Query returns duplicate label copies

[minor crystal]

I have a function to create chapters, which I call once for each chapter file.
I'm adding a label to the chapter headers in order to query for them.

#let Chapter(title) = {
    set text(size: 24pt)
    pagebreak(weak: true)
    stack(
        v(5mm),        
        heading(level:1)[#title #label("chapter-heading")], // Notice label
        line(length: 100%, stroke: 2pt + luma(50%)),
        v(5mm)    
    )
} 

I now wanted to query the labels, in order to show the current chapter name in the header. For testing, I started returning all the chapters.

#let GetChapterName() = {
    return query(selector(<chapter-heading>))
}

That GetChapterName() function gets called from set page to style the header.

// Style the header
#set page(
  header: context {            
        let display = IsShowHeader()     
        if display {                        
            block(
                width: 100%,        
                inset: 5.5pt,
                fill: luma(15%)
            )[
                #grid(
                    columns: (2fr, 1fr, 2fr),
                    rows: 1,
                    align: (left, center, right),
                    [ax], [#here().position()], [#GetChapterName()] // This displays the header.
                )
            ]                
        }
    }
)

For some reason, the list returned by GetChapterName() function has duplicate chapter names (see attached image).

Why the duplicates?

[crimson temple]

can you post a complete example that reproduces the problem? I tried with the code you gave (replacing IsShowHeader() with true) and don't see any duplicate

[minor crystal]

Index is the main file.

I work on this using vscode, with Typst LSP and Typst Preview.

[rapid root]

You may want to look into using the hydra package which does something similar

[minor crystal]

no, thanks. I'd like to learn to do it manually.

[crimson temple]

thanks, I had something smaller in mind 🙂 So it boils down to this:

?r

#set page(width: auto, height: auto, margin: 1cm)

#let GetChapterName() = query(selector(<chapter-heading>))

#let Chapter(title) = heading(level:1, [#title <chapter-heading>])

#outline()

#Chapter[Introduction]

#context GetChapterName()

[crimson temple]

the problem is that you have the label inside of the header, rather than next to the header

normally the label is placed in content after the element rather than inside of it

when you put it inside, it's duplicated because it appears both in the document and in the outline

so instead you can do something like this:

?r

#set page(width: auto, height: auto, margin: 1cm)

#let GetChapterName() = query(selector(<chapter-heading>)).first().body

#let Chapter(title) = [
    #heading(level:1, title) <chapter-heading>
]

#outline()

#Chapter[Introduction]

#context GetChapterName()

[minor crystal]

Interesting. Thanks for troubleshooting that, must have been annoying to get at the root cause.

Appreciate it.