smartcontext/readme.md

# @push.rocks/smartcontext

A module to enrich logs with context, featuring async log contexts and scope management.

Special thanks to Ilias Bhallil for his awesome simple-async-context library.

## Install

Make sure you have Node.js and npm installed, then run:

```bash
npm install @push.rocks/smartcontext
```

This will install the library and its dependencies into your local `node_modules` folder.

## Usage

The `@push.rocks/smartcontext` module provides an efficient way to enrich your code (often for logging) with contextual information. It uses asynchronous context management to support hierarchical scopes—particularly helpful in complex or nested asynchronous operations in Node.js.

### Basic Setup

```typescript
import { AsyncContext } from '@push.rocks/smartcontext';

const asyncContext = new AsyncContext();

// The parent store is always accessible through `asyncContext.store`
asyncContext.store.add('username', 'john_doe');
console.log(asyncContext.store.get('username')); // 'john_doe'
```


### `runScoped`

When you call `asyncContext.runScoped(async () => { ... })`, the library automatically creates a **child** `AsyncStore`. Inside that scoped function, `asyncContext.store` refers to the child store. Any data you add or delete there is isolated from the parent store. However, you can still read parent data if it hasn’t been overridden.

```typescript
await asyncContext.runScoped(async () => {
  // Inside this callback, `asyncContext.store` is a *child* store
  asyncContext.store.add('transactionId', 'txn_abc123');
  console.log(asyncContext.store.get('transactionId')); // 'txn_abc123'

  // We can also see parent data like 'username'
  console.log(asyncContext.store.get('username'));       // 'john_doe'
});

// Outside `runScoped`, asyncContext.store reverts to the parent store
console.log(asyncContext.store.get('transactionId'));    // undefined
```


### Isolating Data

Because each call to `runScoped` returns control to the parent store afterward, any keys added in a child scope disappear once the scope completes (unless you explicitly move them to the parent). This mechanism keeps data from leaking between scopes.

```typescript
// Parent store
asyncContext.store.add('someParentKey', 'parentValue');

// Child scope
await asyncContext.runScoped(async () => {
  asyncContext.store.add('scopedKey', 'childValue');
  console.log(asyncContext.store.get('scopedKey'));    // 'childValue'
});

// Outside, the child key is gone
console.log(asyncContext.store.get('scopedKey'));      // undefined
```


### Deleting Data

If the child deletes a key that exists in the parent, it will only remove it from the child’s view of the store. Once the scope completes, the parent store is unaffected.

```typescript
asyncContext.store.add('deletableKey', 'originalValue');

await asyncContext.runScoped(async () => {
  console.log(asyncContext.store.get('deletableKey')); // 'originalValue'
  asyncContext.store.delete('deletableKey');
  console.log(asyncContext.store.get('deletableKey')); // undefined in child
});

console.log(asyncContext.store.get('deletableKey'));   // 'originalValue' remains in parent
```


### Parallel or Sequential Scopes

You can call `runScoped` multiple times, whether sequentially or in parallel (with `Promise.all`). Each invocation creates its own isolated child store, preventing data collisions across asynchronous tasks.

```typescript
await asyncContext.runScoped(async () => {
  asyncContext.store.add('childKey1', 'childValue1');
  console.log(asyncContext.store.get('childKey1')); // 'childValue1'
});

await asyncContext.runScoped(async () => {
  asyncContext.store.add('childKey2', 'childValue2');
  console.log(asyncContext.store.get('childKey2')); // 'childValue2'
});

// Both keys were added in separate scopes, so they won't exist in the parent
console.log(asyncContext.store.get('childKey1'));   // undefined
console.log(asyncContext.store.get('childKey2'));   // undefined
```


### Testing Example

The following is a complete test script (using [tapbundle](https://www.npmjs.com/package/@push.rocks/tapbundle)) demonstrating how child stores inherit data from the parent but remain isolated. After each scoped block, new child keys vanish, and any parent keys deleted inside the child remain intact in the parent.

```typescript
import { tap, expect } from '@push.rocks/tapbundle';
import { AsyncContext } from '../ts/logcontext.classes.asynccontext.js';

const asyncContext = new AsyncContext();

tap.test('should run a scoped function and add data to a child store', async () => {
  // Add some default data to the parent store
  asyncContext.store.add('parentKey', 'parentValue');
  expect(asyncContext.store.get('parentKey')).toEqual('parentValue');

  // Now run a child scope, add some data, and check that parent data is still accessible
  await asyncContext.runScoped(async () => {
    asyncContext.store.add('childKey', 'childValue');

    // Child sees its own data
    expect(asyncContext.store.get('childKey')).toEqual('childValue');
    // Child also sees parent data
    expect(asyncContext.store.get('parentKey')).toEqual('parentValue');
  });
});

tap.test('should not contaminate the parent store with child-only data', async () => {
  // Create a new child scope
  await asyncContext.runScoped(async () => {
    asyncContext.store.add('temporaryKey', 'temporaryValue');
    expect(asyncContext.store.get('temporaryKey')).toEqual('temporaryValue');
  });
  // After scope finishes, 'temporaryKey' won't exist in the parent
  expect(asyncContext.store.get('temporaryKey')).toBeUndefined();
});

tap.test('should allow adding data in multiple scopes independently', async () => {
  // Add data in the first scope
  await asyncContext.runScoped(async () => {
    asyncContext.store.add('childKey1', 'childValue1');
    expect(asyncContext.store.get('childKey1')).toEqual('childValue1');
  });

  // Add data in the second scope
  await asyncContext.runScoped(async () => {
    asyncContext.store.add('childKey2', 'childValue2');
    expect(asyncContext.store.get('childKey2')).toEqual('childValue2');
  });

  // Neither childKey1 nor childKey2 should exist in the parent store
  expect(asyncContext.store.get('childKey1')).toBeUndefined();
  expect(asyncContext.store.get('childKey2')).toBeUndefined();
});

tap.test('should allow deleting data in a child store without removing it from the parent store', async () => {
  // Ensure parent has some data
  asyncContext.store.add('deletableKey', 'iShouldStayInParent');

  await asyncContext.runScoped(async () => {
    // Child sees the parent's data
    expect(asyncContext.store.get('deletableKey')).toEqual('iShouldStayInParent');
    // Delete it in the child
    asyncContext.store.delete('deletableKey');
    // Child no longer sees it
    expect(asyncContext.store.get('deletableKey')).toBeUndefined();
  });
  // Parent still has it
  expect(asyncContext.store.get('deletableKey')).toEqual('iShouldStayInParent');
});

tap.test('should allow multiple child scopes to share the same parent store data', async () => {
  // Add a key to the parent store
  asyncContext.store.add('sharedKey', 'sharedValue');
  expect(asyncContext.store.get('sharedKey')).toEqual('sharedValue');

  // First child scope
  await asyncContext.runScoped(async () => {
    expect(asyncContext.store.get('sharedKey')).toEqual('sharedValue');
  });

  // Second child scope
  await asyncContext.runScoped(async () => {
    expect(asyncContext.store.get('sharedKey')).toEqual('sharedValue');
  });
});

export default tap.start();
```


With this updated `runScoped` design, there’s no need to explicitly instantiate or manage child stores. The context automatically switches from the parent store to the child store while within the callback, then reverts back to the parent store afterwards. This structure makes it easy to:

- Keep each async operation’s state isolated
- Preserve read-access to parent context data
- Avoid overwriting or polluting other operations’ data

This pattern works particularly well for logging or any scenario where you need to pass metadata through deeply nested async calls without manually juggling that data everywhere in your code.

## License and Legal Information

This repository is under the [MIT License](./license). Please note that the MIT License does not grant permission to use the trade names, trademarks, service marks, or product names of the project, except as necessary for reasonable use in describing the origin of the work.

### Trademarks

This project is owned and maintained by Task Venture Capital GmbH. The names and logos associated with Task Venture Capital GmbH are trademarks of Task Venture Capital GmbH and are not included within the scope of the MIT license granted herein. Usage must be approved in writing by Task Venture Capital GmbH.

### Company Information

Task Venture Capital GmbH  
Registered at District Court Bremen HRB 35230 HB, Germany  

For any legal inquiries, please contact us at hello@task.vc. By using this repository, you acknowledge that you have read this section and agree to comply with its terms.