JSON: Add simple printing and creation (WebAssembly#6265)

src/support/CMakeLists.txt

@@ -8,6 +8,7 @@ set(support_SOURCES
   dfa_minimization.cpp
   file.cpp
   istring.cpp
+  json.cpp
   path.cpp
   safe_integer.cpp
   threads.cpp

src/support/json.cpp

@@ -0,0 +1,43 @@
+/*
+ * Copyright 2024 WebAssembly Community Group participants
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "support/json.h"
+
+namespace json {
+
+void Value::stringify(std::ostream& os, bool pretty) {
+  if (isString()) {
+    // TODO: escaping
+    os << '"' << getCString() << '"';
+  } else if (isArray()) {
+    os << '[';
+    auto first = true;
+    for (auto& item : getArray()) {
+      if (first) {
+        first = false;
+      } else {
+        // TODO pretty whitespace
+        os << ',';
+      }
+      item->stringify(os, pretty);
+    }
+    os << ']';
+  } else {
+    WASM_UNREACHABLE("TODO: stringify all of JSON");
+  }
+}
+
+} // namespace json

src/support/json.h

@@ -54,6 +54,8 @@ struct Value {
     Ref& operator[](IString x) { return (*this->get())[x]; }
   };
 
+  template<typename T> static Ref make(T t) { return Ref(new Value(t)); }
+
   enum Type {
     String = 0,
     Number = 1,

test/gtest/CMakeLists.txt

@@ -4,6 +4,7 @@ include_directories(../../src/wasm)
 set(unittest_SOURCES
   cfg.cpp
   dfa_minimization.cpp
+  json.cpp
   lattices.cpp
   possible-contents.cpp
   printing.cpp

test/gtest/json.cpp

@@ -0,0 +1,16 @@
+#include "support/json.h"
+#include "gtest/gtest.h"
+
+using JSONTest = ::testing::Test;
+
+TEST_F(JSONTest, Stringify) {
+  // TODO: change the API to not require a copy
+  auto input = "[\"hello\",\"world\"]";
+  auto* copy = strdup(input);
+  json::Value value;
+  value.parse(copy);
+  std::stringstream ss;
+  value.stringify(ss);
+  EXPECT_EQ(ss.str(), input);
+  free(copy);
+}