topiary errors on optional parameter that starts with `$`

[maxim-uvarov]

Here is some minor edge case. I'm reporting this just in case you find it important.

> r#'def 'test' [$a?] {$a}'# | save optional.nu -f


> topiary format optional.nu
[2025-02-27T03:04:53Z ERROR topiary] Parsing error between line 1, column 15 and line 1, column 16

# but this works
> r#'def 'test' [a?] {$a}'# | save optional.nu -f

Please, feel free to close without resolution 🙏

[blindFS]

The problem lies in tree-sitter-nu. I'm not sure $a is recommended to use, but it seems nu-parser treated it as a.

[fdncred]

In my opinion, $ in variable assignment and custom command parameters should be removed from nushell. I'm not sure how others feel. I'm gonna ask about it.

[maxim-uvarov]

My current heavy use of those $ in variable assignments is due to the lack of a change symbol functionality in lsp, as it makes changing variable names with a simple bulk replace easier. However, even when that functionality is implemented, I believe there might be people who would benefit from the simplicity of renaming using replacements.

[blindFS]

My current heavy use of those $ in variable assignments is due to the lack of a change symbol functionality in lsp, as it makes changing variable names with a simple bulk replace easier. However, even when that functionality is implemented, I believe there might be people who would benefit from the simplicity of renaming using replacements.

You can just replace the variable name string, if it's not widely used elsewhere, right?

Oh, I get your point when it comes to short names like $a, sounds like a valid use case.

[maxim-uvarov]

Yes, @blindFS,
But it's valid not only for short names but for longer variables too.

As an inexperienced developer, I change variable names quite often, and having the dollar sign in front of all variables (in the declarations and in the code) requires fewer steps for changing them, ensuring that I won't accidentally change some command in the code itself.

For example, I have a variable:

let $sleep = 1sec

sleep $sleep

Then I find that it is a bad name, and I want to change it to $timeout.

With the $ sign, I can do it in one iteration without fearing changing the command.

I understand that mature programers might not have such problems, but for me it exists.

[blindFS]

@maxim-uvarov I kinda buying your point. I had troubles in renaming vars too, so I implemented the renaming feature in nu-lsp. My concern is that if you choose the $ string replacing way, lsp renaming probably won't work as expected anymore.

[blindFS]

@maxim-uvarov Let's wait for other core members' opinions. Personally I don't like too much ambiguity in the language syntax, makes the parser implementation nastier.

[maxim-uvarov]

well, I've just discovered that rename symbol now works in helix editor.
And this means that those leading $ are not necessary for me anymore...

[maxim-uvarov]

If rename symbol is reliable now, I also vote for dropping support for $ in declarations!

[blindFS]

If rename symbol is reliable now, I also vote for dropping support for $ in declarations!

Overlay prefix symbol won't work. Other than that, if you face any unexpected behavior, don't hesitate to open issues on the nushell repo and ping me.

[Larandar]

Sorry to unearth an old issue, but I think this is linked. The following is not recognised as a valid syntax when optional flags are an explicit feature of nushell:

def main [--yes ?] { if $yes { "yes" } else { "no" } }

[2025-11-29T14:37:26Z ERROR topiary::error]   × Parsing error between line 0, column 16 and line 0, column 17
       ╭─[\\?\C:\Users\[[redacted]]\test.nu:1:17]
     1 │ def main [--yes ?] { if $yes { "yes" } else { "no" } }
       ·                 ─┬
       ·                  ╰── (ERROR) node
       ╰────

Same for thee valid:

def main [--yes ?= false] { if $yes { "yes" } else { "no" } }

[fdncred]

This looks like a bug in nushell to me. The ? isn't needed unless you intend it to be a required parameter, which I don't think is valid either.

[maxim-uvarov]

def main [--yes ?]

I can't compile this code in my brain. It seems incorrect to me, so I would argue that it is a bug in nushell.

The following is not recognized as valid syntax when optional flags are an explicit feature of nushell:

Flags are optional by definition. If they are defined but not used when calling the command, it means that the variable of the flag will be assigned the false value.

> def a [--test] {$test}

> a
false

Nushell doesn't have obligatory flags via the standard syntax. If one needs a flag to be set, they need to create an additional check in the command code.

def a [--b: string] {
   if $b == null {error make {msg: 'set `--b` param'}
}

[maxim-uvarov]

but I guess @fdncred said exactly that.

def main [--yes ?] { if $yes { "yes" } else { "no" } }

As Nushell accepts this seemingly invalid code without errors, I probably understand now. Sorry for the disturbance.