"undefined" passed for the "context.metadata" field in a decorator metadata

[mushketyk]

🔎 Search Terms

"decorator metadata" in both closed and opened issues.

🕗 Version & Regression Information

• context.metadata is undefined in a decorator function

⏯ Playground Link

No response

💻 Code

Code mostly copies the example from the TypeScript 5.2 release notes.

function setMetadata(_target: any, context: any) {
    console.log(`@setMetadata - ${context.name}`)
    context.metadata[context.name] = true;
}

class SomeClass {
    @setMetadata
    foo = 123;

    @setMetadata
    accessor bar = "hello!";

    @setMetadata
    baz() { }
}

const ourMetadata = SomeClass[Symbol.metadata];

console.log(JSON.stringify(ourMetadata));

🙁 Actual behavior

Script fails when trying to set a value on the context.metadata field.

@setMetadata - bar
/Users/ivanmushketyk/Development/courses-creation/pluralsight-typescript-decorators/metadata.js:48
    context.metadata[context.name] = true;
                                   ^

TypeError: Cannot set properties of undefined (setting 'bar')
    at setMetadata (/Users/ivanmushketyk/Development/courses-creation/pluralsight-typescript-decorators/metadata.js:48:36)
    at __esDecorate (/Users/ivanmushketyk/Development/courses-creation/pluralsight-typescript-decorators/metadata.js:12:40)
    at /Users/ivanmushketyk/Development/courses-creation/pluralsight-typescript-decorators/metadata.js:78:13
    at /Users/ivanmushketyk/Development/courses-creation/pluralsight-typescript-decorators/metadata.js:82:11
    at Object.<anonymous> (/Users/ivanmushketyk/Development/courses-creation/pluralsight-typescript-decorators/metadata.js:84:2)

🙂 Expected behavior

It should not fail, and metadata should be displayed using the console.log statement

Additional information about the issue

Compiler version:

tsc --version
Version 5.2.1-rc

[a-tarasyuk]

Are you utilizing a polyfill to define Symbol.metadata?

Because this feature is still fresh, most runtimes will not support it natively. To use it, you will need a polyfill for Symbol.metadata.

[mushketyk]

@a-tarasyuk Good catch! Thank you!