log-method-decorator

log-method-decorator

Easily log method calls in Typescript without boilerplate

Logging all method calls can add a lot of boilerplate inside your methods. This clutters your actual code and reduces code readability. Here comes log-method-decorator! By leveraging the experimental feature of typescript decorators, we can log all function calls and their execution time with a reusable one-liner :)

Install

npm install --save log-method-decorator

Usage

class Logger {
    log(message: string): void {
        console.log(message);
    }
}

interface Metadata {}

const logOptions: LogOptions<Logger, Metadata> = {
    onMethodStart: ((logger, method) => {
        logger.log(`[${method.className}.${method.methodName}] was invoked`);
    }),
    onMethodEnd: ((logger, method, executionTimeResult) => {
        logger.log(`[${method.className}.${method.methodName}] completed in ${executionTimeResult.executionTimeMs}ms`);
    }),
}

@LogClass<Logger, Metadata>(MyClass.name, logOptions)
class MyClass {
    constructor(public readonly logger: Logger) {}

    @LogSyncMethod<Metadata>({})
    public myMethod(): void {
        // Do something
    }

    @LogAsyncMethod<Metadata>({})
    public async myNetworkCall(): Promise<void> {
        // Do something
    }
}

const myClass = new MyClass(new Logger());
myClass.myMethod();
await myClass.myNetworkCall();
// Prints:
// [MyClass.myMethod] was invoked
// [MyClass.myMethod] completed in 0ms
// [MyClass.myNetworkCall] was invoked
// [MyClass.myNetworkCall] completed in 1ms

Add method metadata

It is possible to add metadata on each method that is then available on the log callbacks.

interface Metadata {
    normalExecutionTimeMs: number;
}

const logOptions: LogOptions<Logger, Metadata> = {
    onMethodStart: ((logger, method) => {
        // method.metadata.normalExecutionTimeMs
    }),
    ...
}

@LogClass<Logger, Metadata>(MyClass.name, logOptions)
class MyClass {
    constructor(public readonly logger: Logger) {}

    @LogSyncMethod<Metadata>({ normalExecutionTimeMs: 100 })
    public myMethod(): void {}

    @LogAsyncMethod<Metadata>({ normalExecutionTimeMs: 80 })
    public async myNetworkCall(): Promise<void> {}
}

Note: You are responsible to make sure that the Metadata typing is compatible between the class decorator and the method decorator. This package does not yet support this.

FAQ

How do I log all method calls?

Easy! Add the decorators on all the methods that you want to be logged :)

Why do we actually need the class decorator? Isn't the method decorator enough?

We need the class decorator in order to have the class name available and to be able to type check the logger instance. Simple method decorators don't have access to the class scope. log-method-decorator uses a logger from the class scope, rather than having to create a new logger.

This package doesn't quite fit my needs...

Please open a discussion, an issue or a pull request where we can discuss your use case. Please keep in mind that this package will never be able to answer all the use cases. Feel free to star the repo :star: and copy the library code and adapt it to your needs.

For more details

For more details on how to integrate log-method-decorator in your application, have a look at the example folder.

Contibuting

• Star this GitHub repo :star: (it really helps)
• Create pull requests, submit bugs, suggest new features or documentation updates :wrench:. See contributing doc.

License

MIT © Gabriel Bourgault