. These return all nodes, including
the schema-only nodes such as choice and case if end-user needs
to read its schema.

While the implementation is inspired by functions in `SchemaNode`,
imlementation of `Module::parent()` and `Module::siblings()` was omitted
as those do no make sense on `Module`.

Change-Id: I38c8374304f859d65343d04d08302e07deb05f27

Author: bedrich-schindler

include/libyang-cpp/Collection.hpp

@@ -98,6 +98,7 @@ class LIBYANG_CPP_EXPORT Collection {
 public:
     friend DataNode;
     friend Iterator<NodeType, ITER_TYPE>;
+    friend Module;
     friend SchemaNode;
     ~Collection();
     Collection(const Collection<NodeType, ITER_TYPE>&);

include/libyang-cpp/Module.hpp

@@ -34,6 +34,8 @@ class ChildInstanstiables;
 class Identity;
 class SchemaNode;
 class SubmoduleParsed;
+template <typename NodeType, IterationType ITER_TYPE>
+class Collection;
 
 namespace types {
 class IdentityRef;
@@ -86,7 +88,10 @@ class LIBYANG_CPP_EXPORT Module {
 
     std::vector<Identity> identities() const;
 
+    std::optional<SchemaNode> child() const;
     ChildInstanstiables childInstantiables() const;
+    libyang::Collection<SchemaNode, IterationType::Dfs> childrenDfs() const;
+    Collection<SchemaNode, IterationType::Sibling> immediateChildren() const;
     std::vector<SchemaNode> actionRpcs() const;
 
     std::string printStr(const SchemaOutputFormat format, const std::optional<SchemaPrintFlags> flags = std::nullopt, std::optional<size_t> lineLength = std::nullopt) const;

src/Module.cpp

@@ -8,6 +8,7 @@
 
 #include <algorithm>
 #include <libyang-cpp/ChildInstantiables.hpp>
+#include <libyang-cpp/Collection.hpp>
 #include <libyang-cpp/Module.hpp>
 #include <libyang-cpp/Utils.hpp>
 #include <libyang/libyang.h>
@@ -178,6 +179,23 @@ std::vector<Identity> Module::identities() const
     return res;
 }
 
+/**
+ * @brief Returns the first child node of this module.
+ * @return The child, or std::nullopt if there are no children.
+ */
+std::optional<SchemaNode> Module::child() const
+{
+    if (!m_module->implemented) {
+        throw Error{"Module::child: module is not implemented"};
+    }
+
+    if (!m_module->compiled->data) {
+        return std::nullopt;
+    }
+
+    return SchemaNode{m_module->compiled->data, m_ctx};
+}
+
 /**
  * @brief Returns a collection of data instantiable top-level nodes of this module.
  *
@@ -191,6 +209,28 @@ ChildInstanstiables Module::childInstantiables() const
     return ChildInstanstiables{nullptr, m_module->compiled, m_ctx};
 }
 
+/**
+ * @brief Returns a collection for iterating depth-first over the subtree this module points to.
+ */
+Collection<SchemaNode, IterationType::Dfs> Module::childrenDfs() const
+{
+    if (!m_module->implemented) {
+        throw Error{"Module::childrenDfs: module is not implemented"};
+    }
+    return Collection<SchemaNode, IterationType::Dfs>{m_module->compiled->data, m_ctx};
+}
+
+/**
+ * @brief Returns a collection for iterating over the immediate children of where this module points to.
+ *
+ * This is a convenience function for iterating over this->child().siblings() which does not throw even when module has no children.
+ */
+Collection<SchemaNode, IterationType::Sibling> Module::immediateChildren() const
+{
+    auto c = child();
+    return c ? c->siblings() : Collection<SchemaNode, IterationType::Sibling>{nullptr, nullptr};
+}
+
 /**
  * @brief Returns a collection of RPC nodes (not action nodes) as SchemaNode
  *

tests/context.cpp

@@ -713,6 +713,11 @@ TEST_CASE("context")
   +--rw anydataWithMandatoryChild       anydata
   +--rw anyxmlBasic?                    anyxml
   +--rw anyxmlWithMandatoryChild        anyxml
+  +--rw (choiceOnModule)?
+  |  +--:(case1)
+  |  |  +--rw choiceOnModuleLeaf1?   string
+  |  +--:(case2)
+  |     +--rw choiceOnModuleLeaf2?   string
   +--rw choiceBasicContainer
   |  +--rw (choiceBasic)?
   |     +--:(case1)

tests/example_schema.hpp

@@ -390,6 +390,19 @@ module type_module {
         mandatory true;
     }
 
+    choice choiceOnModule {
+        case case1 {
+            leaf choiceOnModuleLeaf1 {
+                type string;
+            }
+        }
+        case case2 {
+            leaf choiceOnModuleLeaf2 {
+                type string;
+            }
+        }
+    }
+
     container choiceBasicContainer {
         choice choiceBasic {
             case case1 {
@@ -787,6 +800,14 @@ module type_module {
 }
 )"s;
 
+const auto empty_module = R"(
+module empty_module {
+    yang-version 1.1;
+    namespace "e";
+    prefix "e";
+}
+)"s;
+
 const auto with_inet_types_module = R"(
 module with-inet-types {
   yang-version 1.1;