Cannot read property 'name' of undefined testing serialize

[AMagistroni]

When I try to test a component that use serialize, I found this error

Cannot read property 'name' of undefined

Using the application it's work.
I use Jest, here the test(simplified, without component)

@Serializable()
export class ClassToTest {
  @JsonProperty() num: number;

  constructor() {}
}

describe('test', () => {

  it('test serialization', () => {
    debugger;
    const obj = new ClassToTest ();
    obj.num= 100;
    const serialized = serialize(obj); // here the error
    const deserialized = deserialize<ClassToTest >(serialized, ClassToTest );
    expect(deserialized .num).toBe(100);
  });

the tsconfig.json

{
  "compilerOptions": {
    "outDir": "../out-tsc/spec",
    "types": [
      "jest",
      "node"
    ],
    "module": "commonjs",
    "experimentalDecorators": true,
    "emitDecoratorMetadata": true,
    "allowJs": true,
    "resolveJsonModule": true,
    "esModuleInterop": true,
    "target": "es5"
  },
  "files": [
    "polyfills.ts"
  ],
  "include": [
    "**/*.spec.ts",
    "**/*.d.ts"
  ]
}

[GillianPerard]

Hi, let me check.

[GillianPerard]

I tested with a little sample and your tsconfig.json and your code and with this package.json and jest.config.js it works properly.

Could you test with the following packages/file please 😊

package.json

{
  "name": "test",
  "version": "1.0.0",
  "main": "index.js",
  "license": "MIT",
  "scripts": {
    "test": "jest"
  },
  "dependencies": {
    "@types/jest": "^26.0.14",
    "@types/node": "^14.11.2",
    "jest": "^26.4.2",
    "jest-junit": "^11.1.0",
    "ts-jest": "^26.4.0",
    "ts-node": "^9.0.0",
    "typescript": "^4.0.3",
    "typescript-json-serializer": "^2.4.0"
  }
}

jest.config.js

module.exports = {
  coverageReporters: ["text", "lcov"],
  reporters: ["default", "jest-junit"],
  roots: ["spec"],
  transform: {
    "^.+\\.tsx?$": "ts-jest",
  },
};

PS: my test file is in a spec folder and call index.spec.ts.

[AMagistroni]

SerializeTest.zip
I've tried but with the same result, so I've created another sample project, and the error is the same.
The code is uploaded. Have you the same result with the code uploaded?

[GillianPerard]

Ok, I'll test soon.

[GillianPerard]

Hi, sorry to be late. I tested your code and it seems that ReflectMetadata package I used in my lib is not able to find the type/prototype of any value 😕

I think is due to the project technology, I can't do anything for you...

[bakatrouble]

Got the same issue with create-react-app project

Solved it using following .babelrc (overrided default settings using @jackwilsdon/craco-use-babelrc):

{
  "presets": ["react-app"],
  "plugins": [
    "babel-plugin-transform-typescript-metadata",
    ["@babel/plugin-proposal-decorators", { "legacy": true }],
    ["@babel/plugin-proposal-class-properties", { "loose": true }]
  ]
}

Setting in tsconfig.json:

"emitDecoratorMetadata": true,
    "experimentalDecorators": true,

And adding import "reflect-metadata"; line at the top of index.tsx

rbuckton/reflect-metadata#104

tl;dr: altering babel settings using 3rdparty plugin is required, by default it does not persist metadata.

[AMagistroni]

I've solved the problem inserting in the package.json this

"jest": {
    "setupFilesAfterEnv": [
      "<rootDir>/src/setup-jest.ts"
    ],    
  }

I think that also setupFiles work

and
import 'reflect-metadata';

at the top of setup-jest.ts

Thank you @bakatrouble for your suggestion

[GillianPerard]

It's great that you can continue to use my lib!