Wrong signature parsing in predecl scan

[amtoine]

related to

• Add --env and --wrapped flags to def #10566

cc/ @kubouch

Describe the bug

i have a script that broke when upgrading today.
i did bisect recent commits of Nushell and found the culprit 😏

it appears #10566 changed how order of definitions matter in a script 😮

when calling a command that is defined later in the script i get a confusing missing_positional error.
the only fix i found so far was to move the command definition above the command call and then it starts working as before 👌

How to reproduce

1. save the following script as foo.nu

def main [] {
    foo
}

def foo []: nothing -> nothing { }

2. run nu foo.nu

Error: nu::parser::missing_positional

  × Missing required positional argument.
   ╭─[foo.nu:1:1]
 1 │ def main [] {
 2 │     foo
   ·        ▲
   ·        ╰── missing ]
 3 │ }
   ╰────
  help: Usage: foo <]>

3. change the signature of foo to [nothing -> nothing]
4. run nu foo.nu

Error: nu::parser::missing_positional

  × Missing required positional argument.
   ╭─[foo.nu:1:1]
 1 │ def main [] {
 2 │     foo
   ·        ▲
   ·        ╰── missing nothing
 3 │ }
   ╰────
  help: Usage: foo <nothing> <nothing>

Expected behavior

i expected one of the two following behaviours

• work as before Add --env and --wrapped flags to def #10566 without any error
• give a better error, maybe something like

Error: nu::shell::external_command

  × External command failed
   ╭─[foo.nu:1:1]
 1 │ def main [] {
 2 │     foo
   ·     ─┬─
   ·      ╰── executable was not found
 3 │ }
   ╰────
  help: No such file or directory (os error 2)

Screenshots

No response

Configuration

key	value
version	0.85.1
branch	main
commit_hash	8c507dc
build_os	linux-x86_64
build_target	x86_64-unknown-linux-gnu
rust_version	rustc 1.70.0 (90c541806 2023-05-31)
rust_channel	1.70.0-x86_64-unknown-linux-gnu
cargo_version	cargo 1.70.0 (ec8a8a0ca 2023-04-25)
build_time	2023-10-04 18:35:49 +02:00
build_rust_channel	release
allocator	mimalloc
features	default, sqlite, trash, which, zip
installed_plugins	gstat, nu_plugin_explore

Additional context

No response

[kubouch]

It seems the parsing got broken somehow, I'll need to take a look.

The ordering should be unchanged. What happens is that if there is an error during parsing in a predecl scan, the definition won't be predeclared, that's why it complains about executable not found because the command was not added. I'll need to look at it because the foo syntax seems correct.

[amtoine]

that's about what i understood yup, when you have time 😌

[amtoine]

@kubouch
i do not think this issue has been fixed by #10637 😮

with tmux-sessionizer.nu in my $env.PATH, i still get the same error 🤔

> tmux-sessionizer.nu list-sessions
Error: nu::parser::missing_positional

  × Missing required positional argument.
    ╭─[/home/amtoine/.local/share/nupm/scripts/tmux-sessionizer.nu:20:1]
 20 │
 21 │     if $session.name not-in (list-sessions | get name) {
    ·                                           ▲
    ·                                           ╰── missing nothing
 22 │         log debug $"creating session ($session.name) at ($session.path)"
    ╰────
  help: Usage: list-sessions {flags} <nothing> <table> <nothing> <table>

my nu-goat-scripts have been installed with nupm and the script is in $env.NUPM_HOME | path join "scripts" 👍

[amtoine]

and nuls gives me two diagnostics

Diagnostics:
1. Missing required positional argument.

on lines 21 and 58 of tmux-sessionizer.nu which are the two only calls to list-sessions that are above the definition of the command itself 😏

[kubouch]

Could you create a minimal example that reproduces the error? The script is quite large and I also don't use tmux on this computer, I can't test it.

[amtoine]

Could you create a minimal example that reproduces the error? The script is quite large and I also don't use tmux on this computer, I can't test it.

yes of course, my bad 😌

i brought it down to the following script 😏

#!/usr/bin/env nu
def main [] {
    foo
}

def foo []: [nothing -> table, nothing -> table] {
    []
}

which gives me

Error: nu::parser::missing_positional

  × Missing required positional argument.
   ╭─[/home/amtoine/foo.nu:2:1]
 2 │ def main [] {
 3 │     foo
   ·        ▲
   ·        ╰── missing nothing
 4 │ }
   ╰────
  help: Usage: foo {flags} <nothing> <table> <nothing> <table>

[amtoine]

looks like it's the multi signature which gives an unhelpful error 😮

#!/usr/bin/env nu
def main [] {
    foo
}

def foo []: nothing -> table {
    []
}

returns an empty list as expected 🤔

[amtoine]

even if i change the signature to something with different types, still the same error

#!/usr/bin/env nu
def main [] {
    foo
}

def foo []: [nothing -> table, string -> list] {
    []
}

[amtoine]

and for each one of these examples, putting foo before main always solves the issue 👍

[kubouch]

OK, thanks. The ordering matters in this case because before parsing def foo, foo is called whose signature is parsed by the predeclaration scan. If you put def foo to the top, it's parsed as a regular declaration which works fine.

The original error was present even before the def --env --wrapped PR btw.

[amtoine]

OK, thanks. The ordering matters in this case because before parsing def foo, foo is called whose signature is parsed by the predeclaration scan. If you put def foo to the top, it's parsed as a regular declaration which works fine.

ooh i see 👍

The original error was present even before the def --env --wrapped PR btw.

strange because i use this script each time i open a terminal every day and never had this issue 🤔
and Git bisecting Nushell gave me #10566 😮