simplify use of RapidYAML for std.parseYaml, improve YAML stream handling

There is really no need to parse the YAML, and then re-serialize it,
and then perform a string-splitting operation into a std::vector,
and then re-parse each chunk individually, in order to convert a YAML
stream into a JSON array.

Author: johnbartholomew

core/vm.cpp

@@ -1686,41 +1686,29 @@ class Interpreter {
 
         std::string value = encode_utf8(static_cast<HeapString *>(args[0].v.h)->value);
 
-        ryml::Tree tree = treeFromString(value);
+        ryml::Tree tree = ryml::parse_in_arena(ryml::to_csubstr(value));
 
         json j;
-        if (tree.is_stream(tree.root_id())) {
-            // Split into individual yaml documents
-            std::stringstream ss;
-            ss << tree;
-            std::vector<std::string> v = split(ss.str(), "---\n");
-
-            // Convert yaml to json and push onto json array
-            ryml::Tree doc;
-            for (std::size_t i = 0; i < v.size(); ++i) {
-                if (!v[i].empty()) {
-                    doc = treeFromString(v[i]);
-                    j.push_back(yamlTreeToJson(doc));
-                }
-            }
-        } else if (tree.type(tree.root_id()).is_notype()) {
+        if (tree.type(tree.root_id()).is_notype()) {
             scratch = makeNull();
             return nullptr;
+        } else if (tree.is_stream(tree.root_id())) {
+            ryml::ConstNodeRef root = tree.crootref();
+            for (ryml::ConstNodeRef node : root.children()) {
+                std::ostringstream jsonText;
+                jsonText << ryml::as_json(node);
+                j.push_back(json::parse(jsonText.str()));
+            }
         } else {
-            j = yamlTreeToJson(tree);
+            std::ostringstream jsonText;
+            jsonText << ryml::as_json(tree);
+            j = json::parse(jsonText.str());
         }
-
-        bool filled;
-
-        otherJsonToHeap(j, filled, scratch);
-
+        bool filled_unused;
+        otherJsonToHeap(j, filled_unused, scratch);
         return nullptr;
     }
 
-    const ryml::Tree treeFromString(const std::string& s) {
-        return ryml::parse_in_arena(ryml::to_csubstr(s));
-    }
-
     const std::vector<std::string> split(const std::string& s, const std::string& delimiter) {
         size_t pos_start = 0, pos_end, delim_len = delimiter.length();
         std::string token;
@@ -1736,12 +1724,6 @@ class Interpreter {
         return res;
     }
 
-    const json yamlTreeToJson(const ryml::Tree& tree) {
-        std::ostringstream jsonStream;
-        jsonStream << ryml::as_json(tree);
-        return json::parse(jsonStream.str());
-    }
-
     void otherJsonToHeap(const json &v, bool &filled, Value &attach) {
         // In order to not anger the garbage collector, assign to attach immediately after
         // making the heap object.

test_suite/stdlib.jsonnet

@@ -1481,6 +1481,8 @@ std.assertEqual(std.parseJson('{"a": {"b": ["c", 42]}}'), { a: { b: ['c', 42] }
 // Empty input evaluates to `null`.
 // Regression test for https://github.com/google/jsonnet/issues/1270
 std.assertEqual(std.parseYaml('   \n'), null) &&
+// Stream input, regression test for https://github.com/google/jsonnet/issues/1148
+std.assertEqual(std.parseYaml('1\n---'), [1, null]) &&
 std.assertEqual(std.parseYaml('{}'), {}) &&
 std.assertEqual(std.parseYaml('[]'), []) &&
 std.assertEqual(