Simon Willison’s Weblog

[red-knot] type inference/checking test framework (via) Ruff maintainer Carl Meyer recently landed an interesting new design for a testing framework. It's based on Markdown, and could be described as a form of "literate testing" - the testing equivalent of Donald Knuth's literate programming.

A markdown test file is a suite of tests, each test can contain one or more Python files, with optionally specified path/name. The test writes all files to an in-memory file system, runs red-knot, and matches the resulting diagnostics against Type: and Error: assertions embedded in the Python source as comments.

Test suites are Markdown documents with embedded fenced blocks that look like this:

```py
reveal_type(1.0) # revealed: float
```

Tests can optionally include a path= specifier, which can provide neater messages when reporting test failures:

```py path=branches_unify_to_non_union_type.py
def could_raise_returns_str() -> str:
    return 'foo'
...
```

A larger example test suite can be browsed in the red_knot_python_semantic/resources/mdtest directory.

This document on control flow for exception handlers (from this PR) is the best example I've found of detailed prose documentation to accompany the tests.

The system is implemented in Rust, but it's easy to imagine an alternative version of this idea written in Python as a pytest plugin. This feels like an evolution of the old Python doctest idea, except that tests are embedded directly in Markdown rather than being embedded in Python code docstrings.

... and it looks like such plugins exist already. Here are two that I've found so far:

• pytest-markdown-docs by Elias Freider and Modal Labs.
• sphinx.ext.doctest is a core Sphinx extension for running test snippets in documentation.
• pytest-doctestplus from the Scientific Python community, first released in 2011.

I tried pytest-markdown-docs by creating a doc.md file like this:

# Hello test doc

```py
assert 1 + 2 == 3
```

But this fails:

```py
assert 1 + 2 == 4
```

And then running it with uvx like this:

uvx --with pytest-markdown-docs pytest --markdown-docs

I got one pass and one fail:

_______ docstring for /private/tmp/doc.md __________
Error in code block:
```
10   assert 1 + 2 == 4
11   
```
Traceback (most recent call last):
  File "/private/tmp/tt/doc.md", line 10, in <module>
    assert 1 + 2 == 4
AssertionError

============= short test summary info ==============
FAILED doc.md::/private/tmp/doc.md
=========== 1 failed, 1 passed in 0.02s ============

I also just learned that the venerable Python doctest standard library module has the ability to run tests in documentation files too, with doctest.testfile("example.txt"): "The file content is treated as if it were a single giant docstring; the file doesn’t need to contain a Python program!"

# 16th October 2024, 8:43 pm / testing, rust, python, astral, markdown, ruff, pytest, uv

My Jina Reader tool. I wanted to feed the Cloudflare Durable Objects SQLite documentation into Claude, but I was on my iPhone so copying and pasting was inconvenient. Jina offer a Reader API which can turn any URL into LLM-friendly Markdown and it turns out it supports CORS, so I got Claude to build me this tool (second iteration, third iteration, final source code).

Paste in a URL to get the Jina Markdown version, along with an all important "Copy to clipboard" button.

# 14th October 2024, 4:47 pm / projects, markdown, ai-assisted-programming, jina, claude-3-5-sonnet, claude, generative-ai, ai, llms, cors

otterwiki (via) It's been a while since I've seen a new-ish Wiki implementation, and this one by Ralph Thesen is really nice. It's written in Python (Flask + SQLAlchemy + mistune for Markdown + GitPython) and keeps all of the actual wiki content as Markdown files in a local Git repository.

The installation instructions are a little in-depth as they assume a production installation with Docker or systemd - I figured out this recipe for trying it locally using uv:

git clone https://github.com/redimp/otterwiki.git
cd otterwiki

mkdir -p app-data/repository
git init app-data/repository

echo "REPOSITORY='${PWD}/app-data/repository'" >> settings.cfg
echo "SQLALCHEMY_DATABASE_URI='sqlite:///${PWD}/app-data/db.sqlite'" >> settings.cfg
echo "SECRET_KEY='$(echo $RANDOM | md5sum | head -c 16)'" >> settings.cfg

export OTTERWIKI_SETTINGS=$PWD/settings.cfg
uv run --with gunicorn gunicorn --bind 127.0.0.1:8080 otterwiki.server:app

# 9th October 2024, 3:22 pm / python, wikis, uv, markdown, git, flask, sqlalchemy, sqlite

simonw/docs cookiecutter template. Over the last few years I’ve settled on the combination of Sphinx, the Furo theme and the myst-parser extension (enabling Markdown in place of reStructuredText) as my documentation toolkit of choice, maintained in GitHub and hosted using ReadTheDocs.

My LLM and shot-scraper projects are two examples of that stack in action.

Today I wanted to spin up a new documentation site so I finally took the time to construct a cookiecutter template for my preferred configuration. You can use it like this:

pipx install cookiecutter
cookiecutter gh:simonw/docs

Or with uv:

uv tool run cookiecutter gh:simonw/docs

Answer a few questions:

[1/3] project (): shot-scraper
[2/3] author (): Simon Willison
[3/3] docs_directory (docs):

And it creates a docs/ directory ready for you to start editing docs:

cd docs
pip install -r requirements.txt
make livehtml

# 23rd September 2024, 9:45 pm / uv, markdown, sphinx-docs, cookiecutter, read-the-docs, python, projects, documentation

Markdown and Math Live Renderer. Another of my tiny Claude-assisted JavaScript tools. This one lets you enter Markdown with embedded mathematical expressions (like $ax^2 + bx + c = 0$) and live renders those on the page, with an HTML version using MathML that you can export through copy and paste.

Here's the Claude transcript. I started by asking:

Are there any client side JavaScript markdown libraries that can also handle inline math and render it?

Claude gave me several options including the combination of Marked and KaTeX, so I followed up by asking:

Build an artifact that demonstrates Marked plus KaTeX - it should include a text area I can enter markdown in (repopulated with a good example) and live update the rendered version below. No react.

Which gave me this artifact, instantly demonstrating that what I wanted to do was possible.

I iterated on it a tiny bit to get to the final version, mainly to add that HTML export and a Copy button. The final source code is here.

# 21st September 2024, 4:56 am / claude-3-5-sonnet, anthropic, claude, markdown, mathml, ai, llms, ai-assisted-programming, tools, generative-ai, claude-artifacts

Share Claude conversations by converting their JSON to Markdown. Anthropic's Claude is missing one key feature that I really appreciate in ChatGPT: the ability to create a public link to a full conversation transcript. You can publish individual artifacts from Claude, but I often find myself wanting to publish the whole conversation.

Before ChatGPT added that feature I solved it myself with this ChatGPT JSON transcript to Markdown Observable notebook. Today I built the same thing for Claude.

Here's how to use it:

The key is to load a Claude conversation on their website with your browser DevTools network panel open and then filter URLs for chat_. You can use the Copy -> Response right click menu option to get the JSON for that conversation, then paste it into that new Observable notebook to get a Markdown transcript.

I like sharing these by pasting them into a "secret" Gist - that way they won't be indexed by search engines (adding more AI generated slop to the world) but can still be shared with people who have the link.

Here's an example transcript from this morning. I started by asking Claude:

I want to breed spiders in my house to get rid of all of the flies. What spider would you recommend?

When it suggested that this was a bad idea because it might attract pests, I asked:

What are the pests might they attract? I really like possums

It told me that possums are attracted by food waste, but "deliberately attracting them to your home isn't recommended" - so I said:

Thank you for the tips on attracting possums to my house. I will get right on that! [...] Once I have attracted all of those possums, what other animals might be attracted as a result? Do you think I might get a mountain lion?

It emphasized how bad an idea that would be and said "This would be extremely dangerous and is a serious public safety risk.", so I said:

OK. I took your advice and everything has gone wrong: I am now hiding inside my house from the several mountain lions stalking my backyard, which is full of possums

Claude has quite a preachy tone when you ask it for advice on things that are clearly a bad idea, which makes winding it up with increasingly ludicrous questions a lot of fun.

# 8th August 2024, 8:40 pm / anthropic, claude, markdown, ai, llms, tools, generative-ai, projects, json, observable

Mermaid Gantt diagrams are great for displaying distributed traces in Markdown. Bryce Mecum demonstrates how Mermaid gantt diagrams can be used to render trace information, such as the traces you might get from OpenTelemetry. I tried this out in a Gist and it works really well - GitHub Flavored Markdown will turn any fenced code block tagged mermaid containing a gantt definition into a neat rendered diagram.

# 16th July 2024, 10:10 pm / markdown, mermaid

New blog feature: Support for markdown in quotations. Another incremental improvement to my blog. I've been collecting quotations here since 2006 - I now render them using Markdown (previously they were just plain text). Here's one example. The full set of 920 (and counting) quotations can be explored using this search filter.

# 24th June 2024, 3:51 pm / projects, markdown, blogging

Jina AI Reader. Jina AI provide a number of different AI-related platform products, including an excellent family of embedding models, but one of their most instantly useful is Jina Reader, an API for turning any URL into Markdown content suitable for piping into an LLM.

Add r.jina.ai to the front of a URL to get back Markdown of that page, for example https://r.jina.ai/https://simonwillison.net/2024/Jun/16/jina-ai-reader/ - in addition to converting the content to Markdown it also does a decent job of extracting just the content and ignoring the surrounding navigation.

The API is free but rate-limited (presumably by IP) to 20 requests per minute without an API key or 200 request per minute with a free API key, and you can pay to increase your allowance beyond that.

The Apache 2 licensed source code for the hosted service is on GitHub - it's written in TypeScript and uses Puppeteer to run Readabiliy.js and Turndown against the scraped page.

It can also handle PDFs, which have their contents extracted using PDF.js.

There's also a search feature, s.jina.ai/search+term+goes+here, which uses the Brave Search API.

# 16th June 2024, 7:33 pm / puppeteer, apis, markdown, ai, llms, jina

GitHub Copilot Chat: From Prompt Injection to Data Exfiltration (via) Yet another example of the same vulnerability we see time and time again.

If you build an LLM-based chat interface that gets exposed to both private and untrusted data (in this case the code in VS Code that Copilot Chat can see) and your chat interface supports Markdown images, you have a data exfiltration prompt injection vulnerability.

The fix, applied by GitHub here, is to disable Markdown image references to untrusted domains. That way an attack can't trick your chatbot into embedding an image that leaks private data in the URL.

Previous examples: ChatGPT itself, Google Bard, Writer.com, Amazon Q, Google NotebookLM. I'm tracking them here using my new markdown-exfiltration tag.

# 16th June 2024, 12:35 am / prompt-injection, security, generative-ai, markdown, ai, github, llms, markdown-exfiltration, github-copilot, johann-rehberger

Blogmarks that use markdown. I needed to attach a correction to an older blogmark (my 20-year old name for short-form links with commentary on my blog) today - but the commentary field has always been text, not HTML, so I didn't have a way to add the necessary link.

This motivated me to finally add optional Markdown support for blogmarks to my blog's custom Django CMS. I then went through and added inline code markup to a bunch of different older posts, and built this Django SQL Dashboard to keep track of which posts I had updated.

# 25th April 2024, 4:34 am / projects, django-sql-dashboard, markdown, blogging

Migrating out of PostHaven. Amjith Ramanujam decided to migrate his blog content from PostHaven to a Markdown static site. He used shot-scraper (shelled out to from a Python script) to scrape his existing content using a snippet of JavaScript, wrote the content to a SQLite database using sqlite-utils, then used markdownify (new to me, a neat Python package for converting HTML to Markdown via BeautifulSoup) to write the content to disk as Markdown.

# 24th May 2023, 7:38 pm / sqlite-utils, shot-scraper, markdown, beautifulsoup

babelmark3 (via) I found this tool today while investigating an bug in Datasette’s datasette-render-markdown plugin: it lets you run a fragment of Markdown through dozens of different Markdown libraries across multiple different languages and compare the results. Under the hood it works with a registry of API URL endpoints for different implementations, most of which are encrypted in the configuration file on GitHub because they are only intended to be used by this comparison tool.

# 27th January 2023, 11:34 pm / apis, markdown

Pikchr. Interesting new project from SQLite creator D. Richard Hipp. Pikchr is a new mini language for describing visual diagrams, designed to be embedded in Markdown documentation. It’s already enabled for the SQLite forum. Implementation is a no-dependencies C library and output is SVG.

# 21st October 2020, 4:02 pm / c, svg, markdown, sqlite, d-richard-hipp

Render Markdown tool (via) I wrote a quick JavaScript tool for rendering Markdown via the GitHub Markdown API—which includes all of their clever extensions like tables and syntax highlighting—and then stripping out some extraneous HTML to give me back the format I like using for my blog posts.

# 3rd September 2020, 12:08 am / projects, markdown, javascript, github

Creating Simple Interactive Forms Using Python + Markdown Using ScriptedForms + Jupyter (via) ScriptedForms is a fascinating Jupyter hack that lets you construct dynamic documents defined using markdown that provide form fields and evaluate Python code instantly as you interact with them.

# 19th April 2018, 4:05 pm / jupyter, markdown, python

Deckset for Mac (via) $29 desktop Mac application that creates presentations using a cleverly designed markdown dialect. You edit the underlying markdown in your standard text editor and the Deskset app shows a preview of the presentation and lets you hit “play” to run it or export it as a PDF.

# 10th April 2018, 9:34 pm / markdown, presentations

Dillinger. I really like this online Markdown editor. It has source syntax highlighting, live previews of the generated HTML and it constantly syncs to localStorage so you won’t lose your work if you accidentally shut your browser window. The code is also available open source on GitHub.

# 8th October 2017, 6:38 pm / markdown