Quarto access within shiny

[danieltomasz]

I want to be able to download the filtered data I am presenting in my shiny app, is there any better way than creating and loading subsequent temporary files? I didnt saw any such example but it would really useful to see if there is any more conventient way (Below some minimal example of the idea)

from shiny import App, Inputs, Outputs, Session, render, ui, reactive
import subprocess
import tempfile
import os
from pathlib import Path
from io import BytesIO

# Define minimal UI with slider and download button
app_ui = ui.page_fluid(
    ui.h3("Simple Quarto Report Download"),
    ui.input_slider("n", "Number of points", min=1, max=100, value=50),
    ui.download_button("download_report", "Download Report"),
)


# Define server
def server(input, output, session):
    # Create QMD content with Python plot
    def create_qmd_content(n_points):
        return f"""---
title: "Example report"
format: typst
---


Generated {n_points} random points.

"""

    @render.download(filename="example.pdf")
    async def download_report():
        with tempfile.TemporaryDirectory() as tmpdirname:
            # Create the QMD file
            source_file = os.path.join(tmpdirname, "example.qmd")

            # Get number of points from slider
            n_points = input.n()

            # Generate QMD content
            qmd_content = create_qmd_content(n_points)

            # Write QMD content to file
            with open(source_file, "w") as f:
                f.write(qmd_content)

            # Render with Quarto using Typst format
            if os.path.isfile(source_file):
                # Run quarto render to create PDF via Typst
                subprocess.run(
                    ["quarto", "render", source_file, "--to", "typst"],
                    capture_output=True,
                    text=True,
                )

                # For debugging: print the output
                #print("Quarto output:", result.stdout)
                #print("Quarto errors:", result.stderr)

                # Get the output file
                output_file = os.path.join(tmpdirname, "example.pdf")

                if os.path.isfile(output_file):
                    with open(output_file, "rb") as fh:
                        buf = BytesIO(fh.read())
                        yield buf.getvalue()
                else:
                    error_msg = "Error: Unable to generate PDF file with Typst. Check if Quarto and Typst are installed correctly."
                    print(error_msg)
                    print(f"Expected file path: {output_file}")
                    print(f"Directory contents: {os.listdir(tmpdirname)}")
                    yield error_msg.encode("utf-8")


# Create the app
www_dir = Path(__file__).parent / "www"
www_dir.mkdir(exist_ok=True)

app = App(app_ui, server, static_assets=www_dir)