Redirection and spinner

[EmilyGraceSeville7cf]

How to run command with redirection with gum spin? I have these functions:

function spin --argument-names title
    set --local color '#1d87da'
    set --erase argv[1]
    gum spin --title.foreground=$color \
        --spinner.foreground=$color \
        --show-output \
        --title=$title -- $argv
end

function to_file --argument-names source output
    jsdoc2md $source >>$output
end

I wanna call spin like this: spin "Generating documentation for $file..." to_file $file $output, but when I do I get all my Markdown documentation discarded. How do I fix this issue?

Full code:

#!/usr/bin/env fish

function error
    echo (set_color red)$argv(set_color normal)
end

function info
    echo (set_color green)$argv(set_color normal)
end

function confirm
    set --local color '#1d87da'
    gum confirm --prompt.foreground=$color \
        --selected.foreground='#e5f6fd' \
        --selected.background=$color -- $argv
end

function spin --argument-names title
    set --local color '#1d87da'
    set --erase argv[1]
    gum spin --title.foreground=$color \
        --spinner.foreground=$color \
        --show-output \
        --title=$title -- $argv
end

function to_file --argument-names source output
    jsdoc2md $source >>$output
end

set generator jsdoc2md

type --query $generator || begin
    error "No '$generator' package found to generate documentation."
    if confirm "Do you want to install '$generator' package?"
        spin "Installing '$generator' package..." npm install --global jsdoc-to-markdown
    else
        info Installation cancelled
        exit
    end
end

set output Documentation.md
set ignored_files ActionInfo_.js SimpleValidator.js ComplexValidator.js

echo >$output
for file in *.js
    contains $file $ignored_files && begin
        error "$file is ignored"
        continue
    end
    spin "Generating documentation for $file..." to_file $file $output # <-- Problem here
end