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Marco Trulla
Marco Trulla

Posted on • Edited on

A Comment Divider for Zed using Nushell

#zed #coding #nushell

Like many of you, I recently switched from VS Code to Zed. Despite having a few limitations compared to the "programming behemoth," I absolutely love it. It’s fast, reliable, and packed with useful features.

However, there is always a "but." Occasionally, I miss specific extensions from my VS Code configuration. One such example is the small but helpful Comment Divider extension, which allows you to select text and convert it into a stylized comment block.

Since Zed doesn't have an equivalent extension yet, I decided to replicate the functionality using Nushell (my daily shell of choice).

Note: I primarily use Arch Linux on WSL, so you may need to adjust the code slightly (specifically the clipboard command) to suit your environment.

1. The Nushell Script

First, I created a command to generate the comments. You can save this as a standalone script or place it in your $nu.user-autoload-dir to ensure it's sourced at startup.

UPDATE 2026-01-07: add the --single-line flag to generate single line comments.

# Generate a comment into the style of a specified programming language.
@example 'Generate a header comment for C, 80 chars width, centered' { comment generate "THIS IS A HEADER" }
@example 'Generate a sub-header comment Python, 75 chars width, centered' { comment generate "THIS IS A SUB-HEADER" -l py -w 75 -s sub-header }
def "comment generate" [
    text: string = ''               # text of the comment; it can be multilines
    --language (-l): string = 'c'   # language
    --width (-w): int = 80
    --align (-a): string = 'center'
    --style (-s): string = 'header' # header, sub-header, divider
    --filled (-f)                   # fill the spaces
    --single-line (-S)              # single line comment
    --list
] {
    const C_STYLE_LANGUAGES = [c cpp c3 d js ts jsonc]
    const BASH_STYLE_LANGAUGES = [sh nu py]

    if $list {
        $C_STYLE_LANGUAGES | append $BASH_STYLE_LANGAUGES | sort
    } else {

        const SAFETY_MARGIN = 2

        let comment_symbol = match $language {
            $lang if $lang in $C_STYLE_LANGUAGES => { '//' }
            $lang if $lang in $BASH_STYLE_LANGAUGES => { '#' }
            _ => { '//' }
        }

        let real_width = $width - $SAFETY_MARGIN - ($comment_symbol | str length) - 1

        match $style {
            "header" => {
                const char = '='
                let filler = if $filled { $char } else { ' ' }
                if not $single_line {
                    ($comment_symbol + ' ' + ('' | fill -w $real_width -c $char) + (char newline) +
                        ($text | lines | each {$comment_symbol + ' ' + ($in | fill -w $real_width -a $align -c $filler) } | str join (char newline)) + (char newline) +
                        $comment_symbol + ' ' + ('' | fill -w $real_width -c $char) + (char newline)
                    )
                } else {
                    $comment_symbol + ' ' + ($text | fill -w $real_width -a $align -c $filler) + (char newline)
                }
            }
            "sub-header" => {
                const char = '-'
                let filler = if $filled { $char } else { ' ' }
                if not $single_line {
                    ($comment_symbol + ' ' + ('' | fill -w $real_width -c $char) + (char newline) +
                        ($text | lines | each {$comment_symbol + ' ' + ($in | fill -w $real_width -a $align -c $filler) } | str join (char newline)) + (char newline) +
                        $comment_symbol + ' ' + ('' | fill -w $real_width -c $char) + (char newline)
                    )
                } else {
                    $comment_symbol + ' ' + ($text | fill -w $real_width -a $align -c $filler) + (char newline)
                }
            }
            "divider" => {
                const char = '~'
                $comment_symbol + ' ' + ('' | fill -w $real_width -c $char) + (char newline)
            }
        }
    }
}
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2. Configuring Zed Tasks

The next step is to add a task in Zed to trigger this command. Open your tasks configuration by pressing Ctrl+Shift+P (or Cmd+Shift+P on Mac) and searching for zed: open tasks. Add the following JSON:

UPDATE 2016-01-07: add tasks for single line comments

[
  {
    "label": "Comment Header",
    "command": "source ($nu.user-autoload-dirs.0)/commands.nu ; comment generate \"$ZED_SELECTED_TEXT\" -l (\"$ZED_FILENAME\" | path parse | get extension) | wl-copy",
    "hide": "on_success",
  },

  {
    "label": "Comment Header Single Line",
    "command": "source ($nu.user-autoload-dirs.0)/commands.nu ; comment generate \"$ZED_SELECTED_TEXT\" -l (\"$ZED_FILENAME\" | path parse | get extension) -S | wl-copy",
    "hide": "on_success",
  },

  {
    "label": "Comment Sub-header",
    "command": "source ($nu.user-autoload-dirs.0)/commands.nu ; comment generate \"$ZED_SELECTED_TEXT\" -l (\"$ZED_FILENAME\" | path parse | get extension) -s sub-header | wl-copy",
    "hide": "on_success",
  },

  {
    "label": "Comment Sub-header Single Line",
    "command": "source ($nu.user-autoload-dirs.0)/commands.nu ; comment generate \"$ZED_SELECTED_TEXT\" -l (\"$ZED_FILENAME\" | path parse | get extension) -s sub-header -S | wl-copy",
    "hide": "on_success",
  },

  {
    "label": "Comment Divider",
    "command": "source ($nu.user-autoload-dirs.0)/commands.nu ; comment generate \"$ZED_SELECTED_TEXT\" -l (\"$ZED_FILENAME\" | path parse | get extension) -s divider | wl-copy",
    "hide": "on_success",
  },

  {
    "label": "Comment Header Filled",
    "command": "source ($nu.user-autoload-dirs.0)/commands.nu ; comment generate \"$ZED_SELECTED_TEXT\" -l (\"$ZED_FILENAME\" | path parse | get extension) -f | wl-copy",
    "hide": "on_success",
  },

  {
    "label": "Comment Header Filled Single Line",
    "command": "source ($nu.user-autoload-dirs.0)/commands.nu ; comment generate \"$ZED_SELECTED_TEXT\" -l (\"$ZED_FILENAME\" | path parse | get extension) -S -f | wl-copy",
    "hide": "on_success",
  },

  {
    "label": "Comment Sub-header Filled",
    "command": "source ($nu.user-autoload-dirs.0)/commands.nu ; comment generate \"$ZED_SELECTED_TEXT\" -l (\"$ZED_FILENAME\" | path parse | get extension) -s sub-header -f | wl-copy",
    "hide": "on_success",
  },

  {
    "label": "Comment Sub-header Filled Single Line",
    "command": "source ($nu.user-autoload-dirs.0)/commands.nu ; comment generate \"$ZED_SELECTED_TEXT\" -l (\"$ZED_FILENAME\" | path parse | get extension) -s sub-header -S -f | wl-copy",
    "hide": "on_success",
  }
]
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You will need to adjust the path to the script being sourced.

How to Use It

  1. Select the text you want to transform into a comment.
  2. Press Alt+Shift+T to open the task list.
  3. Select your desired comment style and press Enter.

The task will generate the formatted comment and copy it to your clipboard (I haven't found a way to inject it directly at the cursor position yet). Simply paste it over your selection, and you're good to go!

Examples

Header

// ===========================================================================
//                              THIS IS A COMMENT
// ===========================================================================
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Header Single Line and Sub-header Single Line

//                              THIS IS A COMMENT
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Header Filled

// ===========================================================================
// ===========================  THIS IS A COMMENT  ===========================
// ===========================================================================
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Header Filled Single Line

// ============================ THIS IS A COMMENT ============================
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Sub-header

// ---------------------------------------------------------------------------
//                              THIS IS A COMMENT
// ---------------------------------------------------------------------------
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Sub-header Filled

// ---------------------------------------------------------------------------
// ---------------------------  THIS IS A COMMENT  ---------------------------
// ---------------------------------------------------------------------------
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Sub-header Filled Single Line

// ---------------------------- THIS IS A COMMENT ----------------------------
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Comment Divider

// ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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Multi-lines Comment Header

// ===========================================================================
//                            THIS IS A MULTI-LINE
//                               COMMENT HEADER
//                          WITH THREE LINES OF TEXT
// ===========================================================================
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Known Limitations

  • Manual Injection: As mentioned previously, there is currently no way to inject the text directly into the editor. You must rely on an external clipboard command to copy and paste the result.
  • File Naming: The command "guesses" the language style by reading the file extension. Therefore, the file must be saved with a filename; it will not work on "Untitled" buffers.

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