JSON parse and stringify API (#70)

* JSON parse and stringify API

* move to functions rather than ctx methods to align closer to C++ API

* value implement json.Marshaler interface

* test parse error cases

* can;t use errors.As in Go 12.x

Author: rogchap

json.go

@@ -0,0 +1,38 @@
+package v8go
+
+// #include <stdlib.h>
+// #include "v8go.h"
+import "C"
+import (
+	"errors"
+	"unsafe"
+)
+
+// JSONParse tries to parse the string and returns it as *Value if successful.
+// Any JS errors will be returned as `JSError`.
+func JSONParse(ctx *Context, str string) (*Value, error) {
+	if ctx == nil {
+		return nil, errors.New("v8go: Context is required")
+	}
+	cstr := C.CString(str)
+	defer C.free(unsafe.Pointer(cstr))
+
+	rtn := C.JSONParse(ctx.ptr, cstr)
+	return getValue(ctx, rtn), getError(rtn)
+}
+
+// JSONStringify tries to stringify the JSON-serializable object value and returns it as string.
+func JSONStringify(ctx *Context, val *Value) (string, error) {
+	if val == nil {
+		return "", errors.New("v8go: Value is required")
+	}
+	// If a nil context is passed we'll use the context/isolate that created the value.
+	var ctxPtr C.ContextPtr
+	if ctx != nil {
+		ctxPtr = ctx.ptr
+	}
+
+	str := C.JSONStringify(ctxPtr, val.ptr)
+	defer C.free(unsafe.Pointer(str))
+	return C.GoString(str), nil
+}

json_test.go

@@ -0,0 +1,47 @@
+package v8go_test
+
+import (
+	"fmt"
+	"testing"
+
+	"rogchap.com/v8go"
+)
+
+func TestJSONParse(t *testing.T) {
+	t.Parallel()
+
+	if _, err := v8go.JSONParse(nil, "{}"); err == nil {
+		t.Error("expected error but got <nil>")
+	}
+	ctx, _ := v8go.NewContext()
+	_, err := v8go.JSONParse(ctx, "{")
+	if err == nil {
+		t.Error("expected error but got <nil>")
+		return
+	}
+
+	if _, ok := err.(*v8go.JSError); !ok {
+		t.Errorf("expected error to be of type JSError, got: %T", err)
+	}
+
+}
+
+func ExampleJSONParse() {
+	ctx, _ := v8go.NewContext()
+	val, _ := v8go.JSONParse(ctx, `{"foo": "bar"}`)
+	fmt.Println(val)
+	// Output:
+	// [object Object]
+}
+
+func ExampleJSONStringify() {
+	ctx, _ := v8go.NewContext()
+	val, _ := v8go.JSONParse(ctx, `{
+		"a": 1,
+		"b": "foo"
+	}`)
+	jsonStr, _ := v8go.JSONStringify(ctx, val)
+	fmt.Println(jsonStr)
+	// Output:
+	// {"a":1,"b":"foo"}
+}

object_template_test.go

@@ -28,6 +28,7 @@ func TestObjectTemplate(t *testing.T) {
 	val, _ := v8go.NewValue(iso, "bar")
 	objVal, _ := v8go.NewObjectTemplate(iso)
 	bigbigint, _ := new(big.Int).SetString("36893488147419099136", 10) // larger than a single word size (64bit)
+	bigbignegint, _ := new(big.Int).SetString("-36893488147419099136", 10)
 
 	tests := [...]struct {
 		name  string
@@ -40,7 +41,9 @@ func TestObjectTemplate(t *testing.T) {
 		{"u64", uint64(1)},
 		{"float64", float64(1)},
 		{"bigint", big.NewInt(1)},
+		{"biguint", new(big.Int).SetUint64(1 << 63)},
 		{"bigbigint", bigbigint},
+		{"bigbignegint", bigbignegint},
 		{"bool", true},
 		{"val", val},
 		{"obj", objVal},

v8go.cc

@@ -273,6 +273,16 @@ TemplatePtr NewFunctionTemplate(IsolatePtr iso_ptr, int callback_ref) {
 
 /********** Context **********/
 
+#define LOCAL_CONTEXT(ctx_ptr)                  \
+  m_ctx* ctx = static_cast<m_ctx*>(ctx_ptr);    \
+  Isolate* iso = ctx->iso;                      \
+  Locker locker(iso);                           \
+  Isolate::Scope isolate_scope(iso);            \
+  HandleScope handle_scope(iso);                \
+  TryCatch try_catch(iso);                      \
+  Local<Context> local_ctx = ctx->ptr.Get(iso); \
+  Context::Scope context_scope(local_ctx);
+
 ContextPtr NewContext(IsolatePtr iso_ptr,
                       TemplatePtr global_template_ptr,
                       int ref) {
@@ -316,15 +326,7 @@ void ContextFree(ContextPtr ptr) {
 }
 
 RtnValue RunScript(ContextPtr ctx_ptr, const char* source, const char* origin) {
-  m_ctx* ctx = static_cast<m_ctx*>(ctx_ptr);
-  Isolate* iso = ctx->iso;
-  Locker locker(iso);
-  Isolate::Scope isolate_scope(iso);
-  HandleScope handle_scope(iso);
-  TryCatch try_catch(iso);
-
-  Local<Context> local_ctx = ctx->ptr.Get(iso);
-  Context::Scope context_scope(local_ctx);
+  LOCAL_CONTEXT(ctx_ptr);
 
   Local<String> src =
       String::NewFromUtf8(iso, source, NewStringType::kNormal).ToLocalChecked();
@@ -339,7 +341,27 @@ RtnValue RunScript(ContextPtr ctx_ptr, const char* source, const char* origin) {
     rtn.error = ExceptionError(try_catch, iso, local_ctx);
     return rtn;
   }
-  MaybeLocal<v8::Value> result = script.ToLocalChecked()->Run(local_ctx);
+  MaybeLocal<Value> result = script.ToLocalChecked()->Run(local_ctx);
+  if (result.IsEmpty()) {
+    rtn.error = ExceptionError(try_catch, iso, local_ctx);
+    return rtn;
+  }
+  m_value* val = new m_value;
+  val->iso = iso;
+  val->ctx.Reset(iso, local_ctx);
+  val->ptr.Reset(iso, Persistent<Value>(iso, result.ToLocalChecked()));
+
+  rtn.value = static_cast<ValuePtr>(val);
+  return rtn;
+}
+
+RtnValue JSONParse(ContextPtr ctx_ptr, const char* str) {
+  LOCAL_CONTEXT(ctx_ptr);
+  RtnValue rtn = {nullptr, nullptr};
+
+  MaybeLocal<Value> result = JSON::Parse(
+      local_ctx,
+      String::NewFromUtf8(iso, str, NewStringType::kNormal).ToLocalChecked());
   if (result.IsEmpty()) {
     rtn.error = ExceptionError(try_catch, iso, local_ctx);
     return rtn;
@@ -353,6 +375,43 @@ RtnValue RunScript(ContextPtr ctx_ptr, const char* source, const char* origin) {
   return rtn;
 }
 
+const char* JSONStringify(ContextPtr ctx_ptr, ValuePtr val_ptr) {
+  Isolate* iso;
+  Local<Context> local_ctx;
+
+  m_value* val = static_cast<m_value*>(val_ptr);
+  m_ctx* ctx = static_cast<m_ctx*>(ctx_ptr);
+
+  if (ctx != nullptr) {
+    iso = ctx->iso;
+  } else {
+    iso = val->iso;
+  }
+
+  Locker locker(iso);
+  Isolate::Scope isolate_scope(iso);
+  HandleScope handle_scope(iso);
+
+  if (ctx != nullptr) {
+    local_ctx = ctx->ptr.Get(iso);
+  } else {
+    local_ctx = val->ctx.Get(iso);
+    if (local_ctx.IsEmpty()) {
+      m_ctx* ctx = static_cast<m_ctx*>(iso->GetData(0));
+      local_ctx = ctx->ptr.Get(iso);
+    }
+  }
+
+  Context::Scope context_scope(local_ctx);
+
+  MaybeLocal<String> str = JSON::Stringify(local_ctx, val->ptr.Get(iso));
+  if (str.IsEmpty()) {
+    return nullptr;
+  }
+  String::Utf8Value json(iso, str.ToLocalChecked());
+  return CopyString(json);
+}
+
 /********** Value **********/
 
 #define LOCAL_VALUE(ptr)                               \

v8go.h

@@ -56,6 +56,8 @@ extern void ContextFree(ContextPtr ptr);
 extern RtnValue RunScript(ContextPtr ctx_ptr,
                           const char* source,
                           const char* origin);
+extern RtnValue JSONParse(ContextPtr ctx_ptr, const char* str);
+const char* JSONStringify(ContextPtr ctx_ptr, ValuePtr val_ptr);
 
 extern void TemplateFree(TemplatePtr ptr);
 extern void TemplateSetValue(TemplatePtr ptr,

value.go

@@ -502,3 +502,12 @@ func (v *Value) finalizer() {
 	v.ptr = nil
 	runtime.SetFinalizer(v, nil)
 }
+
+// MarshalJSON implements the json.Marshaler interface.
+func (v *Value) MarshalJSON() ([]byte, error) {
+	jsonStr, err := JSONStringify(nil, v)
+	if err != nil {
+		return nil, err
+	}
+	return []byte(jsonStr), nil
+}

value_test.go

@@ -1,6 +1,7 @@
 package v8go_test
 
 import (
+	"bytes"
 	"fmt"
 	"math"
 	"math/big"
@@ -462,3 +463,59 @@ func TestValueIsXXX(t *testing.T) {
 		})
 	}
 }
+
+func TestValueMarshalJSON(t *testing.T) {
+	t.Parallel()
+	iso, _ := v8go.NewIsolate()
+
+	tests := [...]struct {
+		name     string
+		val      func() *v8go.Value
+		expected []byte
+	}{
+		{
+			"primitive",
+			func() *v8go.Value {
+				val, _ := v8go.NewValue(iso, int32(0))
+				return val
+			},
+			[]byte("0"),
+		},
+		{
+			"object",
+			func() *v8go.Value {
+				ctx, _ := v8go.NewContext(iso)
+				val, _ := ctx.RunScript("let foo = {a:1, b:2}; foo", "test.js")
+				return val
+			},
+			[]byte(`{"a":1,"b":2}`),
+		},
+		{
+			"objectFunc",
+			func() *v8go.Value {
+				ctx, _ := v8go.NewContext(iso)
+				val, _ := ctx.RunScript("let foo = {a:1, b:()=>{}}; foo", "test.js")
+				return val
+			},
+			[]byte(`{"a":1}`),
+		},
+		{
+			"nil",
+			func() *v8go.Value { return nil },
+			[]byte(""),
+		},
+	}
+
+	for _, tt := range tests {
+		tt := tt
+		t.Run(tt.name, func(t *testing.T) {
+			t.Parallel()
+			val := tt.val()
+			json, _ := val.MarshalJSON()
+			if !bytes.Equal(json, tt.expected) {
+				t.Errorf("unexpected JSON value: %s", string(json))
+			}
+
+		})
+	}
+}