JS backend ignores first command line argument

[marzipankaiser]

The runnables created for the JS backend always ignore the first command line argument.

Minimal Example

When compiling and running

import immutable/list
import immutable/option
import io/args
import text/string

def main() = println(commandLineArgs())

with the js backend:

effekt --compile printCliArgs.effekt
out/printCliArgs 1 2 3

we get:

Cons(2, Cons(3, Nil()))

Which ignores the 1.

Note: I thought we had an issue for that already, but could not find it. If you do, feel free to link and close.

[marzipankaiser]

effekt/libraries/js/io/args.effekt

Line 7 in 2e865ae

extern io def nativeArgs(): Array[String] = "process.argv.slice(2)"

This should be a 1 probably?

[b-studios]

Hmmm maybe this is a copy and paste error from a different backend? I believe Chez had two leading args that you needed to discard.

Excerpt from:
https://nodejs.org/docs/latest/api/process.html#processargv

The process.execArgv property returns the set of Node.js-specific command-line options passed when the Node.js process was launched. These options do not appear in the array returned by the process.argv property, and do not include the Node.js executable, the
name of the script, or any options following the script name. These options are useful in order to spawn child processes with the same execution environment as the parent.

node --harmony script.js --version COPY

Results in process.execArgv:

['--harmony'] COPY

And process.argv:

['/usr/local/bin/node', 'script.js', '--version']

Also the docs on argv say:

Launching the Node.js process as:

node process-args.js one two=three four COPY

Would generate the output:

0: /usr/local/bin/node
1: /Users/mjr/work/node/process-args.js
2: one
3: two=three
4: four 

Also

["/usr/local/bin/node", "/Users/mjr/work/node/process-args.js", "one", "two=three","four"].slice(2)

evaluates to

['one', 'two=three', 'four']

which is what we would expect.

[b-studios]

This seems related to us typically using --eval (nodejs/node#9017) and @dvdvgt wrapper not using eval. In both cases, however, at least the first argument is dropped.

node --eval "console.log(process.argv)" -- 1 2 3
[ '/usr/local/bin/node', '1', '2', '3' ]

whereas

Contents of out/clibug

#!/usr/bin/env node
console.log(process.argv)

and

> ./out/clibug 1 2 3
[
  '/usr/local/bin/node',
  '/Users/jonathan/Desktop/github/effekt/out/clibug',
  '1',
  '2',
  '3'
]

[marzipankaiser]

The other part of the problem seems to be #319.

[b-studios]

I propose the following fix:

1. fix JS backend: Array.toList drops first element #319
2. change code generation of JS apps to not generate module.exports = { main: main_1202 }, but instead main_1202() as the last statement.
3. never use --eval again, but replace with node out/clibug.js

[b-studios]

There might be a tiny problem that the website could potentially rely on the exports, we have to double check that. We really need more automated tests for LSP and the website.

[b-studios]

Another related problem is that we use an absolute path here:

effekt/effekt/jvm/src/main/scala/effekt/Runner.scala

Line 108 in e68b8b3

val out = C.config.outputPath().getAbsolutePath

Moving the js file and the "binary" will not work (/cc @dvdvgt)