Prebuilt package throws "TypeError: Cannot read property 'call' of undefined"

[jamescryer]

Issue or Feature

I guess this is an issue with the pre-built fallback packages for certain environments. Also worth being aware that in my more complex application (not shown) I saw intermittent success of tests and functionality.

      TypeError: Cannot read property 'call' of undefined
          at setSource (node_modules/canvas/lib/image.js:102:14)
          at Image.set (node_modules/canvas/lib/image.js:68:7)
          at expect (nodejs-tests/canvas.test.js:19:39)
          at Object.test (nodejs-tests/canvas.test.js:19:53)

Steps to Reproduce

These simple Jest tests fail on my machine.

/* eslint-env jest*/
const fs = require("fs");
const util = require("util");
const canvas = require("canvas");
const readFile = util.promisify(fs.readFile);

describe("Canvas test", () => {
    test("loadImage", async () => {
        expect.assertions(1);
        const data = await readFile("./image.png");
        await expect(canvas.loadImage(data)).rejects.not.toBeTruthy();
    });
    test("Set Image.src", async () => {
        expect.assertions(1);
        const data = await readFile("./image.png");
        const image = new canvas.Image;
        await expect( () => { image.src = data;} ).not.toThrowError();
    });
});    

Your Environment

• Version of node-canvas: 2.1.0 using prebuilt package (I haven't tried building locally)
• Environment: node v10.14.0 on Windows 10 Enterprise

[LinusU]

Could you post the entire stack trace? Thanks

[jamescryer]

@LinusU, updated, thanks!

[chearon]

Are you sure the issue is with prebuilds? I just reproduced the same stack trace, then forced a manual build and then got the same results again. It's a weird error, since setSource seems to be a function

require('canvas/lib/bindings').Image.prototype.setSource
[Function: setSource]

[zbjornson]

(This is the same error as #1294 and #1250, both unresolved.)

I can finally repro this (thanks!), and it seems to be because of Jest 😞 . The following works with mocha:

const fs = require("fs");
const util = require("util");
const canvas = require("canvas");
const readFile = util.promisify(fs.readFile);
const {expect} = require("chai");

describe("Canvas test", () => {
    it("Set Image.src", async () => {
        const data = await readFile("./image.png");
        const image = new canvas.Image;
        await expect( () => { image.src = data;} ).to.not.throw();
    });
});

I think this is because Jest breaks node's guarantee that require()'d modules are loaded exactly once and returned from cache on subsequent require() calls. With jest, lib/Image.js tries to store a reference to function that was deleted the first time the file is loaded.

(I've complained about this to the Jest folks and they won't change the behavior. It's caused problems in most public repos I've worked on though.)

As much as I don't want to pander to Jest, we can move the setSource/getSource methods off of the prototype to avoid this, I think.

---

@chearon it's defined there in the native code, but deleted here in the JS:

node-canvas/lib/image.js

Line 23 in 65ff59a

delete proto.setSource;

[LinusU]

Should be fixed in 2.2.0 🚀