Deno & REPL – Unsupported Media Type on Display Output

[frankdierolf]

Summary

Hola,

found an issue.

Summary

Running the Zed REPL with deno in a TypeScript file works, but rich display outputs (like HTML, Markdown, SVG, or Observable Plot charts) are not rendered. Instead, Zed shows an “Unsupported media type” message.

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Description

Environment Setup

1. Ensure you have Deno installed.

2. Install the Jupyter extension for Deno:

   deno jupyter --install
   

3. Open a fresh index.ts file in Zed.

Code to Reproduce

Paste the following into index.ts:

// %%
console.log("Hello, World!");

// %%
await Deno.jupyter.display({
  "text/plain": "Hello, world!",
  "text/html": "<h1>Hello, world!</h1>",
  "text/markdown": "# Hello, world!",
}, { raw: true });

// %%
Deno.jupyter
  .svg`<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 100 100">
    <circle cx="50" cy="50" r="40" stroke="green" stroke-width="4" fill="yellow" />
  </svg>`;

// %%
import { document, penguins } from "jsr:@ry/jupyter-helper";
import * as Plot from "npm:@observablehq/plot";

let p = await penguins();

Plot.plot({
  marks: [
    Plot.dot(p.toRecords(), {
      x: "culmen_depth_mm",
      y: "culmen_length_mm",
      fill: "species",
    }),
  ],
  document,
});

Steps to Reproduce

1. Create and open a new TypeScript file in Zed.
2. Run each cell above using Zed’s REPL integration.
3. Observe the output after each block.

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Expected Behavior

• Markdown, HTML, and SVG should render in-place within the REPL output.
• Observable Plot visualizations should display inline.

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Actual Behavior

• Only console.log("Hello, World!") is rendered.
• All other display outputs (Markdown, HTML, SVG, Plot) return: ❌ Unsupported media type

Screenshot

Found related Issues:

Python REPL: Support for plots other than matplotlib #19890

---

Love that zeds has a repl feature. Didn't expect it. Thanks for the great work.

Cheers, Frank ✌

Zed Version and System Specs

Zed: v0.186.7 (Zed Preview) OS: Linux X11 pop 22.04 Memory: 93.5 GiB Architecture: x86_64 GPU: AMD Radeon Graphics (RADV GFX1103_R1) || radv || Mesa 24.2.8-1~bpo12+1pop1~1744225826~22.04~b077665

[schpet]

after watching the video here slowly, they demonstrate a way to use d3 with canvas https://zed.dev/blog/repl#typescript

which was useful to me after trying and failing to use observable Plot charts.