# core/lifecycle/invocation.lifecycle.ts

> 62 lines of code and 13 definitions.

Tree: GovLab Quality
Language: typescript
Layer: runtime
Canonical: https://banes-lab.com/anatomy/quality#file-quality-core-lifecycle-invocation-lifecycle-ts
Source text: https://banes-lab.com/source/quality/core/lifecycle/invocation.lifecycle.ts.txt

Listed in [core/lifecycle](https://banes-lab.com/api/source/quality/core/lifecycle.md).

## Definitions

- `reapSupervised` (lexical_declaration, line 37, exported)
- `stillRunning` (lexical_declaration, line 12)
- `killTree` (lexical_declaration, line 16, exported)
- `hookParentExit` (lexical_declaration, line 46)
- `superviseChild` (lexical_declaration, line 62, exported)
- `WINDOWS` (lexical_declaration, line 5)
- `SIGNAL_EXIT_BASE` (lexical_declaration, line 6)
- `TERMINAL_SIGNALS` (lexical_declaration, line 7)
- `live` (lexical_declaration, line 9)
- `hook` (lexical_declaration, line 10)
- `supervisedCount` (lexical_declaration, line 33, exported)
- `reaped` (lexical_declaration, line 38, exported)
- `release` (lexical_declaration, line 65, exported)

## Contained in

- [core/lifecycle](https://banes-lab.com/anatomy/quality/folder-quality-core-lifecycle.md)

## Used by

- [core/adapters/tool.prettier.adapter.ts](https://banes-lab.com/source/quality/core/adapters/tool.prettier.adapter.ts.md)

## Linked from

- [core/adapters](https://banes-lab.com/anatomy/quality/folder-quality-core-adapters.md)
- [core/lifecycle](https://banes-lab.com/anatomy/quality/folder-quality-core-lifecycle.md)

## Source

```typescript
import type { ChildProcess } from "node:child_process";
import { execFileSync } from "node:child_process";
import process from "node:process";

const WINDOWS = "win32";
const SIGNAL_EXIT_BASE = 128;
const TERMINAL_SIGNALS: Readonly<Record<string, number>> = { SIGHUP: 1, SIGINT: 2, SIGTERM: 15 };

const live = new Set<ChildProcess>();
const hook = { installed: false };

const stillRunning = function stillRunning(child: ChildProcess): boolean {
    return child.pid !== undefined && child.exitCode === null && child.signalCode === null;
};

export const killTree = function killTree(child: ChildProcess): void {
    if (!stillRunning(child)) {
        return;
    }
    if (process.platform !== WINDOWS) {
        child.kill("SIGKILL");
        return;
    }
    try {
        execFileSync("taskkill", ["/PID", String(child.pid), "/T", "/F"], { stdio: "ignore" });
    } catch (error) {
        if (!child.kill("SIGKILL") && stillRunning(child)) {
            throw error;
        }
    }
};

export const supervisedCount = function supervisedCount(): number {
    return live.size;
};

export const reapSupervised = function reapSupervised(): number {
    const reaped = [...live].filter(stillRunning).length;
    for (const child of live) {
        killTree(child);
    }
    live.clear();
    return reaped;
};

const hookParentExit = function hookParentExit(): void {
    if (hook.installed) {
        return;
    }
    hook.installed = true;
    process.on("exit", () => {
        reapSupervised();
    });
    for (const [signal, number] of Object.entries(TERMINAL_SIGNALS)) {
        process.once(signal, () => {
            reapSupervised();
            process.exit(SIGNAL_EXIT_BASE + number);
        });
    }
};

export const superviseChild = function superviseChild(child: ChildProcess): void {
    hookParentExit();
    live.add(child);
    const release = (): void => {
        live.delete(child);
    };
    child.on("close", release);
    child.on("error", release);
};
```