json: add helper for adding variant to array suppressing duplicates

src/shared/json.c

@@ -2093,7 +2093,6 @@ int json_variant_append_array(JsonVariant **v, JsonVariant *element) {
         assert(v);
         assert(element);
 
-
         if (!*v || json_variant_is_null(*v))
                 blank = true;
         else if (json_variant_is_array(*v))
@@ -2151,6 +2150,27 @@ int json_variant_append_array(JsonVariant **v, JsonVariant *element) {
         return 0;
 }
 
+JsonVariant *json_variant_find(JsonVariant *haystack, JsonVariant *needle) {
+        JsonVariant *i;
+
+        /* Find a json object in an array. Returns NULL if not found, or if the array is not actually an array. */
+
+        JSON_VARIANT_ARRAY_FOREACH(i, haystack)
+                if (json_variant_equal(i, needle))
+                        return i;
+
+        return NULL;
+}
+
+int json_variant_append_array_nodup(JsonVariant **v, JsonVariant *element) {
+        assert(v);
+
+        if (json_variant_find(*v, element))
+                return 0;
+
+        return json_variant_append_array(v, element);
+}
+
 int json_variant_strv(JsonVariant *v, char ***ret) {
         char **l = NULL;
         bool sensitive;

src/shared/json.h

@@ -210,7 +210,10 @@ int json_variant_set_field_unsigned(JsonVariant **v, const char *field, uint64_t
 int json_variant_set_field_boolean(JsonVariant **v, const char *field, bool b);
 int json_variant_set_field_strv(JsonVariant **v, const char *field, char **l);
 
+JsonVariant *json_variant_find(JsonVariant *haystack, JsonVariant *needle);
+
 int json_variant_append_array(JsonVariant **v, JsonVariant *element);
+int json_variant_append_array_nodup(JsonVariant **v, JsonVariant *element);
 
 int json_variant_merge(JsonVariant **v, JsonVariant *m);
 

src/test/test-json.c

@@ -726,4 +726,29 @@ TEST(json_array_append_without_source) {
         json_array_append_with_source_one(false);
 }
 
+TEST(json_array_append_nodup) {
+        _cleanup_(json_variant_unrefp) JsonVariant *l = NULL, *s = NULL, *wd = NULL, *nd = NULL;
+
+        assert_se(json_build(&l, JSON_BUILD_STRV(STRV_MAKE("foo", "bar", "baz", "bar", "baz", "foo", "qux", "baz"))) >= 0);
+        assert_se(json_build(&s, JSON_BUILD_STRV(STRV_MAKE("foo", "bar", "baz", "qux"))) >= 0);
+
+        assert_se(!json_variant_equal(l, s));
+        assert_se(json_variant_elements(l) == 8);
+        assert_se(json_variant_elements(s) == 4);
+
+        JsonVariant *i;
+        JSON_VARIANT_ARRAY_FOREACH(i, l) {
+                assert_se(json_variant_append_array(&wd, i) >= 0);
+                assert_se(json_variant_append_array_nodup(&nd, i) >= 0);
+        }
+
+        assert_se(json_variant_elements(wd) == 8);
+        assert_se(json_variant_equal(l, wd));
+        assert_se(!json_variant_equal(s, wd));
+
+        assert_se(json_variant_elements(nd) == 4);
+        assert_se(!json_variant_equal(l, nd));
+        assert_se(json_variant_equal(s, nd));
+}
+
 DEFINE_TEST_MAIN(LOG_DEBUG);