Add json_object_update_recursive()

Support merging values nested within objects. For instance, merging:

    {
	"foo": 1,
	"bar": {
	    "baz": 2
	}
    }

with

    {
	"bar": {
	    "baz": 3
	}
    }

results in

    {
	"foo": 1,
	"bar": {
	    "baz": 3
	}
    }

instead of overwriting the value for the bar key.

doc/apiref.rst

@@ -708,6 +708,12 @@ allowed in object keys.
 
    .. versionadded:: 2.3
 
+.. function:: int json_object_update_recursive(json_t *object, json_t *other)
+
+   Like :func:`json_object_update()`, but object values in *other* are
+   recursively merged with the corresponding values in *object* if they are also
+   objects, instead of overwriting them. Returns 0 on success or -1 on error.
+
 .. function:: json_object_foreach(object, key, value)
 
    Iterate over every key-value pair of ``object``, running the block

src/jansson.def

@@ -41,6 +41,7 @@ EXPORTS
     json_object_update
     json_object_update_existing
     json_object_update_missing
+    json_object_update_recursive
     json_object_iter
     json_object_iter_at
     json_object_iter_next

src/jansson.h

@@ -199,6 +199,7 @@ int json_object_clear(json_t *object);
 int json_object_update(json_t *object, json_t *other);
 int json_object_update_existing(json_t *object, json_t *other);
 int json_object_update_missing(json_t *object, json_t *other);
+int json_object_update_recursive(json_t *object, json_t *other);
 void *json_object_iter(json_t *object);
 void *json_object_iter_at(json_t *object, const char *key);
 void *json_object_key_to_iter(const char *key);

src/value.c

@@ -214,6 +214,26 @@ int json_object_update_missing(json_t *object, json_t *other)
     return 0;
 }
 
+int json_object_update_recursive(json_t *object, json_t *other)
+{
+    const char *key;
+    json_t *value;
+
+    if(!json_is_object(object) || !json_is_object(other))
+        return -1;
+
+    json_object_foreach(other, key, value) {
+        json_t *v = json_object_get(object, key);
+
+        if(json_is_object(v) && json_is_object(value))
+            json_object_update_recursive(v, value);
+        else
+            json_object_set_nocheck(object, key, value);
+    }
+
+    return 0;
+}
+
 void *json_object_iter(json_t *json)
 {
     json_object_t *object;

test/suites/api/test_object.c

@@ -207,6 +207,57 @@ static void test_conditional_updates()
     json_decref(other);
 }
 
+static void test_recursive_updates()
+{
+    json_t *invalid, *object, *other;
+
+    invalid = json_integer(42);
+
+    object = json_pack("{sis{si}}", "foo", 1, "bar", "baz", 2);
+    other = json_pack("{sisisi}", "foo", 3, "bar", 4, "baz", 5);
+
+    if(!json_object_update_recursive(invalid, other))
+        fail("json_object_update_recursive accepted non-object argument");
+
+    json_decref(invalid);
+
+    if(json_object_update_recursive(object, other))
+        fail("json_object_update_recursive failed");
+
+    if(json_object_size(object) != 3)
+        fail("invalid size after update");
+
+    if(json_integer_value(json_object_get(object, "foo")) != 3)
+        fail("json_object_update_recursive failed to update existing key");
+
+    if(json_integer_value(json_object_get(object, "bar")) != 4)
+        fail("json_object_update_recursive failed to overwrite object");
+
+    if(json_integer_value(json_object_get(object, "baz")) != 5)
+        fail("json_object_update_recursive didn't add new item");
+
+    json_decref(object);
+    json_decref(other);
+
+    object = json_pack("{sis{si}}", "foo", 1, "bar", "baz", 2);
+    other = json_pack("{s{si}}", "bar", "baz", 3);
+
+    if(json_object_update_recursive(object, other))
+        fail("json_object_update_recursive failed");
+
+    if(json_object_size(object) != 2)
+        fail("invalid size after update");
+
+    if(!json_object_get(object, "foo"))
+        fail("json_object_update_recursive removed existing key");
+
+    if(json_integer_value(json_object_get(json_object_get(object, "bar"), "baz")) != 3)
+        fail("json_object_update_recursive failed to update nested value");
+
+    json_decref(object);
+    json_decref(other);
+}
+
 static void test_circular()
 {
     json_t *object1, *object2;
@@ -667,6 +718,7 @@ static void run_tests()
     test_update();
     test_set_many_keys();
     test_conditional_updates();
+    test_recursive_updates();
     test_circular();
     test_set_nocheck();
     test_iterators();