Use spawn instead of exec

[srele96]

Read information from: https://github.com/srele96/run-them-all/issues/6!

NodeJS spawn is better for long running processes. It also provides options.detached which (per my understanding) allows us to:

• Terminate run-them-all process without waiting for spawned command.
• Spawned command has control over itself, for example spawning new command prompt.
• When does process with options.detached close?
• Can the process with options.detached create memory leak?

Things to add:

2. Align requires
3. Add cross-spawn 3.1 Update package.json 3.2 Update package-lock.json
4. Use cross-spawn
5. Add loggers for spawned command

[srele96]

Notes:

1. CLI can't exit if command runs long running process (for example: nodemon express server).
2. Using options.stdio = 'inherit' will print the stuff from the executed command in current terminal.

Point 1 is solvable with https://nodejs.org/api/child_process.html#optionsdetached. That opens questions:

• Should all commands be detached processes?
  • Possibly only processes like webpack watch or nodemon make sense to be detached.
  • We don't have a way to know what is the user going to run.
• Should we channel command output to the current terminal?
  • Yes.
  • How do we do that?
  • No.
  • We need to show user some feedback. How do we do that?
• We need a way to kill detached process.
  • We can spawn a window parent of the process. User can kill detached process by closing the window.
  • We can save detached processes and provide kill options.

[srele96]

Long running detached processes get spawned in new OS native terminal.

Run detached process like here https://nodejs.org/api/child_process.html#optionsdetached

const { openSync } = /* */ require('fs');
const { spawn } = /*    */ require('child_process');
const out = openSync('./out.log', 'a');
const err = openSync('./err.log', 'a');

// watch express server using nodemon
const subprocess = spawn('yarn start:serve-data', {
  cwd: 'C:\\Users\\Srecko\\Documents\\MyProjects\\Private\\webstorm-container\\sk-experiments\\tcp-packages',
  detached: true,
  shell: true,
  stdio: ['ignore', out, err],
});

subprocess.unref();

[srele96]

Detached process should behave exactly the same as any terminal.

We can't use ignore for stdin like stdio: ['ignore', out, err]. CTRL+C does not terminate it.

Is it a problem if new detached process runs as NodeJS? (It has the NodeJS icon).

[srele96]

So far i know about the two types of processes.

A process like nodemon app.js. Such process watches file changes and shows command line output.

Another type is echo hello or mkdir test. Those exit immediately, but may have command line output like echo.

I believe we shouldn't treat them differently. Both are the same, but one exits faster.

That means we need to handle processes that are:

• Running
• Exited

Running process interfere with our cli. The cli is a parent process. Parent process waits for child processes to exit.

We currently can't handle user interaction while the child processes are running.

While child processes are running, so is cli. Terefore we need to treat that case accordingly.

Whenever we run commands, we should expect their process to be long running. Actually, we shouldn't even think how long they run. All of them behave the same, whether it's a millisecond, second, minute or more.

Therefore, we should behave as process-watcher.

The cli is in two states:

• Running
• Not running

The watched processes are:

• Running
• Not running

User should be able to use the cli in both states.

[srele96]

Learn how does spawn run command on any OS.

That may provide a way to run command in new shell on any OS.