Markdown Run Book

Turn your Markdown documentation into executable runbooks.

Features

• 🦕 Built with and runs on Deno
• 🌀 Blend documentation with code execution; bring your README.md developer setup to life without losing the narrative format
• ✅ Execute TypeScript and JavaScript fenced code blocks as a multi-step “runbook”
• ✨ Automatic availability of dsherret/dax within code blocks to simplify cross-platform shell execution
• ⬇ Works with local and remote Markdown files and even Markdown content piped to stdin

Motivation and How it Works

How many times have you had to follow along with a set of steps in a README.md in order to setup your development environment to work on a project? Copy-and-Paste-ing from the README to your terminal back and forth, hoping you do each step correctly and don’t miss something gets old; wouldn’t it be nice if you could just execute the code in that README? Well, that’s what mdrb allows you to do!

When provided a Markdown file (or a remote URL that points to one, or pipe the content of one through stdin) to mdrb, it does the following:

1. Extract all of the fenced code blocks which are annotated with a valid TypeScript or JavaScript language code (typescript, ts, javascript, and js)
2. Pull out the code from each and do a bit of processing to allow it to work seamlessly with Deno
   • for example, references to import.meta.url need to be rewritten with the litteral value of the source Markdown file
3. (optionally, but by default) add an import of the bundled version of dax to the code that will be executed
   • From the dax module the $ object is exposed automatically to your code blocks, allowing them to transparently reference the functions and features (of which there are many) of $ - most important of which is the execution of cross-platform shell commands.
4. Execute the code blocks according to the chosen mode; by default the “runbook” mode is used, which treats each code block as an isolated script and execution is paused awaiting your confirmation before going on.
   • “isolated” mode is the same as “runbook” mode, except that there is no pause to prompt between each code block. This is the mode used instead of runbook for all piped content due to the absence of a tty.
   • “single” mode concatenates your code blocks together as if they were all a single script and executes the resulting single block. In this mode, your code blocks can depend on each other, but be careful about things like re-declaring variables across code blocks - at runtime, they aren’t isolated from each other!

Installation

deno install -Arfn mdrb https://deno.land/x/mdrb/mod.ts

Note: if you prefer not to bake --allow-all permissions (with the -A flag) into the installed command, you can specify alternate permissions, e.g. deno install --allow-net -rfn mdrb https://deno.land/x/mdrb/mod.ts but be aware that this means you will be prompted for permissions at runtime.

Demos

Local Markdown

Within the source repository for mdrb, execute mdrb on the local demo.md file. This results in executing the 3 included (ts/js) code blocks as a “runbook”, pausing execution after each step awaiting user confirmation to proceed.

Remote Markdown

Just like when we referenced the local demo.md file, we can also just reference the demo Markdown by a URL.

🧪 Try it yourself with:

mdrb https://deno.land/x/mdrb/demo.md

Note that in this demo, we used “isolated” mode instead of the default “runbook” mode which omits the pauses for confirmation between code blocks

Piped Markdown

We can also pipe the Markdown content to mdrb

Note that for this demo, even though we didn’t manually specify “isolated” mode, mdrb used it instead of the normal default of “runbook” mode because the prompts will fail if we don’t have a tty

Using dax

There are a ton of useful things you can do with dax, so here’s a little showcase of some of what you can do with the automatically added $ object.

Skipping automatic dax addition

If you don’t want dax to be automatically added to your code blocks, you can pass the --dax=false option

Step Configuration

It is possible to (optionally) configure your code blocks using an HTML <details data-mdrb> element which comes immediately before your code blocks. Each ts / js fenced code block can have its own configuration (though one is not required). The contents of your code block configuration can change aspects of how mdrb will execute.

By providing configuration within a preceding <details data-mdrb> element, most places where Markdown is rendered will display the configuration information natively as a collapsed dropdown.

The configuration syntax supports two features within a <details data-mdrb> element:

• a value which specifies a “step name / title”, and this is provided as the <summary> element directly inside of the <details data-mdrb>.
• a value which is TOML formatted configuration placed inside of a <pre> element below the <summary> element.

  Warning the <pre> must have a newline before it (a blank line between the <summary> and the <pre>) and its content must not be indented (otherwise the Markdown parser will classify the content as an “indented code block” which is another feature of Markdown)

If you include the <details data-mdrb> element for step configuration (again, it’s optional), you may specify within it both a <summary> and a <pre>, only a <summary>, only a <pre>, or neither. Basically, everything about this step configuration is optional and mdrb will use default values in the absence of user-provided configuration overrides.

Important Notes About Configuration

Here is an example of a valid, and configured, step:

> ... preceding Markdown content

<details data-mdrb>
<summary>Log a diagnostic message</summary>
</details>

```ts
console.log("hello from this configured step!");
```

> ... the rest of the Markdown

Please note the following:

• The <details> element has an attribute of data-mdrb, which is required to signal to mdrb that this <details> is meant to configure a code block
• The <summary> element is nested inside of the <details data-mdrb> element

With this configuration in place, when executed this Markdown will show (with the first line dimmed in your terminal):

step 1 of 1 // Log a diagnostic message

hello from this configured step!

Here is an example of a step with a “full” configuration:

> ... preceding Markdown content

<details data-mdrb>
<summary>Log a diagnostic message</summary>

<pre>
description = '''
# important step

> I can have blockquotes!

basic demonstration of the fact that
you can log to the console with code
blocks.
'''
</pre>
</details>

```ts
console.log("hello from this configured step!");
```

> ... the rest of the Markdown

In this example notice the following:

• The <pre> has a blank line before it separating it from the <summary>
• The text content of the <pre> is not indented at all and is valid TOML
• This example has a single key-value pair, showing the ability to use multiline TOML strings as well as the fact that the description key can contain Markdown content

Today, the only key from the <pre> which may be used when specified is the description. This key can have either a single-line value or a multi-line value, and further, the value can contain Markdown which will be beautifully rendered in the terminal when you use “runbook” mode or when you use “isolated” mode with the --isolated-desc=true flag.

Beyond the description key, no other configuration values are used, even if they are well defined according to these rules, however in the future, there may be additions to the way you can configure mdrb execution exposed through these configuration values.

Some possible examples of things which may be included are:

• Skip the automatic addition of dax for a given code block
• Conditionally skip a code block entirely (say, for instance, if you were on Windows or Mac but not on Linux)
• Your ideas? Make an issue or PR and it will be considered

Prior Art

• https://github.com/jacobdeichert/mask
• https://github.com/c4spar/deno-dzx
• https://github.com/google/zx

License

MIT. Copyright (c) Andrew Brey