Fix accessing prototypes of Canvas, Image, Context2d

src/Canvas.cc

@@ -13,6 +13,7 @@
 #include <cairo-pdf.h>
 #include <cairo-svg.h>
 
+#include "Util.h"
 #include "Canvas.h"
 #include "PNG.h"
 #include "CanvasRenderingContext2d.h"
@@ -57,10 +58,10 @@ Canvas::Initialize(Nan::ADDON_REGISTER_FUNCTION_ARGS_TYPE target) {
 #ifdef HAVE_JPEG
   Nan::SetPrototypeMethod(ctor, "streamJPEGSync", StreamJPEGSync);
 #endif
-  Nan::SetAccessor(proto, Nan::New("type").ToLocalChecked(), GetType);
-  Nan::SetAccessor(proto, Nan::New("stride").ToLocalChecked(), GetStride);
-  Nan::SetAccessor(proto, Nan::New("width").ToLocalChecked(), GetWidth, SetWidth);
-  Nan::SetAccessor(proto, Nan::New("height").ToLocalChecked(), GetHeight, SetHeight);
+  SetProtoAccessor(proto, Nan::New("type").ToLocalChecked(), GetType, NULL, ctor);
+  SetProtoAccessor(proto, Nan::New("stride").ToLocalChecked(), GetStride, NULL, ctor);
+  SetProtoAccessor(proto, Nan::New("width").ToLocalChecked(), GetWidth, SetWidth, ctor);
+  SetProtoAccessor(proto, Nan::New("height").ToLocalChecked(), GetHeight, SetHeight, ctor);
 
   Nan::SetTemplate(proto, "PNG_NO_FILTERS", Nan::New<Uint32>(PNG_NO_FILTERS));
   Nan::SetTemplate(proto, "PNG_FILTER_NONE", Nan::New<Uint32>(PNG_FILTER_NONE));

src/CanvasRenderingContext2d.cc

@@ -12,6 +12,7 @@
 #include <algorithm>
 #include <string>
 
+#include "Util.h"
 #include "Canvas.h"
 #include "Point.h"
 #include "Image.h"
@@ -127,24 +128,24 @@ Context2d::Initialize(Nan::ADDON_REGISTER_FUNCTION_ARGS_TYPE target) {
   Nan::SetPrototypeMethod(ctor, "_setTextBaseline", SetTextBaseline);
   Nan::SetPrototypeMethod(ctor, "_setTextAlignment", SetTextAlignment);
   Nan::SetPrototypeMethod(ctor, "_getMatrix", GetMatrix);
-  Nan::SetAccessor(proto, Nan::New("pixelFormat").ToLocalChecked(), GetFormat);
-  Nan::SetAccessor(proto, Nan::New("patternQuality").ToLocalChecked(), GetPatternQuality, SetPatternQuality);
-  Nan::SetAccessor(proto, Nan::New("globalCompositeOperation").ToLocalChecked(), GetGlobalCompositeOperation, SetGlobalCompositeOperation);
-  Nan::SetAccessor(proto, Nan::New("globalAlpha").ToLocalChecked(), GetGlobalAlpha, SetGlobalAlpha);
-  Nan::SetAccessor(proto, Nan::New("shadowColor").ToLocalChecked(), GetShadowColor, SetShadowColor);
-  Nan::SetAccessor(proto, Nan::New("fillColor").ToLocalChecked(), GetFillColor);
-  Nan::SetAccessor(proto, Nan::New("strokeColor").ToLocalChecked(), GetStrokeColor);
-  Nan::SetAccessor(proto, Nan::New("miterLimit").ToLocalChecked(), GetMiterLimit, SetMiterLimit);
-  Nan::SetAccessor(proto, Nan::New("lineWidth").ToLocalChecked(), GetLineWidth, SetLineWidth);
-  Nan::SetAccessor(proto, Nan::New("lineCap").ToLocalChecked(), GetLineCap, SetLineCap);
-  Nan::SetAccessor(proto, Nan::New("lineJoin").ToLocalChecked(), GetLineJoin, SetLineJoin);
-  Nan::SetAccessor(proto, Nan::New("lineDashOffset").ToLocalChecked(), GetLineDashOffset, SetLineDashOffset);
-  Nan::SetAccessor(proto, Nan::New("shadowOffsetX").ToLocalChecked(), GetShadowOffsetX, SetShadowOffsetX);
-  Nan::SetAccessor(proto, Nan::New("shadowOffsetY").ToLocalChecked(), GetShadowOffsetY, SetShadowOffsetY);
-  Nan::SetAccessor(proto, Nan::New("shadowBlur").ToLocalChecked(), GetShadowBlur, SetShadowBlur);
-  Nan::SetAccessor(proto, Nan::New("antialias").ToLocalChecked(), GetAntiAlias, SetAntiAlias);
-  Nan::SetAccessor(proto, Nan::New("textDrawingMode").ToLocalChecked(), GetTextDrawingMode, SetTextDrawingMode);
-  Nan::SetAccessor(proto, Nan::New("filter").ToLocalChecked(), GetFilter, SetFilter);
+  SetProtoAccessor(proto, Nan::New("pixelFormat").ToLocalChecked(), GetFormat, NULL, ctor);
+  SetProtoAccessor(proto, Nan::New("patternQuality").ToLocalChecked(), GetPatternQuality, SetPatternQuality, ctor);
+  SetProtoAccessor(proto, Nan::New("globalCompositeOperation").ToLocalChecked(), GetGlobalCompositeOperation, SetGlobalCompositeOperation, ctor);
+  SetProtoAccessor(proto, Nan::New("globalAlpha").ToLocalChecked(), GetGlobalAlpha, SetGlobalAlpha, ctor);
+  SetProtoAccessor(proto, Nan::New("shadowColor").ToLocalChecked(), GetShadowColor, SetShadowColor, ctor);
+  SetProtoAccessor(proto, Nan::New("fillColor").ToLocalChecked(), GetFillColor, NULL, ctor);
+  SetProtoAccessor(proto, Nan::New("strokeColor").ToLocalChecked(), GetStrokeColor, NULL, ctor);
+  SetProtoAccessor(proto, Nan::New("miterLimit").ToLocalChecked(), GetMiterLimit, SetMiterLimit, ctor);
+  SetProtoAccessor(proto, Nan::New("lineWidth").ToLocalChecked(), GetLineWidth, SetLineWidth, ctor);
+  SetProtoAccessor(proto, Nan::New("lineCap").ToLocalChecked(), GetLineCap, SetLineCap, ctor);
+  SetProtoAccessor(proto, Nan::New("lineJoin").ToLocalChecked(), GetLineJoin, SetLineJoin, ctor);
+  SetProtoAccessor(proto, Nan::New("lineDashOffset").ToLocalChecked(), GetLineDashOffset, SetLineDashOffset, ctor);
+  SetProtoAccessor(proto, Nan::New("shadowOffsetX").ToLocalChecked(), GetShadowOffsetX, SetShadowOffsetX, ctor);
+  SetProtoAccessor(proto, Nan::New("shadowOffsetY").ToLocalChecked(), GetShadowOffsetY, SetShadowOffsetY, ctor);
+  SetProtoAccessor(proto, Nan::New("shadowBlur").ToLocalChecked(), GetShadowBlur, SetShadowBlur, ctor);
+  SetProtoAccessor(proto, Nan::New("antialias").ToLocalChecked(), GetAntiAlias, SetAntiAlias, ctor);
+  SetProtoAccessor(proto, Nan::New("textDrawingMode").ToLocalChecked(), GetTextDrawingMode, SetTextDrawingMode, ctor);
+  SetProtoAccessor(proto, Nan::New("filter").ToLocalChecked(), GetFilter, SetFilter, ctor);
   Nan::Set(target, Nan::New("CanvasRenderingContext2d").ToLocalChecked(), ctor->GetFunction());
 }
 

src/Image.cc

@@ -4,6 +4,7 @@
 // Copyright (c) 2010 LearnBoost <[email protected]>
 //
 
+#include "Util.h"
 #include "Canvas.h"
 #include "Image.h"
 #include <stdlib.h>
@@ -45,16 +46,16 @@ Image::Initialize(Nan::ADDON_REGISTER_FUNCTION_ARGS_TYPE target) {
 
   // Prototype
   Local<ObjectTemplate> proto = ctor->PrototypeTemplate();
-  Nan::SetAccessor(proto, Nan::New("source").ToLocalChecked(), GetSource, SetSource);
-  Nan::SetAccessor(proto, Nan::New("complete").ToLocalChecked(), GetComplete);
-  Nan::SetAccessor(proto, Nan::New("width").ToLocalChecked(), GetWidth, SetWidth);
-  Nan::SetAccessor(proto, Nan::New("height").ToLocalChecked(), GetHeight, SetHeight);
-  Nan::SetAccessor(proto, Nan::New("naturalWidth").ToLocalChecked(), GetNaturalWidth);
-  Nan::SetAccessor(proto, Nan::New("naturalHeight").ToLocalChecked(), GetNaturalHeight);
-  Nan::SetAccessor(proto, Nan::New("onload").ToLocalChecked(), GetOnload, SetOnload);
-  Nan::SetAccessor(proto, Nan::New("onerror").ToLocalChecked(), GetOnerror, SetOnerror);
+  SetProtoAccessor(proto, Nan::New("source").ToLocalChecked(), GetSource, SetSource, ctor);
+  SetProtoAccessor(proto, Nan::New("complete").ToLocalChecked(), GetComplete, NULL, ctor);
+  SetProtoAccessor(proto, Nan::New("width").ToLocalChecked(), GetWidth, NULL, ctor);
+  SetProtoAccessor(proto, Nan::New("height").ToLocalChecked(), GetHeight, NULL, ctor);
+  SetProtoAccessor(proto, Nan::New("naturalWidth").ToLocalChecked(), GetNaturalWidth, NULL, ctor);
+  SetProtoAccessor(proto, Nan::New("naturalHeight").ToLocalChecked(), GetNaturalHeight, NULL, ctor);
+  SetProtoAccessor(proto, Nan::New("onload").ToLocalChecked(), GetOnload, SetOnload, ctor);
+  SetProtoAccessor(proto, Nan::New("onerror").ToLocalChecked(), GetOnerror, SetOnerror, ctor);
 #if CAIRO_VERSION_MINOR >= 10
-  Nan::SetAccessor(proto, Nan::New("dataMode").ToLocalChecked(), GetDataMode, SetDataMode);
+  SetProtoAccessor(proto, Nan::New("dataMode").ToLocalChecked(), GetDataMode, SetDataMode, ctor);
   ctor->Set(Nan::New("MODE_IMAGE").ToLocalChecked(), Nan::New<Number>(DATA_IMAGE));
   ctor->Set(Nan::New("MODE_MIME").ToLocalChecked(), Nan::New<Number>(DATA_MIME));
 #endif

src/ImageData.cc

@@ -5,6 +5,7 @@
 // Copyright (c) 2010 LearnBoost <[email protected]>
 //
 
+#include "Util.h"
 #include "ImageData.h"
 
 Nan::Persistent<FunctionTemplate> ImageData::constructor;
@@ -25,8 +26,8 @@ ImageData::Initialize(Nan::ADDON_REGISTER_FUNCTION_ARGS_TYPE target) {
 
   // Prototype
   Local<ObjectTemplate> proto = ctor->PrototypeTemplate();
-  Nan::SetAccessor(proto, Nan::New("width").ToLocalChecked(), GetWidth);
-  Nan::SetAccessor(proto, Nan::New("height").ToLocalChecked(), GetHeight);
+  SetProtoAccessor(proto, Nan::New("width").ToLocalChecked(), GetWidth, NULL, ctor);
+  SetProtoAccessor(proto, Nan::New("height").ToLocalChecked(), GetHeight, NULL, ctor);
   Nan::Set(target, Nan::New("ImageData").ToLocalChecked(), ctor->GetFunction());
 }
 

src/Util.h

@@ -0,0 +1,25 @@
+#include <v8.h>
+#include <nan.h>
+
+// Wrapper around Nan::SetAccessor that makes it easier to change the last
+// argument (signature). Getters/setters must be accessed only when there is
+// actually an instance, i.e. MyClass.prototype.getter1 should not try to
+// unwrap the non-existent 'this'. See #803, #847, #885, nodejs/node#15099, ...
+inline void SetProtoAccessor(
+	v8::Local<v8::ObjectTemplate> tpl,
+	v8::Local<v8::String> name,
+	Nan::GetterCallback getter,
+	Nan::SetterCallback setter,
+	v8::Local<v8::FunctionTemplate> ctor
+	) {
+	Nan::SetAccessor(
+		tpl,
+		name,
+		getter,
+		setter,
+		v8::Local<v8::Value>(),
+		v8::DEFAULT,
+		v8::None,
+		v8::AccessorSignature::New(v8::Isolate::GetCurrent(), ctor)
+	);
+}

test/canvas.test.js

@@ -17,6 +17,15 @@ const os = require('os')
 const Readable = require('stream').Readable
 
 describe('Canvas', function () {
+  it('Prototype and ctor are well-shaped, don\'t hit asserts on accessors (GH-803)', function () {
+    const Canvas = require('../').Canvas;
+    var c = new Canvas(10, 10);
+    assert.throws(function () { Canvas.prototype.width; }, /incompatible receiver/);
+    assert(!c.hasOwnProperty('width'));
+    assert('width' in c);
+    assert(Canvas.prototype.hasOwnProperty('width'));
+  });
+
   it('.parseFont()', function () {
     var tests = [
         '20px Arial'

test/image.test.js

@@ -7,6 +7,7 @@
  */
 
 const loadImage = require('../').loadImage
+const Image = require('../').Image;
 
 const assert = require('assert')
 const assertRejects = require('assert-rejects')
@@ -16,6 +17,14 @@ const png_clock = `${__dirname}/fixtures/clock.png`
 const jpg_face = `${__dirname}/fixtures/face.jpeg`
 
 describe('Image', function () {
+  it('Prototype and ctor are well-shaped, don\'t hit asserts on accessors (GH-803)', function () {
+    var img = new Image();
+    assert.throws(function () { Image.prototype.width; }, /incompatible receiver/);
+    assert(!img.hasOwnProperty('width'));
+    assert('width' in img);
+    assert(Image.prototype.hasOwnProperty('width'));
+  });
+
   it('loads JPEG image', function () {
     return loadImage(jpg_face).then((img) => {
       assert.strictEqual(img.onerror, null)

test/imageData.test.js

@@ -3,10 +3,15 @@
 'use strict'
 
 const createImageData = require('../').createImageData
+const ImageData = require('../').ImageData;
 
 const assert = require('assert')
 
 describe('ImageData', function () {
+  it('Prototype and ctor are well-shaped, don\'t hit asserts on accessors (GH-803)', function () {
+    assert.throws(function () { ImageData.prototype.width; }, /incompatible receiver/);
+  });
+
   it('should throw with invalid numeric arguments', function () {
     assert.throws(() => { createImageData(0, 0) }, /width is zero/)
     assert.throws(() => { createImageData(1, 0) }, /height is zero/)